Nuclear fission products are the atomic fragments left after a large atomic nucleus
fissionsIn nuclear physics and nuclear chemistry, nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts, often producing free neutrons and lighter nuclei, which may eventually produce photons...
. Typically, a large nucleus like that of
uraniumUranium is a silvery-white metallic chemical element in the actinide series of the periodic table that has the symbol U and atomic number 92. Besides its 92 protons, a uranium nucleus can have between 141 and 146 neutrons. The most common uranium isotopes are U-238 and U-235 . A uranium atom has...
fissions by splitting into two smaller nuclei, along with a few neutrons and a large release of energy in the form of heat (kinetic energy of the nuclei), gamma rays and neutrinos. The two smaller nuclei are the "fission products".
Formation and decay
The sum of the
atomic weightAtomic weight is a dimensionless physical quantity, the ratio of the average mass of atoms of an element to 1/12 of the mass of an atom of carbon-12...
of the two atoms produced by the fission of one
atomThe atom is a basic unit of matter consisting of a dense, central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...
is always less than the
atomic weightAtomic weight is a dimensionless physical quantity, the ratio of the average mass of atoms of an element to 1/12 of the mass of an atom of carbon-12...
of the original atom. This is because some of the mass is lost as free
neutronThe neutron is a subatomic particle with no net electric charge and a mass slightly larger than that of a proton.Neutron are usually found in atomic nuclei. The nuclei of most atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of protons in a...
s and large amounts of
energyIn physics, energy is a scalar physical quantity that describes the amount of work that can be performed by a force, an attribute of objects and systems that is subject to a conservation law...
.
Since the nuclei that can readily undergo fission are particularly
neutronThe neutron is a subatomic particle with no net electric charge and a mass slightly larger than that of a proton.Neutron are usually found in atomic nuclei. The nuclei of most atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of protons in a...
-rich (e.g. 61% of the
nucleonIn physics, a nucleon is a collective name for two baryons: the neutron and the proton. They are constituents of the atomic nucleus and until the 1960s were thought to be elementary particles. In those days their interactions defined strong interactions. Now they are known to be composite...
s in uranium-235 are neutrons), the initial fission products are almost always more neutron-rich than stable nuclei of the same mass as the fission product (e.g. stable
rutheniumRuthenium is a chemical element that has the symbol Ru and atomic number 44. A rare transition metal of the platinum group of the periodic table, ruthenium is found associated with platinum ores and used as a catalyst in some platinum alloys....
-100 is 56% neutrons, stable
xenonXenon is a chemical element represented by the symbol Xe. Its atomic number is 54. A colorless, heavy, odorless noble gas, xenon occurs in the Earth's atmosphere in trace amounts...
-134 is 60%). The initial fission products therefore may be unstable and typically undergo
beta decayIn nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted. In the case of electron emission, it is referred to as beta minus , while in the case of a positron emission as beta plus...
towards stable nuclei, converting a neutron to a
protonThe proton is a subatomic particle with an electric charge of +1 elementary charge. It is found in the nucleus of each atom but is also stable by itself and has a second identity as the hydrogen ion, H
+...
with each beta emission. (Fission products do not emit alpha particles.)
A few neutron-rich and short-lived initial fission products first decay by emitting a neutron. This is the source of delayed neutrons which play an important role in control of a
nuclear reactorA nuclear reactor is a device in which nuclear chain reactions are initiated, controlled, and sustained at a steady rate.The most significant use of nuclear reactors is as an energy source for the generation of electrical power and for the power in some ships...
.
The first beta decays are rapid, and may release high energy beta particles or gamma radiation. However, as the fission products approach stable nuclear conditions, the last one or two decays may have a long halflife and release less energy. There are a few exceptions with relatively long halflives and high decay energy, such as:
- Sr-90 (high energy beta, halflife 30 years)
- Cs-137 (high energy gamma, halflife 30 years)
- Sn-126 (even higher energy gamma, but long halflife of 230,000 years means a slow rate of radiation release, and the yield
Nuclear fission splits a heavy nucleus such as uranium or plutonium into two lighter nuclei, which are called fission products. Yield refers to the fraction of a fission product produced per fission.Yield can be broken down by:#Individual isotope...
of this nuclide per fission is very low)
Radioactivity over time
Fission products have half-lives of 90 years (
Samarium-151' is a radioisotope of samarium with a half-life of 90 years, undergoing low-energy beta decay, and has a fission product yield of 0.4203% for thermal neutrons and U-235, about 39% of Sm-149's yield...
) or less, except for seven
long-lived fission productare radioactive materials with a long half-life produced by fission.-Evolution of radioactivity in nuclear waste:Nuclear fission produces fission products, as well as actinides from nuclear fuel nuclei that capture neutrons but fail to fission, and activation products from neutron activation of...
s with half-lives of 211,100 years (
Technetium-99Technetium-99 is an isotope of technetium which decays with a half-life of 211,000 years, emitting soft beta rays but no gamma rays, and has a fission product yield of 6.0507% for thermal neutron fission of uranium-235...
) and more. Therefore the total radioactivity of fission products decreases rapidly for the first several hundred years, before stabilizing at a low level that changes little for hundreds of thousands of years. This contrasts with actinides produced in the open (no
reprocessing)
nuclear fuel cycleThe nuclear fuel cycle, also called nuclear fuel chain, is the progression of nuclear fuel through a series of differing stages. It consists of steps in the front end, which are the preparation of the fuel, steps in the service period in which the fuel is used during reactor operation, and steps in...
, a number of which have half-lives in the missing range of about 10
2 to 10
5 years.
Proponents of nuclear fuel cycles which aim to consume all their actinides by fission, such as the
Integral Fast ReactorThe Integral Fast Reactor was a design for a fast reactor distinguished by a nuclear fuel cycle using reprocessing via electrorefining at the reactor site itself.The U.S. Department of Energy built a prototype but canceled the project in 1994, three years before completion...
and
molten salt reactorA molten salt reactor is a type of nuclear reactor where the primary coolant is a molten salt mixture, which can run high temperatures while staying at low vapor pressure for reduced mechanical stress and increased safety, and is less reactive than molten sodium coolant...
, use this fact to claim that within 200 years, their wastes are no more radioactive than the original uranium ore.
Fission products emit beta radiation, while actinides primarily emit alpha radiation. Many of each also emit gamma radiation.
Yield
Each fission of a parent atom produces a different set of fission product atoms. However, while an individual fission is not predictable, the fission products are statistically predictable. The amount of any particular isotope produced per fission is called its
yield,Nuclear fission splits a heavy nucleus such as uranium or plutonium into two lighter nuclei, which are called fission products. Yield refers to the fraction of a fission product produced per fission.Yield can be broken down by:#Individual isotope...
typically expressed as % per parent fission; therefore, yields total to 200% not 100%.
While fission products include every element from
zincZinc , also known as spelter, is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
through the lanthanides, the majority of the fission products occurs in two peaks. One peak occurs at about (expressed by atomic number)
strontiumStrontium is a chemical element with the symbol Sr and the atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. It occurs naturally in the minerals celestine and...
to
rutheniumRuthenium is a chemical element that has the symbol Ru and atomic number 44. A rare transition metal of the platinum group of the periodic table, ruthenium is found associated with platinum ores and used as a catalyst in some platinum alloys....
while the other peak is at about
telluriumTellurium is a chemical element that has the symbol Te and atomic number 52. A brittle silver-white metalloid which looks similar to tin, tellurium is chemically related to selenium and sulfur. Tellurium is primarily used in alloys and as a semiconductor.-Characteristics:Tellurium is extremely...
to
neodymiumNeodymium is a chemical element with the symbol Nd and atomic number 60. It is a soft silvery metal which tarnishes in air. Neodymium was discovered in 1885. Its various compounds are present in trace amounts in minerals monazite and bastnäsite. Pure neodymium is not found naturally and it is...
