Nuclear Weapons Test Site Research Articles

Spatial distribution of cesium-137 in surface soils on the Araya and Paria Peninsulas (Venezuela)

The activity of cesium-137 (Bq/kg) in surface soils between 2-5 cm was determined for more than ninety sample sites on the Araya Peninsula, the Paria Peninsula and the isthmus in between them in the state of Sucre (Venezuela). The measurements were performed by high-resolution gamma-ray spectroscopy, employing a compatible IBM computer with a Nucleus analog to digital interface card. In general, the values for the 137Cs activities were much greater on the Paria Peninsula than the Araya Peninsula and slightly lower on the isthmus. Even though the peninsulas are only separated by a small isthmus, their environmental characteristics are very different. The large difference in the annual rainfall of the peninsulas could have resulted in a greater amount of deposition of 137Cs on the Paria Peninsula, as well as other environmental characteristics, such as altitude and vegetation. The difference of the environmental characteristics could also affect the degree of disturbances of the soils by natural processes on the peninsulas and the isthmus, which could also have affected the 137Cs activity distribution. Finally, an anomalous high 137Cs activity distribution was found at the farthest southeastern sample sites and one of lesser extent at the most northern sample sites. These anomalies are possibly due the direct affect of the northeasterly winds which transported the 137Cs fallout from the nuclear weapon test sites.

Residual radioactivity in the terrestrial environment of the Mururoa and Fangataufa Atolls nuclear weapon test sites

This paper presents the activity concentration of alpha-emitting Pu isotopes, 2 4 1 Pu, 2 4 1 Am, the pure beta-emitting isotope 9 0 Sr, and the gamma-emitting isotope 1 3 7 Cs measured in geological and biological samples collected in the terrestrial environment of the former French nuclear test sites of Mururoa and Fangataufa. The samples were collected during an international sampling campaign conducted by the IAEA staff and a team of international experts in summer 1996. The IAEA's Seibersdorf Laboratories and a network of test laboratories, selected on the basis of a proficiency test, carried out the analytical determination of the activity concentrations of the radionuclides. The results obtained were compared with the French data. The study concluded that the radioactivity levels are generally low and of no radiological significance.

Plutonium in Lake Sediments of the Taimyr Peninsula

A radiochemical study is made of five cores of lake sediments collected from the Taimyr Peninsula. For the first time quantitative data are reported on the content and vertical distribution of 239,240Pu and 238Pu in lake sediments of this region. The plutonium content was found to range from 0.89 Bq/kg in the surface layers to 0.02 Bq/kg in the lower horizons (5-10 cm) of the sediment cores studied. The observed variations in the Pu vertical distribution are interpreted in terms of bioturbation and specific features of water catchment for the lakes studied. The 239,240Pu and 238Pu contents and the 238Pu/239,240Pu activity ratios obtained in this work (0.02-0.10) correspond to the global level for the North hemisphere, although the region studied is not far from the principal nuclear weapons test site of the former Soviet Union in the Novaya Zemlya Archipelago.

Development and application of marine gamma-ray measurements: a review

The development of instruments to measure gamma radiation in the marine environment, particularly on the sea floor, and the range of uses to which they have been put is reviewed. Since the first steps in the late 1950s, systems have been developed in at least 10 countries with the main thrust occurring in the 1970s. Development has continued up to the present, primarily in Europe and the USA. Marine gamma-ray spectrometers have been used for a range of applications including the mapping of rocks and unconsolidated sediments, mineral exploration (mainly for heavy minerals and phosphorites), sediment transport studies and investigations in relation to discharged and dumped nuclear wastes and at nuclear weapon test sites.

Underwater gamma surveys of Mururoa and Fangataufa lagoons

Underwater γ-ray spectrometry is an effective alternative or complement to traditional sampling and laboratory analyses for applications such as contamination assessment in emergency situations, long-term monitoring of radioactive releases or investigation of sunken radioactive objects. This technique was recently used in a seabed contamination study undertaken at the South Pacific nuclear weapons test sites of the Mururoa and Fangataufa atolls in order to guide and focus sediment core sampling in the areas with highest γ-emitting radionuclide levels. 60Co inventories estimated on the basis of the underwater γ-ray spectrometry survey were in good agreement with results previously obtained by traditional sediment sampling and laboratory analysis.

