Fuel assembly in a BWR type reactor

Purpose : To improve the earthquake-proofness of the reactor core and decrease the power fluctuation upon transient phase in a BWR type reactor. Constitution : The uranium and plutonium charge amount per 175 cm2 area and 2 cm length within a channel box is adjusted to 0.40 - 0.28 kg. at 80% portion of the central area excepting the upper and lower ends of a fuel assembly. Since the fuel temperature can thus be lowered, the fuel can stress upon powerup and the plastic deformation in the fuel can at the final burning stage can be decreased and the fuel rod safety can be improved. Further, since the weight of the fuel rod can be decreased, the responsive displacement of the fuel assembly upon earthquakes can be decreased to thereby improve the earthquake proofness. Furthermore, since the void coefficients can also be decreased, the reactor core safety can be improved. (Moriyama, K.)