Parametric study of PWR pressure vessel integrity during overcooling accidents, considering both 2-D and 3-D flaws
A continuing analysis of the pressurized water reactor pressurized thermal-shock problem indicates that the previously accepted degree of conservatism in the fracture-mechanics model needs to be more closely evaluated and, if excessive, reduced. One feature that was believed to be conservative was the use of two-dimensional as opposed to finite-length flaws. The degree of conservatism could not be adequately investigated because of computational limitations and a lack of knowledge regarding flaw behavior; however, that situation has changed to the extent that some cases involving finite-length flaws can be studied. A flaw of particular interest is one that is located in an axial weld of a plate-type vessel. For those vessels that suffer relatively high radiation damage in the welds, the length of the flaw will be no greater than the length of the weld, and recent calculations indicate that a deep flaw of that length (approx.2 m) is not effectively infinitely long, contrary to previous thinking. The benefit to be derived from consideration of the 2-m flaw and also a semielliptical flaw with a length-to-depth ratio of 6/1 was investigated by analyzing several postulated transients. In doing so the sensitivity of the benefit to a specified maximum crack-arrest toughness and to the duration of the transient was investigated. Results of the analysis indicate that for some conditions the benefit in using the 2-m flaw is substantial, but it decreases with increasing pressure, and above a certain pressure there may be no benefit, depending on the duration of the transient and the limit on crack-arrest toughness. 22 refs., 11 figs., 3 tabs.
- Research Organization:
- Oak Ridge National Lab., TN (USA)
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 5063073
- Report Number(s):
- NUREG/CR-4325; ORNL/TM-9682; ON: TI85016976
- Country of Publication:
- United States
- Language:
- English
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21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
PRESSURE VESSELS
FRACTURE MECHANICS
PWR TYPE REACTORS
LOSS OF COOLANT
CRACK PROPAGATION
FRACTURE PROPERTIES
MATHEMATICAL MODELS
PHYSICAL RADIATION EFFECTS
REACTOR SAFETY
STRESS INTENSITY FACTORS
THERMAL SHOCK
WELDED JOINTS
ACCIDENTS
CONTAINERS
JOINTS
MECHANICAL PROPERTIES
MECHANICS
RADIATION EFFECTS
REACTOR ACCIDENTS
REACTORS
SAFETY
WATER COOLED REACTORS
WATER MODERATED REACTORS
220900* - Nuclear Reactor Technology- Reactor Safety
210200 - Power Reactors
Nonbreeding
Light-Water Moderated
Nonboiling Water Cooled