Thorium-based spent fuel characteristic parameters evolution after irradiation in candu reactors

Abstract EN

The paper investigate Thorium-based mixed oxides fuels behaviour after the irradiation in CANDU reactors by estimation of the spent fuel characteristic parameters (radioactivity, thermal power and gamma energy) evolution with fuel burnup.

Th-based fuel studies interest is related on the further investigation and evaluation of CANDU reactor capabilities to assure a better utilization of fuel resources under proliferation resistance requirements.

The analyses have been performed by considering a cylindrical fuel bundle with 43 fuel elements disposed in an annular geometry, CANDU type fuel bundle with 43 fuel elements developed by INR Pitesti Fuel Performances group.

The fuel bundle elements contain a fuel composition based on mixed oxides of Th/U.

A set of 36 (Th, U)O2 fuel combinations have been analysed, taking into consideration modifications in the fuel pellet density, ratio of U/Th content and enrichment in U235, respectively.

CANDU reactor specific conditions of irradiation have been simulated, considering the burn-up specific power 50 kW/kgHE; the End of Irradiation burn-up was 20 MWd/kg HE (Heavy Element).

The fuel burn-up was simulated using ORIGEN-S code, included in SCALE6 programs package, developed by Oak Ridge National Laboratory.

The spectral neutron cross-sections weighting factors (used as input data for fuel burn-up simulation in CANDU reactor) were given by previous DRAGON3.05E code lattice cell calculations.

The key parameters for the analyses were: radioactivity, thermal power and gamma energy.

The interest parameters evolution during fuel burn-up was analysed and the estimated values evolution with the fuel burnup and at EoI (moment of the spent fuel discharge from the reactor core) have been presented comparatively, emphasizing on the actinides and fission products contribution to the total value of the interest parameter.