Neutron irradiation embrittlement of reactor pressure-vessel steels

The growing application of nuclear power has introduced the problem of materials changed by exposure to high - energy nuclear radiation The steels which make up the primary containment vessels of nuclear reactors may undergo progressive embrittlement with neutron bombardment. Embrittlement is relative and may be small or large; it is important in either case because of the major function served by the vessel and the economic implications of overly conservative design and operating practice as a result of uncertainties. This report reviews the available literature results on the subject so as to highlight their engineering importance. Emphasis is placed upon the role of neutron radiation towards enhancement of brittle fracture of conventional and potential pressure-vessel steels. For perspective, the theoretical considerations involved, the current and projected growth of power reactors which utilize steel containment vessels and the practical aspects of defining the damaging potential of the nuclear environment are reviewed in the first three sections as background to the steel embrittlement data. The embrittlement data are reviewed to demonstrate the specific effects of several environmental and materials factors with emphasis upon those appropriate to light-water reactor service. The implications of large variations in embrittlement are highlighted to indicate the potential for minimizing steel embrittlement. Data for experimental studies and from reactor-vessel surveillance programs are correlated with emphasis upon understanding the role of different nuclear environments. The final section reviews recent developments which suggest several alternatives for correcting embrittlement or minimizing its effects in can't reactors and possibly for avoiding it in future reactors. It is impossible to cover all aspects of radiation embrittlement of all reactor-vessel steels. Accordingly throughout the review, those aspects considered most important to the ultimate engineering use of the results are emphasized and supported by examples from experimental data. (author)