ML20203C178
| ML20203C178 | |
| Person / Time | |
|---|---|
| Issue date: | 02/03/1999 |
| From: | Marlone Davis NRC (Affiliation Not Assigned) |
| To: | Green T GENERAL ELECTRIC CO. |
| Shared Package | |
| ML20203C182 | List: |
| References | |
| TAC-M98500, NUDOCS 9902110243 | |
| Download: ML20203C178 (4) | |
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j - .k UNITED STATES 4 E NUCLEAR REGULATORY COMMISSION I f WASHINGTON, D.C. 20555 4 001
\ # February 3, 1999 Thomas A. Green, Project Manager GE Nuclear Energy Mail Code 182
' 175 Curtner Avenue San Jose, CA 95125 -
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SUBJECT:
SAFETY EVALUATION CONCERNING GENERAL ELECTRIC TOPICAL REPORT NEDC-32721P, " APPLICATION METHODOLOGY FOR THE GENERAL ELECTRIC STACKED D!SK ECCS SUCTION STRAINER," PART I (TAC NO.
l M98500)
Dear Mr. Green:
By letters dated April 3,1997, and November 21,1997, General Electric Company (GE) ,
submitted General Electric Topical Report NEDC-32721P, " Application Methodology for the General Electric Stacked Disk ECCS Suction Strainer," to the Nuclear Regulatory Commission (NRC, the staff) for review. The methodologies described in this report are being used by multiple boiling-water reactor (BWR) licensees (i.e.,12 plants) as part of their resolution of the l
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~ BWR emergency core cooling system (ECCS) suction strainer clogging issue. BWR licensees . !
were requested in NRC Bulletin 96-03, " Potential Plugging of Emergency Core Cooling Suction ;
Strainers by Debris in Boiling Water Reactors," to implement hardware and programmatic modifications, as necessary, to minimize the potential for clogging of ECCS suction strainers l
during a loss-of-coolant accident (LOCA). By facsimile dated August 18,1997, and letter dated March 10,1998, the staff transmitted requests for additionalinformation (RAls) to GE. GE i responded to the staff RAls in letters dated November 21,1997, and April 29,1998.
l The GE topical report encompasses methodologies for two different types of analyses. The first I methodology is used to determine the head loss across the strainer for estimated debris loadings. .The second methodology is used to determine the structuralloads on the ECCS
. penetrations, piping and strainers caused by hydrodynamic forces during an accident. These i two methodologies are separate and distinct. Therefore, the staff has broken its review into two parts . The Enclosure to this letter provides Part I of the staffs safety evaluation (SE) of topical report NEDC 32721P. Part I of this SE provides the staffs evaluation of the methodology used to determine strainer performance (i.e., head loss across the strainer with assumed debris t
- loadings) only. Part ll of this safety evaluation will address the methodology to determine } t structural loadings due to hydrodynamic forces duri ig an accident, and will be provided when that part of the staff's review is complete. f, 10-l. m '*scemq ec(N W7 l - r 1 i d i I6 9902110243 990203 l PDR. TOPRP EPfV0ENE <
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l T. Green 2 February 3, 1999 l
GE's topical report and RAI responses were evaluated by the staff's contractor, Los Alamos National Laboratory (LANL) and LANL's findings relative to GE's methodology for determining the head loss across GE stacked disk strainers are documented in a LANL Technical Evaluation Report (TER) entitled " Technical Review of GE LTR NEDC-32721P: Application Methodology for GE Stacked-Disk ECCS Suction Strainer," dated December 23,1998. LANL's TER is an attachment to the staff's SE. The staff reviewed GE's submittals and LANL's TER, and agreed with the contractor's findings. Based on the staff's review of all relevant information, including the LANL report, the staff has concluded that the test program used by GE for verifying the !
hydraulic performance of the prototype strainer and validating GE's head loss correlation is acceptable. Further, the staff has concluded that extending the test results over a narrow parametric range outside the test range is reasonable. However, the staff believes that in one case (a plant with a sludge-to-fiber mass ratio in excess of those tested), the application of GE
' test data (or the correlation) would be inappropriate without additional testing. GE is conducting an additional test to address this concern.
. GE adopted an empirical means for correlating the test data. Because GE chose to correlate head loss in terms of superficial parameters (such as circumscribed velocity) that are easy to ,
determine in plant applications, concerns were identified regarding the generic applicability of the GE correlation, especially application beyond the test range. However, upon further review, i the staff believes that GE introduced sufficient margin to compensate for any deficienties in the correlation. Therefore, the staff concluded that this margin would allow GE to apply its correlation within a narrow range beyond the range for which the test data was obtained. LANL also conducted independent analyses to evaluate the applicability of GE methodology to each of the plant applications cited in GE's submittals. Based on the results of these calculations, the staff concluded that the use of GE's hydraulics design method is acceptabie for all the plants, with the exception noted above.
The staff has identified the following specific concerns relative to the use of the GE correlation for the one exception noted above. First, neither the GE nor the NUREG/CR-6224 correlations were ever tested to sludge-to-fiber ratios approaching the value for this plant (i.e., thin-bed effects) and second, the controlling insulation in this case may be a different type of fibrous insulation for which no head loss data has previously been obtained. The staff concludes, therefore, that GE's approach of validating its hydraulics methodology using head loss data from GET-1 is the most prudent approach.
The staff also reached the following conclusions:
(1) GE's use of bump-up factors, consistent with the guidance of NEDO-32686A " Utility Resolution Guidance for ECCS Suction Strainer Blockage" (URG), to account for
! miscellaneous debris is acceptable.
(2) GE's approach to estimate head loss contribution from reflective metallic insulation (RMI)
! debris appears reasonable; however, the staff notes that GE should ensure that NRC comments provided in Appendix K to the staff's safety evaluation report on the URG are
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L T. Green 3 February 3, 1999 i
properly reflected in any GE plant-specific analyses. Specifically, GE should not neglect the contribution of RMI debris without supporting analyses establishing that RMI '
contribution is negligible. The staff was unable to verify the contribution to strainer head
- loss from RMI debris because GE did not provide information relative to the assumed RMI loadings for any of the plants using GE strainers.
Sincerely, Original Signed By:
Michael J. Davis, Project Manager i Generic Issues and Environmental Projects Branch Division of Reactor Program Management }
Office of Nuclear Reactor Regulation
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Enclosure:
As stated '
DISTRIBUTION:
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DOCUMENT NAME: GE32721P.SE o W OFFICE PGEB ' /////[] SC:PGEB ,
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l l- T. Green 3 February 3, 1999 ,
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properly reflected in any GE plant-specific analyses. Specifically, GE should not neglect the contribution of RMI debris without supporting analyses establishing that RMI contribution is negligible. The staff was unable to verify the contribution to strainer head ;
loss from RMI debris because GE did not provide information relative to the assumed RMI loadings for any of the plants using GE strainers.
Sincerely, ,
,',,' f. I '
c p"I Michael J. Davis, Project Manager l Generic issues and Environmental Projects Branch j Division of Reactor Program Management ;
o Office of Nuclear Reactor Regulation
Enclosure:
As stated l
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