Samson Pagava

Samples of fish flesh collected in 1999 in the south-western Caspian Sea in the Baku area, important for caviar production (sturgeon – russkyi osyotr, sevruga and beluga), as well as for consumption (roach and carp) were analysed for anthropogenic strontium, caesium, plutonium and americium, and natural polonium. The highest massic activities of 137Cs were found in sevruga and beluga flesh (1.2–1.8 Bq/kg wet weight (ww)), while 90Sr levels were between 5–12 mBq/kg ww, and plutonium and americium levels were close to limits of detection (∼0.2 mBq/kg ww). The observed plutonium and strontium levels are in the same range as in the Mediterranean Sea, whereas caesium has been accumulated in conditions of lower salinity in larger proportions. The 210Po levels in fish were between 0.2–3 mBq/kg ww, in a fresh caviar (spawn) sample they were higher by a factor of 4 than in sturgeons, but comparable with levels observed in other species. The highest radionuclide levels, by one to two orders of magnitude, were measured in a macroalgae sample. The distribution of radionuclides seems to be more related to the species than to environmental conditions. The estimated concentration factors (CFs) for strontium and plutonium in fish and algae are in a reasonable agreement with IAEA recommended values. Caesium in the same species has been accumulated in larger quantities, so that the resulting CF is higher by a factor of two. The highest CFs were found for macroalgae, documenting that algae are suitable biomonitors of radioactive contamination. The measured activities of radionuclides in biota samples do not represent any radiological risk from their consumption.

The development of a spallation neutron source with a mercury target will lead to the production of rare radionuclides. The dose coefficients for many of these radionuclides have not yet been published. A collaboration of universities and national labs has taken on the task of calculating dose coefficients for the rare radionuclides using the software package DCAL. The working group developed a procedure for calculating dose coefficients and a quality assurance (QA) program to verify the calculations completed. The first portion of this QA program was to verify that each participating group could independently reproduce the dose coefficients for a known set of radionuclides. The second effort was to divide the group of rare radionuclides among the independent participants in a manner that assured that each radionuclide would be redundantly and independently calculated, and the results subsequently be submitted for publication in a separate manuscript. The final aspect of this program was to resolve any discrepancies arising among the participants as a group. The output of the various software programs for six QA radionuclides, 144Nd, 201Au, 50V, 61Co, 41Ar, and 38S were compared among all members of the working group. Initially, a few differences in outputs were identified. This exercise identified weaknesses in the procedure, which has since been revised. After the revisions, dose coefficients were calculated and compared to published dose coefficients with good agreement. The present efforts involve generating dose coefficients for the rare radionuclides anticipated to be produced from the spallation neutron source should a mercury target be employed.

Based on a mercury spallation neutron source target, the UNLV Transmutation Research Program has identified 72 radionuclides with a half-life greater than or equal to a minute as lacking an appropriate reference for a published dose coefficient according to existing radiation safety dose coefficient databases. A method was developed to compare the nuclear data presented in the ENSDF and NUBASE databases for these 72 radionuclides. Due to conflicting or lacking nuclear data in one or more of the databases, internal and external dose coefficient values have been calculated for only 14 radionuclides, which are not currently presented in Federal Guidance Reports Nos. 11, 12, and 13 or Publications 68 and 72 of the International Commission on Radiological Protection. Internal dose coefficient values are reported for inhalation and ingestion of 1 μm and 5 μm AMAD particulates along with the f1 values and absorption types for the adult worker. Internal dose coefficient values are also reported for inhalation and ingestion of 1 μm AMAD particulates as well as the f1 values and absorption types for members of the public. Additionally, external dose coefficient values for air submersion, exposure to contaminated ground surface, and exposure to soil contaminated to an infinite depth are also presented.

Georgia has geological formations with high uranium content, and several buildings are built with local materials. This can create potentially high radon exposures. Consequently, studies to mitigate these exposures have been started. This study presents a preliminary investigation of radon in Tbilisi, the capital of Georgia. An independent radiological monitoring program in Georgia has been initiated by the Radiocarbon and Low-Level Counting Section of I. Javakhishvili Tbilisi State University with the cooperation of the Environmental Monitoring Laboratory of the Physics/Health Physics Department at Idaho State University. At this initial stage the E-PERM systems and GammaTRACER were used for the measurement of gamma exposure and radon concentrations in air and water. Measurements in Sololaki, a densely populated historic district of Tbilisi, revealed indoor radon (222Rn) concentrations of 1.5-2.5 times more than the U.S. Environmental Protection Agency action level of 148 Bq m(-3) (4 pCi L(-1)). Moreover, radon-in-air concentrations of 440 Bq m(-3) and 3,500 Bq m(-3) were observed at surface borehole openings within the residential district. Measurements of water from various tap water supplies displayed radon concentrations of 3-5 Bq L(-1) while radon concentrations in water from the hydrogeological and thermal water boreholes were 5-19 Bq L(-1). In addition, the background gamma absorbed dose rate in air ranged of 70-115 nGy h(-1) at the radon test locations throughout the Tbilisi urban environment.