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Kobe, Mitsuru*; Tsunoda, Hirokazu*; Mishima, Kaichiro*; Kawasaki, Akira*; Iwamura, Takamichi
Genshiryoku eye, 48(1), p.23 - 28, 2002/01
no abstracts in English
Uehara, Kazuya; *; *; *
Purazuma, Kaku Yugo Gakkai-Shi, 69(12), p.1550 - 1559, 1993/12
no abstracts in English
; Hishida, Makoto; Takizuka, Takakazu
Genshiryoku Kogyo, 38(1), p.53 - 59, 1992/01
no abstracts in English
Nomura, Norio; Haga, Kazuo;
PNC TN9410 91-298, 74 Pages, 1991/08
High-temperature transpotable liquid-metal-cooled fast reactors are also expected as an energy source in sever environments such as lunar base. Only electricity has been considered as the energy supply system to the lunar base, however, both use of electricity and heat power (co-generation system) may offer better effective use of energy than only the electrification system is considered. In this report, the advantage of co-generation system based on a transpotable reactor examined to a usage in a lunar base. Two energy system diagrams on heat and electricity flows have been compared from the view point of total weight. One is the case of all electrification. The other (co-generation system) is the case in which the exhaust heat from the nuclear reactor is actively utilized to reduce the demand of electricity. A heat transport technique using a chemical process as the heat media is adapted for the latter. In the chemical system, hydrogen and carbon monoxide are formed from methane and steam by adding nuclear heat. Then the gases are transported through a pipe and changes to the original materials generating heat at the consuming spot. As the result of present study, it is clarified that the co-generation system has a possibility to have an advantage over the case of all electrification in total weight of system when the energy demand increase to MWe level. Finally, future R&D items ware mentioned to reduce the weight of this co-generation system and to increase the effectively.
; Haga, Kazuo
PNC TN9410 91-205, 55 Pages, 1991/05
A transportable reactor has been studied in one of activities of frontier research in PNC. Since the reactor is going to be used at an secluded place in the earth, on the surface of the moon or at the deep sea bottom, the operation of the reactor requires wireless communications. Based on the present status of technology, a preliminary study has been performed in this report on a wireless operation method of the reactors on the moon and at the deep sea bottom. A wireless operation system of the reactor on the moon is supposed to exist technically on the extension of a present space communication system and a difficult problem does not seem to remain at the development stage of the wireless operation system. Concerning the wireless operation system of the reactor at the deep sea bottom, a few problems remain to be solved in the field of acoustic communications in sea water. However they seem to be solved technically in future. It takes about three seconds for an electric wave to go and come back between the reactor on the moon and the earth. It takes also about four seconds for an acoustic wave to reach the reactor at the deep sea bottom from the sea surface. Therefore, urgent control of the reactor by wireless communications is impossible in both cases. The urgent control must be performed by the reactors themselves.
Nomura, Norio; Haga, Kazuo;
PNC TN9410 91-107, 40 Pages, 1991/03
Conceptual design of the SPECTRA-L power plant for lunar base is being performed as one of the transportable reactor study. It is necessary to establish an acceptable limit of dose equivalent in space as well as that on the earth so as to design the shield to the reactor. Because the natural radiation dose in space is higher than that on the earth, terrestrial dose equivalent limit can not be directly applied. In this report, we examined the dose equivalent limit on the moon based on the terrestrial one, then analyzed the shielding effect of lunar soil (regolish) which is expected as shielding material in this plant. The study led us to propose some limits on the acceptable radiation in the human activity in space, that is 2.0 Sv in life and 0.4 Sv/year, consequently 0.04 Sv/month. The yearly limit is less than 0.5 Sv which is admitted in the ICRP Publication 60 to emergency situation. A limit of 40 mSv/year is suggested to the radiation from nuclear reactor at the place where stuffs of lunar base is easily accessible. The suggested value is 10% of the proposed yearly limit to the natural radiation in space. A one-dimensional analysis on the shielding effect of the regolish covering SPECTRA-L showed that the neutron dose equivalent rate of the reactor is attenuated to the background level of space at a point about 10 m apart from the reactor center and to that on the earth at about 12 m. Lastly, it is emphasized that the exposure to radiation should be reduced by the following methods. (1)Automatic operating system of the plant. (2)Development of materials for easy-working protection clothes and radiation shield using magnetism ln the living area. (3)Minimum exposure to radiation, especially in the living area, following the spirit of ALARA. (4)Underground base and underground transport routes to other facilities.
Nomura, Norio; Haga, Kazuo;
PNC TN9410 91-100, 73 Pages, 1991/03
Liquid Metal cooled Fast Reactor is a good candidate of a large-scale energy supply system to a manned lunar base because of the compact structure and being free of refueling. A 300 kWe transportable reactor SPECTRA-L is being studied as the power source on the moon. Because the reactor system is launched by a launch vehicle, safety evaluation is necessary to the launch failure accident. We examined (i) the possibility of recriticality, and (ii) the influence of nuclear fuel leakage to the environment in the case of reactor damage. The followings are the main findings of this preliminary study. (1)Under-criticality is maintained even the reactor falls into water or crashes against the earth. (2)The external exposure dose by a radiation cloud of released fuel is less than the natural radiation. (3)The internal exposure dose by inhaling the cloud is less than 1 mSv/year which is a reco㎜ended dose limit to the public. (4)The surface radioactive density increased of land by the accident is be less than 0.4 Bq/square centimeter, which is a limit for things contaminated by alpha radiation to be transported from a controlled area, regardless the whether. This estimation is based on a leakage of five percent fuel, but the exposure dose would be far less than the estimated from the following reasons. (1)Nuclear fuel is in a ceramic form called pellets, and they are inserted in fuel cladding, and contained in the coolant material (metal) and the reactor vessel. (2)The nuclear fuel does not break into fragment as aerosol by the accident.
