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Measurement of TPR distribution in natural Li$$_{2}$$TiO$$_{3}$$/Be assembly with DT neutrons

DT中性子照射による天然Li$$_{2}$$TiO$$_{3}$$/Be体系内のTPR分布測定

近藤 恵太郎; 立部 洋介; 落合 謙太郎; 佐藤 聡; 高倉 耕祐; 大西 世紀; 今野 力  

Kondo, Keitaro; Tatebe, Yosuke; Ochiai, Kentaro; Sato, Satoshi; Takakura, Kosuke; Onishi, Seiki; Konno, Chikara

原子力機構FNS施設で過去に実施したブランケット核特性実験で、以下のような実験と解析の不一致が指摘されている。(1)$$^{6}$$Li濃縮Li$$_{2}$$TiO$$_{3}$$とベリリウムを用いた体系で、SS316製の中性子反射体でDT中性子源を囲むと、トリチウム生成率(TPR)が10%程度過大評価になる。(2)天然Li$$_{2}$$Oペブルをベリリウムで挟んだ体系で、後ろのベリリウム境界付近でTPRが10%程度過大評価になる。これらの問題点をよりはっきり調べるため、本研究では天然Li$$_{2}$$TiO$$_{3}$$とベリリウムを用いた体系を構築し、リチウム層でのTPRを測定して計算値と比較を行った。Li$$_{2}$$CO$$_{3}$$ペレット検出器を用い、リチウム層中でのTPR分布を詳細に測定し、反射体を使用した場合と使用しなかった場合の影響を調べた。その結果、TPRの測定値と計算値は6%の測定誤差の範囲内でよく一致し、過去の実験で見られた反射体による計算の過大評価、及び後ろのベリリウム層との境界付近での計算の過大評価は認められなかった。

In the previous blanket neutronics experiments conducted at the FNS facility of Japan Atomic Energy Agency, the following disagreements between experiments and analyses have been pointed out: (1) In the experiment with a $$^{6}$$Li-enriched Li$$_{2}$$TiO$$_{3}$$ layer and a beryllium layer, approximately 10% overestimation was found for the tritium production rate (TPR) when a neutron reflector composed of SS316 was attached. (2) In the experiment with natural Li$$_{2}$$O pebbles sandwiched by beryllium layers, TPR was overestimated near the rear beryllium layer by up to 10%. In order to confirm the above problems clearly, a new blanket neutronics experiment using a natural Li$$_{2}$$TiO$$_{3}$$ layer and beryllium layers with DT neutrons was conducted at FNS. TPR distributions inside the Li$$_{2}$$TiO$$_{3}$$ layer were measured with Li$$_{2}$$CO$$_{3}$$ pellets with and without the source reflector. The measured TPR well agreed with the calculation within an estimated experimental error of 6% in the both experiments. The influence of the reflector was not remarkable in the present experiment. Contrary to our expectation, no remarkable difference was observed in the TPR distribution around the rear beryllium layer.

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パーセンタイル:49.6

分野:Nuclear Science & Technology

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