SrilAIV ACAOEJIY OF Si I UNI i: Atomic Energy Research ( ooriliiuiiioii 4 OIHHH

Anthropogenic Radioactivity in the Marine Environment

A survey submitted as partial fulfillment of the nuclear science diploma

By: Salah Yousif Hassan Mohammed

Supervised by: Dr. Itifaal Kabbashi llassona

February 2006 "mmm>

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II Acknowledgment

I would like to thank teachers, the thanks is also extending to my colleagues in Sudan academy, special thanks to my supervisor

Dr. Rifaat Kabbashi Hassona For his generous and thoughtful guidance, continuous encouragement and sustained interest throughout this work.

in Dedication

To my parents.... All my family and friends

(V Contents content page

Vtfi n Acknowledgment in

Dedication IV Chapter one V

Introduction 1 Chapter two 3 Global fallout (Chernobyl accident) 4 tests 12 Chapter Three 15 Important elements 16 Cesium (137Cs) 17 Strontium (Sr-90) 21 Strontium Isotopes 22 isotopes 24 Resources of plutonium 26 Plutonium and Weapons 26 Toxicity and Health Effects 28 CHAPTER FOUR 31 Recommendations 32 Conclusion 33 REFERENCES 34 Chapter one

1-1 Introduction: Introduction:

Prior to 1942, man's exposure to ionizing radiation was limited essentially to natural radioactivity and medical x rays. Since then, the use of atomic energy has become an important part of the modern way of life. The first controlled, self- sustaining nuclear chain reaction occurred in December 1942, and the first atomic bomb was tested successfully in 1945. Both kinds of events create man-made radioactivity, i.e. added by human activities (so-called anthropogenic radioactivity). Several hundreds of artificial radionuclides are produced as the result of human activities, such as the applications of nuclear reactors and particle accelerators, testing of nuclear weapons and nuclear accidents. Many of these radionuclides are short-lived and decay quickly after their production, but some of them are longer-lived and are released into the environment. Concentrations of anthropogenic radionuclides generally vary from region to region, according to location and magnitude of the different sources of contamination. Radionuclides have been released to the environment from a multiplicity of sources, both planned and accidental. The main contribution to anthropogenic marine radioactivity, as in the terrestrial environment, is still due to global fallout from nuclear weapon tests performed in the atmosphere, particularly in the 1950s and early 1960s. However, in some regions, like the Irish and North Seas, concentrations of anthropogenic radionuclides in the marine environment have been significantly influenced by discharges from European reprocessing plants. On the other hand, the Baltic and Black Seas were the Seas most affected by the Chernobyl accident. In all these latter regions the spatial and temporal trends in the concentrations of anthropogenic radionuclides have been quite dynamic. They are a result jf changing source terms and marine processes including horizontal and vertical transport in the water column, sedimentation and resuspension, sediment, biological uptake, and food chain transfer. Given that more than 70% of the

1 surface of the Earth is ocean, it is not surprising that much of the anthropogenic radionuclides now reside there. The radionuclides introduced into marine environment undergo various physical, chemical and biological processes taking place in the sea. These processes may be due to physical dispersion or complicated chemical and biological interactions of the radionuclides with inorganic and organic suspend matter, variety of living organisms, bottom sediments, etc. The behaviour of radionuclides in the sea depends primarily on their chemical properties, but it may also be influenced by properties of interacting matrices and other environmental factors. The major route of radiation exposure of man to artificial radionuclides occuring in the marine environment is through ingestion of radiologically contamined marine organisms. This research summarizes the main sources of contamination in the marine environment and presents an overview covering the oceanic distribution of anthropogenic radionuclides in the FAO regions. A great number of measurements of artificial radionuclides have been carried out on various marine environmental samples in different oceans over the world, being cesium-137 the most widely measured . Radionuclide concentrations vary from region to region. according to the specific sources of contamination. In some regions, such as the Irish Sea. the Baltic Sea and the Black Sea, the concentrations depend on the inputs due to discharges from reprocessing facilities and from Chernobyl accident. In Brazil, the artificial radioactivity is low and corresponds to typical deposition values due to fallout for the Southern Hemisphere.

i Chapter two

2 sources of anthropogenic radioactivity.