Marine radioactivity in the Arctic: a retrospect of environmental studies in Greenland waters with emphasis on transport of 90Sr and 137Cs with the East Greenland Current

The waters around Greenland have received radioactive contamination from three major sources: Global fallout, discharges from the nuclear fuel reprocessing plant Sellafield in the UK, and the Chernobyl accident in the Former Soviet Union (FSU). The global fallout peaked in the early 1960s. The radiologically most important radionuclides from this source are 90Sr and 137Cs. The input of global fallout to arctic waters was direct deposition from the atmosphere and indirect delivery through river run off and advection from the Atlantic Ocean via the north-east Atlantic current system. The waterborne discharges from Sellafield which were at their peak between 1974 and 1981 contributed primarily 137Cs, although some 90Sr was also discharged. The Chernobyl accident in 1986 was characterised by its substantial atmospheric release of radiocaesium ( 134Cs and 137Cs). Other sources may, however, also have contributed to the radioactivity in the Greenland waters. Examples include La Hague, France, and radioactive discharges to the great Siberian rivers (Ob, Yenisey and Lena) from nuclear activities in the Former Soviet Union or the local fallout from the Novaya Zemlya nuclear weapons test site. Dumping of nuclear waste in the Kara and Barents Seas may be another, although minor source. From measurements in Greenland waters carried out since 1962 the transport of radionuclides with the East Greenland Current is calculated and compared with the estimated inputs of 90Sr and 137Cs to the Arctic Ocean. This study focus on 90Sr and 137Cs because the longest time series are available for these two radionuclides.

Population dose near the Semipalatinsk test site.

To determine the consequences of atmospheric atomic bomb tests for the population in the surroundings of the former nuclear weapons test site near Semipalatinsk in Kazakhstan, a pilot study was performed by an international cooperation between Kazakh, French, Czech and German institutions at two villages, Mostik and Maisk. Together with Kazakh scientists, eight experts from Europe carried out a field mission in September 1995 to assess, within the framework of a NATO supported project, the radiological situation as far as external doses, environmental contamination and body burden of man were concerned. A summary of the results obtained is presented. The actual radiological situation near the test site is characterized by fallout contaminations. Cs was found in upper soil layers in concentrations similar to those of the global fallout. Also Sr, Am and Co were observed. The resulting present dose to the population is low. Mean external doses from soil contamination for Maisk and Mostik (0.60-0.63 mSv/year) presently correspond to mean external doses in normal environments. Mean values of the annual internal doses observed in these two villages are below 2 microSv/year for 90Sr. For other radionuclides the internal doses are also negligible.

Concentration of Plutonium in Placentas from the Nenetz Autonomous District Close to the Novaya Zemlaye Nuclear Weapons Test Site

The level of alpha radiation from 239.240 Pu was measured in placentas from the Nenetz district south of the nuclear weapons test site at the Novaya Zemlaye archipelago in Russia. A sample of ten placentas was collected consecutively in 1993 from a maternity ward in Narjan Mar and analysed using standard chemical alpha spectrometry. The highest concentration was close to one mBq per kilo fresh-placenta or an order of ten higher than previously reported from England. The study indicates that placentas could be used for biological monitoring of external pollution by plutonium.

Field Measurements of Low Level Plutonium Contaminated Soils Using Modified, Passive Alpha Monitors

Commercially available electret ionisation chambers (EIC) and alpha track detectors (AIDS) have been adapted for the in situ measurement of soils contaminated with low levels of plutonium at the Nevada Nuclear Weapons Test Site. The measurements were made especially challenging by vagaries of the weather, blowing soil, moisture condensation, radon in soil gas, and the need to leave the detectors in place for periods of up to several days. The most successful approach made a differential measurement on scrapings of surface soil loaded into two Petri dishes covered with thermal insulators. One dish was covered with a radon-permeable Tyvek sheet while the other was left uncovered. The Tyvek sheet interrupts alpha particles emitted by plutonium and other transuranics and background actinides. The difference in the two measurements is then due to these two groups of alpha emitters. Using this in situ, passive measuring method, background measurements were made down to a few tens pCi.g -1 . Site-specific samples of soil were ground to improve homogeneity, analysed radiochemically for alpha-emitting isotopes and the calibration factors then determined for the EICs and ATDs.

Plutonium resuspension and airborne dust loadings in the desert environment of Maralinga, South Australia

The radionuclide content of airborne dust has been studied under ambient conditions at the former nuclear weapons test site at Maralinga in the Great Victoria Desert, South Australia. Measurements have been made of radionuclide concentrations and of dust loadings. Resuspension factors for plutonium are derived from airborne activity concentrations of actinides together with measurements of surface contamination. Resuspension factors are typically 10 −10 m −1 in calm conditions, but may increase by up to three orders of magnitude during dust storms with winds in excess of 10 m s −1. The overall geometrical average resuspension factor 4 × 10 −10 m −1. These resuspension factors apply to environmental plutonium that has been deposited during trials involving the single-point (non-nuclear) detonation of a nuclear weapon in a simulated accident. Similar results were obtained at the site of a very low yield (1 kton) nuclear weapon test.

