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NUREG 0933
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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 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 In March 1981, this issue was identified as a USI in NUREG-0705. [1] A program was initiated to evaluate the safety adequacy of the decay heat removal (DHR) function in operating LWRs and to assess the value and impact (i.e., the benefit and …
1
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 Nuclear power plant instrumentation and control systems are composed of safety-related protection systems and non-safety-related control systems. The safety-related protection systems are designed to satisfy the General Design Criteria …
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DESCRIPTION Following a LOCA in an LWR, combustible gases, principally hydrogen, may accumulate inside the primary reactor containment as a result of: (1) metal-water reaction involving the fuel element cladding; (2) the radiolytic decomposition of the …
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DESCRIPTION Neutron irradiation of reactor pressure vessel weld and plate materials decreases the fracture toughness of the materials. The fracture toughness sensitivity to radiation-induced change is increased by the presence of certain materials such as …
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DESCRIPTION Current NRC regulations and practice require that certain operating requirements (Technical Specifications) be made part of each operating license. These Technical Specifications comprise an Appendix A which deals with safety features and an …
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DESCRIPTION There are several inconsistencies in event categorization between the GDC, SRP, Standard Format, and applicant submissions. In addition, categorization by other groups such as ANSI and ANS is not always consistent with NRC positions. In …
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DESCRIPTION Numerical reliability goals and methods of analysis have not been established by the NRC. The current basis for plant licensing continues to be NRC regulations which require, among other things, that the consequences of a LOCA be suitably …
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This item has been divided into two parts which have been evaluated separately. PART I - Ductility of Two-Way Slabs and Shells DESCRIPTION Historical Background This issue was identified in NUREG-0471 [1] and involved concern over the lack of information …
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DESCRIPTION Historical Background This issue was identified as a generic problem in NUREG-0471 [1] and concerns the design of pressure vessels and piping systems components which must be designed to accommodate individual and combined loads due to normal …
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DESCRIPTION This NUREG-0471 [1] task will develop more reliable models and associated computer capability than currently available to the staff for assessing the radiological consequences of accidents that could result in the releases of radioactivity …
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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 calculations of differential pressure that occur in containment subcompartments from a loss-of-coolant event require a complex fluid dynamic analysis to assure that the subcompartment design pressures are not exceeded. To check the various …
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DESCRIPTION Test data from the Marviken containment tests were obtained for the purpose of validating containment pressure codes used for performing independent calculations related to licensing reviews. The Marviken data are containment pressure …
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DESCRIPTION Consistent with the guidelines of Regulatory Guide 1.7, [1] the prevention of local hydrogen concentrations in excess of 4% by volume after a LOCA requires mixing of the containment atmosphere. Preliminary calculations indicate that lower …
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DESCRIPTION The CONTEMPT computer code is used by the NRC staff to perform independent containment analyses. This NUREG-0471 [1] task involves the maintenance and revision of the CONTEMPT code to accommodate new containment designs or new problem areas as …
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DESCRIPTION Historical Background SRP [1] Section 3.6, issued in 1975, addressed pipe breaks outside containment by combining limited design basis breaks for mechanistic protection with unlimited breaks for non-mechanistic protection. Prior to this, …
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DESCRIPTION Historical Background This NUREG-0471 [1] item involved the development of a time criterion for safety-related operator actions (SROA), including a determination of whether or not automatic actuation was to be required. At the time this issue …
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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 NRC staff has a variety of ongoing or planned technical activities related to core physics. For the most part, these activities are directed at improving the NRC staff's analytical and computer capabilities for performing independent …
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DESCRIPTION Historical Background Individual reactor fuel rods sometimes fail during normal operations and many fuel rods are expected to fail during severe accidents. To ensure that these fuel failures do not result in unacceptable releases to the …
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DESCRIPTION This NUREG-0471 [1] task covers a spectrum of technical efforts related to the staff review of LMFBR fuel designs. The efforts include: (1) evaluating licensing requirements for the behavior of stainless steel cladding and hexcans in an LMFBR …
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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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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.