Monte Carlo calculation of gamma spectra inside a hollow lead cylinder / Berechnung von Gammaspektren im Innern eines Hohlzylinders aus Blei mit Hilfe der Monte-Carlo-Methode

Abstract

In a previous work, a simulation study to investigate the enhancement of the fast neutron flux inside a hollow lead cylinder located near the core of a pool type reactor has been carried out. In this complementary work, the calculation of gamma radiation spectra inside the same irradiation device was performed using the MCNP code. Two radiation spectra were considered as input sources: a typical fission gamma spectrum in a nuclear reactor, for the calculation of the socalled fission γ spectrum inside the device; and a fission neutron spectrum, for the calculation of the (n, γ) spectrum. The calculation was made considering two diffusing media adjacent to the reactor core: water and beryllium + water. The lead wall thickness, t, adopted for the hollow lead cylinder ranges from 2 to 10 cm. In order to compare the results with and without the irradiation device, reference cases (t = 0) have also been considered. The values of the attenuation factors F att (fission γ fluence) and F att [(n, γ) fluence] are presented. These results, together with those from the previous work, allow an optimisation of the irradiation conditions in order to maximise the absorbed dose due to fast neutrons.