ML20134J125
| ML20134J125 | |
| Person / Time | |
|---|---|
| Issue date: | 05/29/2020 |
| From: | Eric Benner NRC/NRR/DEX |
| To: | Louise Lund Office of Nuclear Regulatory Research |
| Russell Haskell 301-415-1129 | |
| References | |
| RG-1.091, Rev 2 | |
| Download: ML20134J125 (4) | |
Text
May 29, 2020 MEMORANDUM TO:
Louise Lund, Director Division of Engineering Office of Nuclear Regulatory Research FROM:
Eric Benner, Director
/RA/
Division of Engineering and External Hazards Office of Nuclear Reactor Regulation
SUBJECT:
RESULTS OF PERIODIC REVIEW OF REGULATORY GUIDE 1.91, REVISION 2, EVALUATIONS OF EXPLOSIONS POSTULATED TO OCCUR AT NEARBY FACILITIES AND ON TRANSPORTATION ROUTES NEAR NUCLEAR POWER PLANTS This memorandum documents the US Nuclear Regulatory Commission (NRC) periodic review of Regulatory Guide (RG) 1.91, Revision 2, Evaluations of Explosions Postulated to Occur at Nearby Facilities and On Transportation Routes Near Nuclear Power Plants, Agencywide Documents and Access Management System (ADAMS) Accession No. ML12170A980. This RG provides guidance for evaluating postulated explosions at nearby facilities and transportation routes.
As discussed in Management Directive 6.6, Regulatory Guides, the NRC staff reviews RGs approximately every 10 years to ensure that the RGs continue to provide useful guidance with updated information. Documentation of the NRC staff review is enclosed.
Based on the results of the periodic review, the staff concludes that a revision to RG 1.91, Revision 2, is warranted. The Revision to RG 1.91, Revision 2, will update and expand the scope of the guidance and address several technical issues that require revision.
CONTACT: Kenneth See, NRR/DEX/EXHB 301-415-1508
Enclosure:
Periodic Review
- via email NRR-106 OFFICE NRR/DEX/ESEA NRR/DEX/EXHB NRR/DEX/EXHB NRR/DEX/EXHB/BC NRR/DEX/DD NAME AGhosh*
RTammara*
KSee*
BHayes*
EBenner MSampson*
for DATE 5/15/20 5/15/20 5/15/20 5/18/20 5/29/20
Enclosure Regulatory Guide Periodic Review Regulatory Guide Number:
1.91, Revision 2
Title:
Evaluations of Explosions Postulated to Occur at Nearby Facilities and on Transportation Routes Near Nuclear Power Plants Office/division/branch:
NRR/DEX/EXHB Technical Lead:
Kenneth See Staff Action Decided:
Revise
- 1.
What are the known technical or regulatory issues with the current version of the Regulatory Guide (RG)?
RG 1.91, Revision 2, Evaluations of Explosions Postulated to Occur at Nearby Facilities and on Transportation Routes Near Nuclear Power Plants, is a relevant and useable regulatory guide (RG) that describes methods that the U.S. Nuclear Regulatory Commission (NRC) finds acceptable for evaluating postulated explosions at nearby facilities and transportation routes by applicants and licensees of nuclear power reactors. A Revision of RG 1.91, Revision 2, is not part of a rulemaking effort nor is it related to a significant regulatory issue. The staff performed a review of technical and regulatory issues associated with RG 1.91, Revision 2, which were identified in a recent expert evaluation team report (Report of the U.S. Nuclear Regulatory Commission Expert Evaluation Team on Concerns Pertaining to Gas Transmission Lines Near the Indian Point Nuclear Power Plant, April 8, 2020, ADAMS Accession No. ML20100F635).
The expert evaluation team report (NRC, 2020) identified several recommendations with respect to updates to RG 1.91, Revision 2, that would improve guidance and process, including:
Provide clear guidance for determining mass release, including what assumptions and methods are valid in determining the values to be used.
Provide clear expectations for detailed calculations that would be conducted if the safe-distance criterion is not met.
Address heat flux, which is the subject of Department of Transportation regulations and may be a controlling issue for potential nuclear power plant impacts.
Provide specific values for energy equivalence for different chemicals and include additional information on different classes of chemicals.
Revert back to 4,500 kJ/kg as the heat of detonation of trinitrotoluene (or TNT) from the current use of 4,420 kJ/kg referenced in the RG.
Incorporate minor changes to equations currently in RG 1.91, Revision 2.
2 The staff considers the above issues as guidance enhancements that should be considered in an update to the RG. The staff notes that there are no related agency documents that currently conflict with RG 1.91, Revision 2, and there are no staff positions in related agency documents that need to be made part of the revised RG.
Also, the staff developed the following recommendation that may need additional time for development beyond the scope of the staffs current planned revision.
Development of an alternative method to assess potential damage to structures important to safety from certain explosions (deflagration rather than detonation) of a hydrocarbon-air vapor cloud explosion (VCE).
- 2.
What is the impact on internal and external stakeholders of not updating the RG for the known issues, in terms of anticipated numbers of licensing and inspection activities over the next several years?
If the staff did not pursue a revision to the RG based on the above issues, then the primary impact would be on applicants for new reactors that would have additional costs in preparation of applications due to the lack of the expanded scope and enhancements and bear additional costs related to staff review. Licensees of operating plants and staff may also have impacts related to analysis of changes near their facilities. Applicants or licensees for facilities other than nuclear reactors that use the current version of RG 1.91, Revision 2, could be similarly impacted.
- 3.
What is an estimate of the level of effort needed to address identified issues in terms of full-time equivalent (FTE) and contractor resources?
The staff anticipates an approximate level of effort of 2.0 FTE to complete the revision.
- 4.
Based on the answers to the questions above, what is the staff action for this guide (Reviewed with no issues identified, reviewed with issues identified for future consideration, Revise, or Withdraw)?
Revise.
- 5.
Provide a conceptual plan and timeframe to address the issues identified during the review.
The staff plans to develop the draft RG in March 2021 and issue the draft RG for public comment in July 2021.
NOTE:
This review was conducted in Spring 2020 and reflects the staffs plans as of that date. These plans are tentative and subject to change.
Reference:
U.S. Nuclear Regulatory Commission, Report of the U.S. Nuclear Regulatory Commission Expert Evaluation Team on Concerns Pertaining to Gas Transmission Lines Near the Indian Point Nuclear Power Plant, April 2020, (ADAMS Accession Number: ML20100F635)