Plutonium specific activity

Soil samples collected from some targeted locations in Kosovo and South Serbia where concentration was up to 4,000 mg U kg soil showed a constant ratio of 236U/238U (2.6 X 10 to 2.7 X 10" ) indicating that the used DU ammunition came from a batch of uranium that had been irradiated in a reactor and then reprocessed [114,122]. The presence of U from irradiated uranium could imply the presence of traces of Pu in the DU. The total Pu concentration found in Kosovo soil samples which contained DU [(5.5 1.1) x 10 g g" ] was similar to ones which did not contain DU [(4.4 0.5) x 10" g g ] with the Pu/ Pu ratio of 0.35 0.10 and 0.27 0.07, respectively [104]. Specific activities of 2 Pu in these soil samples, calculated from ICP-MS measurements, were 1.6 and 2.1 Bq kg", respectively. This activity range corresponded to the plutonium specific activity in soil found in central Italy, after contamination with fallout from Chernobyl in 1986... 

Most chemical iavestigations with plutonium to date have been performed with Pu, but the isotopes Pu and Pu (produced by iatensive neutron irradiation of plutonium) are more suitable for such work because of their longer half-Hves and consequendy lower specific activities. Much work on the chemical properties of americium has been carried out with Am, which is also difficult to handle because of its relatively high specific alpha radioactivity, about 7 x 10 alpha particles/(mg-min). The isotope Am has a specific alpha activity about twenty times less than Am and is thus a more attractive isotope for chemical iavestigations. Much of the earher work with curium used the isotopes and Cm, but the heavier isotopes... 

The nuclear power industry (270 nuclear reactors in 25 countries in mid-1982) now has a capacity of 200 GWe, which corresponds to an approximate annual plutonium production of 50 tonnes. The amount of plutonium accumulated from the industry is estimated to be 250 tonnes. The specific activity is 5.3X1011 Bq/g Pu for fresh spent fuel, mostly coning from 2ltlPu (6, 10). It is predicted that by the year 2000, the accumulated plutonium will amount to 2400 tonnes (6). 

Previous experience in the production of plutonium 238 revealed the need for the double alpha containment of the cells where the alpha-emitter isotopes with high specific activity are handled. Thus all the hot cells are equipped with a double ventilation system which provides ventilation of alpha-cells and ventilation between alpha-cells and biological shields. Alpha detectors continuously monitor the exhaust circuits. 

The discovery of Pu has been described in detail by Seaborg in his Plutonium Story (chapter 1 of the book The Transuranium Elements 1958). First, the separation of Pu from Th caused some difficulties, because both elements were in the oxidation state 4-4. After oxidation of Pu(IV) by persulfate to Pu(VI), separation became possible. Pu is produced in appreciable amounts in nuclear reactors (section 14.1), but it has not immediately been detected, due to its low specific activity caused by its long half-life. After the discovery of Pu, plutonium gained great practical importance, because of the high fission cross section of Pu by thermal neutrons. Very small amounts of Pu are present in uranium ores, due to (n, y) reaction of neutrons from cosmic radiation with The ratio Pu/ U is of the order of 10 In 1971, the longest-lived isotope of plutonium, Pu (ri/2 = 8.00 lO y) was found by Hoffman in the Ce-rich rare-earth mineral bastnaesite, in concentrations of the order of 10 gAg-... 

Somewhat different results were found in studies from the British Atomic Weapons Test Site at Maralinga, South Australia, where specific activities were noted to be greater in the soil size fractions >90 pm (Ellis and Wall, 1982). Presumably there are numerous factors that might influence the relationship of plutonium activity with soil particle size including the nature of the contaminating event, the degree of weathering since the contamination event, the chemical nature of the soil, and the particle size distribution of the soil. 

To demonstrate the validity of this procedure for the recovery of trace amount of nlutonium from dilute solutions, 30 liters of solution with a specific activity of 239pu 135 + 12 (counts/ 2000/sec/ml) was percolated through a small column containing 10 ml of A O. About 97% of plutonium were sorbed onto the alumina. 

Another radiation problem arises from fast neutrons produced in spontaneous fission of the even-mass plutonium isotopes. Half-lives and specific activities for spontaneous fission of the plutonium isotopes are listed in Table 8.17. 

Tfie concentration of plutonium in combined core and blanket fuel from the LMFBR is more than 10 times that of LWR fuel. This is the most significant difference between the two fuels with respect to reprocessing. Other important differences are the greater amounts of tritium and the 140 percent greater ruthenium activity, and the 60 percent greater overall specific activity of ISO-day cooled LMFBR fuel. 

The main part of the HLLW is aqueous raffinate from the Purex cycle. It contains 99.9% of the nonvolatile FPs, <0.5% of the uranium, <0.2% of the plutonium, and some corrosion products. For each ton of uranium reprocessed about 5 m of HLLW is produced. This is usually concentrated to 0.5-1 m for interim tank storage specific activity is in the range 10 GBq m. The amounts of various elements in the waste and their concentration in 0.5 m solution is shown in Table 21.9. The HNO3 concentration may vary within a factor of 2 depending on the concentration procedure. The metal salt concentration is 0.5 M it is not possible to keep the salt in solution except at high acidity. The amounts of corrosion products, phosphate, and gadolinium (or other neutron poison added) also may vary considerably. Wastes from the HTGR and FBR cycles are expected to be rather similar. 

Uranium and technetium are soluble in water when oxidized but insoluble in reduced form. Radioisotope pairs, parent-progeny relations, and specific activity may provide guidance in assigning the origin of radioactive material and identify questionable results for a specified location. Certain radioactive materials have signatures of uranium or plutonium isotopes at known ratios. Ratios for other radionuclide pairs, such as and Ru, can suggest the time interval... 

Plutonium-238 administered as the soluble nitrate or as the less soluble dioxide form to dogs was absorbed from the lungs more rapidly than the corresponding forms of plutonium-239, possibly due to the lower mass of plutonium-238 (Dagle et al. 1983 Park et al. 1972) or more likely, due to the higher specific activity of plutonium-238. However, when plutonium-239 nitrate was administered to rats, it was absorbed more readily than the plutonium-238 nitrate (Morin et al. 1972). 

What is the specific activity of plutonium-241, which has a half-Ufe of 14.35 years ... 

Similar figures apply to plutonium-239 and plutonium-240. The mechanisms by which the plutonium might be inhaled are to be evaluated case by case. The specific activity of plutonium-238 is 6.44 x... 

Notwithstanding the Iraqi lesson learned that the possibility of undeclared nuclear activities must be taken seriously and their possible existence sought out, the concern with undeclared activities as a proliferation risk is not new and their possible existence has always been recognized, indeed, presumed, in ary serious analysis of safeguards. Even purified plutonium or highly enriched uranium metals are harmless in bulk form. Further steps, specifically fabrication into weapons components, are necessary before these materials can result in proliferation and these steps, while perhaps not demanding, are not trivial. They are necessarily presumed to exist if the diversion of separated plutonium or HEU is discovered, since no reliable means for their detection are available. 

The above activity levels measured at Mururoa are comparable to the levels observed world-wide in the early 1980s (with the exception of a few specific sites). These concentrations result from earlier safety tests made on the motus in the northern zone of the atoll from 1966 to 1974, and from the cleanup work undertaken in the years 1981-1987. This work resulted in a great reduction of radioactivity on the ground, but produced a slight temporary increase of plutonium in the air. 

---