Secondary intermediate-energy standard neutron field at the MOL-ΣΣ facility

The value and usefulness of the concept of the intermediate-energy standard neutron field has been recognized by a number of international experts including the European-American Committee for Reactor Physics and Euratom Working Group on Reactor Dosimetry. In 1969, the MOL-∑∑ facility was proposed and in the early Spring of 1970 was put into operation. It was selected as one of the five benchmarks for a place to test the ENDF/B Dosimetry File as well as one of the IAEA benchmarks for validation of nuclear data for reactor neutron dosimetry. ∑∑ is a thermal fast-coupled spherical source assembly located within a conventional graphite thermal column. Geometrical data and major radiation field parameters are well defined. The MOL-∑∑ secondary intermediate-energy standard neutron field has met all the requirements to make it suitable for high-accuracy interlaboratory comparisons and standardizations of the major techniques applied in zero-power fast assemblies and in fuels dosimetry. ∑∑ central reaction rates and ratios have been measured and compared to theoretical predictions.