Measurement of Cross Section for the 103Rh(n, n')103mRh Reaction and Its Application to Fast Neutron Flux Measurements

概要

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Making use of monoenergetic neutrons produced by a 2 MeV Van de Graaff accelerator, the cross section for the 103Rh(n, n')103mRh reaction was measured in the energy range from 180 keV to 4.6 MeV. To obtain the relative activity of Rh, the 2103m0keV X-rays emitted by the nuclide were measured with a thin NaI(Tl) scintillator with Be window. For absolute measurement, a standard 103Ru source was made from ruthenium trichloride irradiated with thermal neutrons. The self-shielding effect to the 20 keV X-rays was eliminated by the realization of a thin layer of Ru obtained by electrodeposition. The fission-spectrum-averaged cross section for this reaction determined by the present method is 558±32 mb, and the effective cross section 960±55mb. The reaction was applied to the measurement of the fast neutron flux in the experimental facilities of the Kyoto University Reactor. The present report also gives a discussion on the ad-vantage of using the 103Rh(n, n')103mRh reaction as fast neutron radiation damage monitor.