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NUREG 0933
Displaying 1 - 25 of 110
The objective of this task was to demonstrate by testing and analysis that the relief and safety valves, block valves, and associated piping in the reactor coolant system (RCS) were qualified for the full range of operating and accident conditions; …
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The objectives of this task were to: (1) decrease reliance on the emergency core cooling system (ECCS) for events other than LOCAs; (2) ensure that the ECCS design basis reliability and performance were consistent with operational experience; (3) reach a …
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The objective of this task was to evaluate whether existing requirements for valve testing provided adequate assurance of performance under design conditions. ITEM II.E.6.1: TEST ADEQUACY STUDY DESCRIPTION Historical Background The purpose of this TMI …
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The objective of this task was to increase the reliability and diversification of the electrical power supplies for certain safety-related equipment. ITEM II.G.1: POWER SUPPLIES FOR PRESSURIZER RELIEF VALVES, BLOCK VALVES, AND LEVEL INDICATORS DESCRIPTION …
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The objectives of this task were to perform systems reliability analyses and to effect changes in emergency operating procedures and operator training to improve the capability of plants to mitigate the consequences of the small-break LOCAs and …
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DESCRIPTION The issue was raised after the occurrence of various incidents of water hammer that involved steam generator feedrings and piping, emergency core cooling systems, RHR systems, containment spray, service water, feedwater, and steam lines. The …
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DESCRIPTION Because of the remote possibility of failure of nuclear reactor pressure vessels designed to the ASME Boiler and Pressure Vessel Code, the design of nuclear facilities does not provide protection against reactor vessel failure. Prevention of …
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DESCRIPTION Historical Background Prior to May 1978, tests conducted by GE showed that the presence of steam and/or increased pressure in and above the upper core region of BWRs could adversely affect the distribution of flow from certain types of core …
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DESCRIPTION Pipe cracking has occurred in the heat-affected zones of welds in primary system piping in BWRs since mid-1960. These cracks have occurred mainly in Type 304 stainless steel which is the type used in most operating BWRs. The major problem is …
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DESCRIPTION Historical Background This issue deals with a concern for the availability of adequate recirculation cooling water following a LOCA when long-term recirculation of cooling water from the PWR containment sump, or the BWR RHR system suction …
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DESCRIPTION Numerical reliability goals and methods of analysis have not been established by the NRC. The current basis for plant licensing continues to be NRC regulations which require, among other things, that the consequences of a LOCA be suitably …
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DESCRIPTION Historical Background This NUREG-0471 [1] item concerned staff positions [2] BTP EISCB 18 and BTP RSB 6-11 which required physical locking out of electrical sources to specific MOVs in the ECCS. The existing staff positions established the …
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DESCRIPTION Historical Background SRP [1] Section 3.6, issued in 1975, addressed pipe breaks outside containment by combining limited design basis breaks for mechanistic protection with unlimited breaks for non-mechanistic protection. Prior to this, …
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DESCRIPTION A number of applicants for operating licenses have been performing sump tests to demonstrate ECCS operability during the recirculation phase following a postulated loss-of-coolant accident. These tests have shown that vortex formation is not …
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DESCRIPTION Most vendors, in the conduct of internal audits of emergency core cooling performance computer codes, discovered errors in coding and/or logic which had significant effects on the prediction results of approved models. This NUREG-0471 [1] task …
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DESCRIPTION Applicants are required to provide confirmation of the adequacy of computer programs used in the structural analysis and design of piping systems and components. At the time this issue was identified, this consisted of applicants providing, …
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DESCRIPTION Surface cracks have been discovered in control rod drive internal parts at some operating BWR plants. Although only observed to be localized in nature, this cracking, if propagated, could potentially affect the capability of the control rod …
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DESCRIPTION GDC-53, "Provisions for Containment Testing and Inspection," requires in part that the reactor containment be designed to permit: (1) periodic inspection of all important areas, and (2) an appropriate surveillance program. 10 CFR 50, Appendix …
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DESCRIPTION The BWR pressure relief system is designed to prevent overpressurization of the reactor coolant pressure boundary (RCPB) under the most severe abnormal operational transient: closure of the main steam line isolation valves (MSIVs) with failure …
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DESCRIPTION Historical Background This issue was identified in NUREG-0471 [1] and addressed the establishment of surveillance test intervals and allowable equipment outage periods, using analytically-based TS criteria and methods. At the time the issue …
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DESCRIPTION Historical Background This NUREG-0471 [1] item, as presently formulated, involves the conduct of analytical and experimental work to determine whether or not destructive overspeeds could be attained and to determine if corrective actions are …
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DESCRIPTION Following a plant transient or accident, provisions are required for long-term decay heat removal. Redundancy of components is required as necessary to assure that a failure in the RHR system will not impair the ability to maintain the plant …
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DESCRIPTION Offsite power system frequency decay, depending on the rate of decay, could provide an electrical brake on the reactor coolant pump motors that could slow the pumps faster than the assumed flywheel coastdown flow rates normally used in …
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DESCRIPTION Historical Background As identified in NUREG-0471, [1] Appendix K of 10 CFR 50 specifies the requirements for LWR ECCS analysis. These requirements call for specific conservatisms to be applied to certain models and correlations used in the …
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DESCRIPTION Combinations of fabrication, stress, and environmental conditions have resulted in isolated instances of stress corrosion cracking of low pressure Schedule 10 Type 304 stainless steel piping systems. Although these systems are not part of a …
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