Concentrations Of 241Am Research Articles

Transuranic elements determination in spanish NPP-wastes on the basis of gross alpha activity

Summary The characterisation of alpha-emitting nuclides in low and medium level radioactive waste from Spanish nuclear power reactors leads to several difficulties because they cannot be assayed by non-destructive methods due to their low concentration. Thus, long and complex radiochemical procedures are required. In this paper an alternative method for establishing a sufficiently accurate and reliable inventory of long-lived alpha emitting nuclides, is described. The method is based on the application of the factors obtained by correlating the gross alpha activity and the concentration of 238Pu, 239/40Pu, 241Am, 242Cm and 244Cm in a set of samples of concentrates and resins from Spanish NPP's. Several statistical tests are performed to evaluate the validity of the assumed relationship and the quality of the correlation. Also, uncertainties are calculated for the parameters of the linear equation relating the concentrations. This work has been performed in the framework of the CIEMAT-ENRESA Association Agreement.

Plutonium isotopes, 241Am and 137Cs activity concentrations in marine sediments of Gökova Bay, Aegean Turkish Coast

Samples of marine surface sediments of different grain sizes collected in Gokova, a small bay on the Aegean Turkish Coast, have been examined to measure alpha- and gamma-radioactivity. The purpose of this research is to define a baseline study of man-made radionuclides on sediments along Gokova Bay, using a combination of direct gamma-spectrometry, radiochemical separation and alpha spectrometry. The analysis of these samples revealed measurable quantities of some artificial radionuclides namely: 239+240Pu (from 0.13±0.017 to 0.85±0.15 Bq.kg–1). 137Cs, 241Am and 238Pu were identified at a very low level. Concentration ratios of 238Pu to 239+240Pu obtained seem to confirm that this artificial radioactivity is due mainly to Chernobyl accident.

Monitors for the Prediction of Alternate Nuclear Material Concentrations for Pressurized Water Reactor Spent Fuel

A methodology for determining alternate nuclear material (237Np, 241Am, and 243Am) concentrations in spent nuclear fuel based on the use of various monitors was developed and validated for use with several pressurized water reactor fuels. The monitors studied included the fuel burnup, the total plutonium concentration, the 240Pu/239Pu isotopic ratio, the 148Nd/238U isotopic ratio, and the 137Cs activity. Calculations were performed using the HELIOS-1.4 lattice physics code for spent fuel from the Mihama Unit 3, Genkai Unit 2, and Calvert Cliffs Unit 1 reactors. These calculations were compared to measured values for the fuel. It was determined that the 240Pu/239Pu isotopic ratio and the 137Cs activity were the most useful and accurate for use in predicting alternate nuclear material concentrations at reprocessing facilities for safeguards purposes. Based on these comparisons, it was determined that measurements of these monitors would allow for determination of 237Np, 241Am, and 243Am concentrations to within ±4, ±6, and ±15%, respectively. It is suggested that these uncertainties may be decreased through improvements in measurement techniques and additional benchmarking. These monitors may be used to provide an accurate prediction of the concentrations of the alternate nuclear materials while decreasing the need for direct measurement of these isotopes. This will translate into a monetary savings for reprocessing facility safeguards.

Methods of high-sensitive analysis of actinides in liquid radioactive waste

A set of methods has been developed to determine actinides in liquid radioactive waste for solving the problems of radiation, nuclear and ecological safety of nuclear reactors. The main method is based on the radiochemical separation of U, Np–Pu, Am–Cm on ion-exchange and extraction columns. An identification of radionuclides and determination of their content are performed using alpha-spectrometry. The microconcentrations of the sum of the main fissile materials 235U and 239Pu are determined with plastic track detectors. An independent method of 238U content determination is the neutron activation analysis. 241Am content is possible to be determined by gamma-spectrometry. A chemical composition of macrocomponents is determined by the atomic-absorption spectrophotometry method.