. The exact yield is somewhat dependent on the parent atom, and also on the energy of the initiating neutron.
In general the higher the energy of the state that undergoes nuclear fission, the more likely that the two fission products have similar mass. Hence as the neutron energy increases and/or the energy of the
fissileIn nuclear engineering, a fissile material is one that is capable of sustaining a chain reaction of nuclear fission.All known fissile materials are capable of sustaining a chain reaction in which either thermal or slow neutrons or fast neutrons predominate...
atom increases, the valley between the two peaks becomes more shallow.
For instance, the curve of yield against mass for Pu-239 has a more shallow valley than that observed for
U-235U235 or U-235 may be:* German submarine U-235, a German U-boat of World War II* Uranium-235, an isotope of uraniumbang bang there goes the ship...
when the neutrons are thermal neutrons. The curves for the fission of the later actinides tend to make even more shallow valleys. In extreme cases such as
259Fm, only one peak is seen.
The adjacent figure shows a typical fission product distribution from the fission of uranium. Note that in the calculations used to make this graph, the activation of fission products was ignored and the fission was assumed to occur in a single moment rather than a length of time. In this bar chart results are shown for different cooling times — time after fission.
Because of the stability of nuclei with even numbers of protons and/or neutrons, the curve of yield against element is not a smooth curve but tends to alternate. Note that the curve against mass number is smooth.
Characteristics
The adjacent tables provides information on the half-life, yield and decay energies for some more important fission products. A more detailed description of individual products is provided in
Fission products (by element)On this page, a discussion of each of the main elements in the fission product mixture from the nuclear fission of an actinide such as uranium or plutonium is set out by element.- Krypton 83-86 :Krypton-85 is formed by the fission process with...
and in Long-lived fission products, and in articles on specific radionuclides.
The chart below provides information on the electronegativity of the fission products:
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1The alkali metals are a series of chemical elements forming Group 1 of the periodic table: lithium , sodium , potassium , rubidium , caesium , and francium ....
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3 The Group 3 elements are chemical elements comprising the third vertical column of the periodic table.IUPAC has not recommended a specific format for the periodic table, so different conventions are permitted and are often used for group 3...
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4The Group 4 elements are a group of chemical elements in the periodic table. In the modern IUPAC nomenclature, Group 4 of the periodic table contains titanium , zirconium , hafnium and rutherfordium . This group lies in the d-block of the periodic table...
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5 A Group 5 element is one in the series of elements in group 5 in the periodic table, which consists of vanadium , niobium , tantalum , and dubnium ....
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6 A Group 6 element is one in the series of elements in group 6 in the periodic table, which consists of the transition metals chromium , molybdenum , tungsten , and seaborgium ....
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7 A Group 7 element is one in the series of elements in group 7 in the periodic table, which consists of the transition metals manganese , technetium , rhenium , and bohrium ....
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8 A Group 8 element is one in the series of elements in group 8 in the periodic table, which consists of the transition metals iron , ruthenium , osmium and hassium ....
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9 In modern IUPAC nomenclature, Group 9 of the periodic table contains the elements cobalt , rhodium , iridium , and meitnerium . These are all d-block transition metals...
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10 A Group 10 element is one in the series of elements in group 10 in the periodic table, which consists of the transition metals nickel , palladium , platinum , and darmstadtium ....
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12 A group 12 element is one of the elements in group 12 in the periodic table, consisting of zinc , cadmium and mercury . The inclusion of ununbium in group 12 is conjectural as sufficient quantity of that element has not been prepared to allow its chemistry to be evaluated.All elements in this...
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13 The boron group is the series of elements in group 13 in the periodic table. The boron group consists of boron , aluminium , gallium , indium , thallium , and ununtrium ....
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14 The carbon group is group 14 in the periodic table. The group was once also known as the tetrels , stemming from the earlier naming convention of this group as Group IVA...
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16 The chalcogens are the chemical elements in group 16 of the periodic table. This group is also known as the oxygen family...
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17The halogens or halogen elements are a series of nonmetal elements from Group 17 IUPAC Style of the periodic table, comprising fluorine, ; chlorine, ; bromine, ; iodine, ; and astatine,...
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18The noble gases are a group of chemical elements with very similar properties: under standard conditions, they are all odorless, colorless, monatomic gases, with a very low chemical reactivity...
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| 4 A period 4 element is one of the chemical elements in the fourth row of the periodic table of the elements.These are:
...
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Ionization energy increases → Electronegativity Electronegativity, symbol χ, is a chemical property that describes the ability of an atom to attract electrons towards itself in a covalent bond. An atom's electronegativity is affected by both its atomic weight and the distance that its valence electrons reside from the charged nucleus...
increases → |
GaGallium is a chemical element that has the symbol Ga and atomic number 31. Elemental gallium does not occur in nature, but as the Ga salt, in trace amounts in bauxite and zinc ores. A soft silvery metallic poor metal, elemental gallium is a brittle solid at low temperatures. As it liquefies...
1.81 |
GeGermanium is a chemical element with the symbol Ge and atomic number 32. It is a lustrous, hard, grayish-white metalloid in the carbon group, chemically similar to its group neighbors tin and silicon. Germanium has five naturally occurring isotopes ranging in atomic mass number from 70 to 76...
2.01 |
AsArsenic is the chemical element that has the symbol As, atomic number 33 and atomic mass 74.92. Arsenic was first documented by Albertus Magnus in 1250. Arsenic is a notoriously poisonous metalloid with many allotropic forms, including a yellow and several black and grey forms...
2.18 |
SeSelenium is a chemical element with the atomic number 34, represented by the chemical symbol Se, an atomic mass of 78.96. It is a nonmetal, chemically related to sulfur and tellurium, and rarely occurs in its elemental state in nature....
2.55 |
BrBromine , is a chemical element with the symbol Br and atomic number 35. A halogen element, bromine is a reddish-brown volatile liquid at standard room temperature that is intermediate in reactivity between chlorine and iodine. Bromine vapors are corrosive and toxic. Approximately 556,000 metric...
2.96 |
KrKrypton is a chemical element with the symbol Kr and atomic number 36. It is a member of Group 18 and Period 4 elements. A colorless, odorless, tasteless noble gas, krypton occurs in trace amounts in the atmosphere, is isolated by fractionally distilling liquified air, and is often used with other...
3.00 |
| 5 A period 5 element is one of the chemical elements in the fifth row of the periodic table of the elements. They all have 5 electron shells.These are:
...
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Rb Rubidium is a chemical element with the symbol Rb and atomic number 37. Rb is a soft, silvery-white metallic element of the alkali metal group....
0.82 |
SrStrontium is a chemical element with the symbol Sr and the atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. It occurs naturally in the minerals celestine and...
0.95 |
YYttrium is a chemical element with symbol Y and atomic number 39. It is a silvery-metallic transition metal chemically similar to the lanthanoids and has historically been classified as a rare earth element. Yttrium is almost always found combined with the lanthanoids in rare earth minerals and is...
