Evaluation of a neutron spectrum in the WWER-SM reactor channels

Full text: To provide the well-quality and improved experimental works directly related to the reactor irradiation and to control the effective and stable operation of the reactor it is necessary to monitor continuously the neutron flux energy density distribution into reactor core. The purpose of the given work was determination of the neutrons energy spectrum in the vertical channel of the INP AS RU WWR-SM nuclear reactor. Evaluation of the neutrons spectrum was carried out by means of monitors with appropriate threshold and resonance activation reactions. For evaluation of a fast neutrons spectrum in experimental channels of the reactor the following nuclear reactions were used: Ti 46 (n, p) Sc 46, Mg 24 (n, p) Na 24, Ti 48 (n, p) Sn-tilde 48, Ni 58 (n, p) Co 58, Fe58 (n, p) Mn 54, Ni 60 (n, p) Co 60, Y 60(n, 2n) Y 88. The Ni, Ti, Fe monitors were made of 0.1-mm thick 2 to 10 mg metal foil, and Y and Mg were taken as 5-mg MgO and Y 2O3 chemical compounds. The Co, In, Au foils were used as resonance monitors. Monitors' gamma activity was registered by using the DSA-1000 multichannel analyzer (Canberra Ind., USA) coupled to GC 1518 HPGe detector (relative efficiency - 15 percent and the resolution - 1.7keV for 1173.2 keV of n-tildei-circumflex 60). Genie-2000 software package was used for processing the spectrometer information. For determination of neutron energy spectrum, functions were calculated by means of power polynomials for the every monitor. The function was used for description of neutron flux energy density distribution by means of least squares method. Basing on the experimental data the technique was developed for evaluation of the neutron spectrum in the range from 1 to 12MeV in the experimental channels of the nuclear reactor