Verification of tritium production evaluation procedure using Monte Carlo code MCNP for in-pile test of fusion blanket with JMTR

To evaluate exactly the total amount of tritium production in tritium breeding materials during in-pile test with JMTR, the ‘tritium monitor’ has been produced and evaluation of total tritium generation was done by using ‘tritium monitor’ in preliminary in-pile mock-up, and verification of procedure concerning tritium production evaluation was conducted by using Monte Carlo code MCNP and nuclear cross section library of FSXLIBJ3R2. LiAl alloy (Li 3.4 wt.%, 95.5% enrichment of 6Li) was selected as tritium monitor material for the evaluation on the total amount of tritium production in high 6Li enriched materials. From the results of preliminary experiment, calculated amounts of total tritium production at each ‘tritium monitor’, which was installed in the preliminary in-pile mock-up, were about 50–290% higher than the measured values. Concerning tritium measurement, increase of measurement error in tritium leak form measuring system to measure small amount of tritium (0.2–0.7 mCi in tritium monitor) was found in the results of present experiment. The tendency for overestimation of calculated thermal neutron flux in the range of 1–6×1013 n cm−2 per s was found in JMTR and the reason may be due to the beryllium cross section data base in JENDL3.2.