[en] This issue is the collection of the paper presented at the title meeting. The 34 of the presented papers are indexed individually. (J.P.N.)

[en] This study examines two issues: the benefit of dose reduction measures excluding collective dose reduction and the distribution of individual dose among workers. Examples are taken from actual cases of dose reduction measures during the current reactor dismantling work at the Japan power demonstration reactor (JPDR) at the Japan Atomic Energy Research Institute (JAERI) since 1986. 6 refs, 1 fig

[en] From the view of radiation control, the main features of the JPDR reactor dismantling are: 1. the work under high-level radiation and high level radioactive air contamination area is expected; the new dismantling techniques which have not been experienced in the controlled area before will be adopted; and a great amount of materials, tools, radioactive waste and so on will be taken out from the controlled area. Considering these features, five instruments were developed to adapt for the JPDR decommissioning; i.e., remote high dose rate measuring instruments (underwater and in the air), contamination inspection monitor, respirable dust monitor, respirable dust monitor, extremely low level waste γ-scanner, and waste package contamination and dose rate monitor. These instruments are described

[en] To make a contribution to radiological safety evaluation, this aerosol characterization study of Japan Power Demonstration Reactor (JPDR) decommissioning was undertaken. In the case of radioactively contaminated stainless steel pipe segmentation with mechanical cutting tools, radioactive aerosol generation was about 10 times greater than that with thermal cutting tools. Underwater cutting methods effectively reduced aerosol generation compared with in-air cutting methods. (author)

[en] The decommissioning of Japan Power Demonstration Reactor (JPDR) has started on December 1986 to intend for complete removal of all the reactor installations and buildings. In order to reduce external exposure, highly activated reactor internals and a Reactor Pressure Vessel (RPV) were dismantled using remote cutting devices. An air curtain system and/or temporary containment enclosures equipped with ventilation systems were installed to prevent the spread of airborne contamination whenever the work involving radioactive aerosols was carried out. The maximum individual dose equivalent and the collective dose equivalent to the workers who were engaged in the dismantling work by December 1991 were 8.4 mSv and 0.29 man · Sv, respectively. Approximately 85 % of the collective dose was due to the dismantling work of the reactor internals, pipes connected to the RPV and the RPV. The collective dose equivalent at the actual cutting work of the reactor internals and the RPV was reduced using remote underwater cutting methods, but at the work in relation to these dismantling, such as installation and removal of the cutting system, the collective dose equivalent was increased. Internal exposure to the workers was below the screening level. (author)

[en] The JPDR decommissioning program was begun in 1986, by the end of March 1991 most of activated and contaminated equipment were removed. The cumulative collective dose equivalent since initiation of the program is about 0.28 man-Sv. Dose distribution of workers engaged in dismantling of the reactor internals and the RPV showed hybrid log-normal distribution. Radioactive aerosol generation with mechanical cutting tools was higher than that with thermal cutting tools. (author)

[en] It has become important recently to study plasma impurities in an actual tokamak machine from the standpoint of the material development for the next-step fusion reactors. In order to study the behaviour of plasma impurities in the tokamak machine, experiments of sampling impurities and analyses of the sampled impurities by RBS and ISS were performed. In the sampling experiments, specimens, which sample the impurities implanted in them during plasma exposure, were set in the scrape-off layer in the JIPP T-II tokamak. Exposed specimens were then observed by RBS and ISS, and spatial distributions and depth profiles of impurity elements in specimens were obtained. Some impurities, C, O, Fe, Mo, Ta and Ti, were identified in the specimens, and they were considered to originate from residual gases, the torus wall, sample holders and the limiter. From depth profiles analysed by ISS, it was found that most impurity atoms implanted in sampling specimens during plasma exposure are present within a short range of the specimen surface. Our results, as the first attempt, will contribute towards the studied of plasma behavior. (orig.)