The verification and validation processes including uncertainty analysis are now mandatory when utilizing a numerical model in safety analysis. The uncertainty analysis of a numerical model for calculating an effective source height has not been carried out. One of the reasons is a lack of experiment data with uncertainty obtained by the repetition of experiments. In this study, we repeated wind tunnel experiments to obtain uncertainty-quantified experiment data to validate the numerical model under various terrain conditions. Using the obtained wind tunnel data, the uncertainty analysis of the numerical model was carried out to quantify an estimated error of the numerical model. We suggested an adjustment method for the practical application of the numerical model using the estimated error. This method allows us to evaluate an effective source height without the need for wind tunnel results under the same experimental conditions.

Up to now, conventional calculation codes have played a major role in skyshine dose evaluations. On the other hand, evaluations using Monte Carlo simulation require lengthy calculation times and yield results that are difficult to validate. We have devised a method in which the radiation behavior in the shielding materials around a radiation source is calculated using Monte Carlo simulation and then the results are input into a simplified skyshine dose calculation that uses a database constructed by the prior method of Monte Carlo calculation. The method was implemented in PHITS to verify its effectiveness. A comparison of the calculation speed with that of the usual Monte Carlo method showed an increase of 10 to 1,000 times while maintaining a certain degree of reliability, confirming the effectiveness of the methodology.

Fission yield is an important physical quantity used to evaluate the amount of fission products after irradiation. The fission yield used in Japanese Evaluated Nuclear Data Library (JENDL) employs ENDF/B data for many nuclides. On the other hand, the fission yield has recently been evaluated in Japan on the basis of various theories. As one of the evaluations, the fission yield has been newly evaluated by a team from Tokyo Institute of Technology (Tokyo Tech). It is necessary to confirm the validity of the fission yield evaluated by Tokyo Tech because the fission yield is used as the sublibrary of JENDL-5. In this study, the analysis of the post-irradiation examination results of UO₂ fuel and MOX fuel was performed for the validation of the fission yield evaluated by Tokyo Tech, and the result is compared with that of JENDL FP Fission Yields Data File 2011 (FPY-2011). Using the integrated burnup calculation code system SWAT4.0, the results of the post-irradiation examinations of Fukushima-Daini-2 and Beznau-1 were analyzed. The difference in the production of fission products observed from the fission yields evaluated by Tokyo Tech and those by FPY-2011 is about 5% at maximum.

The sorption and desorption of a ³He, hydrogen and air mixture by activated charcoal cooled to 25 K were experimentally investigated to obtain basic data for designing a tritium recovery system from aged tritium waste. The results showed that the mixture of 100 cm³ under a room-temperature condition can be treated with 10 g of charcoal at 25 K.