2-1 global fallout(Chernobyl accident)

2-2 nuclear weapon test

.-> 2-1 Global fallout (Chernobyl accident): The annotated citations pertaining to Chernobyl-derived fallout, the following comments and observations: Nuclear safety experts had not anticipated that a nuclear accident would release this large an inventory of radio nuclides. These nuclides were dispersed further, more erratically, and in much greater quantities than had been anticipated prior to the accident. At the time the accident was occurring, and during the weeks and months that followed, there was a widespread lack of accurate information about the seriousness and the radiological impact (deposition levels) oi~ the accident. During and after the accident, official information sources ranged from unreliable (Russian and French government sources) to inaccurate (IA1-A. National Radiological Protection Board, etc.). Political considerations and partisan prejudice in favor of nuclear energy production combined with the lack of environmental monitoring information and skewed objective accident analysis with the result that the impact of the accident was and continues to be minimized. This underestimation of the extent of the Chernobyl accident continues today in most official versions in terms of where and in what quantity deposition from the accident occurred. Only a few locations were equipped with sufficient instrumentation to make accurate real-time nuclide-specific measurements of the passage of the fallout cloud and its erratic rainfall-associated deposition. Rainfall events were the fundamental mechanism responsible for the extremely high deposition levels in some locations, including areas located thousands of kilometers from the accident site. Dry deposition played a lesser role in the spread of Chernobyl fallout than in weapons testing fallout events. Only a minimum of information has been collected about the actual levels of the dietary intake of Chernobyl-derived radio nuclides for persons living in areas with high fallout - greater than 1 Ci/km2 (37,000 Bq/m2).

4 The failure to measure accurately the dietary intake of specific population groups in the most affected areas, and the general tendency to average dose equivalents over large population groups (including estimating projected deaths as a percentage of hemispheric death rates) is particularly reprehensible. A reconsideration of the accident ten years later can only conclude that accurate information is still unavailable about actual deposition levels over vast areas of the Northern Hemisphere where millions of residents do not have access to accurate radiological monitoring data (Turkey, Iran. Iraq, North Africa, etc.). Even in countries with modest to excellent radiological monitoring capabilities, accurate information about the impact of the accident was not available in a timely manner and, in some cases, has never been made available. The United Stales serves as an example of the problem of freedom of information. While most areas of the United States received only a minimum of Chernobyl-derived fallout, some locations (See Dibbs, Maryland) received fallout which exceeded weapons testing deposition. The radiological surveillance data collected by the KM I. (Environmental Measurements Laboratory) and the EPA were cither limited to a very small number of locations or, in the case of the EPA, did not include ground deposition data (Bq/m2) or accurate air concentrations expressed in u.Bq/m.3 (microbecquerels). Kxtensive data collected by the National Reconnaissance Office pertaining to the Chernobyl accident is not yet available to the general public. Articles cited in this section but not annotated were not present at hand for review.

5 Tablel. ESTIMATED RELEASE OF LONG-LIVED RADIONUCLIDES FROM THE CHERNOBYL ACCIDENT

Radionuclide Total released radioactivity (Curies)

1J7Cs 2,700,000

_m^ l 1,350,000 216,000

~TORy 948,000" 144Ce 2,430,000 ^TOH^g 40,500 mSb 81,000

2^,240pu 1,480 2>u 700 241 Pu 135,000 241 - 162 Am IOCm ' 1630" " 24j>244Cm 162

6 This incomplete source term release will be updated with a more complete description of the total nuclide inventories released from the Chernobyl accident if and when the tenth anniversary report of the Chernobyl accident listing the revised release estimates is received from the OECD/NTA. The current estimates listed above derive from a world health organization report in 1989 which may underestimate the actual release activity during the accident. Many earlier reports contain even larger underestimations of the actual release during the accident, and, in fact, an exact source term estimate for all radio nuclides released in the Chernobyl accident may never be possible. For a more detailed analysis of the release dynamics of the Chernobyl accident and the many mysteries surrounding exactly what transpired during the accident, see the publications of Alexander Sich, 1994 etc., which are reviewed in the following pages. It has taken almost a decade for an accurate analysis of the accident dynamics to emerge from the official evasions and misinformation which characterized the early reports on Chernobyl

7 Table2. Aarkrog, A., Tsaturov, Y. and Polikarpov, G.G. (1993). Sources to environmental radioactive contamination in the former USSR. Riso National Laboratory. Roskilde, Denmark.

Sizes of contaminated territories, km States 37-185 185-555 0.55-1.5 >1.5 kBqm2 kBqm2 MBqm2 MBq2 Russia 48100 5450 2130 310 Byelorussia 29920 10170 4210 12150 ' Ukraine 37090 1990 820 640

Moldova 50 - Total 115160 17160 7160 3100

8 The Chernobyl accident, if contaminated areas outside the USSR are included, resulted in the deposition of long-lived radio nuclides in excess of 37,000 Bq/m2 (1 Ci/km2) on +/- 200,000 km2 of the world's surface. Areas impacted by iodine-131. ruthenium-103, tellurium-132. barium-140, and other short-lived isotopes (1/2 T ^ 1 week to I yt\), along with the longer-lived isotopes, to levels exceeding 37,000 Bq/m2, may have exceeded 1,000,000 km2 in the weeks after the accident.

