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NUREG 0933
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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 Prior to 1978, operating experience with PWR steam generators was characterized by extensive corrosion and mechanically-induced degradation of the steam generator tubes, frequent plant shutdowns to repair primary-to- secondary leaks, and two …
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DESCRIPTION This item was originally identified in NUREG-0371 [1] and was later declared a USI in NUREG-0510. [2] (See Item A-3 for further details.) CONCLUSION This item was RESOLVED and requirements were established. (See Item A-3 for further details.) …
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DESCRIPTION During the course of the licensing action for North Anna Units 1 and 2, a number of questions were raised as to the potential for lamellar tearing and low fracture toughness of the steam generator and RCP support materials for these …
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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 Historical Background This issue effects all PWR-type reactors (Westinghouse, CE, B&W). The issue as described, [1] , [2] , [3] concerns postulated accidents resulting from a steam line break which consequentially results in a steam generator …
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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] after AEOD completed a study on internal appurtenances in LWRs. This study, AEOD/E101, [2] was initiated because of the relatively high number of LERs that described events in which internal …
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DESCRIPTION In AEOD/CO05, [1] AEOD identified potential safety problems concerning steam generator overfill due to control system failures and combined primary and secondary blowdown. As a result of discussions with the Commissioners and the EDO, NRR …
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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 AEOD issued a memorandum [1] in which a potential safety issue involving combined primary and secondary system LOCAs was raised. The issue was discussed at Commission meetings on October 16, 1980 and on November 10, 1980. NRR informed AEOD of …
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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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Page Last Reviewed/Updated 3/1/2026
Disclaimer: Some of the formatting in NUREG-0933 may not be correct. We are currently working on fixing the formatting.