Zirconium Alloys for Fuel Element Structures

Abstract

Today more than 400 light water power reactors (LWRs) operate worldwide providing approximately 17% of the world's electricity demand. One important component for their successful operation is the fuel tube, made out of a zirconium alloy. A huge number of out-of-pile and in-pile experiments have been performed to improve step by step the fuel for higher burn-up and to reduce the failure rates of fuel pins close to zero. The influencing parameters for excellent or poor cladding behaviour are numerous and sometimes counteract each other. The process of cladding corrosion is slow, difficult to follow, the mechanistic understanding at best incomplete. A vast amount of literature documents the abundant tests and comes up with hypotheses and models for the materials behaviour. PSI has supported for the past 20 years the development of high burn-up fuel cladding by microstructural research studies and service work in post-irradiation examination of test pins. This article reviews the development of the cladding tubes, focussing on the chemical and materials science aspects.

Review of the Licensing Basis for RIA and LOCA Transients in Light of New Evidence on High Burnup Fuel Behavior

“…The current licensing rules rely on experiments mainly derived from fuel with limited burnup, yet the burnup of both PWR and BWR cores has been increased for economic reasons and accordingly new cladding materials, less susceptible to oxidation, have been developed and are successfully used ( [12]). In addition, the 239 Pu produced at the fuel pin periphery due to the accumulated neutron capture in 238 U yields peripheral peaking of the radial power profile.…”

Nuclear Reactors: Physics and Materials

“…The ZrO 2 forms a thin film on the exposed surface of the cladding, while some of the hydrogen is picked up and remains in the cladding. These effects can clearly be influenced by the chemistry of the coolant [13].…”