Large-scaled thermohydraulic tests plan for cooling systems in fast reactors; effect of primary system and DRACS system on dynamics

not registered; not registered; Kamide, Hideki 

Large-scaled thermohydraulic tests are planned for new key technologies in the heat transport systems of a fast reactor with power of 600MWe. The test facility consists of components from a reactor vessel to a steam generator. Basic design of the large-scaled thermohydraulic test facility is 1/3 scale of the large scale fast reactor with two primary cooling loops. However the primary piping length and plenum volume are larger than those of the 1/3 scale of the fast reactor, because a sodium is heated by a gas burner which is placed between pump and reactor vessel. And, design of a direct reactor auxiliary cooling system (DRACS) in the test facility is also of interests. Therefore, dynamics analyses of the thermal transition tests have been done in which parameters were the primary cold leg piping length, the plenum volume and Euler numbers of the DRACS system. It was shown that the shortening of the primary cold leg piping length was not important to improve the transient response, and the reduction of the lower plenum volume in the reactor vessel was effective. And, it was found that the Euler numbers of the DRACS should be 1/3 scale condition, and the heat capacity of an air cooler, i.e. its tube size, reduction was of importance. Analyses have been done in which only electrical heaters in the core were used and a temperature difference between hot and cold legs was set 1/3 of the fast reactor. It was shown that the thermal transition just after the scram agreed fairly well between the test facility and the reactor. Analyses of the primary pump stick tests have been done. It was shown that the thermal transition of the fast reactor could be simulated roughly, and a prevention of reverse rotation of the primary pump due to the reverse flow was not very influential to improve the response.