An economically optimum PWR reload core for a 36-month cycle

Cycle length extension in currently operating PWRs may be economically interesting if the benefits stemming from capacity factor improvement offset the higher fuel costs of the longer cycle. A PWR reload core is presented that meets current physics and fuel performance design limits for a cycle of 33.9 EFPM or 36 calendar months when operating at a capacity factor of 94.1%. Fuel is enriched to 6.5% U-235 and selected pins use gadolinia as burnable absorber mixed with UO₂. The power is evenly distributed over a broad region of the core by including pins with two different concentrations of gadolinia in the assemblies. The core periphery is loaded with reused assemblies. The rest of the assemblies are discharged after one cycle in the core. The fuel performance is acceptable, although the parameters analyzed are closer to the limits than in a contemporary reference 18-month cycle multibatch loading strategy. The 36-month core is economically competitive with an 18-month reference core under certain operational conditions. Potential reductions in fuel enrichment costs would make the 36-month cycle cost competitive with the 18-month reference cycle under a wide range of conditions.