29th Symposium on Fusion Technology (SOFT 2016)

P4.072 Validation of 23Na(n,2n) cross section as neutron flux monitor in D-T fusion reactors

8 Sep 2016, 14:20

1h 40m

Foyer 2A (2nd floor), 3A (3rd floor) (Prague Congress Centre)

Board: 72

Poster D. Diagnostics, Data Acquisition and Remote Participation P4 Poster session

Speaker

Evzen Losa (Research Centre Rez)

Description

The intended fusion reaction for ITER project is D + T → ⁴4He (3.5 MeV) + ⁰0n (14.1 MeV), which produces high energy neutrons. Portion of these neutrons is effectively captured in breeder blanket, however, many neutrons leak and can cause radiation damage. Monitoring of the neutron damage in ITER internals is necessary due to the aging management. ²³23Na(n,2n) reaction has been selected among many possible, thank to its sufficiently high threshold (12.96 MeV, in ENDF/B-VII.1), making it sensitive to fusion neutrons and insensitive for scattered neutrons with lower energy. Reference neutron spectrum is crucial point for determination of nuclear parameters in investigated elements. In case of Research Centre Rez, the reference spectrum was generated in special core assembled in LR-0 fission reactor due to very good description and many validations performed. Unlike D-T reaction, fission produces neutron spectrum with mean energy of 2.5 MeV, however still about 0.14 % of neutrons have got energy over 10 MeV. Despite the very high reaction threshold, the integral cross section has been determined to be 0.91 ± 0.02 µb, or 26.6 mb in fission spectrum above 13 MeV. Comparison of the experiment with computer simulation using available nuclear data libraries shows distinctive discrepancies reaching up to 40 % in case of ENDF/B-VII.1. The data from International Reactor Dosimetry and Fusion File show difference -7.7 %. The best agreement yiealds ROSFOND-2010 with -1.9 %. The first step of validation works on ²³23Na has been performed and it can be concluded, the ²³23Na(n,2n)²²22Na is suitable flux monitor for fusion devices. The research works in well described spectrum are necessary step before validation of ²³23Na in Gradel neutron generator, acting as volumetric neutron source, which will be used in next phases of fusion research in RC Rez.