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

Cycle length extension in currently operating PWRs may be economically inte resting if the benefits stemming from capacity factor improvement offset th e higher fuel costs of the longer cycle. A PWR reload core is presented tha t meets current physics and fuel performance design limits for a cycle of 3 3.9 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 burnabl e absorber mixed with UO2. The power is evenly distributed over a broad reg ion of the core by including pins with two different concentrations of gado linia in the assemblies. The core periphery is loaded with reused assemblie s. The rest of the assemblies are discharged after one cycle in the core. T he fuel performance is acceptable, although the parameters analyzed are clo ser to the limits than in a contemporary reference 18-month cycle multibatc h loading strategy. The 36-month core is economically competitive with an 1 8-month reference core under certain operational conditions. Potential redu ctions in fuel enrichment costs would make the 36-month cycle cost competit ive with the 18-month reference cycle under a wide range of conditions. (C) 1999 Elsevier Science Ltd. All rights reserved.