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NUREG 0933
Displaying 101 - 125 of 162
DESCRIPTION Historical Background This NUREG-0471 [1] item deals with two concerns regarding the ice condenser containment design. The first concern arises from an ACRS comment on the D. C. Cook Unit 1 review. The normal procedure used by the staff (CSB) …
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DESCRIPTION The BWR pressure relief system is designed to prevent overpressurization of the reactor coolant pressure boundary (RCPB) under the most severe abnormal operational transient: closure of the main steam line isolation valves (MSIVs) with failure …
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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 …
1
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 Historical Background This NUREG-0471 [1] task involves a review of valve failure data in a systematic manner to verify the staff's present judgment regarding the likelihood of passive mechanical valve failures, to categorize these and other …
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DESCRIPTION Historical Background The majority of the presently operating BWRs and PWRs are designed to operate with less than full reactor coolant flow. If a PWR RCP or a BWR recirculation pump becomes inoperative, the flow provided by the remaining …
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DESCRIPTION The presence of a loose (i.e., disengaged and/or drifting) object in the primary coolant system can be indicative of degraded reactor safety resulting from failure or weakening of a safety-related component. A loose part, whether it be from a …
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DESCRIPTION Historical Background This issue was identified in NUREG-0471 [1] and addressed the establishment of surveillance test intervals and allowable equipment outage periods, using analytically-based TS criteria and methods. At the time the issue …
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DESCRIPTION The methods used to establish safe operating limits for reactor cores were developed about 10 years ago. At present, safety margins are reviewed utilizing previous staff judgments based on individual plant reviews. A uniform staff position …
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DESCRIPTION There are several systems connected to the reactor coolant pressure boundary that have design pressures that are considerably below the reactor coolant system operating pressure. The NRC has required that valves forming the interface between …
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DESCRIPTION Decommissioning is defined as the orderly retirement of a nuclear facility from service and the safe disposition of the remaining radioactivity. 10 CFR 50.82 provides the regulations that govern the termination of licenses. The NRC may require …
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DESCRIPTION Historical Background This NUREG-0471 [1] task is to develop and confirm a model for the iodine spiking phenomenon, in which the iodine concentration in the reactor coolant rises to many times its equilibrium concentration level (peak …
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DESCRIPTION The control room area ventilation systems and control building layout and structures are reviewed to assure that plant operators are adequately protected against the effects of accidental releases of toxic and radioactive gases and to assure …
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DESCRIPTION According to NUREG-0471, [1] the nature of this problem is described as follows: "Monitoring of radioactivity in gaseous and liquid effluent streams from nuclear power plants is required for several purposes: (a) assessment of the adequacy of …
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DESCRIPTION Historical Background This NUREG-0471 [1] item, as presently formulated, involves the conduct of analytical and experimental work to determine whether or not destructive overspeeds could be attained and to determine if corrective actions are …
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DESCRIPTION Following a plant transient or accident, provisions are required for long-term decay heat removal. Redundancy of components is required as necessary to assure that a failure in the RHR system will not impair the ability to maintain the plant …
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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 Present NRC actions taken in response to a serious incident are directed from an Incident Response Center (IRC). To implement an adequate response, it is necessary that the IRC be equipped with appropriate communications services, information …
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DESCRIPTION Practice in health impact assessments at the time of identification of this issue was to convert radiation exposure estimates into estimates of health effects, such as cancer deaths, illness, and life shortening. However, the models that were …
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DESCRIPTION Historical Background The ACRS raised a concern that there is a need to develop criteria for vibration monitoring systems which could provide early warning of excessive vibration inside the reactor vessel. This item is documented 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 Inadvertent operation of containment sprays can result in a rapid depressurization of the containment building. Where containment external design pressure may be exceeded, many plants have been provided with vacuum breakers or control system …
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DESCRIPTION Various kinds of insulation are used on piping and components inside the containment of a nuclear power plant. The concern of this NUREG-0471 [1] item was the behavior of insulation under pipe break accident conditions where the potential …
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DESCRIPTION Historical Background As identified in NUREG-0471, [1] Appendix K of 10 CFR 50 specifies the requirements for LWR ECCS analysis. These requirements call for specific conservatisms to be applied to certain models and correlations used in the …
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DESCRIPTION Historical Background As identified in NUREG-0471, [1] this issue involved following the work of research groups in determining best estimate decay heat data and associated uncertainties for use in LOCA calculations. Safety Significance No …
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Page Last Reviewed/Updated 3/1/2026
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