Monte Carlo calculation of gamma spectra inside a hollow lead cylinder

In a previous work, a simulation study to investigate the enhancement of th e 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 c alculation of gamma radiation spectra inside the same irradiation device wa s performed using the MCNP code. Two radiation spectra were considered as i nput sources: a typical fission gamma spectrum in a nuclear reactor for the calculation of the so-called fission gamma spectrum inside the device; and a fission neutron spectrum, for the calculation of the (n, gamma) spectrum . The calculation was made considering two diffusing media adjacent to the reactor core: water and beryllium + water. The lend wall thickness, t, adop ted for the hollow lend cylinder ranges from 2 to 10 cm. In order to compar e 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 gamma fluence) and F-att [(n, gamma) fluence] are presented These r esults, together with those from the previous work, allow an optimisation o f the irradiation conditions in order to maximise the absorbed dose due to fast neutrons.