Epithermal neutron lifetime logging in partially saturated formations and large-diameter holes

A prototype logging tool which measures hydrogen content using epithermal neutron lifetime was operated in air-filled holes through partially saturated formations at the US Department of Energy's Nevada test site. Data from model formations of known hydrogen content show that the tool can be calibrated to provide volume fraction of water in partially saturated formations. Such calibrations were obtained for air-filled holes 12 inches in diameter and 8 feet in diameter, which are typical hole sizes at the nuclear weapons test site. Data from the calibration models also allowed determination of the effects on the measurement caused by tool standoff from the wall of the hole. An 8-foot diameter hole was logged for 1000 feet through a partially saturated silica formation. Comparison to the standard, steady-state neutron log, in this hole showed good agreement in calculated water volume. Water volume percentages were generally in the range 10-20%, although values as high as about 30% were encountered for one extended interval. >

An impact assessment for the French nuclear weapon test sites in French Polynesia

A numerical dispersion model for cesium-137 data was used to elaborate an impact assessment for the French nuclear weapon testing site in French Polynesia. The three dimensional equation of advection/diffusion was solved by the Monte Carlo Technique. The mean transport field, isotropic horizontal and vertical turbulent exchange and radioactive decay were taken into consideration, but no biochemical processes were included. Over a period of 10 yr the dispersion of the as conservative assumed radionuclide cesium-137 was monitored considering two different scenarios of its introduction into the marine environment. The results of both scenarios are quite different in the farfield. However, in both cases the local environment of French Polynesia is the most affected.

THE ESTIMATION OF PLUTONIUM CONCENTRATIONS IN SOIL

summaryIn this paper we examine the consequences, for statistical analysis and interpretation, of the particulate nature of radioactive contamination of a nuclear weapons test site. We propose a probabilistic model which incorporates the particulate nature of the contamination and which is simple enough to be statistically fitted to the data. Parameter estimation involves the reconciliation and combination of measurements of (a) 59.5 ke V gamma rays from americium‐241, a decay product of plutonium‐241, using a portable medium resolution NaI detector, on a regular survey grid at a test site and (b) 59.5 ke V radiation from soil samples obtained at grid points. The implications of the model for measurement of levels of contamination are considered.

Studies of high-frequency seismic noise in eastern Kazakhstan

Abstract Three seismographic stations have been established in the region of the principal underground nuclear weapons test site in the republic of Kazakhstan in the Soviet Union. Instrumentation includes both surface and borehole seismometers with a bandwidth of 100 Hz and a system dynamic range of 180 dB. Power spectra of the regional ambient ground acceleration peak between 4 and 6 Hz, and are, on average, frequency independent above 10 Hz, where levels are approximately equal to 10−15 to 10−16 (m sec−2)2Hz−1. Kazakh noise levels are roughly equivalent to those observed by the Regional Seismic Test Network between 1 and 20 Hz, and about 10 to 20 dB higher than the very low noise model for Lajitas, Texas, in the same band. Noise observed by the borehole sensors is about 10 dB less than that observed by the surface instruments above about 20 Hz under low wind conditions at two of the three Kazakh sites; borehole improvement is greater under high winds. The third Kazakh site, Karasu, is characterized by much higher surface noise levels (15 to 20 dB higher than the borehole levels from 4 to 40 Hz) under both low or high wind conditions, which is attributed to amplification by local site conditions and the exposed terrain. Power spectra of individual runs of ambient vertical ground acceleration measured down the borehole show that high-frequency slopes (between 10 and 80 Hz) vary between f−0.60 and f0.22, depending on wind and site conditions.

External dose estimates for future inhabitants of eniwetok atoll.

Measurements of environmental γ radiation levels on Eniwetok Atoll were combined with pertinent population distributions and expected future life styles to assess the external doses that could be received by the Marshallese people on their return to the former US nuclear weapons test site in the Pacific.

Radioactivity levels in Eniwetok soil.

A radiological survey was performed to define the distributions of radioactivity within the soil on the islands in the Eniwetok Atoll, a former U.S. nuclear weapons test site in the Pacific. Soil samples were collected on each of the 40 islands within the atoll. Special emphasis, in terms of increased sample collections, was given to islands expected to have been the most affected by the testing program as well as those considered to be the most likely sites for future habitation. Approximately 3000 soil samples were analyzed by Ge(Li) gamma spectrometry and by wet chemistry. The predominant radionuclides observed in the samples were 90Sr, 137Cs, 239Pu and 60Co. In general, the activities appeared to approximate log-normal distributions. Geometric mean values were determined for each area exhibiting significantly different radiological characteristics. The southern islands showed the lowest levels of activity and they were distributed in a fairly uniform way over the surface of the islands. On the northern islands, where weapons testing was most intensive, the highest activities were observed toward the island interiors or in proximity to ground zero sites, and could usually be related directly to the surrounding vegetation density. The distribution of activity with soil depth shows a wide range of variations. On the southern islands the activities are low to the depth sampled. Within areas subjected to fallout, but excluding ground zeros and construction areas, the activities generally show a rapid decrease immediately below the surface and then level off. Beaches exhibit lower activities than the interiors and the depth distributions are essentially homogeneous. Profiles obtained in the ground zero and construction areas show highly variable depth distributions with layers of buried contamination indicated at some locations. The island of Yvonne is the most contaminated land area within the atoll. Particles containing as much as several milligrams of plutonium are randomly scattered on or near the surface over most of the northern part of the island. In addition, the northern tip of the island includes the highest external gamma levels (500μ750 μR/hr) due to soil radioactivity found on the atoll.