UO2 - Zr chemical interaction of PHWR fuel pins under high temperature

At high temperature Zircaloy clad interacts with the UO2 fuel as well as with the steam to produce oxide layer of a-Zr(O) and ZrO2. This layer formation significantly reduces the structural strength of the clad. A computer code SFDCPA/MOD1 has been developed to simulate the interaction and predict the oxide layer thickness for any accidental transient condition. It is well validated with published experimental data on the isothermal and transient temperature condition. The program is applied to Indian Pressurized Heavy Water Reactor (PHWR) fuel pin under certain severe transient condition where it experiences temperature above 1000 C. The study gives an idea of the un-oxidized thickness of Zircaloy, which is an important criterion for fuel integrity. (author)