ML100570343

Summary of February 22, 2010, Meeting with Carolina Power & Light Company to Discuss Supplemental Responses to Generic Letter 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents

ML100570343
Person / Time
Site:	Harris
Issue date:	03/09/2010
From:	Vaaler M Plant Licensing Branch II
To:	Office of Nuclear Reactor Regulation
Vaaler, Marlayna, NRR/DORL 415-1998
References
TAC MC4688
Download: ML100570343 (17)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555*0001 March 9, 201a LICENSEE:

Carolina Power & Light Company FACILITY:

Shearon Harris Nuclear Power Plant, Unit 1

SUMMARY

OF FEBRUARY 22,2010, MEETING WITH CAROLINA POWER &

LIGHT COMPANY TO DISCUSS SUPPLEMENTAL RESPONSES TO GENERIC LETrER 2004-02, "POTENTIAL IMPACT OF DEBRIS BLOCKAGE ON EMERGENCY RECIRCULATION DURING DESIGN BASIS ACCIDENTS AT PRESSURIZED WATER REACTORS" (TAC NO. MC4688)

On February 22,2010, a Category 1 public meeting was held between the U.S. Nuclear Regulatory Commission (NRC) and representatives of Carolina Power & Light Company (the licensee), which is now doing business as Progress Energy Carolinas, Inc. The meeting was held via a toll-free audio telephone conference call that was available to interested members of the public. (See the Meeting Notice dated January 7,2010 (Agencywide Document Access and Management System (ADAMS) Accession No. ML093640695).) The purpose of the meeting was to discuss remaining issues identified during the NRC staff review of the Shearon Harris Nuclear Power Plant (HNP) Generic Letter (GL) 2004-02 Supplemental Responses. A list of attendees is provided in Enclosure 1.

The NRC staff issued a request for additional information (RAI) regarding GL 2004-02 to the licensee on December 30, 2009 (ADAMS Accession No. ML093510115). (Note that the RAI numbering reflects the previous supplemental submittal dated January 27, 2009 (ADAMS Accession No. ML090300267).) The letter requested that the licensee be prepared to discuss their proposed RAI responses with the NRC staff prior to formal submittal. Accordingly, the licensee provided draft RAI responses (attached as Enclosure 2) prior to the meeting and the NRC staff discussed each proposed response in detail with the licensee. The following summarizes the discussion of each proposed RAI response:

The licensee agreed to supplement the proposed response by adding a statement that Min-K insulation, other than that already discussed, would not be damaged by a loss-of-coolant accident (LOCA). The NRC staff found this approach acceptable.

RAI6 The proposed response was considered sufficient and the approach adequate.

RAI8 The proposed response was considered sufficient and the approach adequate.

RAI10 The proposed response was considered sufficient and the approach adequate.

However, the NRC staff noted that if the licensee believes the ongoing Alion testing, which will conclude in the near future, supports something lower than an erosion percentage of 10 percent for small and large pieces of unjacketed

- 2 low-density fiberglass, the licensee should engage the staff prior to utilizing a number less than 10 percent in any subsequent testing or calculation.

RAI13 The proposed response was considered sufficient and the approach adequate.

RAI14 The proposed response was considered sufficient and the approach adequate.

RAI15 The proposed response was considered sufficient and the approach adequate.

RAI16 The proposed response was considered sufficient and the approach adequate.

RAI19 The proposed response was considered sufficient and the approach adequate.

RAI21 The proposed response was considered sufficient and the approach adequate.

RAI26 The licensee clarified that the methodology used to determine residual heat removal (RHR) pump flow rate continues to assume a 4500 gallon per minute (gpm) flow rate for determining net positive suction head in the scenarios being examined. However, a -3800 gpm flow rate is used to determine the pump head loss for these scenarios.

The licensee agreed to further expand upon this distinction in the RAI response and to provide a discussion of the differences between the single train and the single RHR pump failure scenario. The licensee also stated that its latest RAI response did not modify previous assumptions in this evaluation. The NRC staff found this approach acceptable.

The licensee and the NRC staff briefly discussed HNP's plans for conducting future debris testing, ongoing testing of impacts of debris intrusion on AREVA fuel (since AREVA is the fuel vendor for HNP) and its potential impact on the overall project, and the various strategies for successfully closing out GL 2004-02. The licensee also agreed to verify and inform the NRC staff whether there are any untopcoated inorganic zinc coatings within the zone of influence of a LOCA at HNP. The licensee agreed to provide formal RAI responses by April 20, 2010, and both parties agreed that no further meetings are required relative to the GL 2004-02 supplemental responses.

