Measurement of very high threshold reactions using 252Cf source

Abstract

Only neutron spectrum standard is ²⁵²Cf spontaneous fission neutron spectrum. However, the high energy tail of this spectrum is loaded with high uncertainty. To reduce this uncertainty, it is crucial to use validated cross sections with low uncertainty. The explored set of reactions covers ⁵⁸Ni(n,X)⁵⁷Co, ¹⁶⁹Tm(n,3n)¹⁶⁷Tm, ¹⁹⁷Au(n,3n)¹⁹⁵Au, ²⁰⁹Bi(n,3n)²⁰⁷Bi and ²⁰⁹Bi(n,4n)²⁰⁶Bi threshold reactions. Measurement of dosimetric ¹⁶⁹Tm(n,3n)¹⁶⁷Tm, ²⁰⁹Bi(n,3n)²⁰⁷Bi and ²⁰⁹Bi(n,4n)²⁰⁶Bi reactions spectral averaged cross sections (SACS) is included in NEA's High Priority Nuclear Data Request List. All these reactions SACS were measured for the first time. All SACS were derived from experimentally determined reaction rates by gamma spectrometry using the same high-purity germanium detector. In the case of ¹⁶⁹Tm(n,3n)¹⁶⁷Tm reaction, the difference between experimental and calculated value using the IRDFF-II library is only 1.45%. Concerning ¹⁹⁷Au(n,3n)¹⁹⁵Au reaction, the reasonable agreement is achieved only using the TENDL-2017 library. In the case of ²⁰⁹Bi(n,3n)²⁰⁷Bi reaction, agreement within uncertainty is not achieved with any library unlike ²⁰⁹Bi(n,4n)²⁰⁶Bi reaction where the agreement within uncertainty is achieved with IRDFF-II library. The best agreement for ⁵⁸Ni(n,X)⁵⁷Co reaction is achieved using ENDF/B-VIII library.

Keywords: (252)Cf; (n,3n) reactions; Spectral averaged cross sections.