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PubMed1983

Microdosimetry of plutonium in lungs.

Chord length distributions for alveolar cells and cell nuclei were determined by superimposing computer-generated alpha-particle tracks on magnified images of randomly selected rat lung sections using the Quantitative Television Microscope. Specific energy distributions were then calculated by applying image analysis techniques. These microdosimetric calculations suggest that radiation carcinogenesis can be described in physical terms by the number of cells hit in a defined tissue volume, the specific energy distribution in these cells, the resulting number of non-lethally damaged cells which are susceptible to transformation, and their spatial distribution. If multicellular effects are involved in radiation carcinogenesis, then hot spots might be more carcinogenic than the uniform distribution at low doses and less carcinogenic at high doses.

Alpha Particles↗
PubMed1983

Differential clearance of plutonium and americium oxides from the human lung.

External X- and gamma-ray counting techniques have been used to study the retention of 238PuO2 and 241AmO2 in the lungs of a worker between 7 and 869 days after simultaneous exposure to aerosols of both oxides. From these data and measurements of early faecal excretion, it is concluded that approx. 50% of the amount of each nuclide initially deposited in the subject was removed during the first few days by ciliary clearance mechanisms. The lung clearance patterns of the other 50% differed for the two nuclides. The 238Pu was apparently cleared with a biological half-life of approximately 800 days, predominantly by systemic or lymphatic uptake, with at least part of the translocated material being subsequently deposited in bone. There was no evidence for the presence of a 30-day component of lung clearance, such as has been suggested elsewhere. In contrast, most of the residual 241Am was cleared relatively quickly, with a half-life of approximately 11 days, although a small proportion was apparently subject to long-term retention, with a half-life of approximately 900 days. The data for both oxides conflict in important respects with the patterns of lung clearance postulated by the ICRP.

Aerosols↗
PubMed1983

In vitro dissolution of respirable aerosols of industrial uranium and plutonium mixed-oxide nuclear fuels.

Dissolution characteristics of mixed-oxide nuclear fuels are important considerations for prediction of biological behavior of inhaled particles. Four representative industrial mixed-oxide powders were obtained from fuel fabrication enclosures. Studies of the dissolution of Pu, Am and U from aerosol particles of these materials in a serum simulant solution and in 0.1M HCl showed: (1) dissolution occurred at a rapid rate initially and slowed at longer times, (2) greater percentages of U dissolved than Pu or Am: with the dissolution rates of U and Pu generally reflecting the physical nature of the UO2-PuO2 matrix, (3) the temperature history of industrial mixed-oxides could not be reliably related to Pu dissolution except for a 3-5% increase when incorporated into a solid solution by sintering at 1750 degrees C, and (4) dissolution in the serum simulant agreed with the in vivo UO2 dissolution rate and suggested the dominant role of mechanical processes in PuO2 clearance from the lung. The rapid initial dissolution rate was shown to be related, in part, to an altered surface layer. The advantages and uses of in vitro solubility data for estimation of biological behavior of inhaled industrial mixed oxides, such as assessing the use of chelation therapy and interpretation of urinary excretion data, are discussed. It was concluded that in vitro solubility tests were useful, simple and easily applied to individual materials potentially inhaled by humans.

Aerosols↗
PubMed1984

Contribution of a nuclear fuel chemical separations facility to the plutonium content of a tobacco crop.

Tobacco, an important crop in the southeastern United States, can potentially contribute via the inhalation pathway to the dose-to-man from radionuclides. To evaluate this potential dose-to-man from the interception and retention of Pu aerosols, a tobacco crop was grown near a chemical separations facility at the Savannah River Plant (SRP) which releases Pu to the atmosphere. Average leaf 238Pu and 239, 240Pu concentrations were 9.8 and 5.1 fCi /g X dry wt, respectively. These concentrations indicate that 2.5% of the deposition occurring during the tobacco growth period was on merchantable leaves. Leaf Pu concentrations were slightly greater than Pu concentration of stem tissue. Tobacco grown near the facility had 10 times higher Pu concentrations than that grown off the SRP. Pu concentrations of tobacco were similar to other broadleaf crops. Dose commitment would be 1000 times greater for tobacco usage than wheat or soybean consumption when these crops were all grown under identical Pu deposition situations.

Aerosols↗
PubMed1984

A Si(Li)-NaI(Tl) detector for direct measurement of plutonium in vivo.

A Si(Li)-NaI(Tl) detector system is shown to be very promising for measurements of Pu in human lungs via the L x rays. The Si(Li) detectors are mounted on their edge to permit the front surface to view the lung and the back surface to view a NaI(Tl) anticoincidence scintillator for background suppression. Silicon has high intrinsic efficiency for detection of low-energy x rays and low sensitivity to background-producing gamma rays. By virtue of the high-energy resolution of the Si(Li) detectors, the UL x-ray peaks are separated from the NpL x-ray peaks thereby making it feasible to measure Pu in the presence of 241Am. The high resolution further reduces background thereby providing for high sensitivity. Measurements of Pu in lung phantoms were made with a prototype Si(Li)-NaI(Tl) detector system to simulate a pair of six-Si(Li)-detector arrays using a 2.5-cm-thick tissue-equivalent absorber. With a lung burden of 15 nCi 239Pu and 0.1% 241Am, a 2000-sec measurement gave a total UL x-ray count (UL beta and UL gamma) to square-root-of-background ratio of 2.1 which corresponds to a confidence level of 85%.