• The primitive maps reproduced in this publication show extensive contamination not only in Byelorussia, but also throughout central Russia. With each passing year, our knowledge of the extent of the deposition from the Chernobyl accident grows larger as more information is collected and collated and the parameters of Chernobyl-derived deposition in excess of one per square kilometer are expanded. • An accurate radiometric survey of the hemispheric impact of the Chernobyl accident would probably reveal significant additional contamination in locations such as Turkey, Iran, Iraq. North Africa, and possibly even areas in the Far East and in North America. • The National Reconnaissance Office has extensive additional radiological surveillance data pertaining to the Chernobyl accident which is not available to the general public because it is classified.

9 Table3. Radioactivity in Mediterranean waters:

1984 Aegean Sea Fish ,37Cs 0.53 Bq/kg mean value 1984 Tryrhenian Fish ,37Cs 0.10 Bq/kg mean Sea value 1986 Aegean Sea Fish ,37Cs 4.9 Bq/kg mean value 1986 Black Sea Fish ,37Cs 2.0 Bq/kg mean value 1990 Black Sea Fish ,37Cs 3.3 Bq/kg mean value 1985 Tyrrhenian Shellfish ,37Cs 0.36 Bq/kg mean Sea value 1986 Tyrrhenian Shellfish ,37Cs 14.0 Bq/kg mean Sea value 1990 Tyrrhenian Shellfish 137Cs 3.2 Bq/kg mean Sea value 1990 Black Sea Surface 164.0 Bq/kg mean sediments value

10 The Black Sea was more impacted by the Chernobyl accident than the other Mediterranean sea basins; it was still showing the cumulative effects of the The reactor incident in Cchernobyl happened on April 26, 1986. As a result of this accident a quantity of 2 x 1018 Bq radiation was released into the atmosphere (ZIFFERO 1988). That is the greatest amount of radioacitvity that has ever been released over the short term from a radioactive source (IAEA 1991). About half of this amount settled out within 60 km of the accident site, while the remainder was spread unevenly over all of Europe

11 2-2 Nuclear weapon tests! Weapons testing radioactive contamination were spread world-wide not only in tropospheric fallout (often associated with rainfall events but with extensive, close-in. dry deposition) but also in stratospheric fallout. The patterns of stratospheric fallout which provide a baseline of contamination against which to compare the impact of the Chernobyl accident resulted in a fairly even distribution of contamination over most of the earth's surface. Peak concentrations of stratospheric fallout were achieved between 1962 and 1964. The 1963 joint U.S.­ Russian-British test ban treaty effectively ended atmospheric weapons testing, at which time fallout rates began declining, with occasional interruptions from Chinese weapons tests, until the Chernobyl accident in 1986. Prior to the Chernobyl accident, world-wide fallout levels had reached the lowest level of yearly accumulation since 1950. Other important source points of anthropogenic radioactive contamination include fuel reprocessing facilities such as Sellafielcl. the Savannah River Reservation, accidents such as the SNAP satellite failure in 1958. and the many other U.S. and Russian military weapons production sites, such as the Hanford Reservation in Washington. These sites are not only sources of significant releases in the past but they also pose a risk of substantial releases to the environment for centuries to come.

12 Table4. Nuclear Weapons Testing Fission Yield and Waste Production:

Nuclide Half- Representative fission Normalized production (PBq life yield (%) per Mt fission energy) Sr-89 50.5 d 2.56 590 Sr-90 28.67 3.50 3.9 Zr-95 64.0 d 5.07 920 Ru-103 39.4 d 5.20 1500 Ru-106 368 d 2.44 78 1-131 8.04 d 2.90 4200 Cs-136 13.2 d 0.036 32 ~CsT37 30.2a 5.57 5.9 ...... s

. 1 PBq = 27,000 Ci

1 ^ Transfer factors are strongly influenced by seasonal and geographical distributions. For example, if 1,000 Bq of 137 per m2 are deposited over a barley field three months before harvest, the concentration in the mature grain will be 1 Bq 137Cs/kg. If on the other hand contamination, with the same deposition, occurs one month before harvest, the mature grain will contain approximately 100 Bq 137Cs/kg." ."The mean concentration in Danish grain in 1962-74 was 7.1 Bq 137Cs/kg. In 1986 the mean level was 3.3 Bq." This illustrates the efficiency and uniformity of stratospheric fallout contamination compared to the erratic distribution patterns of Chernobyl-derived radiocesium, which did not significantly affect during the growing season.

