[en] ETDOSE (Environmental Tritium model for DOSE estimation), was developed by M.A. Andoh, T. Takahashi and H. Amano for dose assessment of tritium emissions in the surface environment. ETDOSE calculates tritium concentrations in air; soil, plant free water and OBT, and estimates dose impact by inhalation of air and ingestion of food for an acute and a chronic release of HT and HTO. (author)

[en] A smoke-heating system with increased radiation of far infrared rays was produced. Logs of a thinned Sugi (Cryptomeria japonica D. Don) stand were smoke-heated directly by this system, and the quality improvement of the heated wood was examined. The rupture of pit membranes by this treatment was observed using SEM (scanning electron microscopy). This system increased the temperatures inside the logs homogenously. The great increase of steaming pressure inside the logs probably caused the rupture of the pit membranes. The rupture ratios of the pit membranes were about 51% for sapwood and about 23% for heartwood. The rupture of pit membranes increased the permeability of the wood, which decreased the gradient of the temperature and the moisture inside the logs. It is considered that the homogeneous distribution of moisture inhibited the generation of drying stress and as a result, damage inside the logs did not occur. In this experiment. the reduction in residual stresses in logs was achieved by smoke-heating of about 34 hours at a temperature inside the logs of more than 80°C

[en] A method for quantification of the ²²²Rn flux from the ground surface into the atmosphere is described. A chamber made of polymethylmethacrylate (PMMA) was embedded in the soil of ²²²Rn concentration and various affecting environmental factors were measured every hour. How environmental factors affect the ²²²Rn concentration was considered and it was found that there were clear relationships between the variations of ²²²Rn concentration and various environmental factors, especially air pressure. A simple lumped-parameter model approach was developed to obtain the undisturbed ²²²Rn flux, which is the hypothetical situation without the chamber. The values of the parameter were found by fitting the model to the measured data for air pressure and ²²²Rn concentration in the chamber. The effective diffusion coefficient obtained by the analysis agreed well with that obtained by the relation reported by Rogers and Nielson. The undisturbed ²²²Rn flux from the ground surface into the atmosphere was estimated by using the parameter values obtained. (author)

[en] A new method was developed to determine HT deposition velocity and to investigate how environmental factors affect the deposition processes including the diffusion into soil and the biochemical conversion by microorganisms to HTO in soil. This method, using a chamber and two tritium samplers, enables determination of the HT deposition velocity in situ without a large scale experiment and an additional tritium source. The main problem concerning the use of a flow-through method is the possible effect of flow rate on flux measurement. Since the tritium sampler used in this study has many collecting columns, the flow rate is limited. Experimental results showed no significant effect of flow rate over a low range from 0.48 to 0.95 l.min^-1. From the increase of HT deposition velocity with increase of water content, it was indicated that biochemical oxidation rather than physical diffusion dominantly affects the HT deposition velocity under examined site conditions. No clear relationship between the HT deposition velocity and atmospheric temperature, relative humidity or soil temperature was observed. The soil temperature was only of secondary importance as a factor controlling the HT deposition velocity. (author)

No abstract available

[en] Doppler effect experiments on resonance materials for rock-like oxide (ROX) fuels were carried out to examine the calculation accuracy in the intermediate neutron spectrum of the Fast Critical Assembly (FCA) of the Japan Atomic Energy Research Institute. This study is the second phase of a series of Doppler effect experiments on the resonance materials, which follows the measurements in the fast neutron spectrum. The Doppler effect was measured as the sample reactivity change between the heated and unheated samples. Cylindrical samples of resonance materials such as erbium metal (Er), tungsten metal (W) and thorium dioxide (ThO₂) were used. The sample was heated up to 1073 K at the center of the FCA core. The experiments were analyzed by the SRAC code system with the use of the JENDL-3.2 cross-section library. The calculated Doppler effects of the W and ThO₂ samples agreed with the measured values within the experimental error, while the calculation overestimated the measured Doppler effect of the Er sample by 12%

No abstract available

[en] For a metallic fuel liquid metal fast breeder reactor, we studied a core concept for improving the Doppler coefficient and the sodium void reactivity without much sacrificing the breeding ratio and the burnup reactivity loss. In the concept, several ordinary fuel pins in all fuel assemblies of a core are substituted by pins containing only zirconium hydride (ZrH). A parametric survey for the ZrH fraction from about 1 to about 5% was performed in this study to investigate the reactivity coefficients and the associated demerits in order to search the optimum fraction of ZrH. The metallic fuel core containing about 3% of ZrH showed the good results for all parameters. Following the parametric study, the effect of hydrogenous material in a metallic fuel core was experimentally confirmed. Doppler reactivity, sodium void reactivity and sample reactivity worths of plutonium and B₄C were measured in a series of critical experiment at FCA of JAERI. The experimental results showed that the hydrogenous material significantly improved the Doppler and the sodium void reactivities. Analysis of experimental results was performed to check the applicability of the present design codes for a fast reactor with hydrogenous materials

[en] Results of the benchmark test of reactor physics parameters of a nitride-, metallic- and oxide-fuel LMFBR was reported. Sodium void reactivity worth and plutonium and B₄C sample worth were measured systematically on the mockup assemblies with different fuel composition. The analyses were made by using the JENDL-3.2 cross-section library and JAERI's standard calculation system for fast reactor neurotics. Predicts of criticality, sample worth and sodium void reactivity worth in the central small zone agreed well with the measured values in the three assemblies. The difference of calculation accuracy among the nitride-, metal- and oxide-fuel assembly was found in the sodium void reactivity worth of the large zone and the discrepancy between the calculated and the measured value was obvious in the nitride-fuel assembly. (author)

No abstract available