ML20080D967
| ML20080D967 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 09/30/1992 |
| From: | Marchleuba J OAK RIDGE NATIONAL LABORATORY |
| To: | NRC |
| Shared Package | |
| ML20080D949 | List: |
| References | |
| CON-FIN-L-1697 ORNL-NRC-LTR-92, ORNL-NRC-LTR-92-14, NUDOCS 9501090283 | |
| Download: ML20080D967 (4) | |
Text
ORNL/NRC/LTR-92/14 1
Contract Program:
Technical Support for the Reactor Systems Branch (L1697/P2)
Subject of Document:
Review of Oyster' Creek Technical Specification Change Request No 191 to Implement Long Term Solution 11 Type of Document:
Technical Evaluation Report Author:
Jos6 March-Leuba Date of Document:
September 1992 NRC Monitor:
T. L. Huang, Office of Nuclear Reactor Regulation Prepared for U.S. Nuclear Regulatory Commission Office of Nuclear Reactor Regulation under DOE Interagency Agreement 1886-8947-8A NRC FIN No. Ll697, Project 2 Prepared by Instrumentation and Controls Division OAK RIDGE NATIONAL LABORATORY managed by MARTIN MARIETTA ENERGY SYSTEMS, INC.
for the U.S. DEPARTMENT OF ENERGY under Contract No. DE-AC05-840R21400 1
9501090283 941229 PDR ADOCK 05000219 P
SUMMARY
- CONCLUSIONS AND RECOMMENDATIONS This report documents our review of the Technical Specification Change request No.
1918 and the associated GPU Technical Report No. 068/R2,2 " Licensing Basis for Oyster Creek Long Term Solution to Reactor Instability," which deal with technical specification modifications to satisfy the "long Term Solution" requirements for the stability issue in Oyster Creek. The main conclusions of our review are two:
(1)
A Long Term Solution of " Type II" is applicable to Oyster Creek because of its quadrant APRM and flow biased scram system.
(2)
The solution implementation, as defined in the proposed Tech Spec changes, appears to satisfy the main criteria of a long Term Solution by providing a viable detect and suppress function that will guarantee, in the case of an instability, a very small likelihood of core damage without the need of operator intervention. Therefore General Design Criteria (GDC) 12 is satisfied by Oyster Creek even if unstable power oscillations were to develop.
Based on this review, we recommend that the technical specification change No.191 be approved, and that it be the basis for Oyster Creek conformance with the Long Term Solution requirements caused by the stability issue.
BASIS FOR REVIEW CONCLUSIONS Based on the analyses in GPU TR-068/R2,2 GPU has demonstrated that either core-wide (in-phase) or regional (out-of-phase) oscillations are likely to be detected by the existing flow-biased, quadrant APRM (average power range monitor) scram system in Oyster Creek without exceeding specified acceptable fuel design limits (SAFDLs). To guarantee this margin to SAFDLs, Oyster Creek requires that the operating limit MCPR be greater than 1.47, and that no more than one LPRM (local power range monitor) per quadrant at level A be out-of-service. These restrictions have been incorporated to Oyster Creek technical specifications (request No.191 ).
For these calculations, GPU postulated " credible" oscillation contours that were superimposed on the initial 3-D power distribution. The " credible" oscillation contours included core-wide and "first-order side-to-side" regional oscillations. Based on previous BWROG (Boiling Water Reactor Owners' Group) analyses," GPU concluded that higher order regional oscillations and single channel thermohydraulic oscillations are highly unlikely. We have concurred with this BWROG position in ref. 5.
The APRM response was simulated for several conditions based on the above contours and a random number of failed LPRM sensors. Based on these analyses, GPU 1
determined that as long as the operating limi; CPR is greater than 1.47 and at least one LPRM at level A is operable per quadrant, the postulated oscillations did not result in SAFDLs violation.
RESERVATIONS Although we agree with most of the technical basis in GPU Technical Report No.
068/R2, we have a series of reservations with respect to this implementation that do not invalidate the previous conclusions but are worth mentioning:
(1) lAng Term Solutions of Type II (the one implemented in Oyster Creek) do not provide automatic protection in the event of single channel thermohydraulic instabilities. However, as argued convincingly by the BWR Owners Group, the likelihood of single channel thermohydraulic instability without first triggering a core-wide or out-of-phase instability is very small. Nevertheless, since automatic protection is not provided, we might want to restrict Oyster Creek to load only fuel elements that satisfy the recent NRC stability criteria of being at least as stable as existing fuels. This restriction would apply specially to lead use assemblies (LUAs) which are the ones that could lead to a loading a one or two unstable channels (if a really unstable LUA were to be used). In other words, it might be prudent to ask Oyster Creek to analyze the channel stability of any LUA's that they may want to load.
(2)
The Justification report No. TR-068/R2 uses Fig. 4.1 that has been discredited by the BWROG. In particular, BWROG has decided to modify Solution Type III so that the use of a figure like Fig. 4.1 is unnecessary because they feel (and rightly so) that it is difficult if not impossible to generate a universal correlation for ACPR versus oscillation amplitude that applies to many fuel types and operating conditions. Fig.
4.1 is used in report TR-068/R2 to justify that the m1rgins for the in-phase instability mode are very large. Certainly, the in-phase mode margins are larger that for the out-of-phase; so that if the solution is acceptable for the out-of-phase mode, it should be acceptable for the in-phase mode. In this respect, the use of Fig 4.1 is only as an example or an approximate justification given the large margins available in this case.
We should be careful, however, that our approval of Oyster Creek's submittal with Fig. 4.1 in it is not interpreted as an implicit approval of this figure. In particular, the use of this general figure for Solution I-D (for small cores with inlet orifices) would probably not be acceptable unless the same type of margins are shown.
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REFERENCES' l
1.
Oyster Creek Nuclear Generating Station, Technical Specifcation Change Request No.
191, Docket No. 50-219, October 9,1991.
l 2.
GPU Technical Report No. %81R2, Licensing Basisfor Oyster Creek Long Term
' Solution to Reactor instability, Rev 2. August 1991 3.
General Electric Company, BWR Owners' Group Long-Tenn Stability Solutions Licensing Methodology, NEDO-31960, May 1991.
l-4.
General Electric Company, BWR Owners' Group Long-Tenn Stability Solutions.
Licensing Methodology, NEDO-31960 Supplement 1, March 1992, t
5.
Jose March-Lxuba, Licensing Basisfor Long-Tenn Solutions to BWR Stability Proposed by the BWR Owners' Group, Oak Ridge National laboratory ORN11NRC/LTR-92/15, August 1992 l
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