Materials management strategies for pressurized water reactors (PWRs) - Materials' Ageing and Degradation in Light Water Reactors - page 254

Table 7.2 Materials ageing management for PWR

RPV components Ageing

mechanisms

Management
categories

Management techniques Description of techniques

Beltline region welds Radiation

embrittlement;
fatigue

Mitigation Thermal stress reduction Change operating procedures so as to create

off-normal sequences; change of plant system
(e.g. installing monitoring instrumentation)

Neutron fl ux reduction Low leakage loading pattern (Moylan et al . 1987)

Thermal
annealing

Annealing below 343°C (650°F) (Wet anneal) or
at 430°C (806°F) (Dry anneal) per ASTM E509
(ASTM 1988c)

Inspection and
Surveillance

Ultrasonic examination Per ASME Section XI code requirements

Acoustic emission Per ASME Section XI code requirements

Surveillance programme Surveillance capsule of base metal, weld metal

and HAZ metal hung between thermal shield
and RPV inner wall

Repair Repair of beltline welds

by temper bead
technique

Automated gas tungsten arc welding process
having temper bead effect with no grinding of
fi rst layer of the welds

Inlet-outlet nozzles Fatigue Mitigation Reduction of cyclic stress Change operating procedures so as to create

off-normal sequences

CRDM,
instrumentation
nozzles

IGSCC, fatigue,
boric acid
corrosion

Mitigation Reduction of cyclic stress

and residual stress

Change operating procedures so as to create
off-normal sequences

Material change Use of corrosion-resistant materials (Alloy 690)

Improvement of water
chemistry

Optimized hydrogen, temperature reduction
operation

Flange closure studs Fatigue, boric acid

corrosion

Inspection and
surveillance

UT inspection, replacement Per ASME Section XI code requirements

The references are from Morgan W.C & Livingston J.V. (1995) except for noted.