| 摘要 |
PURPOSE: To reduce the cost of assembling work, maintenance work, fuel and operation by selecting a specific combination of pellets of weak and strong neutron absorbing materials thereby attaining a specific reaction value. CONSTITUTION: The cladding tube 36 of a gray rod 34 is composed of stainless steel or Inconel having inside diameter of about 8.75mm and outside diameter of about 9.68mm and a plurality of pellets 54 in the cladding tube 36 comprise solid pellets 52 of weak absorbing material, e.g. stainless steel or Inconel, and solid pellets 54 of strong absorbing material, e.g. hafnium. The pellet 54 is set shorter than the pellet 52 in order to attain a desired value or it may be hollow or annular in order to regulate the volumetric rate of the absorbing material. A space 58 is formed between the pellet 50 and the inner circumferential surface of the cladding tube 36. Since a hybrid type pellets of strong and weak absorbing materials are employed, a reaction value required for zero boron variation load follow-up(ZBCLF) can be attained.
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