One member of the public was in attendance. Public Meeting Feedback forms were not received.

- 3 Please direct any inquiries to me at 301-415-3178, or Ma_rla~n.vaa!er~v.

$/~

Marlayna Vaaler, Project Manager Plant Licensing Branch 11-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-400

Enclosures:

1. List of Attendees

2. Draft RAI Responses cc w/encls: Distribution via Listserv

LIST OF ATTENDEES FEBRUARY 22, 2010, MEETING WITH THE CAROLINA POWER &LIGHT COMPANY TO DISCUSS REQUESTS FOR ADDITIONAL INFORMATION ASSOCIATED WITH GENERIC LETrER 2004-02 FOR THE SHEARON HARRIS NUCLEAR POWER PLANT, UNIT 1 Carolina Power & Light Company Japan Nuclear Energy Safety Org.

Michael Scott John Lehning Steve Smith Marlayna Vaaler Sean O'Connor Tim Canter Tony Zimmerman David Corlett Wes McGoun Masao Nagai Kara Stacy Jay Darrell

SHEARON HARRIS NUCLEAR POWER PLANT, UNIT NO.1 DOCKET NO. 50-400fRENEWED LICENSE NO. NPF-63 DRAFT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING SUPPLEMENTAL RESPONSES TO GENERIC LETTER 2004-02 For use in Category 1 Meeting scheduled for February 22, 2010 The emergency core cooling system (ECCS) and the containment spray (CS) recirculation functions for Harris Nuclear Plant (HNP) continue to comply with the requirements listed in the applicable Regulatory Requirements section of Generic Letter (GL) 2004-02 with regard to debris loading conditions. As previously submitted, HNP's Supplemental Response to GL 2004 02 describes the completed corrective actions that ensure this compliance.

NRC Request 4:

The RAI noted that a zone ofinjluence (ZOI) reductionfor encapsulated Min-Kfrom 28.6D to 4D was used based on Continuum Dynamics, Inc. testing ofDiamond Power reflective metal insulation. The RAI requested the details ofthe testing conducted to justifY the ZOI reductions.

The response provided additional information regarding the construction ofthe insulation system installed in the plant and the testing conducted on the Diamond Power reflective metal insulation. The staffreviewed the additional information as well as the test reports that were cited. The staffcould not verifY that the seams in the test cassettes were riveted similarly to the plant cassettes.

The response claimed that the Min-K insulation is less likely to deform than the aluminumfoils within the cassettes that were tested. The staffconsiders that the assertion that a less deformable fill material would result in less damage does not have a technical basis because less deformation may cause increased stresses in other components ofthe insulation system. In addition, the licensee reduced the destruction pressure from that measured in testing for conservatism.

The assertion that the cassettes would not be damaged outside a 4D ZOI rests on a comparative analysis between the tested and installed insulation systems. However, the comparative analysis did not show that the tested and installed cassettes were constructed similarly enough to ensure that the 4D ZOI is sufficiently conservative.

Although some conservatism was added to the evaluation, the staffis not able to conclude that the 4D ZOI assumption is conservative because ofthe large variability in cassette construction, test results, and questions regarding the scaling ofjet impingement tests. Therefore, please provide additional information to demonstrate that the 4D ZOI is justified.

HNP Response:

Rather than providing additional information to justify a 40 201 for encapsulated Min-K, HNP has opted to replace the Min-K insulation on the pressurizer PORV and SRV loop seal piping with an alternate insulation material that is less problematic from a strainer head loss standpoint.

HNP will either perform additional strainer head loss testing with the replacement material or demonstrate that the debris transported to the strainer due to a break of the pressurizer PORV or Page 1 of 11

SHEARON HARRIS NUCLEAR POWER PLANT, UNIT NO. ]

DOCKET NO. 50-400/RENEWED LICENSE NO. NPF-63 DRAFT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING SUPPLEMENTAL RESPONSES TO GENERIC LETTER 2004-02 For use in Category 1 Meeting scheduled for February 22, 2010 SRV piping is bounded by the debris generated by another tested break. Head loss testing will be consistent with the guidance in "NRC Staff Review Guidance Regarding Generic Letter 2004-02 Closure in the Area of Strainer Head Loss and Vortexing" (ADAMS Accession No. ML080230038). Walkdowns to prepare for the replacement of insulation material will take place during Refueling Outage 16 in the fall of 20 10 with replacement during Refueling Outage 17 in the spring of2012.