長崎県西山水源地堆積物に記録された原爆の「黒い雨」

The explosion of a plutonium atomic bomb over Nagasaki city took place on 9 August 1945. After the explosion, a cloud formed, which passed over the Nishiyama district, where 'black rain' fell. Thus, the Nishiyama reservoir, located approximately 3 km from the hypocenter, received the heaviest radioactive fallout from the Nagasaki atomic bomb. Sediment samples were collected from the bottom of the Nishiyama reservoir in 1999 and analyzed for their 137Cs, 241Am and charcoal concentrations. The stratigraphic distribution of 137Cs and charcoal clearly indicate that the 'black rain' horizon is recognized in the Nishiyama reservoir sediments. The 'black rain' horizon contains anthropogenic radionuclides (137Cs and 241Am) and charcoal in high concentrations.

In situ measurement of transuranics using a calcium fluoride scintillation detection system

A prototype scintillation spectrometer capable of measuring low energy photons from transuranic elements in groundwater has been developed for in situ applications. The detector is a CaF2 (Eu) crystal enclosed in a stainless steel casing with a 19 mg·cm-2 stainless steel entrance window. Evaluation of the system was performed in the laboratory by submersing the probe into a number of aqueous solutions containing varying concentrations of 241Am in a simulated well environment. Spectra obtained had easily discernible peaks associated with the low energy L X-rays and the 60 keV gamma-ray photopeak of 241Am.

The EFTTRA-T4 experiment on americium transmutation

In the EFTTRA-T4 experiment the irradiation behaviour of a target containing americium dispersed in MgAl 2O 4 was studied. Pellets containing 10–12 wt% 241Am were fabricated by the infiltration method. However, it was found that the americium, intended to be present as AmO 2− x , formed a compound, probably AmAlO 3, during sintering. The T4 target was irradiated in the High Flux Reactor (HFR) Petten from August 1996 to January 1998 (358.4 fpd's). Post-test burn-up calculations indicated that the 241Am concentration is reduced to 4% of the initial value at the end of the irradiation. The fraction of the initial americium atoms that were fissioned is 28%. Non-destructive and destructive examinations of the target indicated that swelling of the target pellets occurred. This is attributed to accumulation of helium, produced by alpha decay of 242Cm that occurs in the transmutation scheme of 241Am.

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.

Comparisons of HELIOS, ORIGEN2, and Monteburns Calculated 241 Am and 243 Am Concentrations to Measured Values for PWR, BWR, and VVER Spent Fuel

A study was performed at Los Alamos National Laboratory to explore the accuracy of several reactor analysis codes in calculating 241 Am and 243Am concentrations in light water reactor spent fuel. Calculated higher-actinide concentrations were compared to measured values from the literature for three reactor fuels. The fuel samples were taken from the Mihama Unit 3 pressurized water reactor, the Garigliano boiling water reactor, and a VVER-440. The 241Am and 243Am concentrations were calculated using the HELIOS-1.4 lattice-physics code, the ORIGEN2 burnup code, and a linked MCNP/ORIGEN2 code named Monteburns 3.01. Comparisons were made between the calculated and measured values. It was determined that all codes performed consistently well for the Mihama Unit 3 measurements (within ±5% for 241Am and ±20% for 243Am) and the Garigliano measurements (within ±12% for 241 Am and ±20% for 243Am). It was determined that the ORIGEN2 pressurized water reactor libraries are insufficient for the VVER-440 measurements. The HELIOS and MONTEBURNS codes both demonstrated good ability to calculate these isotopes for VVER-440 fuel (±10% for 241Am and ±12% for 243Am). The accuracies of these codes and the associated radiochemical measurements of these higher-actinide isotopes may be insufficient for safeguards and fuel management purposes; thus, development of new methods and modification to existing data libraries may be necessary in order to enable cost-effective safeguarding of these higher-actinide materials.

