Sadao Hattori

Development of the SESAME Metallic Fuel Performance Code

A simple fuel performance code, SESAME, has been developed to analyze the steady-state irradiation behavior of metallic fuels. Important characteristics of metallic fuels such as fission product gas release, swelling, material redistribution, bonding sodium infiltration, and axial elongation are studied. Simple models have been developed for the SESAME code, which are successful in predicting irradiation data and useful in investigating the basic mechanisms that contribute to these particular irradiation behaviors of metallic fuels.

A Method of State Transition Analysis Under System Interactions: An Analysis of a Shutdown Heat Removal System

Taking the decay heat removal system of a liquid metal fast breeder reactor (LMFBR) as an example, a new reliability analysis method has been developed that can estimate how a failure occurring in a subsystem of a redundant system proliferates to another subsystem and how the independence of the redundant system is gradually lost. The Monte Carlo method is employed in the state transition representation. Environment changes evaluated from physical parameters, which correspond to failure time and to time- and sequence-dependent failure rates, are used to evaluate the stress-strength model. The failure rates derived are used to identify subsequent sequences. The investigation of the interaction between the system and the pipe in the decay heat removal system has revealed that the influence is small under conditions set for this study.

Clinical significance of low-dose radiation therapy: radiation hormesis

This study was designed to investigate the clinical significance of low-dose radiation therapy, radiation hormesis, and accuracy of therapeutic regimen. Radiation hormesis was performed in six patients (four patients with malignant diseases and two patients with benign diseases) in the experimental room where they could be exposed to a low level of direct gamma ray and inhale radon gas (radon-222). No significant side-effect was found in any patient during the clinical course. Biopositive effects could be observed regardless of malignant or benign background. Our study result suggested that radiation hormesis should be recognised as one of the alternative treatments for cancer. The definition of low-dose radiation therapy and the standardisation of its specification and therapeutic regimen are thus called for.

Potential Solutions in Radiation Hormesis

Abstract: This study summarizes up-to-date information about the biopositive effects of low radiation treatment (LRT), radiation hormesis, and our experimental devices. In addition, we present a favorable treatment result in a patient with advanced rectal carcinoma who received LRT at home using a radon gas aspirator. The patient was a 61-year-old man who underwent proctectomy in 2010. During the additional first-line chemotherapy, apparent increases in tumor makers identified multiple remote metastases in the lung, sacrum and liver. Sacrum pain limited his activity of daily living and impeded his coming to our facility for LRT. Then, we decided to provide him home LRT using a radon gas aspirator. He inhaled radon gas for 15 minutes at least 3 times a day at home, resulting in remarkably reduced tumor markers and sacrum pain relief. He could walk, keep sitting up without support and sleep in the spine position again after receiving home LRT. No influence of radon gas inhalation on the second-line chemotherapy was observed. The favorable effects of LRT lead us to believe that the newly-developed devices will provide the clinical significance on malignant diseases. To establish the LRT regimen, further clinical investigation and data accumulation are thus called for.

Energy Source for the Human Demand

Lack of water and food, extinction of plants and animals, human catastrophe and other serious environmental crises are occurring as a result of the large increase in the population of mankind. Yet, the Asian countries are experiencing strong technical and economical development.

A Logical Selection of Measures for Quality Assurance on the Integrity of Liquid-Metal Fast Breeder Reactor Primary Boundaries

An example of a logical approach to standardization of in-service inspection requirements is introduced, analyzing each measure according to risk reduction factors in order to develop a systematic configuration of safety measures. Comparison of a heavy pressure vessel section fabricated to resist pressure from the many nozzles in a light water reactor vessel with a thin-walled reactor vessel in a liquid-metal fast breeder reactor (LMFBR) operating at high temperatures and low pressure indicated no apparent difference in the failure probability of the reactor vessel. If both large failures and cracks are considered, 10/sup -5//vessel.yr is to be assumed. In assessing the unreliability of the guard vessel, dominant factors are common cause failures and subordinate modes. The coupling factor of the common cause failure of the guard vessel with reactor vessel failure is assumed 10/sup -3/. The subordinate mode failure of the guard vessel when the sodium leak from the reactor vessel is left unattended should be considered in the rate of 10/sup -2//reactor vessel failure. Especially in LMFBRs, visual tests are more practicable than volumetric tests for primary sodium boundaries, and the risk reduction factor by periodic in-service inspections is limited to only 5%.

Studies on the Applicability of a Flow Coupler to a Liquid-Metal Fast Breeder Reactor Plant

A flow coupler is considered as an alternative to the conventional primary pump in a liquid-metal fast breeder reactor (LMFBR). A conceptual design of a flow coupler combined with an intermediate heat exchanger in a pool-type LMFBR was done. Based on this design, a one-tenth-scale flow coupler model was built and successfully operated in a high-temperature sodium loop. To estimate the flow coupler characteristics, a quasi-one-dimensional code was developed. From these studies, the flow coupler pump concept appears to be feasible for actual use in an LMFBR.

Probabilistic fracture evaluation of a fast breeder reactor cover

The structural reliability of a fast breeder reactor cover was evaluated using probabilistic fracture mechanics. The effects of important factors (initial crack distribution, crack detection level, crack growth rate, incidence of events such as earthquakes, in-service inspection for cracks, weld toughness, residual stresses, and environmental effects) on the reliability of structures were estimated, and methods for maintaining proper reliability were studied. It was found that the probability of the reactor losing its function is --10/sup -8/ in the terminal stage of the plant lifetime, even when the most conservative initial crack distribution and crack detection level are assumed. However, the prerequisite of such a condition is the use of appropriate leak monitors or proper atmospheric control. It was also confirmed that the degree of improvement in reliability through in-service crack detection, which was considered to be important, is not necessarily significant for the reactor cover.