1.22 |
ZrZirconium is a chemical element with the symbol Zr and atomic number 40. It is a lustrous, gray-white, strong transition metal that resembles titanium. Zirconium is used as an alloying agent due to its high resistance to corrosion. It is never found as a native metal; it is obtained mainly from...
1.33 |
NbNiobium , or columbium , is the chemical element with the symbol Nb and the atomic number 41...
1.6 |
MoMolybdenum , is a Group 6 chemical element with the symbol Mo and atomic number 42. The free element, which is a silvery metal, has the sixth-highest melting point of any element. It readily forms hard, stable carbides, and for this reason it is often used in high-strength steel alloys...
2.16 |
Tc Technetium is the lightest chemical element with no stable isotope, and is therefore the lightest radioactive element. It has atomic number 43 and symbol Tc. Technetium occurs in nature only in minute amounts; as a spontaneous fission product in uranium ore or by neutron capture in molybdenum...
1.9 |
RuRuthenium is a chemical element that has the symbol Ru and atomic number 44. A rare transition metal of the platinum group of the periodic table, ruthenium is found associated with platinum ores and used as a catalyst in some platinum alloys....
2.2 |
RhRhodium is a chemical element that is a rare, silvery-white, hard transition metal and a member of the platinum group. Rhodium is found in platinum ores and is used in alloys with platinum and as a catalyst. It is abbreviated to Rh and has atomic number 45...
2.28 |
PdPalladium is a chemical element with the chemical symbol Pd and an atomic number of 46. Palladium is a rare and lustrous silvery-white metal that was discovered in 1803 by William Hyde Wollaston, who named it after the asteroid Pallas, which in turn, was named after the epithet of the Greek...
2.20 |
AgSilver is a chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...
1.93 |
CdCadmium is a chemical element with the symbol Cd and atomic number 48. The soft, bluish-white transition metal is chemically similar to the two other metals in group 12, zinc and mercury. Similar to zinc it prefers oxidation state +2 in most of its compounds and similar to mercury it shows a low...
1.69 |
InIndium is a chemical element with chemical symbol In and atomic number 49. This rare, soft, malleable and easily fusible post-transition metal is chemically similar to aluminium or gallium but more closely resembles zinc .Indium's current primary application is to form transparent electrodes from...
1.78 |
SnTin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead, like the two possible oxidation states +2 and +4...
1.96 |
SbAntimony is a chemical element with the symbol Sb and atomic number 51. A metalloid, antimony has four allotropic forms. The stable form of antimony is a blue-white metalloid. Yellow and black antimony are unstable non-metals...
2.05 |
TeTellurium is a chemical element that has the symbol Te and atomic number 52. A brittle silver-white metalloid which looks similar to tin, tellurium is chemically related to selenium and sulfur. Tellurium is primarily used in alloys and as a semiconductor.-Characteristics:Tellurium is extremely...
2.1 |
IIodine , is a chemical element that has the symbol I and atomic number 53. Naturally-occurring iodine is a single isotope with 74 neutrons....
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XeXenon is a chemical element represented by the symbol Xe. Its atomic number is 54. A colorless, heavy, odorless noble gas, xenon occurs in the Earth's atmosphere in trace amounts...
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| 6 A period 6 element is one of the chemical elements in the sixth row of the periodic table of the elements, including the lanthanides.These are:
...
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CsCaesium or cesium is the chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of , which makes it one of only five metals that are liquid at or near room temperature...
0.79 |
BaBarium is a chemical element. It has the symbol Ba, atomic number 56, and is the fifth element in Group 2. Barium is a soft silvery metallic alkaline earth metal. It is never found in nature in its pure form due to its reactivity with air. Its oxide is historically known as baryta but it reacts...
0.89 |
LaLanthanum is a chemical element with the symbol La and atomic number 57.Lanthanum is a silvery white metallic element that belongs to group 3 of the periodic table and is a lanthanoid. It is found in some rare-earth minerals, usually in combination with cerium and other rare earth elements...
1.1 |
Ce Cerium is a chemical element with the symbol Ce and atomic number 58. It is a soft, silvery, ductile metal which easily oxidizes in air. Cerium was named after the dwarf planet . Cerium is the most abundant of the rare earth elements, making up about 0.0046% of the Earth's crust by weight. It is...
1.12 |
Pr Praseodymium is a chemical element that has the symbol Pr and atomic number 59.-Physical:Praseodymium is a soft, silvery, malleable and ductile metal in the lanthanoid group...
1.13 |
NdNeodymium is a chemical element with the symbol Nd and atomic number 60. It is a soft silvery metal which tarnishes in air. Neodymium was discovered in 1885. Its various compounds are present in trace amounts in minerals monazite and bastnäsite. Pure neodymium is not found naturally and it is...
1.14 |
Pm Promethium is a chemical element with the symbol Pm and atomic number 61. It is notable for being the only other exclusively radioactive element besides technetium which is followed by chemical elements that have stable isotopes.-Physical:...
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Sm Samarium is a chemical element with the symbol Sm and atomic number 62.-Physical:Samarium is a rare earth metal, with a bright silver luster. Three crystal modifications of the metal also exist, with transformations at 734 and 922 °C, making it polymorphic...
1.17 |
EuEuropium is a chemical element with the symbol Eu and atomic number 63. It was named after the continent of Europe.-Physical:Europium is about as hard as lead and quite ductile...
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Gd Gadolinium is a chemical element that has the symbol Gd and atomic number 64. It is a silvery-white, malleable and ductile rare-earth metal. Gadolinium has exceptionally high absorption of neutrons and therefore is used for shielding in neutron radiography and in nuclear reactors...
1.2 |
TbTerbium is a chemical element with the symbol Tb and atomic number 65. It is a silvery-white rare earth metal that is malleable, ductile and soft enough to be cut with a knife...
1.1 |
DyDysprosium is a chemical element with the symbol Dy and atomic number 66. It is a rare earth element with a metallic silver luster. Dysprosium is never found in nature as a free element, though it is found in various minerals, such as xenotime...
1.22 |
Lanthanides act like Group 3 |
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Ac Actinium is a radioactive chemical element with the symbol Ac and atomic number 89, which was discovered in 1899. It was the first non-primordial radioactive element to be isolated. Polonium, radium and radon were observed before actinium, but they were not isolated until 1902...
1.1 |
ThThorium is a chemical element with the symbol Th and atomic number 90. It is a naturally occurring, slightly radioactive metal. Thorium is estimated to be about three to four times more abundant than uranium in the earth's crust...
1.3 |
Pa Protactinium is a chemical element with the symbol Pa and atomic number 91. Its longest-lived and most abundant naturally-occurring isotope by far, Pa-231, is a decay product of uranium-235 , and it has a half-life of 32,760 years...
1.5 |
UUranium is a silvery-white metallic chemical element in the actinide series of the periodic table that has the symbol U and atomic number 92. Besides its 92 protons, a uranium nucleus can have between 141 and 146 neutrons. The most common uranium isotopes are U-238 and U-235 . A uranium atom has...
1.38 |
Np Neptunium is a chemical element with the symbol Np and atomic number 93. A radioactive metallic element, neptunium is the first transuranic element and belongs to the actinide series. Its most stable isotope, 237Np, is a by-product of nuclear reactors and plutonium production and it...
1.36 |
PuPlutonium is a rare transuranic radioactive element. It is an actinide metal of silvery-white appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation states. It reacts with carbon, halogens, nitrogen and...
