Section
Resolution Product Category
Facilities Type
Related Technical Area
Image
NUREG 0933
Displaying 51 - 75 of 88
DESCRIPTION Historical Background The containment flooding issue stems from a flooding event that occurred at the Indian Point 2 reactor in October 1980. [1] A large quantity of water leaked from fan coolers onto the containment building floor and …
1
DESCRIPTION Historical Background The SRVs of a BWR plant provide protection against overpressurization of the reactor primary system. During normal operation, the SRVs which are mounted in the main steam lines open on high pressure permitting steam to …
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 In BWRs, SRVs are mounted on the main steam line inside the drywell. Each SRV discharge is piped through its own discharge line (tailpipe) to a point below the minimum water level in the primary containment suppression …
1
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 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 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 …
1
DESCRIPTION Historical Background This issue was identified during the staff review of the Indian Point 2 and Zion PRAs [1] ; in both of these studies, the dominant interfacing systems LOCA events were estimated to be through the RHR suction valves. The …
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 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 …
1
DESCRIPTION Historical Background BWRs are equipped with SRVs to control primary system pressurization. Upon SRV actuation and following the clearing of air from the discharge lines, essentially pure steam is injected into the pool. Experiments indicate …
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 On January 27, 1985, a dented and leaking tendon grease cap was found during inspections at Farley Unit 2 prior to the integrated leak rate test of the prestressed concrete containment structure. Subsequent detailed …
1
DESCRIPTION In December 1984, the staff recommended in SECY-83-357B [1] that rulemaking with regard to H 2 control for LWRs with large, dry containments could be safely deferred due to the greater inherent capability of these containments to accommodate …
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
DESCRIPTION Historical Background The issue of deinerting upon discovery of RCS leakage was identified [1] by DL/NRR, based on data collected by OIE. The related but separate concern of deinerting with one train of a safety system inoperable was also …
1
DESCRIPTION The issue, as originally proposed, [1] addressed the concern for fission product removal by the containment sprays and suppression pools in PWRs and BWRs, respectively; however, it was expanded to include PWR plants that use ice condenser …
1
DESCRIPTION Historical Background This issue was raised in SECY-89-170 [1] and addressed the potential for control system vulnerabilities as a result of fire-induced alternate shutdown/control room panel interactions. Concern for these interactions arose …
1
DESCRIPTION Historical Background This issue was identified [1] by DSIR/RES and addressed the concern for overpressurization of containment piping penetrations following a containment isolation and subsequent heat-up. Containment isolation at all nuclear …
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.