Humans↗
PubMed1985

Plutonium in gonads: a summary of the current status.

A review of the literature was carried out to investigate the following: the fraction of Pu in the body that was in the gonads; the necessity for a localization factor in calculating the genetic dose to humans; and the possibility that an unexpectedly high relative biological effectiveness (RBE) causing genetic effects could occur for alpha particles. Human autopsy data from both occupationally exposed persons and the public were relied on to determine the amount of Pu in the gonads. It was found that an average fraction of 3 X 10(-3) of the Pu in the body was in the ovaries and testes but there was a wide variation among individuals. While a localization factor over the average of 2.5-4 is needed to calculate the dose to the sensitive cells for rodents, no such factor is required for the human. Information on the RBE for various genetic effects shows RBEs for Pu alpha's about as would be expected from neutron irradiation. The usual quality factor applied in calculating dose equivalent is appropriate and may be conservative, particularly for females.

Alpha Particles↗
PubMed1988

Plutonium mining for cleanup.

Cleanup is the act of making a contaminated site relatively free of Pu so it may be used without radiological safety restrictions. Contaminated ground is the focus of major cleanups. Cleanup traditionally involves determining Pu content of soil, digging up soil in which radioactivity exceeds guidelines, and relocating excised soil to a waste-disposal site. Alternative technologies have been tested at Johnston Atoll (JA), where there is as much as 100,000 m3 of Pu-contaminated soil. A mining pilot plant operated for the first 6 mo of 1986 and made 98% of soil tested "clean", from more than 40 kBq kg-1 (1000 pCi g-1) to less than about 500 Bq kg-1 (15 pCi g-1) by concentrating Pu in 2% of the soil. The pilot plant is now installed at the U.S. Department of Energy Nevada Test Site for evaluating cleanup of other contaminated soils and refining cleanup effectiveness. A full-scale cleanup plant has been programmed for JA in 1988. In this paper, previous cleanups are reviewed, and the mining endeavor at JA is detailed. "True soil cleanup" is contrasted with the classical "soil relocation cleanup." The mining technology used for Pu cleanup has been in use for more than a century. Mining for cleanup, however, is unique. It is envisioned as being prominent for radiological and other cleanups in the future.

Decontamination↗
PubMed1988

Plutonium, Am, Cm and Sr in ducks maintained on radioactive leaching ponds in southeastern Idaho.

Concentrations of 90Sr, 238Pu, 239,240Pu, 241Am, 242Cm and 244Cm were determined in tissues of mallard ducks (Anas platyrhynchos) maintained for 43-145 d on radioactive leaching ponds in southeastern Idaho. Highest concentrations of transuranics occurred in the gastrointestinal tract, followed closely by feathers. Approximately 75%, 18%, 6% and 1% of the total transuranic activity in tissues analyzed were associated with the bone, feathers, GI tract and liver, respectively. Concentrations in GI tracts were similar to concentrations in vegetation and insects in the littoral area of the ponds. The calculated total dose rate to the ducks from both 90Sr and the transuranic nuclides was 0.69 mGy d-1 (69 mrad d-1), of which 99% was to the bone. The potential effective dose equivalent to a human consuming the entire muscle and liver mass of one experimental duck with average nuclide concentrations was 0.46 microSv (0.046 mrem). Based upon average concentrations in experimental ducks and on surveys of wild waterfowl using this area, a conservative estimate of transuranic activity exported by wild ducks using the ponds during one year was 11.3 kBq (305 nCi). Similarly, the total amount of 90Sr exported in muscle, bone and lung of wild ducks in one year was 2.5 MBq (68.7 microCi).

Americium↗
PubMed1991

Comparison of systemic plutonium deposition estimates from urinalysis and autopsy data in five whole-body donors.

The systemic deposition of (239 + 240)Pu was determined by postmortem radiochemical analysis of the tissues from five whole-body donors to the United States Transuranium Registry (USTR). All were males with intakes typically occurring many years prior to death. The postmortem radiochemical results were compared with estimates of systemic deposition made with 13 different biokinetic models using urinary excretion data obtained during life. In general, estimates made with older biokinetic models were severalfold greater than those obtained from radiochemical analysis of the tissues. For all five cases, agreement within a factor of two with the tissue analysis results was obtained with two of the biokinetic models evaluated: the Langham power function model as modified by Leggett and Eckerman and the two compartment exponential model proposed in ICRP Publication Nos. 19 and 30.

