ML19291C053
| ML19291C053 | |
| Person / Time | |
|---|---|
| Issue date: | 06/16/1978 |
| From: | Mattson R, Stello V Office of Nuclear Reactor Regulation |
| To: | Knight K, Ross D, Tedesco R Office of Nuclear Reactor Regulation |
| References | |
| REF-GTECI-B-06, REF-GTECI-PI, REF-GTECI-RV, TASK-B-06, TASK-B-6, TASK-OR NUDOCS 8001110197 | |
| Download: ML19291C053 (5) | |
Text
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MEMORANDUM FOR:
J. Knight, Assistant Director for Engineering, DSS D. Ross, Assistant Director for Reactor Safety, DSS R. Tedesco, Assistant Director for Plant Systems, DSS D. Eisenhut, Assistant Director for Systems & Projects, D0R B. Grimes, Assistant Director for Engineering & Projects, D0R FROM:
V. Stello, Director, Division of Operating Reactors R. Mattson, Director, Division of Systems Safety
SUBJECT:
A-2 WORKING GROUP ON METHODOLOGY FOR COMBINING LOADS As we discussed on May 17, 1978, DOR and DSS have established a Working Group to develop a position regarding the use of an appropriate methodo-logy (e.g., SRSS) for combining transient dynamic loads.
This Working Group is charged with the development of a reconmended position which reflects appropriate technical justification and policy considerations.
Although this Working Group effort is inmediately and directly related to staff efforts on Technical Activity A-2, Asynnetric Blowdown Loads for Reactor Primary Coolant Systems, the Group's reconmendation should be sufficiently generic to also address other uses of such methodology, e.g., SRV and OBE load combinations.
The Working Group members are as follows:
R. Cudlin, DOR, Chairman S. Hosford, D0R K. Wichman, D0R R. Mattu, DSS F. Schauer, DSS Since this is a high priority task that is needed for a number of generic technical review efforts. every effort should be made by the i
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Mul tiple assigned reviewers and their respective management, to ensure that this effort is completed by July 24, 1978.
The charter for the Working Group is attached.
At R. Ma tson/ Director V. S 110,-
re tor Division of Systens Safety Division /of Operating Reactors Of fice of Nuclear Reactor Regulation Office of Nuclear Reactor Regulation cc:
E. Case R. Cudlin J. Guibert W. Butler I. Sibweil L. Shao R. Bosnak M. Ayccck S. Pawlicki 1734 203 1
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Contact:
D. Eisenhut, Ext. 27221 1
CHARTER FOR WORKING GROUP ON METHODOLOGY FOR COMBINING LOAD'S Problem Definition In the analysis of structures, systems, and componets important to safety the NRC has required the combination of structural / mechanical responses due to various accident loads and loads due to natural phenomena, particularly earthquakes. This requirement flows from 10 CFR Part 50, Appendix A, General Design Criterion 2 which calls for an appropriate combination of the loads to be reflected in the design bases of such equipment. The requirement has been variously interpreted both within the NRC and industry.
The loads in question are generally rapidly varying dynamic loads and have no physical time phased relationship in the accident analysis.
The degree of independence of the loads is also variable, and in some cases (e.g., LOCA plus earthquake) is subject to considerable controversy.
Lacking a physical basis for relating some of the loads in question, they have been required to be combined in the licensing process according to the absolute or linear sum methodology, i.e., summation of peak structural responses due to each of the individual loads. This approach may lead to overly conservative design requirements for new plants and design requirements which are not able tobe met for operating plants which were licensed before promulgation of GDC 2.
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. Co.nbination of loads is of significance to a number of current staff technical activities, including BWR containment loads and asymetric blowdown loads on the reactor coolant system and other safety-related equipment. These activities include consideration of the combination of various accident loads (e.g., LOCA discharge loads plus suppression pool dynamic loads), combination of accident loads and earthquake (SSE) loads, and combination of operational loads (e.g., SRV discharge) with earthquake (0BE) loads.
Objective The objective of the work group is to develop a recomendation for combining transient dynamic loads in the analysis of structures, systems, and components important to safety.
The working group will conduct its evaluation according to the following task outline:
(1) Review work done to date on load combination methodologies including technical studies, policy considerations, and staff evaluations.
(2) Identify possible combination methodologies such as absolute sum, SRSS, etc.
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(3) Evaluate the merits of each methodology.
It is expected that SRSS will receive the most intensive scrutiny, however other methodologies will be evaluated to the extent practicable.
(4) Develop recommendation and supporting bases.
Identify further work if necessary.
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