ML20206R862
| ML20206R862 | |
| Person / Time | |
|---|---|
| Issue date: | 05/11/1998 |
| From: | Nataraja M NRC |
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| ML20206R845 | List: |
| References | |
| NUDOCS 9905210004 | |
| Download: ML20206R862 (3) | |
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- 1998 Intemational High Level Radioactive Waste Management Conference Las Vegas, NV -- May 11-14,1998 RESOLUTION OF SEISMIC ISSUE USING TOPICAL REPORT APPROACil ,
M 3sore S. Nataraja The U.S. Nuclear Regulatory Commission Washington, DC 20555 (301) 115-6695 l
l ABSTRACT II. IMPORTANCE OF SEISMIC DESIGN TO REPOSITORY PERFORMANCE This paper documents the prele sing review process being adopted by the U.S Nuclear Regulatory Commission There are two preclosure performance objectives in in resolving the issue of the U S Department of Energy's Part 60, namely, meeting 10 CFR Part 20 requirements fbr seismic and fault displacement design of the high-level radiation protection [Section 60.111(a)l and meeting the l
nuclear waste repository at the Yucca Mountain site. retrievabihty requirements [Section 601 I l(b)J DOE designs for both the surface and underground facihty structures, I. INTRODUCTION systems and components (SSCs) must adequately address seismic cifects and direct fault disruption to demonstrate {
One of the primary objectives of the U S Nuclear comphance with these two performance objectives. Failure of Regulatog Commission's (NRC's) relbeussed preheensing any of the structures, systems, and components important to program is to direct its activities toward resolving the 10 key safety (SSCIS), due to vibratory ground motion or direct fault technical issues (KTis) it considers to be most important to displacement, could severely impact the repositoy repository perfcnnance. Issue resolution at the statT level perfonnance during the preclosure penod of 100 to 150 years during prehcensing is achieved when the statT has no further questions or comments at a point in time, regarding how the Design of the repository for the etTects of seismic events U S. Depanment of Energy's (DOE's) program is addressing and direct fault disruption also has several postclosure an issue. The status of issue resolution is documented in implications The particular etTects of seismic events and formal Issue Resolution Status Reports (IRSRs), which are direct fault disruption and, consequently, their importance to provided to DOE on a penodic basis. long-term perfinnance are design dependent. In general, the ,
repository design and the methodology used to develop that The adequacy of DOE's repository design in the context design must consider: (i) seismic etrects on the waste of the performance objectives and design entena of 10 CFR packages (WPs) and other engmeered barriers, as well as the Part 60 is the pnmay focus of the Repository Design and surroundmg rock mass, and (ii) key aspects of the Thermal-Mechanical EITects (RDTME) KTI. The RDTME emplacement configuration, particularly fault offset distance.
KTl has been divided into several subissues, one of w hich is The WPs, backfill, drip shields, and other elements of the the design of the repository for the effects of seismic events engineered barner system that DOE may choose to deploy, as and direct fault disruption This paper summarizes the statT well as the surroundmg rock mass, will all be subjected to approach taken to resolve the seismic subissue using the repeated episodes of seismic loadmg during the postclosure Topical Report (TR) approach period 9905210004 990329
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III. TOPICAL REPORT APPROACH IV. ACCEPTANCE CRITERIA l
l Among several approaches to resolving potential The statY uses two sets of acceptance criteria lbr a j
- licensing issues is the use of TRs. Historically, the purpose submitted TR--one for the acceptance review and the second l l- of the NRC TR program has been to provide a procedure for a detailed tecimical review. The stalT will accept the TR j l whereby industrial organizations may submit reports on for review if, during an initial acceptance review, the l specific important to-safety subjects to the NRC and have following four acceptance criteria are satisfied
l them reviewed independently of any construction permit or operating license review. The benefits resulting from this program are a nummization of duplicative time and etTort that (1) The TR addresses all important-to-safety (or the applicants and the NRC stalTspend on these subjects and important-to-waste-isolation) issues pertaining to the scope etliciencies gained in NRC reviews. of the TR; NRC statThas documented in its " Topical Report Review (2) The subject of the TR is currently undergoing i Plan" the conditions under which DOE can prepare a TR on pre-licensing evaluation; l a given issue (such as, a design or analytical method) and l submit it ihr staff review. Under this TR process, DOE (3) NRC acceptance of the TR would result in increased l submits an annotated outline of the proposed TR to get NRC etliciencies in the statireview of DOE's license appli.ation; l agreement on the scope and content of the report befbre and spending significant resources. Subsequently, the completed TR is submitted for staffrevicw that takes place in two stages, (4) The TR contains complete and detailed information namely, an acceptance review (in which the stafT checks the on each elcment of the scope of the report.
acceptability of the TR before agreeing to conduct a detailed technical review), and a detailed, irdependent technical Under the detailed technical review, the staff will find the review by the stati. Several rounds of staff comments and methodology proposed in the TR adequate for use in DOE responses, either during discussions in meetings and/or repository design if the fbliowing 10 criteria are satisfied.