1.28 |
AmAmericium is a synthetic element that has the symbol Am and atomic number 95. A radioactive metallic element, americium is an actinide that was obtained in 1944 by Glenn T. Seaborg who was bombarding plutonium with neutrons and was the fourth transuranic element to be discovered. It was named for...
1.13 |
CmCurium is a synthetic chemical element with the symbol Cm and atomic number 96. A radioactive metallic transuranic element of the actinide series, curium is produced by bombarding plutonium with alpha particles and was named for Marie Curie and her husband Pierre.- Characteristics :The isotope...
1.28 |
Bk Berkelium is a synthetic element with the symbol Bk and atomic number 97. A radioactive metallic element in the actinide series, berkelium was first synthesized by bombarding americium with alpha particles and was named after the University of California, Berkeley...
1.3 |
Cf Californium is a metallic chemical element with the symbol Cf and atomic number 98. A radioactive transuranic element, californium is used in starting nuclear reactors, optimizing coal-fired power plants and cement production facilities , medical treatment of cancer, and oil exploration via down...
1.3 |
Not all Actinides act like Group 3 |
| 4 A period 4 element is one of the chemical elements in the fourth row of the periodic table of the elements.These are:
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Valence (chemistry)In chemistry, valence, also known as valency or valency number, is a measure of the number of chemical bonds formed by the atoms of a given element...
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| ** Actinide The actinoid or actinide series encompasses the 15 chemical elements that lie between actinium and lawrencium included on the periodic table, with atomic numbers 89 - 103...
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Fission product production
Small amounts of fission products are naturally formed as the result of either
spontaneous fissionSpontaneous fission is a form of radioactive decay characteristic of very heavy isotopes. It is theoretically possible for any atomic nucleus whose mass is greater than or equal to 100 atomic mass units , i.e. elements near ruthenium. In practice, however, spontaneous fission is only energetically...
of natural uranium, which occurs at a low rate, or as a result of neutrons from radioactive decay or reactions with cosmic ray particles. The microscopic tracks left by these fission products in some natural minerals (mainly
apatiteApatite is a group of phosphate minerals, usually referring to hydroxyapatite, fluorapatite, chlorapatite and bromapatite, named for high concentrations of OH
−, F
−, Cl
− or...
and
zirconZircon is a mineral belonging to the group of nesosilicates. Its chemical name is zirconium silicate and its corresponding chemical formula is ZrSiO4. A common empirical formula showing some of the range of substitution in zircon is 1-x4x-y...
) are used in
fission track datingFission track dating is a radiometric dating technique based on analyses of the damage trails, or tracks, left by fission fragments in certain uranium-bearing minerals and glasses...
to provide the cooling ages of natural rocks. The technique has an effective dating range of 0.1 Ma to >1.0 Ga depending on the mineral used and the concentration on uranium in that mineral.
About 1.5 billion years ago, in a uranium ore body in Africa, a
natural nuclear fission reactorA natural nuclear fission reactor is a uranium deposit where analysis of isotope ratios has shown that self-sustaining nuclear chain reactions have occurred. The existence of this phenomenon was discovered in 1972 by French physicist Francis Perrin. The conditions under which a natural nuclear...
operated for a few hundred thousand years and produced approximately 5 tonnes of fission products. These fission products were important in providing proof that the natural reactor had occurred. More details are provided in the
linked articleA natural nuclear fission reactor is a uranium deposit where analysis of isotope ratios has shown that self-sustaining nuclear chain reactions have occurred. The existence of this phenomenon was discovered in 1972 by French physicist Francis Perrin. The conditions under which a natural nuclear...
.
Fission products are produced in
nuclear weaponA nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission or a combination of fission and fusion...
explosions, with the amount depending on the type of weapon.
The largest source of fission products is from nuclear reactors. In current nuclear power reactors, about 3% of the uranium in the fuel is converted into fission products as an unavoidable by-product of energy generation. Most of these fission products remain in the fuel unless there is fuel failure, or an accident, or the fuel is reprocessed.
Supply of radioactive isotopes
Some fission products (such as Cs-137) are used in medical and industrial radioactive sources.
Nuclear reactor control
Some fission products decay with the release of a neutron. Since there may be a short delay in time between the original fission event (which release its own "prompt" neutrons immediately) and the release of these neutrons, the latter are termed "delayed neutrons". These delayed neutrons are important to nuclear reactor control.
Nuclear reactor poisons
Some of the fission products have a high neutron absorption capacity, such as
xenon-135Xenon is a chemical element represented by the symbol Xe. Its atomic number is 54. A colorless, heavy, odorless noble gas, xenon occurs in the Earth's atmosphere in trace amounts...
and
samarium-149Samarium is a chemical element with the symbol Sm and atomic number 62.-Physical:Samarium is a rare earth metal, with a bright silver luster. Three crystal modifications of the metal also exist, with transformations at 734 and 922 °C, making it polymorphic...
. Since a nuclear reactor depends on a balance in the neutron production and absorption rates, these fission product remove neutrons from the reactor and will tend to shut the reactor down or "poison" the reactor. Nuclear fuels and reactors are designed to address this phenomena through such features as burnable poisons and control rods. More details are provided in the article on
nuclear reactor poisonsA nuclear poison, also called a neutron poison is a substance with a large neutron absorption cross-section in applications, such as nuclear reactors, when absorbing neutrons is an undesirable effect...
.
Fission product decay with time
For fission of
uranium-235Uranium-235 is an isotope of uranium making up about 0.72% of natural uranium. Unlike the predominant isotope uranium-238 it is fissile, i.e. it can sustain fission chain reaction...
, the predominant radioactive fission products include isotopes of
iodineIodine , is a chemical element that has the symbol I and atomic number 53. Naturally-occurring iodine is a single isotope with 74 neutrons....
,
caesiumCaesium or cesium is the chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of , which makes it one of only five metals that are liquid at or near room temperature...
,
strontiumStrontium is a chemical element with the symbol Sr and the atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. It occurs naturally in the minerals celestine and...
,
xenonXenon is a chemical element represented by the symbol Xe. Its atomic number is 54. A colorless, heavy, odorless noble gas, xenon occurs in the Earth's atmosphere in trace amounts...
and
bariumBarium is a chemical element. It has the symbol Ba, atomic number 56, and is the fifth element in Group 2. Barium is a soft silvery metallic alkaline earth metal. It is never found in nature in its pure form due to its reactivity with air. Its oxide is historically known as baryta but it reacts...
. It is important to understand that the size of the threat becomes smaller with the passage of time. Locations where radiation fields once posed immediate mortal threats, such as much of the Chernobyl power plant on day one of the accident and the ground zero sites of Japanese atomic bombings (6 hours after detonation), are now safe as the radioactivity has decayed to a very low level.
See for instance the graph (below right) of the gamma dose rate due to Chernobyl fallout as a function of time after the accident. Many of the fission products decay through very short-lived isotopes to form stable isotopes, but a considerable number of the radioisotopes have
half livesHalf-life is the period of time, for a substance undergoing decay, to decrease by half. The name originally was used to describe a characteristic of unstable atoms , but may apply to any quantity which follows a set-rate decay....
longer than a day.
