Atmospheric pressure changes (APC) due to a tornado may lead to large loads on air-tight buildings, such as nuclear facilities which contain radioactive materials inside. However, each building has several openings for ventilation. Taking into account their pressure equalization effect, the loads can be evaluated more realistically. This study introduces the numerical calculation code “TAIPEC”, based on Bernoulli’s theorem and the state equation of air, which was developed to analyze the inner pressure change and air flow rate through an opening of a building due to a pressure difference caused by APC. It runs on widely available computer software, Microsoft® Excel or Matlab®. TAIPEC was verified by the experimental results from the blow-out test conducted in this study and a wind tunnel test and a simulated tornado test in previous studies. Then, the calculation results are discussed from the standpoint of the Reynolds number. Finally, an example simulation was conducted to show the effect of a blow-out panel on reducing the load on a building.
Ambient dose equivalent (H*(10)) rates in the environment in Fukushima prefecture were measured by NaI(Tl) and CsI(Tl) scintillation detectors whose crystal shapes are different. The indicated values of H*(10) measured by a CsI(Tl) scintillation detector with a rectangular parallelepiped crystal (13×13×20 mm3) were approximately 40% higher than those of a CsI(Tl) scintillation detector with a rectangular parallelepiped crystal (38×38×25 mm3) and 20% higher than those of a NaI(Tl) scintillation detector with a cylindrical crystal (25.4 mm in diameter and height) in the case where G(E) functions were used in parallel irradiation geometry. It was found that cylindrical crystals are more appropriate than rectangular parallelepiped crystals with respect to directional dependence in environmental dose rate monitoring. However, using a spectrum-dose conversion operator determined in a rotational irradiation geometry, the values of H*(10) agreed within 10% among all the detectors. These results indicate that the directional dependence of scintillation detectors should be carefully considered for H*(10) dose rate monitoring in the environment.
A plan of an advanced fusion neutron source (A-FNS) using the d-Li reaction is being developed at Rokkasho site of National Institutes for Quantum and Radiological Science and Technology (QST). Although the main objective of the A-FNS facility is fusion material irradiation, applications using fusion neutrons are being investigated. We calculated production yields of 99Mo, which is the parent nuclide of 99mTc and important in medical diagnosis, as one of the applications in order to evaluate the potential of the A-FNS. A modified IFMIF test cell design for the A-FNS was used to calculate the production of 99Mo by using the McDeLicious-11 code and FENDL-3.1b and FENDL/A-3.0 nuclear data libraries. At a position on the surface of a high-flux test module, we estimated the activity of 99Mo to be 83 TBq, which was obtained from the 100Mo(n,2n)99Mo reaction in a 2-day irradiation, for a 100%-enriched 100Mo sample of 250 g. This amount covers almost all of the demand for 99Mo in Japan per week. The use of a natural molybdenum sample is also a promising candidate as an inexpensive 99Mo production method, because the 98Mo(n,γ)99Mo reaction has large capture cross sections in the resonance energy region.
Indoor as well as outdoor ambient dose rates of 24 private premises with Japanese style wooden houses, which had been decontaminated in advance, were measured by a NaI(Tl) γ ray survey meter in Naraha city, Fukushima prefecture from October 2013 through July 2015. Four of the target premises were also measured before decontamination. The rates were corrected for attenuation by consideration of the radioactive half-lives of 134Cs and 137Cs to compensate the time gap between the surveyed dates. Measuring points were categorized by an index of a pair of indoor positions and the height from the floor as well as outdoor positions and the height from the ground. The observed differences among the dose rates under this categorization, for example, the rate on the second floor is lower than that of the ceiling of the first floor, qualitatively agree with the reported results of simulations, suggesting that some assumptions used by the simulations coincide reasonably well with actual conditions. The observed ratio of the doses inside and outside of wooden houses also essentially agrees with the reported ratio measured by different methods in different cities. The ratio has been confirmed to decrease with increasing open air dose rate when the open air dose rate is less than 0.5 μSv/h.