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Abstract: The results of γ analyses of soil samples obtained from 50 locations in Fukushima prefecture on April 20, 2011, revealed the presence of a spectrum of radionuclides resulted from the accident of the Fukushima Dai-ichi nuclear power plant (FDNPP). The sum γ radioactivity concentration ranged in more than 3 orders of magnitude, depending on the sampling locations. The contamination of soils in the northwest of the FDNPP was considerable. The 131I/137Cs activity ratios of the soil samples plotted as a function of the distance from the F1 NPPs exhibited three distinctive patterns. Such patterns would reflect not only the different deposition behaviors of these radionuclides, but also on the conditions of associated release events such as temperature and compositions and physicochemical forms of released radionuclides. The 136Cs/137Cs activity ratio, on the other hand, was considered to only reflect the difference in isotopic compositions of source materials. Two locations close to the NPP in the northwest direction were found to be depleted in short-lived 136Cs. This likely suggested the presence of distinct sources with different 136Cs/137Cs isotopic ratios, although their details were unknown at present. Vertical γ activity profiles of 131I and 137Cs were also investigated, using 20–30 cm soil cores in several locations. About 70% or more of the radionuclides were present in the uppermost 2-cm regions. It was found that the profiles of 131I/137Cs activity ratios showed maxima in the 2–4 cm regions, suggesting slightly larger migration of the former nuclide. [Copyright &y& Elsevier]

Abstract In the more than 40 years of operational history of pressurized water reactors (PWRs) in Japan, sustainable development of water chemistry technologies has resulted in the world's highest secondary system component integrity; additionally, secondary system components, especially steam generator (SG) tubing, with excellent material integrity have been developed to prevent leakage of radioactive contamination from the primary to the secondary system and to maintain the heat removal function of the secondary system. Although reasonable control and diagnostic parameters for water chemistry are utilized by each PWR owner, the specific values are not shared. To ensure reliable PWR operation and to achieve the highest safety level, relevant members of the Standards Committee and the related committee organized by the Atomic Energy Society of Japan (AESJ) decided to establish water chemistry guidelines for PWRs. The Japanese PWR secondary water chemistry guidelines provide strategies for improving material integrity and the heat removal function. The guidelines also provide reasonable "action levels" for control parameters and "control values" and "diagnostic values" for multiple parameters, and they stipulate the responses when these levels are exceeded. Specifically, "conditioning parameters" are adopted in the guidelines. Good operational practice conditions are also discussed with reference to long-term experience. This paper introduces the purpose, technical background and framework of preliminary secondary water chemistry guidelines for Japanese PWRs. Addition, the differences in bases of parameter settings between the Japanese and overseas guidelines are discussed. Highlights • Framework of PWR secondary water chemistry guidelines in Japan are presented. • Guideline necessity, definitions, philosophy and technical background are mentioned. • Some guideline settings for control conditioning and diagnostic parameters and recommendations are explaines. • Chemistry strategy is also mentioned. [ABSTRACT FROM AUTHOR]

Abstract: Measurements of primary g-values (at ∼10−7 s after the initial ionizing event) of , OH and H2O2 were extended to the very high linear energy transfer (LET) region (∼700eV/nm) near the Bragg peak. Heavy ions (4He2+, 12C6+, 20Ne10+, 28Si14+, 40Ar18+ and 56Fe26+) of energies up to 28GeV were provided by the Heavy Ion Medical Accelerator in Chiba (HIMAC) of the National Institute of Radiological Sciences (NIRS) in Chiba, Japan. Energies of the ions were decreased down to about 10MeV/u for 4He2+ using an energy absorber made of polymethylmethacrylate (PMMA) plates in order to vary the LET values. Beam was visualized after passing through the energy absorber using agarose gel of aqueous solution containing methyl viologen and sodium formate in order to determine how long ions can penetrate into water. Based on the information of the penetration depth of ions in samples, much attention was paid to dose correction and LET evaluation. The obtained data were plotted as a function of (Z eff/β)2 also instead of LET in order to discuss effects of physical track structures on product yields, resulted in better universality. [Copyright &y& Elsevier]