The radioactivity in the fission product mixture is mostly due to short lived isotopes such as
I-131Iodine-131 , also called radioiodine, is a radioisotope of iodine which has medical and pharmaceutical uses. It is also a radioactive hazard and was a significant contributor to the health effects of the Chernobyl disaster....
and
140Ba, after about four months
141Ce,
95Zr/
95Nb and
89Sr take the largest share, while after about two or three years the largest share is taken by
144Ce/144Pr,
106Ru/
106Rh and
147Pm. Later
90Sr and
137Cs are the main radioisotopes, being succeeded by
99Tc. In the case of a release of radioactivity from a power reactor or used fuel, only some elements are released; as a result, the isotopic signature of the radioactivity is very different from an open air nuclear detonation, where all the fission products are dispersed.
Fission products in power reactors
In a nuclear power reactor, the main types of radioactivity are fission products, actinides and activation products. Fission products are the largest amount of radioactivity for the first several hundred years, while actinides are dominant roughly 10
3 to 10
5 years after fuel use.
Fission occurs in the nuclear fuel, and the fission products are primarily retained within the fuel close to where they are produced. These fission products are important to the operation of the reactor because (as noted above) some fission products contribute delayed neutrons that are useful for reactor control while others are neutron poisons that tend to inhibit the nuclear reaction. The buildup of the fission product poisons is a key factor in determining the maximum duration a given fuel element can be kept within the reactor. The decay of short-lived fission products also provide a source of heat within the fuel that continues even after the reactor has been shutdown and the fission reactions stopped. It is this decay heat that sets the requirements for cooling of a reactor after shutdown. More details on these topics are provided in the articles on nuclear power plants and used nuclear fuel.
If the fuel cladding around the fuel develops holes, then fission products can leak into the primary
coolantA coolant is a fluid which flows through a device to prevent its overheating, transferring the heat produced by the device to other devices that use or dissipate it. An ideal coolant has high thermal capacity, low viscosity, is low-cost, non-toxic, and chemically inert, neither causing nor...
. Depending on the fission product chemistry, it may settle within the reactor core or travel through the coolant system. Coolant systems include chemistry control systems that among other purposes, will tend to remove such fission products. In a well-designed power reactor running under normal conditions, the radioactivity of the coolant is very low.
Fission products in nuclear weapons
Nuclear weapons use fission as either the partial or the main energy source. Depending on the weapon design and where it is exploded, the relative importance of the fission product radioactivity will vary compared to the activation product radioactivity in the total fallout radioactivity.
The immediate fission products from nuclear weapon fission are essentially the same as those from any other fission source, depending slightly on the particular nuclide that is fissioning. However, the very short time scale for the reaction makes a difference in the particular mix of isotopes produced from an atomic bomb.
For example, the
134Cs/
137Cs ratio provides an easy method of distinguishing between fallout from a bomb and the fission products from a power reactor. Almost no Cs-134 is formed by nuclear fission (because
xenonXenon is a chemical element represented by the symbol Xe. Its atomic number is 54. A colorless, heavy, odorless noble gas, xenon occurs in the Earth's atmosphere in trace amounts...
-134 is stable). The
134Cs is formed by the
neutron activationNeutron activation is the process in which neutron radiation induces radioactivity in materials, and occurs when atomic nuclei capture free neutrons, becoming heavier and entering excited states. The excited nucleus often decays immediately by emitting particles such as neutrons, protons, or alpha...
of the stable
133Cs which is formed by the decay of isotopes in the
isobarIsobar may refer to:* A contour line of equal or constant pressure in meteorology* Isobar , in nuclear physics, one of multiple nuclides with equal numbers of nucleons* A heat pipe* Isobar , a 2009 science fiction film...
(A = 133). so in a momentary criticality by the time that the
neutronThe neutron is a subatomic particle with no net electric charge and a mass slightly larger than that of a proton.Neutron are usually found in atomic nuclei. The nuclei of most atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of protons in a...
flux becomes zero too little time will have passed for any
133Cs to be present. While in a power reactor plenty of time exists for the decay of the isotopes in the
isobarIsobar may refer to:* A contour line of equal or constant pressure in meteorology* Isobar , in nuclear physics, one of multiple nuclides with equal numbers of nucleons* A heat pipe* Isobar , a 2009 science fiction film...
to form
133Cs, the
133Cs thus formed can then be activated to form
134Cs only if the time between the start and the end of the criticality is long.
According to Jiri Hala's textbook the radioactivity in the fission product mixture (due to an atom bomb) is mostly caused by short-lived isotopes such as
I-131Iodine-131 , also called radioiodine, is a radioisotope of iodine which has medical and pharmaceutical uses. It is also a radioactive hazard and was a significant contributor to the health effects of the Chernobyl disaster....
and
BaBarium is a chemical element. It has the symbol Ba, atomic number 56, and is the fifth element in Group 2. Barium is a soft silvery metallic alkaline earth metal. It is never found in nature in its pure form due to its reactivity with air. Its oxide is historically known as baryta but it reacts...
-140. After about four months
CeCerium is a chemical element with the symbol Ce and atomic number 58. It is a soft, silvery, ductile metal which easily oxidizes in air. Cerium was named after the dwarf planet . Cerium is the most abundant of the rare earth elements, making up about 0.0046% of the Earth's crust by weight. It is...
-141,
ZrZirconium is a chemical element with the symbol Zr and atomic number 40. It is a lustrous, gray-white, strong transition metal that resembles titanium. Zirconium is used as an alloying agent due to its high resistance to corrosion. It is never found as a native metal; it is obtained mainly from...
-95/
NbNiobium , or columbium , is the chemical element with the symbol Nb and the atomic number 41...
-95, and
SrStrontium is a chemical element with the symbol Sr and the atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. It occurs naturally in the minerals celestine and...
-89 represent the largest share of radioactive material. After two to three years,
CeCerium is a chemical element with the symbol Ce and atomic number 58. It is a soft, silvery, ductile metal which easily oxidizes in air. Cerium was named after the dwarf planet . Cerium is the most abundant of the rare earth elements, making up about 0.0046% of the Earth's crust by weight. It is...
-144/
PrPraseodymium is a chemical element that has the symbol Pr and atomic number 59.-Physical:Praseodymium is a soft, silvery, malleable and ductile metal in the lanthanoid group...
-144,
RuRuthenium is a chemical element that has the symbol Ru and atomic number 44. A rare transition metal of the platinum group of the periodic table, ruthenium is found associated with platinum ores and used as a catalyst in some platinum alloys....
-106/
RhRhodium is a chemical element that is a rare, silvery-white, hard transition metal and a member of the platinum group. Rhodium is found in platinum ores and is used in alloys with platinum and as a catalyst. It is abbreviated to Rh and has atomic number 45...
-106, and
Promethium-147Promethium-147 is one of the isotopes of promethium, with a half-life of 2.62 years, and is a fission product from nuclear reactors via beta decay from neodymium-147...
are the bulk of the radioactivity. After a few years, the radiation is dominated by
Strontium-90-Radioactivity:Strontium-90 is a radioactive isotope of strontium, with a half life of 28.8 years. Natural strontium is nonradioactive and nontoxic, but 90Sr is a radioactivity hazard...
and
Caesium-137Caesium-137 is a radioactive isotope of caesium which is formed mainly as a fission product by nuclear fission. It has a half-life of 30.17 years, and decays by beta decay to a metastable nuclear isomer of barium-137 . Barium-137m has a half-life of 2.55 minutes and is responsible for all of the...
, whereas in the period between 10,000 and a million years it is
TechnetiumTechnetium is the lightest chemical element with no stable isotope, and is therefore the lightest radioactive element. It has atomic number 43 and symbol Tc. Technetium occurs in nature only in minute amounts; as a spontaneous fission product in uranium ore or by neutron capture in molybdenum...