Aged↗
PubMed1994

Fallout radioactivity in soil and food samples in the Ukraine: measurements of iodine, plutonium, cesium, and strontium isotopes.

To estimate the level and distribution of fallout attributable to the 26 April 1986 Chernobyl nuclear power station accident in the Ukraine, we sampled several kinds of substances at Korosten, Zhitomir and at Katyuzhanka, Vishgorod, Kiev in the Ukraine, and measured the radioactivity of 137Cs, 134Cs, 90Sr, 129I, 238Pu, 239,240Pu, and the density of 127I (stable). The substances investigated were soil, dry milk, wheat, rye, drinking water, and mushrooms. Except for the mushrooms collected, which were sampled at Katyuzhanka, Vishgorod, and at Kiev, all substances were at Korosten, Zhitomir. The activity of 137Cs, 134Cs, 90Sr, 238Pu, and 239,240Pu were all higher in soil and mushrooms than in the other four substances. The activity of 137Cs was 960 and 1,210 Bq kg-1 in the two soil samples and 6,110 Bq kg-1 in the mushrooms. The activity of 134Cs was approximately 15% of 137Cs in the two soil samples while < 3% of 137Cs in the mushrooms. The activity concentration level of 90Sr as compared to 137Cs concentration was 15-31% in food samples other than mushrooms but only 1.9% in mushrooms and 1.4 and 1.2% in the two soil samples. The radioactivity ratios, 238Pu: 239,240Pu and 239,240Pu: 137Cs, suggested that the proportion of cesium radioisotopes and 239,240Pu in the soil attributable to the Chernobyl accident was approximately 100% and 10-20%, respectively, while approximately 100% of 239,240Pu in the mushrooms was attributable to the accident. The activity of 129I was small but the ratio of 129I: 127I in the two soil samples was 4.3 x 10(-8) and 1.0 x 10(-7), which is approximately 10 times larger than that in the global fallout. These results suggest that the areas where the soil was sampled are iodine-deficient and were contaminated slightly by the Chernobyl accident.

Accidents↗
PubMed1998

Causes of death in a cohort of 260 plutonium workers.

The United States Transuranium and Uranium Registries (USTUR) is a unique postmortem research study of the biokinetics, dosimetry, and possible biological effects of actinide elements in persons with occupational exposure to these radioelements. Evaluation of the causes of death in the admittedly biased self-selected cohort of the first 260 deceased participants in the USTUR revealed, in general, no apparently elevated causes of death except for six cases of mesothelioma and six cases of astrocytoma glioblastoma multiforme. The mesothelioma cases had a documented occupational exposure to asbestos, and the six brain tumor deaths all occurred at a single work site and were not radiation related but rather are likely attributable to a factor specific to the work site or surrounding area. Incidental findings in this cohort did not suggest any radiation related illness or cause of death.

Aged↗
PubMed1999

Soil concentration, vertical distribution and inventory of plutonium, 241Am, 90Sr and 137Cs in the Marche Region of Central Italy.

Soil concentrations of 239+240Pu, 238Pu, 241Am, 90Sr, and 137Cs are investigated in the Marche Region of Central Italy. Mean values in uncultivated soils (0.721 +/- 0.456, 0.023 +/- 0.014, 0.241 +/- 0.165, 5.40 +/- 3.32, and 62.3 +/- 33.9 Bq kg(-1), respectively) are 3.5-8 times higher than the corresponding values in cultivated soils (0.147 +/- 0.054, 0.005 +/- 0.002, 0.047 +/- 0.021, 1.53 +/- 0.44, and 7.70 +/- 2.07 Bq kg(-1)). Radionuclide inventories and ratios are consistent with values reported by the United Nations Scientific Committee on the Effect of Atomic Radiation for this latitude (40-50 degrees N). This suggests that radiocontamination in this region is mainly due to atmospheric deposition of nuclear weapon test fallout. The vertical distribution of these radionuclides is also studied. The results show that, with the exception of 90Sr (68%), more than 90% of these radionuclides are contained in the first 20 cm of soil and that mobility follows the order 90Sr > 241Am > 239+240Pu, 238Pu > 137Cs.

Americium↗
PubMed2000

Alpha spectormetry measurement reproducibility study for uranium, plutonium, and americium in water at Rocky Flats environmental technology site.

An evaluation of alpha-spectrometry measurement reproducibility of low level 241Am, 239pU, 238U, and 234U concentrations in surface and ground waters at the Rocky Flats Environmental Technology Site was performed using the known and measured values of laboratory control samples. Tile purpose of the evaluation was to determine the lower limits of reliable quantitative measurement performed on recent surface water samples and historic ground water samples using alpha spectrometry. At known concentrations between 0.1 and 30 pCi L(-1) (3.7 x 10(-3) to 1.11 Bq (L-1)), the reproducibility is dependent on the magnitude of the measurement and is quantifiably reproducible to one significant figure.

Americium↗