NRC Request 6:

Part 1: The RAJ requestedfurther just(fication for crediting the settlement offine debris assuming that the analyses used Stokes' Lm,j! as the basis. The stal/deduced that more than 15 percent inactive pool volume was likely creditedfor holdup offine debris (a value which the safety evaluation recommended as a limit).

Latentfibrous debris is a significant contributor to the limiting strainer head loss based on existing testing. Therefore, please clarifY whether more than 15 percent oflatent debris was credited with being held up in inactive volumes (including non-operating sumps). Ifso, provide a basis for this assumption considering Section 3.6.3 ofthe associated safety evaluation.

Part 2: The RAJ requestedfurther justificationfor crediting the settlement offine debris assuming that Stokes' Law was used as the basis. The staffunderstood the following main points based on the supplemental responses: (1) the case where the Stokes' Law approach is credited is not considered to be the limiting break based on existing strainer testing, and (2) the quantity of fine fiber assumed to settle during recirculation is fairly limited (about 5.1 cubic feet, which is approximately 7.6 percent ofthe fine fiber quantity at the strainer).

The staffdid not consider that the response adequatelyjustified the settlement, however, because (1) it was not clear that the crossover leg testing was performed in a prototypical manner, and (2) given the uncertainties with the Stokes' Law settling approach, when combined with uncertainties associated with latent debris being held up in inactive pool volumes and with the estimation ofdebris erosion, it was not clear that the limiting quantity offine fibrous debris was considered in the licensee's evaluation.

As such, it was not clear to the staffthat the fine fibrous debris credited with settling during recirculation can be considered insignificant. Therefore, please provide a technical basis to justifY the current Stokes' Law approach used to credit the settlement affine debris, or else demonstrate that a bounding quantity offine fibrous debris was included in the strainer head loss tests.

Page 2 of 11

SHEARON HARRIS NUCLEAR POWER PLANT, UNIT NO.1 DOCKET NO. 50-400/RENEWED LICENSE NO. NPF-63 DRAFT RESPONSE TO REQUEST FOR ADDIT10NAL INFORMAT10N REGARD1NG SUPPLEMENTAL RESPONSES TO GENER1C LETTER 2004-02 For use in Category 1 Meeting scheduled for February 22, 2010 HNP Response:

Part 1: In the current analysis, more than 15 percent of latent fine debris is credited with being held up in inactive volumes. The latent debris capture in the incore instrumentation tunnel/reactor cavity was truncated at 15 percent (calculated value was 23 percent), but then the non-operating sump was credited with capturing an additional 8 percent of the latent debris.

Debris transport calculations will be revised to credit no more than 15 percent latent fine debris as being held up in inactive volumes. HNP will perform additional strainer head loss testing using the revised debris loads consistent with the guidance in "NRC Staff Review Guidance Regarding Generic Letter 2004-02 Closure in the Area of Strainer Head Loss and Vortexing" (ADAMS Accession No. ML080230038).

Part 2: In order to ensure a bounding quantity offine fibrous debris is considered, the assumption that this type of debris will settle per Stokes' Law will be removed. Applicable debris transport calculations will be revised and HNP will perform additional strainer head loss testing using the revised debris loads consistent with the guidance in "NRC Staff Review Guidance Regarding Generic Letter 2004-02 Closure in the Area of Strainer Head Loss and Vortexing" (ADAMS Accession No. ML080230038).

NRC Request 8:

The RAJ requestedfurther justification for the crediting ofdebris retention on gratings in upper containment. The staffdid not consider the response to have fully addressed the question for the following reasons:

a. It appears the analysis may have assumed a 50 percent capture percentage for each level in a series ofgratings. The staffwould expect downstream gratings to have reduced capture percentages, since the less transportable debris pieces would be preferentially filtered out on upstream gratings.

b. Part ofthe response was based on datajor 6-inch x 4-inch debris pieces, which, although grouped with small pieces in the HNP analysis, would be considered large pieces, per Nuclear Energy Institute (NEI) 04-07, "Pressurized Water Reactor Sump Performance Evaluation Methodology, " guidance, rather than small pieces.

