Computational methods for global decay heat calculation in nuclear reactors

When exposed to neutron flux, materials are subject to nuclear reactions that generate radioactive nuclides (e.g., fission or neutron activation). Their decay releases also thermal energy (decay heat). Decay heat calculations in nuclear reactors are computed by coupled neutronic-inventory spatially finite-differences models. Specific decay heat is a result of the calculation. The global decay heat in a component is then calculated adding the values of specific decay heat in each zone, multiplied for the volume of that zone. The paper illustrates an alternative method for computing global decay heat, with application to tokamak fusion reactors, starting from discrete values of specific decay heat. The paper compares the proposed method with more traditional approaches. Application to the calculation of decay heat induced in the ITER blanket is shown. Finally, a comparison of global decay heat in a tokamak power reactor and in a PWR of the same power is carried out.