[en] The heavy-water-moderated power reactor has been studied mainly at Japan Atomic Energy Research Institute (JAERI) since 1963, and the boiling light-water-cooled type was selected for further development in Japan in 1966. After this decision many investigations have been made on the characteristics of the above reactor at JAERI and, based on the results, the five nuclear power consortia in Japan have made preliminary designs individually. A report is made on the results obtained from the investigations and designs. The study and investigation based on the principle of using natural uranium led to the adoption of a Pu self-sustaining cycle, from the standpoint of fuel-cycle cost and power cost. This cycle has the following advantages: it is equivalent to a slightly enriched fuel cycle giving much flexibility in the core design, and about 15 000 MWd/t of burnup might be expected with natural uranium when enriched by Pu produced in its own spent fuel. The positive void coefficient, which decreases the stability and safety of this reactor type, would no longer be a major problem when using Pu enrichment. However, it must be noted that a slightly enriched uranium would be loaded in the initial cycle, which might have a positive void coefficient. The problem can be partially overcome by placing inter-lattice tubes in the core as in the SGHW in order to adjust the moderator to fuel ratio, making a lower ratio for the U-loaded core and a higher ratio for the Pu-loaded core. This would give rise to a higher quality of reactor exit steam or higher dryout limit in the Pu-loaded than in the U-loaded core. On-power refuelling is one of the major problems to be solved for the reactor. Two refuelling methods (access from the reactor top and from the reactor bottom) were investigated and the corresponding refuelling machines were designed. An outline of some reshuffling schemes, stability and safety analysis and plant design (stressed to the reactor structure) are also given. (author)
Source
International Atomic Energy Agency, Vienna (Austria); 1001 p; Apr 1968; p. 285-296; Symposium on Heavy-Water Power Reactors; Vienna (Austria); 11-15 Sep 1967; IAEA-SM--99/16; ISSN 0074-1884; 
; 19 refs., 4 figs., 4 tabs.
; 19 refs., 4 figs., 4 tabs.