ML20133A458

Environ Assessment Re Proposed Regulation to Modify GDC 4. EIS Unnecessary

ML20133A458
Person / Time
Issue date:	08/02/1985
From:	NRC
To:
References
FRN-50FR27006, FRN-51FR12502, RULE-PR-50 AB76-1, AB76-2-12, NUDOCS 8508050478
Download: ML20133A458 (4)

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4 I= b676-\ l PDPs ENVIRONMENTAL ASSESSMENT FOR PROPOSED REGULATION TO MODIFY GENEFAL DESIGN CRITERION 4 l

l Identification of the Proposed Action The Nuclear Regulatory Commission is proposing to modify General Design Criterion 4 of Appendix A,10 CFR Part 50 to allow demonstration of piping integrity by analyses to serve as a basis for excluding consideration of dynamic effects associated with postulated pipe ruptures in primary coolant loop piping in pressurized water reactors (PWRs). The modification will permit the selective removal of pipe whip restraints and jet impingement barriers from operating plants, plants under construction, and future plant designs.

The Need for the Proposed Action j Advances in technology have led to the acceptance by NRC staff of procedures that estimate the likelihood of ruptures in nuclear reactor piping. However, General Design Criterion 4 (GDC 4) does not allow use of this new technical approach except by exemption granted pursuant to 10 CFR 50.12. Rulemaking is therefore needed to accommodate this engineering advance, i Prior to the last few years, there was no sound technical basis for excluding certain pipe ruptures from the design basis. Now it is clear that it is possible to defend the exclusion of pressurized water reactor

,i primary loop double-ended guillotine pipe ruptures, and that the scope may be extended to other piping, including piping in boiling water reactors.

Rulemaking action will promote investigations to determine which other 8508050478 850802 5050N27006 PDR

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2 situations will permit the removal of pipe whip restraints and jet impingement barriers. Acceptance criteria for generally applying these results pertaining to leak-before-break have been published by the NRC staff in " Report of the U.S. Nuclear Regulatory Comission Piping Review Committee", NUREG-1061, Volume 3, and are being proposed by the American Nuclear Society in ANS-58.2 entitled " Design Basis for Protection of Light Water Nuclear Power Plants Against Effects of Postulated Pipe Rupture."

In sumaary, the requirements of GDC 4 have led to a situation where protective devices have been added to nuclear power plants to forestall events which are now regarded as extremely unlikely. These protective devices reduce safety and increase worker radiation exposures. A need exists to allow exclusion other than by exemption from compliance with General Design Criterion 4 requirements when supported by acceptable analyses.

Alternatives Considered Three alternatives to the proposed rule were evaluated as indicated below:

1. Maintain the status quo Given that further use of exemptions is prohibited, this alternative requires that all primary loop piping in PWRs would have pipe whip restraints and jet impingement barriers. This alternative is rejected because analyses have shown that for a forecasted population of 85 PWRs, cost savir.gs of $186 million will be realized. Additionally, total man-rem exposures will be reduced by 34,000 man-rem. Finally, safety

3 would actually be enhanced since misalignment or not maintaining tolerances when installing or reinstalling pipe whip restraints actually increases the probability of pipe ruptures.

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2. Reinterpret the existing text of GDC 4 For more than fifteen years the staff has interpreted GOC 4 to require the placement of pipe whip restraints and jet impingement barriers near nuclear reactor piping. Because of legal restraints on issuing exemptions, this alternative is rejected. Rulemaking is necessary to justify the departure from long-standing past practices.

3. Use Exemptions to Accomplish the Removal of Pipe Whip Restraints and Jet Impingement Barriers The use of plant specific exemptions to the regulations on a system unique basis entails significant allocation of NRC resources. The use of repeated GDC 4 exemptions amounts to an amendment to a fundamental NRC .

rule in the absence of rulemaking procedures, leading to potential legal difficulties. For these reasons, this alternative is also rejected.

Based on this evaluation, the staff recommends that the NRC proceed with the proposed rulemaking because:

1. It firmly secures the legal basis for staff actions.

2. It removes impediments to the application of new technology in the licensing arena, thereby allowing the realization of improved safety, lower costs and reduced worker exposures.

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4 Environmental Impacts of the Proposed Action The proposed action would not significantly affect the quality of the human environment. The rule may result in the removal of certain plant hardware; however, this will not alter the environmental impact of the licensed activities. It is anticipated that removed hardware would be stored at the plant site to be available for any potential future r.eeds.

The proposed action would substantially reduce occupational radiation exposures received by workers undertaking inservice inspection, and may actually reduce the probability of core melt accidents when potential errors in installation or reinstallation are considered. The staff has already granted exemptions allowing two utilities to remove pipe whip restraints. In summary, the proposed action would have no measurable negative environmental impacts.

Agencies and Persons Consulted The proposed action has been reviewed by the NRC staff and two NRC con-tractors (Lawrence Livermore National Laboratory and Battelle Pacific Northwest Laboratories). A proposed rule will be published and public comments will be requested.

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Findings of No Significant Impact The Commission has determined not to prepare an environmental impact l

statement for the proposed action because it would not have a significant l effect on the quality of the human environment; the impact will be a

' benefical, not a deleterious, one.

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