-99 that dominates.
Countermeasures against the worst fission products found in accident fallout
The purpose of radiological emergency preparedness is to protect people from the effects of radiation exposure after an accident at a nuclear power plant. Evacuation is the most effective protective measure in the event of a radiological emergency because it protects the whole body (including the thyroid gland and other organs) from all radionuclides and all exposure pathways. However, in situations where evacuation is impossible, calling for in-place sheltering, there are measures which lend some degree of protection against harmful radioisotopes
The mixture of radioactive fission products found in the
falloutFallout is the residual radiation hazard from a nuclear explosion, aptly named because it "falls out" of the atmosphere into which it is spread during the explosion. It commonly refers to the radioactive dust created when a nuclear weapon explodes. This radioactive dust, consisting of hot...
from a nuclear bomb are very different in nature to those found in spent power
reactorReactor can mean:* Bioreactor, any device or system that supports a biologically active environment.* Chemical reactor, a device for containing and controlling a chemical reaction* Nuclear reactor, a device for containing and controlling a nuclear reaction...
fuel. This is because the reactor fuel will have had more time for the short lived isotopes to decay, and because for many accident types that the volatile elements are liberated while the involitiles are retained at the accident site. As a result the contribution of many short-lived (eg
97Zr) and/or involtiles to the off site gamma dose is less for accident fallout than it is for local fallout from a bomb detonation.
Iodine
At least three
isotopes of iodineThere are 37 isotopes of iodine and only one, 127I, is stable.In many ways, 129I is similar to 36Cl. It is a soluble halogen, fairly non-reactive, exists mainly as a non-sorbing anion, and is produced by cosmogenic, thermonuclear, and in-situ reactions...
are important.
129IIodine-129 is long-lived radioisotope of iodine which occurs naturally, but also is of special interest in the monitoring and effects of man-made nuclear fission decay products, where it serves as both tracer and potential radiological contaminant.-Formation and decay:129I is primarily...
,
131IIodine-131 , also called radioiodine, is a radioisotope of iodine which has medical and pharmaceutical uses. It is also a radioactive hazard and was a significant contributor to the health effects of the Chernobyl disaster....
(Radioiodine) and
132I. An overview of
iodineIodine , is a chemical element that has the symbol I and atomic number 53. Naturally-occurring iodine is a single isotope with 74 neutrons....
exposure in the USA (resulting from bomb tests) can be seen at
http://rex.nci.nih.gov/massmedia/Fallout/contents.html. Open air nuclear testing and the
Chernobyl disasterThe Chernobyl disaster was a nuclear reactor accident that occurred on 26 April 1986 at the Chernobyl Nuclear Power Plant in Ukraine . It is considered to be the worst nuclear power plant disaster in history and the only level 7 event on the International Nuclear Event Scale...
both released iodine-131.
The short-lived isotopes of iodine are particularly harmful because the
thyroidThe thyroid is one of the largest endocrine glands in the body. This gland is found in the neck inferior to the thyroid cartilage and at approximately the same level as the cricoid cartilage...
collects and concentrates iodide—radioactive as well as non-radioactive—for use in the production of metabolic hormones. Absorption of radioiodine can lead to acute, chronic, and delayed effects. Acute effects from high doses include
thyroiditisThyroiditis is the inflammation of the thyroid gland. The thyroid gland is located on the front of the neck below the laryngeal prominence, and makes hormones that control metabolism.-Classification:...
, while chronic and delayed effects include
hypothyroidismHypothyroidism is the disease state in humans and in animals caused by insufficient production of thyroid hormone by the thyroid gland. Cretinism is a form of hypothyroidism found in infants.-Causes:...
, thyroid nodules, and
thyroid cancerThyroid neoplasm or thyroid cancer usually refers to any of four kinds of malignant tumors of the thyroid gland: papillary, follicular, medullary or anaplastic. Most patients are 25 to 65 years of age when first diagnosed; women are more affected than men. Papillary and follicular tumors are the...
. It has been shown that the active iodine released from Chernobyl and Mayak has resulted in an increase in the incidence of thyroid cancer in the former
Soviet UnionThe Union of Soviet Socialist Republics was a constitutionally socialist state that existed in Eurasia from 1922 to 1991. The name is a translation of the , tr. Soyuz Sovetskikh Sotsialisticheskikh Respublik, abbreviated СССР, SSSR. The common short name is Soviet Union, from , Sovetskiy Soyuz...
.
One measure which may protect against this risk is taking large doses of
potassium iodidePotassium iodide is an inorganic compound with formula KI. This white salt is the most commercially significant iodide compound, with approximately 37,000 tons produced in 1985. It is less hygroscopic than sodium iodide, making it easier to work with...
before exposure to radioiodine—the non-radioactive iodide 'saturates' the thyroid, causing less of the radioiodine to be stored in the body. Because this countermeasure simply takes advantage of the
pharmacokineticsPharmacokinetics is a branch of pharmacology dedicated to the determination of the fate of substances administered externally to a living organism...
regarding iodide uptake, it affords no protection against other causes of
radiation poisoningRadiation poisoning, also called radiation sickness or a creeping dose, is a form of damage to organ tissue due to excessive exposure to ionizing radiation...
.
Administering potassium iodide reduces the effects of radio iodine by 99%, and is a prudent, inexpensive supplement to
fallout shelterA fallout shelter is an enclosed space specially designed to protect occupants from radioactive debris or fallout resulting from a nuclear explosion. Many such shelters were constructed as civil defense measures during the Cold War....
s. The
Food and Drug AdministrationThe Food and Drug Administration is a Government agency of the United States Department of Health and Human Services and is responsible for regulating and supervising the safety of foods, tobacco products, dietary supplements, Medication drugs, vaccines, Biopharmaceutical, blood transfusion,...
(FDA) has approved potassium iodide as an over-the-counter
medicationA pharmaceutical drug, also referred to as medicine, medication or medicament, can be loosely defined as any chemical substance intended for use in the medical diagnosis, cure, treatment, or prevention of disease.- Classification :...
. As with any medication, individuals should check with their doctor or pharmacist before using it.
A low-cost alternative to commercially available iodine pills is a saturated solution of potassium iodide. It usually possible to obtain several thousand doses for prices near US$ 0.01/dose. Long term storage of KI is normally in the form of reagent grade crystals, which are convenient and available commercially. The purity is superior to "pharmacologic grade". Its concentration depends only on temperature, which is easy to determine, and the required dose is easily administered by measuring the required volume of the liquid. At room temperature, the U.S. standard adult radiological protective dose of 130 mg is four drops of a saturated solution. A baby's dose is 65 mg, or two drops. It should be noted that these doses are sufficient to cause
nauseaNausea is the sensation of unease and discomfort in the stomach with an urge to vomit.-Causes:...
and sometimes emesis in most individuals. It's normally administered in a ball of bread, because it tastes incredibly bad. Use is contraindicated in individual known to be allergic to iodine; for such persons
sodium perchlorateSodium perchlorate is a perchlorate of sodium and has the formula NaClO4. Sodium perchlorate melts with decomposition at 480 °C. Its heat of formation is −382.75 kJ mol−1. It is a white crystalline, hygroscopic solid that is soluble in water and in alcohol...
is one alternative (see chap 13, Kearney).
