Estimation of heat sources in nuclear reactors

Abstract

Knowledge of local heating rates is needed for estimation of operating temperatures, thermal stresses, and cooling requirements in nuclear reactor components. Heat is liberated by the dissipation of the energy of fission fragments, beta particles, fast neutrons, and gamma photons. Heating rates are formulated in terms of either neutron or gamma flux densities, the corresponding collision probabilities, and appropriate energy transfer coeficients, the forms of which are given. Special methods of estimating the flux densities are discussed. The data on the magnitudes of the various energy sources are reviewed.The designer of nuclear reactors needs to know the local rates of heat liberation in the various reactor components in order to estimate temperatures, cooling requirements, thermal stresses, corrosion rates, radiationdamage annealing rates, and temperature-dependent reactivity changes. The heat-liberation rates can be formulated in terms of the local neutron and gamma fluxes, +, , and 9, . Admittedly, isotope N'. The nucleus is "knocked on," Vol. 2, No. 2 A.1.Ch.E. Journal Page 177 Jo(2.405plR) cos ( r~/ 2 R ) 3.87 cos ( r z / A ) cos ( * y / A ) cos ( r z / A )