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NUREG 0933
Displaying 1 - 25 of 32
DESCRIPTION Background This issue was identified [1] after a review of LERs involving the failure or degraded performance of essential equipment that resulted from the failure of protective devices such as fuses and circuit breakers. The affected systems …
1
DESCRIPTION Historical Background This issue is identified in Appendix D of NUREG-0572 [1] and is one of the key observations made after the ACRS requested its members and consultants to make comprehensive reviews of all LERs issued during the years 1976, …
1
DESCRIPTION Historical Background In the event of a LOCA in which offsite power remains available, the reactor operator may choose to shut down the emergency diesel generators shortly after the LOCA. If, after the diesels are shut down, offsite power is …
1
DESCRIPTION On November 10, 1979, an event occurred at the Oconee Power Station, Unit 3, that resulted in loss of power to a non-Class 1E 120-volt AC single-phase power panel that supplied power to the integrated control system (ICS) and the nonnuclear …
1
DESCRIPTION Historical Background This concern was raised [1] because of the potential for a high-altitude nuclear weapon detonation causing a large electromagnetic pulse (EMP) which subsequently could induce large currents and voltages in electrical …
1
DESCRIPTION This issue concerns the slow loss of control air pressure in the scram system of BWRs. [1] Air pressure dropping at a certain rate will first allow some of the CRD scram outlet valves to open slightly, thus filling the scram discharge volume …
1
DESCRIPTION In a San Onofre Unit 1 Preliminary Notification issued in September 1980, it was reported that, during testing, the licensee had identified a problem with the design of the diesel generator sequencing circuitry. This problem occurred when a …
1
DESCRIPTION This issue was identified during plant design and emergency procedure reviews which raised questions as to whether certain safety actions have to be accomplished automatically or whether manual operator action is acceptable. CONCLUSION This …
1
DESCRIPTION Historical Background This issue corresponds to AEOD recommendation 4 highlighted in an AEOD memorandum [1] to NRR in December 1980. The AEOD recommendation resulted from a natural circulation cooldown event from full power at St. Lucie Unit …
1
DESCRIPTION This issue was identified in an AEOD memorandum [1] to NRR in May 1980. The concern is related to a feature on some B&W reactors in which the failure of the Non-Nuclear Instrumentation and Integrated Control System (NNI/ICS) power supply …
1
DESCRIPTION Concerns for inoperability of instrumentation due to extreme cold weather were raised [1] by AEOD after an event at Arkansas Nuclear One, Unit 2 (ANO-2) in which all four RWST instrumentation channels were lost when the level transmitters …
1
DESCRIPTION An AEOD memorandum [1] to NRR on July 15, 1980, identified the concern that some operating nuclear power plants do not have technical specifications or Administrative controls governing operational restrictions for Class 1E 120 VAC vital …
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 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 …
1
DESCRIPTION Historical Background Protection systems in nuclear power plants are required to meet the design criteria of IEEE-279, "Criteria for Protection Systems for Nuclear Power Generating Stations." [1] One of the criteria of IEEE-279 requires that …
1
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 …
1
DESCRIPTION Historical Background This issue was identified [1] when a number of concerns regarding DC power systems were raised during the review of the proposed resolution of Issue A-30, "Adequacy of Safety-Related DC Power Supplies." The main concerns …
1
DESCRIPTION Historical Background Reactor protection systems (RPS) or "scram" systems are tripped by many diverse signals. The purposes of these various signals can be broadly divided into three classes: protection of the reactor core (e.g., overpower …
1
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 …
1
DESCRIPTION Historical Background This issue was identified in a DST/NRR memorandum [1] which addressed a condition in which some protective devices intended to trip active engineered safety features (ESF) components, under indication of equipment …
1
DESCRIPTION Historical Background In February 1983, the Westinghouse Owners Group submitted WCAP-10271, "Evaluation of Surveillance Frequencies and Out of Service Times for the Reactor Protection Instrumentation System," to the NRC for review and …
1
DESCRIPTION Historical Background The ATWS rule [1] , [2] for W plants requires the implementation of a diverse ATWS mitigation system, Auxiliary [or ATWS] Mitigating Systems Actuation Circuitry (AMSAC). The functions prescribed for AMSAC are turbine trip …
1
DESCRIPTION Historical Background This issue was identified in the U.S. Nuclear Regulatory Commission (NRC) incident investigation team (IIT) report on the loss of integrated control system (ICS) power event at Rancho Seco Nuclear Generating Station …
1
DESCRIPTION Historical Background This issue was identified in a May 1986 DSI memorandum [1] in which 21 instances of BWR vessel draining through various paths in the RHR system piping were described. Later, in August 1986, AEOD/E609 [2] was issued …
1
DESCRIPTION Historical Background Potential seismic interaction involving the movable in-core flux mapping systems was identified as a generic issue in August 1985. [1] This potential interaction exists because portions of the in-core flux mapping system, …
1
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.