14 Chapter Three

3-1 important elements 3-2 Cesium (137Cs) 3-3 Strontium(Sr-90) 3-4 plutonium (Pu)

15 3-1 Important elements: From the radiological point of view the most important radionuclides are cesium-137, strontium-90 and plutonium-239. due to their chemical and nuclear characteristics. The two first radioisotopes present long half life (30 and 28 years), high fission yields and chemical behaviour similar to potassium and calcium, respectively. No stable element exists for plutonium-239, which presents high radiotoxicity, long half-life (24000 years) and some marine organisms accumulate plutonium at high levels. The cumulative deposition in a wide mid-latitude band of the northern hemisphere of weapons testing derived ~ •"' Pu is now -50 Bq/m2

1 "I -7 (3,000 d.p.m./m2); testing derived Cs exceeding 1,000 Bq/m2 remains in many locations. Other long-lived radionuclide accompany these isotopes, some 9 11 "growing in" as daughter products from inert gases; others such as Am "grow- in" as daughter products of more dangerous isotopes such as ' Pu.

16 3-2 Cesium (" Cs): Cesium-137 in the environment came from a variety of sources. The largest single source was fallout from atmospheric nuclear weapons tests in the 1950s and 1960s, which dispersed and deposited cesium-137 world-wide. However much of the cesium-137 from testing has now decayed. waste and accidental releases such as the Chernobyl accident in the Ukraine release some cesium-137 to the environment. Spent nuclear fuel reprocessing plant wastes may introduce small amounts to the environment. However, the U.S. does not currently reprocess spent nuclear fuel. Although hospitals and research laboratories generate wastes containing ccsium- 137, they usually do not enter the environment. Occasionally, industrial instruments containing cesium-137 are lost or stolen. Anyone who unwittingly handles them may be exposed. These devices are typically metal, and may be considered scrap metal and sold for recycling. If they find their way into a steel mill and are melted, they can cause significant environmental contamination. They may also be discarded and sent to a municipal landfill, or sold for other reasons. These devices should be considered dangerous. Cesium-137 undergoes radioactive decay with the emission of beta particles and relatively strong gamma radiation. Cesium-137 decays to barium-137m, a short­ lived decay product, which in turn decays to a nonradioactive form of barium. The half-life of cesium-137 is 30.17 years. Because of the chemical of cesium, it moves easily through the environment. This makes the cleanup of cesium-137 difficult. Hveryone is exposed to very small amounts of cesium-137 in soil and water as a result of atmospheric fallout. In the Northern Hemisphere, the average annual dose from exposure to cesium-137 associated with atmospheric fallout is less titan 1 mrem: this dose continues to diminish every year as cesium-137 decays. People may also be exposed from contaminated sites: Walking on cesium-137 contaminated soil could result in external exposure to

17 gamma radiation. Leaving the contaminated area would prevent additional exposure. Coming in contact with waste materials at contaminated sites could also result in external exposure to gamma radiation. Leaving the areaa would also end the exposure. If cesium-137 contaminated soil becomes air-borne as dust, breathing the dust would result in internal exposure. Because the radiation emitting material is then in the body, leaving the site would not end the exposure. Drinking cesium-137 contaminated water, would also place the cesium-137 inside the bod\'. where it would expose living tissue to gamma and beta radiation. People may ingest cesium-137 with food and water, or may inhale it as dust. If cesium-137 enters the body, it is distributed fairly uniformly throughout the body's soft tissues, resulting in exposure of those tissues. Slightly higher concentrations of the metal are found in muscle, while slightly lower concentrations are found in bone and fat. Compared to some other radionuclides, cesium-137 remains in the body for a relatively short time. It is eliminated through the urine. Exposure to cesium-137 may also be external (that is. exposure to its gamma radiation from outside the body). Like all radionuclides, exposure to radiation from cesium-137 results in increased risk of . Everyone is exposed to very small amounts of cesium-137 in soil and water as a result of atmospheric fallout. Exposure to waste materials, from contaminated sites, or from nuclear accidents can result in cancer risks much higher than typical environmental exposures. Great Britain's National Radiological Protection Board predicts that there will be up to 1,000 additional over the next 70 years among the population of Western Europe exposed to fallout from the nuclear accident at Chernobyl, in part due to cesium-137 If exposures are very high, serious burns, and even death, can result. Instances of such exposure are very rare. One example of a high-exposure situation would be the mishandling a strong industrial cesium-137 source. The

