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NUREG 0933
Displaying 1 - 25 of 58
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 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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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 Historical Background Operation of a LWR results in slow corrosion of the interior metal surfaces of the primary coolant system. The resulting corrosion products circulate through the reactor core and are activated by neutron flux from the …
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DESCRIPTION Historical Background This NUREG-0371 [1] item involves the development of consistent and formalized acceptance criteria regarding the conversion to higher density storage racks (increased storage capacity) in existing spent fuel storage …
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DESCRIPTION At all nuclear plants, overhead cranes are used to lift heavy objects in the vicinity of spent fuel. If a heavy object such as a spent fuel shipping cask or shielding block were to fall onto spent fuel in the storage pool or reactor core …
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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 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 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 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 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 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 The operating experience of nuclear power plants indicates that a number of valves, valve operators, and pumps fail to operate as specified in the technical specifications either under testing conditions or when they are …
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DESCRIPTION Background Flow-induced vibrations caused by vortex shedding resulting from rapid area change, buffeting due to random flow turbulence, fluid structures interaction instability, leakage excitation, steady operation of positive displacement …
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DESCRIPTION This issue involves a potential deficiency in the ability to control leakage past the main steam isolation valves (MSIV) in BWR plants. Requirements for MSIV leakage control systems outlined in Regulatory Guide 1.96 [1] were developed as a …
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DESCRIPTION Background This issue addressed the high rate of reactor coolant pump (RCP) seal failures that challenge the makeup capacity of the ECCS in PWRs. At the time this issue was identified [1] in 1980, RCP seal failures in BWRs occurred at a …
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DESCRIPTION Historical Background This issue was identified [1] when AEOD expressed concerns about the use inside containment of a particular polymer coating that could flake off and fail when subjected to DBA conditions. In addition to the concern for …
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DESCRIPTION Historical Background This issue was initiated in response to an immediate action memorandum [1] issued by AEOD in September 1981 regarding desiccant contamination of instrument air lines. NRR responded to the AEOD memorandum by establishing a …
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DESCRIPTION Historical Background In December 1981, AEOD completed a survey of valve operator-related events that occurred during 1978, 1979, and 1980 and submitted a draft report [1] to NRR for comment. In this study, AEOD established that motor- …
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DESCRIPTION Historical Background This issue was identified at an NRC Operating Reactor Events meeting on January 7, 1982, [1] and addressed fire protection system (FPS) actuations that resulted in adverse interactions with safety-related equipment at …
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DESCRIPTION Historical Background Increasing attention has recently been focused on the integrity of RCP seals due to loss of cooling to the seals both in connection with PRA studies which are currently under review and from operating experience. [1] , …
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DESCRIPTION Historical Background PORVs and block valves were originally designed as non-safety components in the reactor pressure control system for use only when plants are in operation. The block valves were installed because of expected leakage from …
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DESCRIPTION Historical Background This issue was raised [1] by DSI/NRR in August 1982 [2] following a search of LERs which suggested that additional licensing attention was needed for certain ancillary power plant equipment. The available information …
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DESCRIPTION Historical Background The risks of beyond design basis accidents in the spent fuel storage pool were examined in WASH-1400 [1] (App. I, pp. I-96ff). It was concluded that these risks were orders of magnitude below those involving the reactor …
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Page Last Reviewed/Updated 3/1/2026
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