Internal Dose Estimates for Workers Exposed to Plutonium by Performing In Vivo Measurements of 241Am

Individual dose estimates for workers chronically exposed to plutonium is an important task in the investigation of possible health effects from internal plutonium depositions. Systemic and total body deposition of plutonium is usually estimated from urinalysis. However, this technique used alone results in uncertainty in individual dose assessment, by about an order of magnitude. Direct in vivo measurements of 241Am content in lungs, skeleton and liver by whole-body counting allows one to improve the result of dose assessment. First of all the improvement is due to the additional qualitative information about the route of intake (sorting out subjects with contaminated wounds) and solubility of plutonium aerosol particles (estimating the lung/skeleton ratio). This paper develops an algorithm for performing quantitative estimates of individual doses for workers, using the results of in vivo measurements of 241Am by whole-body counting. The algorithm applies the new ICRP Publication 66/67 models and takes into account such parameters as the 241Pu/239Pu ratio, effective aging time of mixed fission products and actinides, particle size distribution of plutonium aerosols and some other parameters. The uncertainties in individual dose assessment due to application of these parameters were analysed. It was shown that regular in vivo measurements of 241Am in the lungs allow the detection of single intake of plutonium at a level of the order of one ALI and can be a good monitoring programme for individuals involved in operations with plutonium treated in nuclear fuel cycle.

The fate of plutonium, 241Am, 90Sr and 137Cs in the Antarctic ecosystem

A radioecological survey around Terra Nova Bay showed that 239 + 240Pu, 238Pu, 241Am, 90Sr and 137Cs activities were detectable in nearly all the samples. The 239 + 240Pu and 241Am concentrations in seawater were slightly lower than those in the northern Pacific Ocean. The activity level of 239 + 240Pu, 241Am and 137Cs in Antarctic sediments (Ross Sea) was c. 5–20 times lower than in northern Adriatic sediments (Mediterranean Sea), but the 238Pu activities were relatively high. The 90Sr concentrations in all the sediment samples from both the Ross and Adriatic seas tended to be low which might be due to an easier exchange of 90Sr in seawater. On the other hand, high concentrations were detected in Antarctic mosses, lichens and algae and their activity levels are comparable to those in central Italy. The radionuclide ratio analyses show that the major part of 239 + 240Pu, 241Am, 90Sr and 137Cs is the result of nuclear weapon tests. A higher 241Am/239 + 240Pu ratio might be due to the fallout of earlier atmospheric nuclear tests. The 238Pu239 + 240Pu ratio in the Antarctic matrices is about seven times higher than in the Northern Hemisphere and this could suggest that the major part of 238Pu originated from the SNAP-9A satellite accident.

Plutonium and other alpha-emitters in bones of wild, herbivorous animals from north-eastern Poland

The results of the investigation of 239+240Pu, 241Am and thorium isotope activity concentrations in bones of wild herbivorous animals (deer, roe-deer, boars, elks) from north-eastern Poland are presented. The area on which the animals were living had relatively high Chernobyl plutonium fallout. Possible traces of plutonium were seen only in four samples, but only for one it was it 3σ above background, at 6.2 ± 2.4 mBq/kg (ash). The 241Am activity concentration was below the detection limits in all samples. The maximum 228Th concentration in the samples was 7.81 ± 0.44 Bq/kg (ash), calculated under the assumption of 100% thorium recovery. This isotope seems to originate in bones not from direct incorporation but from the decay of 228Ra. Large variations in activity concentration wose observed, as well as some differences between boars and the chewing animals.

Air monitoring data reveal previously unknown contamination at radioactive waste disposal area, Los Alamos National Laboratory

