Investigations of low-temperature neutron embrittlement of ferritic steels

Conference · Thu Dec 31 00:00:00 EST 1992

OSTI ID:10162568

Farrell, K; Mahmood, S T; Stoller, R E; Mansur, L K

Investigations were made into reasons for accelerated embrittlement of surveillance specimens of ferritic steels irradiated at 50C at the High Flux Isotope Reactor (HFIR) pressure vessel. Major suspects for the precocious embrittlement were a highly thermalized neutron spectrum,a low displacement rate, and the impurities boron and copper. None of these were found guilty. A dosimetry measurement shows that the spectrum at a major surveillance site is not thermalized. A new model of matrix hardening due to point defect clusters indicates little effect of displacement rate at low irradiation temperature. Boron levels are measured at 1 wt ppM or less, inadequate for embrittlement. Copper at 0.3 wt % and nickel at 0.7 wt % are shown to promote radiation strengthening in iron binary alloys irradiated at 50 to 60C, but no dependence on copper and nickel was found in steels with 0.05 to 0.22% Cu and 0.07 to 3.3% Ni. It is argued that copper impurity is not responsible for the accelerated embrittlement of the HFIR surveillance specimens. The dosimetry experiment has revealed the possibility that the fast fluence for the surveillance specimens may be underestimated because the stainless steel monitors in the surveillance packages do not record an unexpected component of neutrons in the spectrum at energies just below their measurement thresholds of 2 to 3 MeV.

• Research Organization: Oak Ridge National Lab., TN (United States)
• Sponsoring Organization: Nuclear Regulatory Commission, Washington, DC (United States)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 10162568
• Report Number(s): CONF-921007-32; ON: DE93015460; TRN: 93:015439
• Resource Relation: Conference: 20. water reactor safety information meeting,Bethesda, MD (United States),21-23 Oct 1992; Other Information: PBD: [1992]
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
22 GENERAL STUDIES OF NUCLEAR REACTORS
HFIR REACTOR
PRESSURE VESSELS
FERRITIC STEELS
PHYSICAL RADIATION EFFECTS
SURVEILLANCE
EMBRITTLEMENT
COPPER ADDITIONS
BORON ADDITIONS
NICKEL ADDITIONS
FAST NEUTRONS
360106
360103
220600
RADIATION EFFECTS
MECHANICAL PROPERTIES
RESEARCH
TEST
TRAINING
PRODUCTION
IRRADIATION
MATERIALS TESTING REACTORS