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Abstract  

The increase of environmental radiation dose rate during rainfall at environmental monitoring posts (MPs) was calculated by using the correlation relationship with the dose rate at the neighboring MP. The calculated dose rate agreed with the observed one within less than 20% of the maximum increase height of the observed one for each rainfall. Furthermore, when the dose rate increased due to Krypton-85 (85Kr) discharged from the Tokai Reprocessing Plant (TRP) at the environmental monitoring station (MS) downwind of the stack during rainfall, the dose rate due to the 85Kr was tried to discriminate. The discriminated dose rate agreed with that calculated by the atmospheric dispersion calculation code system, SIERRA-II, using stack monitor data and local meteorological observation data.

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Simulation of the atmospheric dispersion of 85Kr from a reprocessing plant over a coastal area

Performance examination of an emergency environmental radiation dose evaluation code system, SIERRA-II

Journal of Radioanalytical and Nuclear Chemistry
Authors: M. Takeyasu, T. Iida, H. Watanabe, M. Takeishi, and A. Yamamoto

Abstract  

The performance of the computer code system, SIERRA-II, for calculating the environmental radiation dose due to an accident was assessed over a coastal area, using the environmental monitoring data around the coastally located Tokai Reprocessing Plant (TRP) when 85Kr was discharged during its operation. The agreement within a factor of 5 between the calculated and observed air concentrations of 85Kr in areas of a few km from the TRP was achieved in 57% of the comparison data, disregarding the internal boundary layer. The mean fraction bias was −0.6, which meant a slight overestimation. According to the vertical profile of the atmospheric temperatures, the internal boundary layer was modeled with the SIERRA-II and the agreement became better than when the internal boundary layer was not considered.

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Summary  

A simple and reliable sampling system for 3H and 14C in airborne release from nuclear facilities was designed. The sampling system can collect 3H and 14C simultaneously with a condensation technique using a commercially available cold trap equipment and a CO2 absorption technique using an organic alkali monoethanolamine solution, respectively. In situ performance tests for the effluent from a reprocessing plant showed that the system has high and stable efficiencies for collecting 3H and 14C for a one-week batch sampling at a sampling flow rate of 0.4 l . min-1. These collection techniques also provided a simple procedure of following sample preparation for activity measurements by liquid scintillation counting. The detectable concentrations of the proposed monitoring method were 3.0 Bq . m-3 for 3H and 1.6 Bq . m-3 for 14C, respectively. The sensitivity would be on an acceptable level for routine monitoring of airborne release at nuclear facilities.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: M. Pham, M. Betti, P. Povinec, M. Benmansour, R. Bojanowski, P. Bouisset, E. Calvo, G. Ham, E. Holm, M. Hult, C. Ilchmann, M. Kloster, G. Kanisch, M. Köhler, J. La Rosa, F. Legarda, M. Llauradó, A. Nourredine, J.-S. Oh, M. Pellicciari, U. Rieth, A. Rodriguez y Baena, J. Sanchez-Cabeza, H. Satake, J. Schikowski, M. Takeishi, H. Thébault, and Z. Varga

Abstract  

A new Reference Material (RM) for radionuclides in mussel (Mytilus galloprovincialis) from the Mediterranean Sea (IAEA-437) is described and the results of the certification process are presented. Four radionuclides (40K, 234U, 238U, and 239+240Pu) have been certified, and information values on massic activities with 95% confidence intervals are given for nine radionuclides (137Cs, 210Pb(210Po), 226Ra, 228Ra, 228Th, 230Th, 232Th, 235U, and 241Am). Results for less frequently reported radionuclides (90Sr, 129I, 238Pu, 239Pu, and 240Pu) are also reported. The RM can be used for quality assurance/quality control of the analysis of radionuclides in mussel samples, for the development and validation of analytical methods and for training purposes. The material is available in 200 g units.

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