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NUREG 0933
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The objective of this task was to improve the reliability and capability of nuclear power plant systems for removing decay heat and achieving safe shutdown conditions following transients and under post-accident conditions. ITEM II.E.3.1: RELIABILITY OF …
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DESCRIPTION Historical Background The Class 1E power sources provide the electric power for the plant systems that are essential to reactor shutdown, containment isolation, reactor core cooling, containment heat removal or are otherwise essential in …
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DESCRIPTION Historical Background This issue is documented in NUREG-0371 [1] and addresses the adequacy of safety-related DC power supplies which was questioned by a nuclear consultant in a letter to the ACRS in April 1977 (NUREG-0305, [2] Attachment B). …
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DESCRIPTION This issue was raised in NUREG-0371 [1] following a series of events at operating plants that involved the offsite power systems. These events indicated that the reliability of the preferred source of emergency power might have been less than …
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DESCRIPTION The complete loss of AC electrical power to the essential and nonessential switchgear buses in a nuclear power plant is referred to as a "Station Blackout." Because many safety systems required for reactor core decay heat removal are dependent …
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DESCRIPTION The design criteria and methods for the seismic qualification of mechanical and electrical equipment in nuclear power plants underwent significant changes during the course of the licensing of commercial nuclear power plants. Consequently, it …
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DESCRIPTION Some prototype electrical penetration failures have occurred to date. In addition, failures of low voltage penetration modules have occurred at a licensed facility. It was originally postulated that failures of the low voltage penetration …
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DESCRIPTION The seismic qualification of complex electrical and mechanical components has undergone rapid changes in the past several years. Revisions in industry standards (IEEE 344) have resulted in the need to audit the qualification programs of NSSS …
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DESCRIPTION NRC environmental information needs for licensing fall into the categories of: (1) detailed site-specific investigations at a preferred site, and (2) reconnaissance level information to support alternative site assessment and selection, …
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DESCRIPTION The effects of entrainment on phytoplankton and zooplankton populations are often minimal and occasionally beneficial. Numerous studies of the effects of entrainment on plankton organisms, phytoplankton, and zooplankton have shown impacts to …
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DESCRIPTION Historical Background This NUREG-0471 [1] item arose in the course of the NRC review of the McGuire application, where the applicant proposed relying on the generator load break switch for isolating the generator from the stepup transformer …
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DESCRIPTION Historical Background This issue was documented in NUREG-0471 [1] and resulted from a review of LERs which indicated that onsite emergency diesel generators (EDGs) at operating plants were demonstrating an average starting reliability of about …
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DESCRIPTION This NUREG-0471 [1] task will make a determination as to whether plants should be designed to accommodate a total loss of all AC power for a limited period of time. CONCLUSION This issue is covered in USI A-44, "Station Blackout." [1] …
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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 This NUREG-0471 [1] item was developed because of concerns regarding the long-term capability of hermetically- sealed instruments and equipment which must function in postaccident environments. Certain classes of …
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DESCRIPTION This NUREG-0471 [1] item was an ACRS generic concern that initially addressed the common mode failure of identical components exposed to identical or nearly-identical conditions or environments. This concern was later expanded to include other …
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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 …
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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 …
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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 …
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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 …
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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 This proposed generic issue has its origin in a January 1981 event at Millstone Unit 2. [1] An operator inadvertently opened a 125V DC main feeder breaker, causing the loss of one of the two redundant emergency systems …
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DESCRIPTION Historical Background On April 7, 1980, Arkansas Nuclear One (ANO) Units 1 and 2 experienced a significant event resulting from a loss of offsite power. Although both units were safely shut down, the analysis and evaluation of the event …
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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 …
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DESCRIPTION Historical Background In an AEOD memorandum [1] to NRR, it was concluded that the design of the Point Beach Nuclear Plant, Units 1 and 2, under certain conditions, allowed manual interconnection of redundant electrical load groups, thereby …
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