- Cresson Kearny, Nuclear War Survival Skills, available on line at Oregon Institute of Science and Medicine, created with the permission of the author. The information on KI is near the end of chapter 13. This manual has proven technical info on expedient fallout shelter
A fallout shelter is an enclosed space specially designed to protect occupants from radioactive debris or fallout resulting from a nuclear explosion. Many such shelters were constructed as civil defense measures during the Cold War....
s, and assorted shelter system needs that can be created from common household items. OISM also offers free downloads of other civil defense and shelter information as well.
Caesium
The
ChernobylChornobyl , orChernobyl , is a city in northern Ukraine, in Kiev Oblast , near the border with Belarus. It is twinned with Larne, in Ireland....
accident released a large amount of caesium isotopes, these were dispersed over a wide area. For instance they can be found in the soil of
FranceFrance , officially the French Republic , is a country located in Western Europe, with several overseas islands and territories located on other continents. Metropolitan France extends from the Mediterranean Sea to the English Channel and the North Sea, and from the Rhine to the Atlantic Ocean...
at low levels while in some areas of the former
Soviet UnionThe Union of Soviet Socialist Republics was a constitutionally socialist state that existed in Eurasia from 1922 to 1991. The name is a translation of the , tr. Soyuz Sovetskikh Sotsialisticheskikh Respublik, abbreviated СССР, SSSR. The common short name is Soviet Union, from , Sovetskiy Soyuz...
the concentration in soil is sometimes much higher. For a review of the methods used to decontaminate an urban environment please see the
scopeScope or Scopes may refer to:* SCOPE , a technique of creating gene libraries* Scope , the range in which a variable can be referenced* Scope , a mouthwash brand by Procter & Gamble* SCOPE...
report
Behaviour and Decontamination of Artificial Radionuclides in the Urban Environment. Also see chapter four of the
NEAThe Nuclear Energy Agency is an intergovernmental multinational agency that is organized under the Organisation for Economic Co-operation and Development...
reports
Chernobyl ten years on and
Chernobyl twenty years on for details of how farming methods can be changed to reduce the impact of accident fallout.
Prussian blue
In
livestockLivestock are one or more domesticated animals raised in an agricultural setting to produce commodities such as food or fiber, or labor...
farming an important countermeasure against
137Cs is to feed to animals a little
prussian bluePrussian blue is a dark blue pigment – one of the first synthetic pigments – which was synthesized for the first time in Berlin around the year 1706. It was named "Preußisch blau" and "Berlinisch Blau" in 1709 by its first trader...
. This
ironIron is a metallic chemical element with the symbol Fe and atomic number 26. Iron is a group 8 and period 4 element and is therefore classified as a transition metal. Iron and iron alloys are by far the most common metals and the most common ferromagnetic materials in everyday use...
potassiumPotassium is the chemical element with the symbol K , atomic number 19, and atomic mass 39.0983. Potassium was first isolated from potash...
cyanideA cyanide is any chemical compound that contains the cyano group , which consists of a carbon atom triple-bonded to a nitrogen atom. Inorganic cyanides are hydrogen cyanide salts in which cyanide is generally the anion CN
-. Organic compounds that have a -C≡N functional group bonded to...
compound acts as a ion-exchanger. The cyanide is so tightly bonded to the iron that it is safe for a human to eat several grams of prussian blue per day. The prussian blue reduces the biological half life (different from the
nuclear half lifeHalf-life is the period of time, for a substance undergoing decay, to decrease by half. The name originally was used to describe a characteristic of unstable atoms , but may apply to any quantity which follows a set-rate decay....
) of the caesium. The physical or nuclear half life of
137Cs is about 30 years. This is a constant which can not be changed but the biological half life is not a constant. It will change according to the nature and habits of the organism it is expressed for.
CaesiumCaesium or cesium is the chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of , which makes it one of only five metals that are liquid at or near room temperature...
in humans normally has a biological half life of between one and four months. An added advantage of the prussian blue is that the caesium which is stripped from the animal in the droppings is in a form which is not available to plants. Hence it prevents the caesium from being recycled. The form of prussian blue required for the treatment of humans or animals is a special grade. Attempts to use the
pigmentA pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...
grade used in
paintPaint is any liquid, liquifiable, or mastic composition which after application to a substrate in a thin layer is converted to an opaque solid film.-History:...
s have not been successful. For further details of the use of prussian blue please see the IAEA report on the
Goiânia accidentThe Goiânia accident was an incident of radioactive contamination in central Brazil that killed 4, injured 28, and produced over 200 cases of detectable radiation poisoning. On 13 September 1987, an old radiation source was scavenged from an abandoned hospital in Goiânia, the capital of the...
.
http://www-pub.iaea.org/MTCD/publications/PDF/Pub815_web.pdf
Ploughing or the removal of the top layer
137Cs is an isotope which is of long term concern as it remains in the top layers of soil. Plants with shallow root systems tend to absorb it for many years. Hence
grassGrasses, or more technically graminoids, are monocotyledonous, usually herbaceous plants with narrow leaves growing from the base. They include the "true grasses", of the Poaceae family, as well as the sedges and the rushes . The true grasses include cereals, bamboo and the grasses of lawns...
and
mushroomA mushroom is the fleshy, spore-bearing fruiting body of a fungus, typically produced above ground on soil or on its food source. The standard for the name "mushroom" is the cultivated white button mushroom, Agaricus bisporus, hence the word mushroom is most often applied to those fungi that have...
s can carry a considerable amount of
137Cs which can be transferred to humans through the
food chainFood chains describe the eating relationships between species within an ecosystem or a particular living place. Many types of food chains or webs are applicable depending on habitat or environmental factors...
. One of the best countermeasures in dairy farming against
137Cs is to mix up the soil by deeply ploughing the soil. This has the effect of putting the
137Cs out of reach of the shallow
rootIn vascular plants, the root is the organ of a plant that typically lies below the surface of the soil. This is not always the case, however, since a root can also be aerial or aerating . Furthermore, a stem normally occurring below ground is not exceptional either...
s of the grass, hence the level of radioactivity in the grass will be lowered. Also after a nuclear war or serious accident the removal of top few cm of
soilSoil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics. It is composed of particles of broken rock that have been altered by chemical and...
and its burial in a shallow trench will reduce the long term gamma dose to humans due to
137Cs as the gamma
photonIn physics, a photon is an elementary particle, the quantum of the electromagnetic field and the basic "unit" of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force...
s will be attenuated by their passage through the
soilSoil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics. It is composed of particles of broken rock that have been altered by chemical and...
. The deeper and more remote the trench is, the better the degree of protection which will be afforded to the human population.
Release from the Chernobyl fire
More details about the caesium release from the Chernobyl accident can be found at
http://www.icsu-scope.org/downloadpubs/scope50/chapter02.html#t2.7 . A definitive report on Chernobyl is at
http://www.nea.fr/html/rp/chernobyl/allchernobyl.html - table 1 in chapter two lists the radioisotopes released in the fire. The percentage of the inventory which was released was controlled largely by how volatile the fission product is. Hence a greater proportion of
xenonXenon is a chemical element represented by the symbol Xe. Its atomic number is 54. A colorless, heavy, odorless noble gas, xenon occurs in the Earth's atmosphere in trace amounts...
and
iodineIodine , is a chemical element that has the symbol I and atomic number 53. Naturally-occurring iodine is a single isotope with 74 neutrons....
were released than of
ceriumCerium is a chemical element with the symbol Ce and atomic number 58. It is a soft, silvery, ductile metal which easily oxidizes in air. Cerium was named after the dwarf planet . Cerium is the most abundant of the rare earth elements, making up about 0.0046% of the Earth's crust by weight. It is...
and
plutoniumPlutonium is a rare transuranic radioactive element. It is an actinide metal of silvery-white appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation states. It reacts with carbon, halogens, nitrogen and...