18 magnitude of the health risk depends on exposure conditions. These include such factors as strength of the source, length of exposure, distance from the source, and whether there was shielding between you and the source (such as metal plating). there are several. However, they are not routinely available in a doctor's office, because they require special laboratory equipment. Some tests can measure the amount of radionuclides in urine, or in fecal samples, even at very low levels. A technique called "whole-body counting" can detect gamma radiation emitted by cesium-137 in the body. A variety of portable instruments can directly measure cesium-137 on the skin or hair. Other techniques include directly measuring the level of cesium-137 in soft tissues samples from organs or from blood, bones, and milk. Cesium-137 that is dispersed in the environment, like that from atmospheric testing, is almost impossible to avoid. However the exposure from cesium-137 in the environment is very small. Serious exposure is unlikely. People most likely to accidentally encounter a cesium-137 source typically work in scrap metal sorting, sales and brokerage, metal melting and casting, and in municipal landfill operations. They may unwittingly encounter an industrial instrument containing a sealed cesium-137 radiation source.

19 Table5. Most of the following baseline data are pre-Chernobyl peak concentrations unless otherwise noted.

Fallout rates and accumulated fallout (Bq ,37Csm -2) in Denmark 1986- 1991 Denmark Jutland Islands Year di Ai(30.02) di Ai(30.02) di Ai(30.02) 1986 1210.000 3725.984 1340.000 4137.847 1080.000 3314.232

1987 29.000 " 3669.280 " 32.000 ~ 4074.674 26.000 3263.994 1988 11.900 3597.161 13.400 3994.768 10.300 3199.562 1989 T500 3518.480 4.510 ~""" 3907.998 2.530 3129.007 1990 2.63 34407744 3.85 3822.564 1.41 3058.968 1991 1.63 3363.805 1.92 "37 37".'194" T.36 2990.480

20 3-3 Strontium (Sr-90) A radioactive isotope of the heavy metal strontium, Strontium-90 is a by-product of uranium and plutonium fission. SR-90 is linked to bone, and other, cancers. Acting chemically in vivo like calcium, it tends to concentrate in bones and teeth. Used as a radioactive tracer in medical and agricultural studies. controlled amounts of strontium-90 have also been used as a treatment for bone cancer. Due to its extreme reactivity to air, this element always naturally occurs combined with other elements and compounds, as in the minerals strontianite. celestite, etc. It is isolated as a yellowish metal and is somewhat malleable. It is chiefly employed (as in the nitrate) to color pyrotechnic flames red. Strontium is a bright silvery metal that is softer than calcium and even more reactive in water; Strontium will decompose on contact to produce Strontium hydroxide and hydrogen gas. It burns in air to produce both a Strontium oxide and strontium nitride, but since it does not react with nitrogen below 380 °C it will only form the oxide spontaneously at room temperature. It should be kept under kerosene to prevent oxidation; freshly exposed Strontium metal rapidly turns a yellowish color with the formation of the oxide. Finely powdered Strontium metal will ignite spontaneously in air. Volatile Strontium salts impart a beautiful crimson color to flames, and these salts are used in pyrotechnics and in the production of flares. Natural Strontium is a mixture of four stable isotopes. Strontium commonly occurs in nature, averaging 0.034% of all igneous rock and is found chiefly as the form of the sulfate mineral celestite (SrS04) and the carbonate strontianite (SrC03). Of the two, celestite occurs much more frequently in sedimentary deposits of sufficient size to make development of mining facilities attractive. Strontianite would be the more useful of the two common minerals because Strontium is used Most often in the carbonate form, but few deposits have been discovered that are suitable for development. The metal can be prepared

21 by electrolysis of melted strontium chloride mixed with : Sr2+ + 2 e- -> Sr 2 CI- -> CI2 (g) + 2e- Alternatively it is made by reducing Strontium oxide with aluminium in a vacuum at a temperature at which Strontium distills off. Three allotropes of the metal exist, with transition points at 235 and 540 °C. Strontium metal (98% pure) in January 1990 cost about $5/oz. The largest commercially exploited deposits are found in England. Strontium was among the radioactive material released by the Windscale fire.

