BN及びBFS炉心解析システムの整備(2)

Development of a code system for the BN and BFS reactor analysis (II); Development of a three-dimensional Hex-Z Geometry transport code system for reactor core analysis

船曳 淳*; 角田 弘和*

not registered; not registered

BN及びBFS炉心体系を正確にモデル化することのできる3次元Hex-Z体系用解析コードの汎用性を向上させ、高精度な核特性解析を実現するために以下の整備を行った。 NSHEX用3次元Hex-Z体系用輸送摂動計算コードのノード内中性子束再構築法を改良した。併せて、ノード内中性子束再構築法を用いて得られる中性子束分布を基に、ピーキング係数、最大線出力等の設計パラメータを計算するための機能を3次元Hex-Z体系用輸送ノード法計算コードNSHEX-BURNに追加した。 3次元Hex-Z体系用有限差分法輸送計算コードMINIHEXを実用レベルに改良するため、キャッシュチューニング等のプログラム構造の改良、加速法の適用、並列計算版の整備を実施した。プログラム構造の改良及び中性子束外挿法の適用によって約3.8倍の速度向上を得た。 さらに並列化を実施することにより共有メモリ型並列計算機GP7000上で約5.3倍(9PE使用)、EWSクラスタ上で1.5倍(4PE使用)の速度向上が得られた。また、並列計算機を整備したことにより、MINIHEXとのインターフェイス機能を追加整備した。 これにより、MINIHEXで計算した中性子束を用いた反応率計算が可能となった。MINIHEX用の3次元輸送摂動計算コードSNPERT-HEXZをベースにMINIHEX用3次元摂動計算コードを整備した。これにより、MINIHEXで計算した中性子束及び固有値を用いた摂動計算が可能となった。

The following codes were developed to enhance the applicability of the three-dimensional Hex-Z geometry codes that can model the BN and BFS reactor core accurately. The neutron flux reconstruction method in the three-dimensional transport-based perturbation code SNPERT-HEXZ was modified to improve the calculation accuracy. New functions to calculate design parameters, such as peaking coefficients, maximum linear power etc., based on the reconstructed neutron flux were added to the three dimensional Hex-Z geometry transport burn-up code NSHEX-BURN. The three-dimensional Hex-Z finite difference transport code MINIHEX was modified to improve the computational performance. First, cash-tuning and a flux extrapolation method were applied to MINIHEX. This modification reduced the computational time by a factor of 3.8 at most. Second, the modified MINIHEX was parallelized with MPI by an angular space decomposition method. A series of performance check calculations was performed on GP7000 and DEC/alpha EWS cluster. Speed-up obtained on GP7000 was at most 5.3 for 9 PE and that on DEC/alpha cluster was at most 1.5 for 4 PE. The parallelization of MINIHEX also enhanced the applicability of the code to larger scale computational problems and more detailed reactor core modeling. An interface to MINIHEX was added to the three-dimensional Hex-Z geometry reaction rate calculation code LAGOON-HEXZ. The added interface enables the code to calculate reaction rates using neutron flux obtained by MINIHEX. A three-dimensional transport-based perturbation code for MINIHEX was developed based on the three-dimensional tansport-based perturbation code NSHEX-HEXZ. This code makes it possible to evaluate reactivity cbange from the neutron flux and eigenvalue obtained by MINIHEX.