PWR pressure vessel integrity during overcooling accidents

Conference · Thu Jan 01 04:00:00 EST 1981

OSTI ID:5869170

Cheverton, R D

Pressurized water reactors are susceptible to certain types of hypothetical accidents that under some circumstances, including operation of the reactor beyond a critical time in its life, could result in failure of the pressure vessel as a result of propagation of crack-like defects in the vessel wall. The accidents of concern are those that result in thermal shock to the vessel while the vessel is subjected to internal pressure. Such accidents, referred to as pressurized thermal shock or overcooling accidents (OCA), include a steamline break, small-break LOCA, turbine trip followed by stuck-open bypass valves, the 1978 Rancho Seco and the TMI accidents and many other postulated and actual accidents. The source of cold water for the thermal shock is either emergency core coolant or the normal primary-system coolant. ORNL performed fracture-mechanics calculations for a steamline break in 1978 and for a turbine-trip case in 1980 and concluded on the basis of the results that many more such calculations would be required. To meet the expected demand in a realistic way a computer code, OCA-I, was developed that accepts primary-system temperature and pressure transients as input and then performs one-dimensional thermal and stress analyses for the wall and a corresponding fracture-mechanics analysis for a long axial flaw. The code is briefly described, and its use in both generic and specific plant analyses is discussed.

• Research Organization: Oak Ridge National Lab., TN (USA)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 5869170
• Report Number(s): CONF-811042-10; ON: TI85004515
• Country of Publication: United States
• Language: English

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ACCIDENTS
COMPUTER CODES
CONTAINERS
COOLING SYSTEMS
CRACK PROPAGATION
CRACKS
ECCS
ENERGY SYSTEMS
ENGINEERED SAFETY SYSTEMS
FRACTURE MECHANICS
LOSS OF COOLANT
MECHANICS
PRESSURE VESSELS
PRIMARY COOLANT CIRCUITS
PWR TYPE REACTORS
REACTOR ACCIDENTS
REACTOR COMPONENTS
REACTOR COOLING SYSTEMS
REACTOR PROTECTION SYSTEMS
REACTOR SAFETY
REACTORS
RELIABILITY
SAFETY
STRESS ANALYSIS
STRESSES
THERMAL SHOCK
THERMAL STRESSES
WATER COOLED REACTORS
WATER MODERATED REACTORS