A microstructural study of phosphorus segregation and intergranular fracture in neutron irradiated submerged-arc welds

Conference · Tue Dec 31 04:00:00 EST 1996

OSTI ID:524806

Bischler, P J.E. ^[1]; Wild, R K ^[2]

---

1. Nuclear Electric plc, Berkeley (United Kingdom). Berkeley Technology Centre
2. Univ. of Bristol (United Kingdom). Interface Analysis Centre

Accelerated irradiation experiments have been carried out on submerged-arc welds to obtain validation of trend curves built up from surveillance results. This was done by withdrawing surveillance specimens and re-irradiating them in higher flux positions. One batch, from weld HS, showed a significantly higher increase in the Charpy {Delta}T{sub 40J} value than that for weld LS at a similar dose. Work done to explain this difference is described in this paper. Selected Charpy specimens were examined using a shielded scanning electron microscope to determine the fracture modes present. Regions of mixed cleavage, micro-void coalescence (MVC) and intergranular failure (IGF) were found on HS weld specimens fractured in the transition region. The IFG was confined to certain regions within each weld bead. Significantly less IGF was found on LS weld specimens. Sub-fracture surface matchstick specimens were removed from embrittled regions and fractured within a scanning Auger microscope. IGF occurred in these specimens, and phosphorus was found to be the main grain boundary segregant. The levels of phosphorus increased with increasing neutron dose. No other embrittling element was consistently found at any significant level, but carbon was also found on grain boundary surfaces in some cases. The grain boundary coverage of phosphorus was determined for each weld at several neutron dose levels.

• OSTI ID: 524806
• Report Number(s): CONF-940657--
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
EMBRITTLEMENT
FRACTURES
MICROSTRUCTURE
PHOSPHORUS
PHYSICAL RADIATION EFFECTS
PRESSURE VESSELS
SUBMERGED ARC WELDING
WELDED JOINTS