Air monitoring at Area G, the low-level radioactive waste disposal area at Los Alamos National Laboratory, revealed increased air concentrations of 239Pu and 241Am at one location along the north boundary. This air monitoring location is a couple of meters north of a dirt road used to access the easternmost part of Area G. Air concentrations of 238Pu were essentially unaffected, which was puzzling because both 238Pu and 239Pu are present in the local, slightly contaminated soils. Air concentrations of these radionuclides increased about a factor of ten in early 1995 and remained at those levels until the first quarter of 1996. During the spring of 1996 air concentrations again increased by a factor of about ten. No other radionuclides were elevated, and no other Area G stations showed elevations of these radionuclides. After several formal meetings did not provide an adequate explanation for the elevations, a gamma-survey was performed and showed a small area of significant contamination just south of the monitor location. We found that in February 1995, a trench for a water line had been dug within a meter or so of the air stations. Then, during early 1996, the dirt road was rerouted such that its new path was directly over the unknown contamination. It appears that the trenching brought contaminated material to the surface and caused the first rise in air concentrations and then the rerouting of the road over the contamination caused the second rise, during 1996. We also found that during 1976 and 1977 contaminated soils from the clean-up of an old processing facility had been spread over the filled pits in the vicinity of the air monitors. These soils, which were probably the source of the air contamination, were very low in 238Pu which explains why we saw very little 238Pu in the increased air concentrations. A layer of gravel and sand was spread over the contaminated area. Although air concentrations of 239Pu and 241Am dropped considerably, they have not returned to pre-1995 levels.

Comparisons of HELIOS, ORIGEN2, and Monteburns Calculated 241Am and 243Am Concentrations to Measured Values for PWR, BWR, and VVER Spent Fuel.

Comparisons of HELIOS, ORIGEN2, and Monteburns Calculated 241Am and 243Am Concentrations to Measured Values for PWR, BWR, and VVER Spent Fuel.

Comparisons of Calculated and Measured 237Np, 241Am, and 243Am Concentrations as a Function of the 240Pu/239Pu Isotopic Ratio in Spent Fuel

The Los Alamos National Laboratory (LANL) has developed a system for determining 237Np, 241Am, and 243Am concentrations in spent fuel from measurements of the 240Pu/239Pu isotopic ratio using calculations performed with the HELIOS lattice-physics code. Benchmark calculations for several pressurized water reactors (PWRs) were performed and compared to measured values from the literature for fuels with burnups ranging from 0 to 50 000 MWd/tonne U. A direct correlation can be found between the 240Pu/239Pu isotopic ratio and the higher-actinide concentrations for each fuel type. Comparisons of calculated with measured values suggests that the LANL technique would yield 237Np and 241Am concentrations within ±5% and 243Am concentrations within ±15% for PWRs. Expanding this system for all reprocessing applications will require more measured data (especially for boiling water reactors and VVER-type reactors), but the existing results show a marked improvement over the previous ORIGEN calculations. Also, a better determination of the 243Am concentrations may support a greater confidence in the calculated results or suggest an alteration to the existing nuclear data. The present state of these neutronics calculations suggests that the technology exists to reduce the need for direct measurement of the 237Np, 241Am, and 243Am concentrations in spent fuel.

241Am concentration and241Pu/239(240)Pu ratios in soils contaminated by weapons-grade plutonium

241Am and238,239(240)Pu concentrations have been determined in soil samples from the Atolls of Mururoa and Fagataufa as well as from Palomares for comparison. Mean activity ratios of241Am/239(240)Pu for Mururoa, Fangataufa and Palomares with 0.017±0.005, 0.050±0.012 and 0.25±0.07 respectively, show, that also in the most unfavorable case the241Am contamination remains less than about one third of the239(240)Pu level. The estimated isotopic composition of the different types of weapons-grade Pu based on these data suggests generally a much lower241Pu/239(240)Pu ratio for Pu used in the first fisson bombs than for the material taken later on for construction of thermonuclear devies.241Pu/239(240)Pu activity ratios of 0.9±0.2 have been found at the safety shot area of the Colette motu and 8.4±0.8 at Palomares, with some hints to a lower one, viz. 5.7±1.5 for at least one of the accidentally involved bombs.