.
Strontium
Also by the addition of
limeAgricultural lime, also called garden lime or liming, is a soil additive made from pulverized limestone or chalk. The primary active component is calcium carbonate...
to soils which are poor in
calciumCalcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft grey alkaline earth metal, and is the fifth most abundant element by mass in the Earth's crust...
the uptake of
strontiumStrontium is a chemical element with the symbol Sr and the atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. It occurs naturally in the minerals celestine and...
by plants can be reduced, likewise in areas where the soil is low in
potassiumPotassium is the chemical element with the symbol K , atomic number 19, and atomic mass 39.0983. Potassium was first isolated from potash...
, the addition of a potassium fertiliser can discourage the uptake of caesium into plants. However such treatments with either
limeAgricultural lime, also called garden lime or liming, is a soil additive made from pulverized limestone or chalk. The primary active component is calcium carbonate...
or
potashPotash is the common name given to potassium carbonate and various mined and manufactured salts that contain the element potassium in water-soluble form. In some rare cases, potash can be formed with traces of organic materials such as plant remains....
should not be undertaken lightly as they can alter the soil chemistry greatly so resulting in a change in the plant
ecologyEcology is the interdisciplinary scientific study of the interactions between organisms and the interactions of these organisms with their environment....
of the land.
Caesium
It is known that the isotope responsible for the majority of the external gamma exposure in
fuel reprocessingNuclear reprocessing separates components of spent nuclear fuel.Reprocessing serves multiple purposes, whose relative importance has changed over time:*Producing plutonium for nuclear weapons...
plants (and the Chernobyl site in 2005) is Cs-137.
137Cs does appear to be an indicator of nuclear fission, as it is only formed by nuclear fission of an actinide.
137Cs is often removed from waste waters in the nuclear industry by means of solid
ion exchangeIon exchange is an exchange of ions between two electrolytes or between an electrolyte solution and a complex. In most cases the term is used to denote the processes of purification, separation, and decontamination of aqueous and other ion-containing solutions with solid polymeric or mineralic 'ion...
rs. A range of
zeoliteZeolites are microporous, aluminosilicate minerals commonly used as commercial adsorbents. The term zeolite was originally coined in 1756 by Swedish mineralogist Axel Fredrik Cronstedt, who observed that upon rapidly heating the material stilbite, it produced large amounts of steam from water that...
s can be used for this task. In nuclear reactors both
137Cs and
90Sr are found in locations remote from the
fuelFuel is any material that is burned or altered to obtain energy and to heat or to move object. Fuel releases its energy either through a chemical reaction means, such as combustion, or nuclear means, such as nuclear fission or nuclear fusion...
, this is because these isotopes are formed by the beta decay of noble gases (xenon-137 {halflife of 3.8 minutes}and krypton-90 {halflife 32 seconds}) which enable these isotopes to be deposited in locations remote from the fuel (eg on control rods and in the space inside a fuel pin between the fuel and the cladding)
Iodine
133I decays by
beta particleBeta particles are high-energy, high-speed electrons or positrons emitted by certain types of radioactive nuclei such as potassium-40. The beta particles emitted are a form of ionizing radiation also known as beta rays. The production of beta particles is termed beta decay...
decay (with a half life of 20.8 hours) to
133Xe which in turn decays by
beta decayIn nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted. In the case of electron emission, it is referred to as beta minus , while in the case of a positron emission as beta plus...
(with a half life of 5.2 days) to
133Cs. The isotopes which decay to
133I are very short lived.
129IIodine-129 is long-lived radioisotope of iodine which occurs naturally, but also is of special interest in the monitoring and effects of man-made nuclear fission decay products, where it serves as both tracer and potential radiological contaminant.-Formation and decay:129I is primarily...
is very long lived and this is one of the major radioactive elements which enter the sea from reprocessing plants.
Fission products which form anions
Some fission products are very long lived, examples of these include
iodineIodine , is a chemical element that has the symbol I and atomic number 53. Naturally-occurring iodine is a single isotope with 74 neutrons....
-129 and
technetiumTechnetium is the lightest chemical element with no stable isotope, and is therefore the lightest radioactive element. It has atomic number 43 and symbol Tc. Technetium occurs in nature only in minute amounts; as a spontaneous fission product in uranium ore or by neutron capture in molybdenum...
-99. Both of these are very mobile in solid/water as they form
anionicIn chemistry, an anionic species is one that contains a full negative charge. These types of compounds can range in reactivity, but most are fairly reactive....
species (Iodide and
99TcO
4-).
Tc
It is interesting to note that in common with
chromateChromates and dichromates are salts of chromic acid and dichromic acid, respectively. Chromate salts contain the chromate anion, CrO, and usually have an intense yellow color. Dichromate salts contain the dichromate anion, Cr2O, and usually have an intense orange color...
and
molybdateIn chemistry a molybdate is a compound containing an oxoanion with molybdenum in its highest oxidation state of 6. Molybdenum can form a very large range of such oxoanions which can be discrete structures or polymeric extended structures, although the latter are only found in the solid state.The...
that
99TcO
4- ion can react with steel surfaces to form a
corrosionCorrosion is the disintegration of a material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means a loss of electrons of metals reacting with water and oxygen. Weakening of iron due to oxidation of the iron atoms is a...
resistant layer. In this way these metaloxo anions act as
anodicAn anode is an electrode through which electric current flows into a polarized electrical device. Mnemonic: ACID . Electrons flow in the opposite direction to the electric current...
corrosion inhibitorA corrosion inhibitor is a chemical compound that, when added to a fluid or gas, decreases the corrosion rate of a metal or an alloy.The effectiveness, or corrosion inhibition efficiency, of a corrosion inhibitor is a function of many factors like: fluid composition, quantity of water, flow regime......
s. The formation of
99TcO
2 on steel surfaces is one effect which will retard the release of
99Tc from nuclear waste drums and nuclear equipment which has become lost prior to decontamination (eg
submarineA submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has only limited underwater capability...
reactors which have been lost at sea). This
99TcO
2 layer renders the steel surface passive, it inhibits the anodic
corrosionCorrosion is the disintegration of a material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means a loss of electrons of metals reacting with water and oxygen. Weakening of iron due to oxidation of the iron atoms is a...
reaction.
I
In a similar way the release of iodine-131 in a serious power reactor accident could be retarded by absorption on metal surfaces within the nuclear plant.
- H. Glänneskog. Interactions of I
Iodine , is a chemical element that has the symbol I and atomic number 53. Naturally-occurring iodine is a single isotope with 74 neutrons....
2 and CH3I with reactive metals under BWR severe-accident conditions, Nucl. Engineering and Design, 2004, 227, pages 323-329.
- H. Glänneskog. Iodine chemistry under severe accident conditions in a nuclear power reactor, Ph.D. Thesis, Chalmers University of Technology, October, 2005.
A lot of other work on the iodine chemistry which would occur during a bad accident has been done.
http://www.sbf.admin.ch/htm/services/publikationen/international/frp/eu-abstracts/html/fp/fp5/5eu99.0423.htmlhttp://www.nea.fr/html/nsd/docs/2000/csni-r2000-12.pdfhttp://www.ing.unipi.it/~dimnp/CD/supporto/pdf/paci03.pdf