Full Core Analysis for SSSR; First Step to Apply SRAC to VVER Type Reactors; Study on optimal burnable poison loading in PBMR-400 Early Research Achievements

An optimal loading principle of burnable poisons (BPs) is proposed to eliminate the problem of an excessively high power peaking factor in once-through-then-out (OTTO) PBMR-400 cores. The effectiveness of the principle is confirmed through neutronic calculations for an PBMR core with thermal power of 400MWt. Spherical BP particles are distributed uniformly together with TRISO-coated fuel particle inside the free fuel zones of fuel pebbles to maintain constant k_∞ during burnup. The applicability of BP materials, such as B₄C, Gd₂O₃ is investigated. The complete BP depletion is demonstrated by a burning fraction at the target burnup. The power density is excessively high at the core top and the power peaking factor is 4.44 when no BP is added to the fuel pebbles. Optimal BP loading reduces the power peaking factor from 4.44 to about 1.7.

Besides, in this seminar the detailed results of the benchmark investigating the physics of a whole VVER-1000 reactor core types such as the first step approaching VVER-1000 reactor core types. It is also the first step for the computer code certification process and to the verification of calculation methods used in the Centre for Nuclear Power.

Hoang Van Khanh - INST