Anthropogenic radionuclides in sediments in the NW Pacific Ocean and its marginal seas: results of the 1994–1995 Japanese–Korean–Russian expeditions

Assessment of contamination of anthropogenic radionuclides from past dumping of radioactive waste in areas of the Okhotsk Sea, NW Pacific Ocean and the Sea of Japan/East Sea has been performed. Two joint Japanese–Korean–Russian scientific expeditions were carried out in 1994–1995, where seawater and seabed sediments were samples from 22 sites. Results of sediment analysis are reported here, where concentrations of 90Sr, 137Cs, 238Pu, 239,240Pu and 241Am in surface layer and bulk sediments showed on large spatial variations, ranging between <0.04 and 0.75 Bq kg −1 dry wt., <0.2 and 7.2 Bq kg −1 dry wt., <0.001 and 0.08 Bq kg −1 dry wt., 0.006 and 2.0 Bq kg −1 dry wt., 0.03 and 1.8 Bq kg −1 dry wt., respectively. However, the concentrations are comparable with those found in reference sites outside the dumping areas and they generally fall within ranges previously reported for non-dumping areas of the investigated seas. Estimates of sediment inventories indicated differences in radionuclide load between shelf/slope and basin type sediments as well as dependence on water depth. Except for the shallow areas, most of the inventories of 90Sr, 137Cs and Pu isotopes are still to be found in the water column. Total inventories (in water+sediment) show a surplus of 137Cs and Pu-isotopes compared to expected integrated global fall-out deposition, which is consistent with previous observations in non-dumping areas in the seas investigated. Analysis of sediment 238Pu/ 239,240Pu activity ratios showed values in accord with that of global fall-out. Analysis of radionuclide depth distributions in core samples from areas of the Sea of Okhotsk showed sedimentation rates of 0.2–0.4 g cm −2 year −1 and 0.03 g cm −2 year −1 for shelf and basin areas respectively, which is similar to values found in the Sea of Japan/East Sea. Depth profiles of 90Sr, 137Cs and Pu isotopes in cores of the basin area indicate a typical delay compared to the input records of global fall-out.

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.

Dissolved plutonium and americium in surface waters of the Irish Sea, 1973–1996

The Irish Sea contains elevated levels of 239+240Pu and 241Am discharged, over several decades, from the British Nuclear Fuels reprocessing plant at Sellafield, Cumbria. Data on both the temporal and spatial variations of these radionuclides are provided from surveys carried out over the period 1973–1996. Seawater concentrations have varied from year to year, concomitant with reductions in discharges, differences in transport behaviour (dependent upon the prevailing hydrographic conditions) and remobilisation. Over the period considered, the most noticeable change from the end of the 1970s to the most recent time is a decrease in dissolved 239+240Pu levels (≈4-fold). Concentrations of 241Am have remained relatively unchanged since 1976. Reductions in discharges have been significantly greater (e.g. ≈40-fold for 239+240Pu) and remobilisation from sediments contaminated by large discharges in the 1970s is presently the predominant source term to the water column. Estimates of the inventory in the dissolved phase are small (≈0.3 and 0.03% for 239+240Pu and 241Am, respectively) in comparison with that residing on the sub-tidal sediments. The dissolution half-time of 239+240Pu and 241Am from the surface sediment layer (top 5 cm) is estimated to be in the order of 58 and 1000 years, respectively.

The use of sediment cores from stable and developing salt marshes to reconstruct historical contamination profiles in the Mersey Estuary, UK

Depth-profiled sediment cores from two marshes in the Mersey Estuary were analysed for concentrations of 137Cs, 238Pu, 239,240Pu, 241Am, As, Cr, Cu, Pb, Hg and Zn. Mersey sediments contain three diagnostic and persistent chemical species arising from either a unique, or a dominant, source – 137Cs, Hg and DDT. Dating of features in these cores has been completed using up to four benchmark events identifiable from these chemical species – the initial expansion of the chemical industry, commencement of DDT manufacture, initial appearance of radionuclides from a reprocessing site in NW England, and the introduction of new technology to reduce mercury discharges. The sediment pollutant profiles depend on the rate of sediment accumulation but clearly record the historical increase in discharges of metals to the environment between the mid-19th and 20th centuries. They also reflect recent regulatory and technological efforts to minimise estuarine contamination and the discontinuation of specific manufacturing and refining processes. ©