3-3-1 Strontium Isotopes

The alkali earth metal Strontium has four stable, natural!}' occurring isotopes: Sr-84 (0.56%). Sr-86 (9,86%), Sr-87 (7.0%) and Sr-88 (82.58%). Only Sr-87 is radiogenic; it is produced by decay from the radioactive alkali metal rubidiuin-87. which has a half-life of 48.800.000 years. Thus, there arc two sources oi" Sr-87 in any material: that formed during primordial nucleo-synthesis along with Sr-84. Sr-86 and Sr-88. as well as that formed by radioactive decay o\" Rb-87. The ratio Sr-87/Sr-86 is the parameter typically reported in geologic investigations. Because Strontium has an atomic radius similar to that of calcium. it readily substitutes for Ca in minerals. Sr-87/Sr-86 ratios in minerals and rocks have values ranging from about 0.7 to greater than 4.0. Sixteen unstable isotopes are known to exist. Of greatest importance is Sr-90 with a half-life of 20 years, i! is a by-product of and presents a health problem since it substitutes for calcium in bone, preventing expulsion from the body. This isotope is One ol^ the best long-lived high-energy beta emitters known, and is used in SNAP (S\ stems for Nuclear .Auxiliary Power) dexices. i hese devices hold promise for use in spacecraft, remote weather stations, navigational buoys, etc. where a lightweight, long-lived, nuclear-electric power source is required.

22 Table6. Sr-90 and Csl37 activities of different plant species from the sample area Bl, Bodenmais, Bavaria. Samples taken July 1993.

Sr:90 Cs-137 Ratio Plant species [Bq/kg] [Bq/kg] Cs-137:Sr- (leaves) DW DW 90

Dryopteris 82.2 26420 321 carthusiana Vaccinium 78.8 8730 1 111 myrtillus Athyrium filix 68.7 11510 168 femina Rubus fruticosus 43.2 5900 137 Prenanthes 29.0 8190 282 ' purpurea Rubus idaeus 24.9 5500 221

23 3-4 pi u to iiin in isotopes

Plutonium is a by-product of the fission process in nuclear reactors, due to neutron capture by uranium-238 in particular. When operating, a typical nuclear reactor contains within its uranium fuel load about 325 kilograms of plutonium. with phitonium-239 being the most common isotope. Pu-239 is fissile, yielding much the same energy as the fission of a U-235 atom, and complementing it.

Well over half of the plutonium created in the reactor core is "burned" in situ and is responsible for about one third of the total heat output. Of the rest, one sixth through neutron capture becomes Pu-240 (and Pu-24l). the balance emerges as Pu-239 in the spent fuel.

An ordinary large nuclear power reactor (1000 MWe LWR) gives rise to about 25 tonnes of spent fuel a year, containing up to 290 kilograms of plulonium. Plutonium, like uranium, is an immense energy source. The plutonium extracted from used reactor fuel can be used as a direct substitute for U-235 in the usual fuel, the Pu-239 being the main fissile part but Pu-241 also contributing.

[f the spent fuel is reprocessed, the recovered plutonium oxide is mixed with depleted uranium oxide to produce mixed-oxide (MOX) fuel, with about 5% Pu- 239. Plutonium can be used on its own in fast neutron reactors, where the Pu-240 also fissions, and so functions as a fuel (along with U-238). it is thus said to be "fissionable", as distinct from fissile.

One kilogram of Pu-239 being slowly consumed over three years in a conventional nuclear reactor can produce sufficient heat to generate nearly 10 million kilowatt- hours of electricity - sufficient to meet the needs of over 1000 typical households.

Plutonium-240 is the second most common isotope, formed by occasional neutron capture by Pu-239. Its concentration in nuclear fuel builds up steadih. since it

24 does not undergo fission to produce energy in the same way as Pu-239. (In a fast neutron reactor it is fissionable, which means that such a reactor can utilise recycled I.WR plutonium more effectively than a I.WR.)

The 1.15% of plutonium in the spent fuel removed from a commercial power reactor (burn-up of 42 GWcl/t) consists of about 55% Pu-239, 23% Pu-240. 12% Pu-241 and lesser quantities of the other isotopes, including 2% of Pu-238 which is the main source of heat and radioactivity. Reactor-grade plutonium is defined as that with 19% or more of Pu-240.

Plutonium stored over several years becomes contaminated with the Pu-241 decay- product Americium. which interferes with normal fuel fabrication procedures. Alter long storage. Am-241 must be removed before She Pu can be used in a normal MOX plant.

While of a different order of magnitude to the fission occurring within a nuclear reactor. Pu-240 has a relatively high rate of spontaneous fission with consequent neutron emissions. This makes reactor-grade plutonium entirely unsuitable lor use in a bomb (see below).

