A helium accumulation fluence monitor (HAFM) has been developed at the Japan Nuclear Cycle Development Institute's experimental fast reactor JOYO. This monitor provides high-precision neutron dosimetry and direct measurements of helium production in the fast reactor structural component materials. The measurement accuracy of neutron fluence by the HAFM has been evaluated.
Calibration tests using helium ion implanted samples showed that the HAFM measurement system can measure helium atoms with an uncertainty of about 5%. The HAFMs were irradiated in the standard neutron spectrum field of the fast neutron source reactor YAYOI at the University of Tokyo. The HAFM measurement system measured neutron fluence of typical fast reactor spectrum fields and low energy neutron fields with an uncertainty of about 7%.
The last stage of this study confirmed the applicability of HAFM to fast reactors. In these tests at JOYO, enriched boron-type HAFMs were irradiated and the neutron fluence was measured. The results obtained are in good agreement with those from the existing foil activation method within the experimental uncertainty and verified the reliability of the HAFM.
As a result of this study, it was confirmed that the HAFM could be applicable for fast reactor dosimetry.
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