in writing, may be required before the NRC completes its i review and documents the status of the resolution of a (1) The proposed methodology is based on sound particular issue or a subissue in an IRSR. technical principles; DOE decided, and NRC agreed, that the issue of (2) The proposed methodology has been previously seismicity and fault displacement is an appropriate one to be applied to the design of SSCIS or, if not, no serious problems
, dealt with using the TR process. The issue of seismic design have been identified that would impede applying the i has a long history of both staff and public interest during methodology; licensing In:arings of nuclear power plants. The TR approach
( is expected to facilitate eflicient reviews during the limited (3) The proposed methodology does not contradict licensing revie v period available urvier the Nuclear Waste established methodologies and principles te 1ed and l
Policy Act. documented in the license applications for nuclear power l plants and independent spent fuel storage installations; i After discussions with the statT, DOE decided that the issue of seismicity and fault displacement is too unwieldy to be (4) There are no uncertainties associated with the covered under one TR. Therefore, DOE developed a plan to proposed methodology that would significantly impact the address the issue using three TRs. The first TR (TR-1) deals repository design process and development ofinputs to pas; with the proposed DOE methodology to assess seismic hazards. The second TR (TR-2) deals with the proposed (5) The various steps involved in the proposed DOE seismic design methodology. The third TR (TR-3), methodology are transparent; which is stated for completion during FY 1998, deals with vibratory ground motion and fault displacement inputs that (6) The proposed design methodology depends upon j will be usal in repository design and performance assessments site-specific test data (such data are available or are being I (pas).
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9 gathered, or there are plans for collecting such data during site hazards. Seismic design considerations for WPs are also characterization before submittal of the license application); discussed m TR-2.
(7) To the extent that the proposed methodology depends VL STAFF REVIEW OF TR-2 on analytical / computer models, such models have been venfied, cahbrated, and/or validated to the extent practical, or After conducting the acceptance review and a detailed there are plans for such activities prior to license application technical review and several interactions (meetings and submittal or during the perfonnance confirmation period, as wntten correspondence), NRC found DOE seismic and fault appropnate; displacement hazard assessment methodology and seismic and fault displacement design methodology to be acceptable. A (8) Any major assumptions or limitations to the proposed fmal decision on the overall acceptability of DOE's approach methodology are identified and the implications regarding will be made upon completion of the TR-3 review and design and performance are discussed in the TR; preparation of a prelicensing evaluation report.
(9) Documented case histories of the performance of VIL CONCLUSION SSCIS designed, using the proposed methodology, are presented in the TR; and Based on the review of TR-2, Rev. 2, as documented in the IRSR provided to DOE by letter dated October 29, 1997 (10) The contents of TR-: are consistent with the contents (Reference), the seismic design methodology presented by of TR-1 and, together, the two TRs support the development DOE is acceptable to NRC. The concems related to repeated ofinputs for design and pas in accordance with TR-3. seismic loading for the preclosure design have been closed based on the rationale presented in TR-2. The NRC statT has V. SEISMIC DESIGN METHODOLOGY. no further questions on this subissue at the present time and PRESENTED BY DOE concludes that the TR approach has been ven etrective in dealing with the issue of seismic design and in resolving the DOE's preclosure seismic design methodology and issue at the NRC stafflevel. It is expected that the resources criteria are described in TR-2. If implemented properly by being spent by DOE in the preparation of the three TRs and DOE, this methodology is expected to provide reasonable the stafTefforts spent in conducting the review s will result in assurance that vibratory ground motions and fault considerable saving of time and expedite the license
- displacements will not compromise the preclosure safety application review process in the future.
functions of SSCIS. The scismic design methodology and enteria implement the requirements of Part 60, including the ACKNOWLEDGMENTS latest amendments related to design basis events (DBEs).
Accordingly, the report summarizes the DOE approach to The author is thankful to NRC management for identifying Categon-1 and Category-2 DBEs and establishes permitting the publication of this paper. The author hazard probability levels that are appropriate for determining acknowledges the review and supervision provided by his the two levels of design basis vibratory ground motions and Section Leader, Mr. Richard A.Weller, and the secretanal the two levels of design basis fault displacements. DOE support provided by Ms. Edith Barbely.
intends to use mean annual probabilities of I x 104 and
' I x 10d, respectively, as reference values in determining the REFERENCE frequency of the above two design basis vibratory ground motions. Acceptance enteria for both surface and underground N.K. Stablein, U.S. Nuclear Regulatory Commission, facilities are provided for vibratory ground motion and fault letter to S. Brocoum, U.S. Department of Energy,
- Issue displacement design. In addition, the report provides criteria Resolution Status Report, Key Technical issue: Repositmy for fault avoidance, which is the DOE preferred (and NRC Design and Thermal-Mechanical EfTects", October 29,1997.
recommended) approach for mitigating fauh displacement I
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