Recovered plutonium can only be recycled through a light water reactor once or twice, as the isotopic quality deteriorates. However, fast neutron reactors can then use this material and complete its consumption. Such reactors can also be configured to be net breeders of plutonium (as original!} envisaged), but the need for litis is remote. Meanwhile research on fast neutron reactors is focused on maximising consumption of plutonium and incineration of actinides formed in the light water reactors.

25 3-4-1 Resources of plutonium

Total world generation of reactor-grade plutonium in spent fuel is some 50 tonnes per year. About 1300 tonnes have been produced so far, and most of this remains in the spent fuel, with some 370 tonnes extracted. About one third of the separated Pu (130 t) has been used in MOX over the last 30 years. Currently 8-10 tonnes of Pu is used in MOX each year.

Three US reactors are able to run fully on MOX, as can Canadian heavy water reactors. All Western and the later Soviet light water reactors can use 30% MOX in their fuel.

Some 32 European reactors are licensed to use MOX fuel, and several in France are using it as 30% of their fuel.

About 22 tonnes of reactor-grade plutonium is separated by reprocessing plants in the OFCD each year and this is set to double by 2003. by which time its usage in MOX is expected to outstrip this level of production so that stockpiles diminish.

The UK has 65 tonnes of separated plutonium and this stockpile is expected to grow to 106 tonnes by 2012 - some 8It from fuel and 25t from AGR fuel. Using it all in MOX fuel rather than immobilising it as waste is expected to yield a £700-1200 million resource cost saving to UK. along with 300 billion kWh of electricity (about one year's UK supply). The 106t Pu could be consumed in two 1000 MWe light water reactors using 100% MOX fuel over 35 years.

2.4.2 Plutonium and Weapons

It takes about 10 kilograms of nearly pure Pu-239 to make a bomb. Producing this would require 30 megawatt-years of reactor operation, with frequent fuel changes and reprocessing the 'hot' fuel. Weapons-grade Pu is made

26 by burning natural uranium fuel to the extent of only about 100 MWd/t (effectively 3 months), instead of the 45,000 MWd/t typical of power reactors

(or even the 8000 - 10,000 MWd/t in Magnox reactors used for power).

For weapons use, Pu-240 is considered a serious contaminant and it is not feasible to separate Pu-240 from Pu-239. An explosive device could be made from plutonium extracted from low burn-up reactor fuel (ie. if the fuel had only been used for a short time), but any significant proportions of Pu-240 in it would make it hazardous to the bomb makers, as well as unreliable and unpredictable. Typical plutonium recovered from reprocessing used power reactor fuel has about one- third non-fissile isotopes (mainly Pu-240).

* In 1962 a nuclear device using low- plutonium from a UK power reactor was detonated in USA. The isotopic composition of this plutonium has not been disclosed, but it was evidently about 90% Pu-239.

Plutonium for weapons is made differently, in simple reactors (usually fuelled with natural uranium) run for that purpose, with frequent fuel changes (ic. low burn-up). This, coupled with the application of international safeguards, effectively rules out the use of commercial nuclear power plants.

International safeguards arrangements applied to traded uranium extend to the plutonium arising from it, ensuring constant audits.

Disarmament will give rise to some 150-200 tonnes of weapons-grade plutonium. over half of it in former USSR. Discussions arc progressing as to what should be done with it. The main options for the disposal of weapons-grade plutonium are:

• Vitrification with high-level waste - treating plutonium as waste .

27 • Fabrication with uranium oxide as a mixed oxide (MOX) fuel for burning in existing reactors. • Fuelling fast-neutron reactors.

The US Government has declared 38 tonnes of weapons-grade plutonium to be surplus, and planned to pursue the first two options above, though only the MOX is proceeding. Meanwhile the US has developed a "spent fuel standard", which means that plutonium, including weapons Pu, should never be more accessible than if it is incorporated in spent fuel.

F.urope has a well-developed MOX capacity and this suggests that weapons plutonium could be disposed of relatively quickly. Input plutonium in facilities such as 's new MOX plant would need to be about half reactor grade and half weapons grade, but using such MOX as 30% of the fuel in one third of the world's reactor capacity would remove about 15 tonnes of warhead plutonium per year. This would amount to burning 3000 warheads per year to produce 110 billion kWh of electricity.

Canada is promoting the use of its CANDU heavy water reactors as having very flexible fuel requirements and hence as suitable for disposing of military plutonium. Various mixed oxide fuels have been tested in these reactors, which can be operated economically with a full MOX core.

