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NUREG 0933
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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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DESCRIPTION Historical Background A memorandum [1] from AEOD to NRR dated May 23, 1980 drew attention to the generic issue of BWR jet pump integrity. The concern that motivated the AEOD memo was a February 1980 jet pump failure at Dresden Unit 3, together …
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DESCRIPTION Historical Background Many PWRs have no positive means of detecting boron dilution during cold shutdown. [1] Some operations carried out during outages (e.g., steam generator decontamination) reduce the RCS volume thereby speeding up dilution. …
1
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 Prior to 1981, the number of bolting-related incidents reported by licensees was on the increase. A large number of these were related to primary pressure boundary applications and major component support structures. As a …
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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 …
1
DESCRIPTION Historical Background In January 1982, AEOD published a report (AEOD/C201 [1] ) on safety concerns associated with reactor vessel level instrumentation in BWRs. The report was forwared to NRR for further action. Safety Significance BWRs use …
1
DESCRIPTION Historical Background This issue was raised in a DL memorandum [1] to DST in March 1982 and addressed the subject of service water system (SWS) fouling at operating plants primarily by aquatic bivalves. Prior to and following this memorandum, …
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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 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 On two occasions (February 22 and 25, 1983), Salem Unit 1 failed to scram automatically due to failure of both reactor trip breakers to open on receipt of an actuation signal. In both cases, the unit was successfully …
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DESCRIPTION Historical Background On March 18, 1983, B&W expressed [1] concern for unanalyzed reactor vessel thermal stress that could occur during natural convection cooldown of PWRs. The concern emerged from a preliminary B&W evaluation of a voiding …
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DESCRIPTION Historical Background On August 18, 1982, the ACRS issued a letter [1] to the Commission which: (1) identified deficiencies in the maintenance and testing of engineered safety features designed to maintain control room habitability; (2) …
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DESCRIPTION Historical Background In March 1982, leaks were detected in the heat-affected zones of the safe-end-to-pipe welds in two of the 28 in. diameter recirculation loop safe ends at Nine Mile Point Unit 1. Subsequent UT revealed extensive cracking …
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DESCRIPTION Historical Background The HPCI steam supply line has two containment isolation valves in series: one inside and one outside of the containment. Both are normally open in most plants; however, two plants were found to operate with the HPCI …
1
DESCRIPTION Historical Background This issue was recommended [1] for prioritization by DSI after a review of the AEOD engineering evaluation report (AEOD/E325) [2] on vapor binding of the AFW pumps at H.B.Robinson Unit 2. Further AEOD study of the event …
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DESCRIPTION Historical Background Low temperature overpressurization originally identified in NUREG 0371 [1] as item A-26. This issue later became USI A-26 and was resolved in September 1978 with a revision to SRP [2] Section 5.2. The resolution of USI …
1
DESCRIPTION Historical Background This concern was raised by an NRC resident inspector who questioned the practice of leaving the refueling canal drain valve in the closed position during operations at H. B. Robinson Unit 2. [1] A subsequent investigation …
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DESCRIPTION Historical Background On April 17, 1984, a DSI memorandum [1] on the subject of RHR interlocks for W plants described staff concerns that the design basis for RHR interlocks had been misunderstood and that these concerns had not been …
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DESCRIPTION Historical Background Issue 50 addressed several areas of concern with BWR water level instrumentation and its resolution involved voluntary implementation of water level measurement improvements for all of the staff concerns, except the one …
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DESCRIPTION Historical Background In January 1984, AEOD issued a special study report (AEOD/S401) [1] describing the number of events that resulted from human error in identification of the correct unit or train. This study focused on LERs issued during …
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DESCRIPTION Historical Background The issue of using the most recent NOAA procedures for determining probable maximum precipitation (PMP) was raised [1] after an OL applicant disputed the NRC use of NOAA Hydrometeorological Report (HMR) Nos. 51 [2] and …
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DESCRIPTION Historical Background Issue B-63, which was resolved and implemented as MPA B-45, required leak-testing of the check valves that isolate those low pressure systems that are connected to the RCS outside the containment. However, except for …
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DESCRIPTION Historical Background Combustible gases such as H 2 , propane, and acetylene are used during normal operations of nuclear power plants in limited quantities and for relatively short periods of time. H 2 , the most prevalent of these gases in …
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DESCRIPTION Historical Background Indications of possible stress corrosion cracking (SCC) in the Indian Point Unit 3 (IP-3) steam generator prompted MTEB to review foreign and domestic operating experiences related to possible indications of SCC in …
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Page Last Reviewed/Updated 3/1/2026
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