Notch Ductility and Fracture Toughness Degradation of Pressure Vessel Steel Reference Plates from Pool Side Facility (PSF) Irradiation Capsules

Abstract

The Light Water Reactor-Pressure Vessel Surveillance Dosimetry Improvement Program of the Nuclear Regulatory Commission (NRC) has irradiated, in a pressure vessel wall/thermal shield mock up facility, mechanical test specimens of the ASTM A302-B correlation monitor reference plate and the A533-B Plate 03 from the Heavy Section Steel Technology Program. This report presents Charpy-V, compact tension, and tension test results from simultaneous irradiations in simulated surveillance capsule and through-vessel-wall locations. The investigation is part of a broad NRC effort developing key neutron physics-dosimetry-metallurgy correlations for use in making highly accurate projections of radiation-induced embrittlement to reactor vessels. Irradiation in the surveillance capsule location was found to reproduce reasonably well the irradiation effect to the vessel inner surface and quarter thickness positions. The toughness gradient observed between in-wall locations after irradiation was small for both materials; the difference between transition temperatures for wall surface versus mid-thickness locations was 31°C or less, independent of the test method used. The adjustment of the ASME lower bound, that is, dynamic, KIR toughness curve by the radiation-induced elevation of the Charpy-V 41-J or the compact specimen 100 MPa√m temperature was conservative when compared against static toughness data. The elevation of the Charpy-V (Cv) curve (41-J index) by irradiation frequently did not provide a conservative estimate of the temperature elevation defined by fracture toughness tests (100 MPa√m index); on the other hand, correction of the fracture toughness data for the lack of test specimen constraint (βIc correction) did result in a transition temperature elevation less than the 41-J elevation, in most cases.

Influence of manganese on mechanical properties, irradiation susceptibility and microstructure of ferritic steels, alloys and welds

“…Figure 18, from data reviewed by Odette and Lucas,62 shows high embrittlement and hardening in PWR welds with 0·1–1·7%Ni in accelerated irradiations at ∼290°C to 1·0–10×10 23 n m −2 ( E >1 MeV) (15–150 mdpa) (original data of Leitz et al 63 and Pachur and Sievers64). Hawthorne et al 65 and Odette and Lucas9 have also reported large increases in embrittlement and hardening with increasing Ni. There is little evidence on the role of Mn, but it is clear that enhanced irradiation sensitivity in high Ni materials occurs with Mn within the manufacturing specification range (i.e.…”

Radiation embrittlement in the pressure-vessel steels of nuclear power plants

“…They also found that the upper-shelfKJc fracture toughness is essentially insensitive to radiation for current practice low-copper welds. For these same materials, McGowan and Nanstad 44 reported that the radiation-induced shifts in ductile-tobrittle transition temperature are similar, whether estimated from Charpy V-notch impact tests at the 41 J level" ~T(C), or from KJc at the 90 MPa·m Y level, ~T(KJc)' On the other hand, for a wider array of materials, Hiser4 5 and Hawthorne et al46 reported ~T(C) < ~T(KJc) by about 22°C for base plate and ~T(KJc) < ~T(Cv) by about 5°C, for welds, where ~T(C) is keyed, as bef~re, to the 41 J level, and ~T(KJc) is keyed to the lOO MPa·m Y level. When a "PIc correction" is applied to K Jc ' as200 ....---,....-------:--,---..Temperature (,e)…”