Russia is strongly committed to using its plutonium in mixed-oxide fuel, burning it in both late-model conventional reactors and BN series fast neutron reactors.

3-4-2 Toxicity and Health Effects

Despite being toxic both chemically and because of its ionising radiation, plutonium is far from being 'the most toxic substance on earth' or so hazardous that 'a speck can kill'. On both counts there are substances in daily use that, per

28 unit of mass, have equal or greater chemical toxicity (arsenic, cyanide, caffeine) and radiotoxicity (smoke detectors).

There are three principal routes by which plutonium can reach human beings:

• ingestion, • contamination of open wounds, • Inhalation.

Ingestion is not a significant hazard, because plutonium passing through the gastro-intestinal tract is poorly absorbed and is expelled from the body before it can do harm.

Contamination of wounds has rarely occurred although thousands of people have worked with plutonium. Their health has been protected by the use of remote handling, protective clothing and extensive health monitoring procedures.

The main threat to humans comes from inhalation. While it is very difficult to create airborne dispersion of a heavy metal like plutonium, certain forms, including the insoluble plutonium oxide, at a particle size less than 10 microns, are a hazard.

If inhaled, much of the material is immediately exhaled or is expelled by mucous flow from the bronchial system into the gastro-intestinal tract, as with any particulate matter. Some however will be trapped and readily transferred, first to the blood or lymph system and later to other parts of the body, notably the liver and bones. It is here that the deposited plutonium's alpha radiation may eventually cause cancer.

However, the hazard from Pu-239 is similar to that from any other alpha-emitting radionuclides which might be inhaled. It is less hazardous than those which are

29 short-lived and hence more radioactive, such as radon daughters, the decay products of radon gas, which (albeit in low concentrations) are naturally common and widespread in the environment.

In the 1940s some 26 workers at US nuclear weapons facilities became contaminated with plutonium. Intensive health checks of these people have revealed no serious consequence and no fatalities that could be attributed to the exposure. In the 1990s plutonium was injected into and inhaled by some volunteers, without adverse effects.

30 CHAPTER FOUR

4-1 Recommendations 4-2 Conclusion

31 4-1 Recommendations: Human activities have added to the marine environment the transuranium nuclides and other radioactive elements, both from the atmospheric testing of nuclear devices and from authorized discharges of radioactive wastes into coastal waters and deep sea. Among these radioactive elements, only those of longer half-lives remain at the present time. Studies have therefore been made worldwide to understand the chemistry of these radionuclides in seawater, their association with sedimentary material, and their accumulation by marine organisms, the last of these being of particular interest because the transuranics are essentially "novel" elements to the marine fauna and flora. The need to predict the long-term behavior of these nuclides has, in turn, stimulated research on those naturally occurring nuclides which may behave in a similar manner. There is still, however, a real need for further research. Although the distributions and rates of dispersal of many nuclides are becoming increasingly understood, little is known of how these processes relate to subtle changes in speciation. Many more data are also required on the biological accumulation of these nuclides, and how their chemical form affects this. Indeed, a better understanding of the aquatic behavior of natural alpha emitters would be useful, such as their association with organic materials. In developing countries the need for such studies has increased greatly in recent years.

32 4-2 Conclusion The addition of anthropogenic radionuclides to the pool of naturally occurring radionuclides, as the result of the progressive development of the nuclear industry and other contaminating technologies and the widespread and ever increasing use of radiation in many aspects of modern lite has changed the radioactive environment of the space-ship and has made it necessary to conduct radiological surveys to evaluate the background of natural radiation in order to detect the level of man-made contamination, assess its impact, and implement appropriate counter measures to protect the populace and the environment from future radiation emergencies. 1-. Smith, J. N.; Bewers, J. M.; Canadian Chem. News 1993, October, 23. 2-UNEP/SPC/SPEC/ESCAP. "Radioactivity in the South Pacific. UNEP Regional Seas Reports and Studies no 0". UNEP, 1984. 3-Edgington, D.N. "The Chemical Behaviour of Long-Lived Radionuclides in the Marine Environment". In: International Symposium on the Behaviour of Long- lived Radionuclides in the Marine Environment. Proceedings, Comission of the European Communities, Luxembourg, Office for Official Publications of the European Communities. (EUR-9214-EN), 1984. 4- ANPA 2000: SEMINAT. Long-term dynamics of radionuclides in semi-natural environ-ments: derivation of parameters and modelling. Final report 1996-1999, European Commission- Safety Programme. 5- Institute of Radiological Sciences. "Radioactvity Survey Data in Japan no 94, Part 1 - Environmental Materials". Chiba, Japan, 1991

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