Furthermore, per the blowdown data in NUREGICR-6369, "Drywell Debris Transport Study, " these 6-inch x 4-inch pieces would seemingly tend not to pass through gratings to the extent the analyses assumed during the blowdown phase (which would impact the credit taken for such pieces subsequently being retained on the upper side ofgratings during washdown).

Page 3 of II

SHEARON HARRIS NUCLEAR POWER PLANT, UNIT NO. ]

DOCKET NO. 50-400/RENEWED LICENSE NO. NPF-63 DRAFT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING SUPPLEMENTAL RESPONSES TO GENERIC LETTER 2004-02 For use in Category 1 Meeting scheduled for February 22, 2010

c. Although the uniform spray jlow areal densities in pressurized water reactors are typically significantly lower than the sprayjlow rate tested in NUREG/CR-6369. a substantialfraction ofthe debris interdicted by gratings would likely be exposed to more concentrated streams ofdrainage.

d. It is not clear to the staffwhy a significant amount ofdebris blown to upper containment would be capable ofgravitationally settling in sheltered areas ofcontainment where spray cannot reach.

Please address these remaining points related to the credit taken for retention ofdebris pieces on gratings in upper containment, or demonstrate that the total fiber used in the strainer testing was prototypical or conservative.

HNP Response:

HNP has opted to conservatively assume no debris retention on gratings and upper containment.

Applicable debris transport calculations will be revised and HNP will perform additional strainer head loss testing using the revised debris loads consistent with the guidance in "NRC Staff Review Guidance Regarding Generic Letter 2004-02 Closure in the Area of Strainer Head Loss and Vortexing" (ADAMS Accession No. ML080230038).

NRC Request 10:

This RAI requestedfurther justification to demonstrate the adequacy ofthe testing credited to support an erosion percentage of10 percentfor small and large pieces ofunjacketed low-density fiberglass. Based on the information provided in the supplemental response, the staffconsiders it possible that the erosion testing being credited could be the generic testing performed by Alion as reported in the February 23, 2009, RAI re5ponsefrom the San Onofre Nuclear Generating Station (ADAMS Accession No. I\\l1L09(580024).

The staff is concerned that these test results may be spurious, because the longer-duration tests showed a significantly lower cumulative erosion percentage than the shorter-duration tests.

Therefore, please identify the vendor that performed the debris erosion testing credited by HNP andprovide a graph ofthe percent oferoded debris as afunction oftime for the erosion tests that were performed. In addition, please provide justification that the tests are valid if anomalous behavior is apparent in the test results.

HNP Response:

Alion performed the fiber erosion testing initially credited by HNP. Alion has since revised their 30-day erosion testing protocol and retested, with results available soon. HNP will evaluate the new test results, make any necessary revisions to debris transport calculations and then perform Page 4 of I I

SHEARON HARRIS NUCLEAR POWER PLANT, UNIT NO.1 DOCKET NO. 50-400/RENEWED LICENSE NO. NPF-63 DRAFT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING SUPPLEMENTAL RESPONSES TO GENERIC LETTER 2004-02 For use in Category 1 Meeting scheduled for February 22, 2010 additional strainer head loss testing using any revised debris loads consistent with the guidance in "NRC StaffReview Guidance Regarding Generic Letter 2004-02 Closure in the Area of Strainer Head Loss and Vortexing" (ADAMS Accession No. ML080230038).

NRC Request 13:

This RAJ requested the basis for (l) attributing the lower head loss associated with the test without debris bypass eliminators (DBEs) installed solely to the removal ofthis mesh and (2) the position that the expected variation associated with a repeat test pellormedfor the HNP strainer design without DBEs could not exceed the small demonstrated margin (0.12 ft) available for the residual heat removal pumps.

The supplemental re!>ponse provided additional information regarding the tests conducted with (test 3) and without (test 4) the DBE mesh. The RAJ response states that the tests were conducted identically with the exception ofthe installation ofthe DBE. Graphs ofthe test results were provided; however, the graphs were too compressed along the time scale to allow the staffto compare behavior ofthe head loss during the addition ofthe various debris types.

Jn addition, the difference in bedformation was attributed to the DBE. The supplemental response stated that a bedforms across the DBE and also that the DBE affects the bedformation on the strainer surface, resulting in a more uniform bed. However, the staffhas not observed or been made aware ofother cases in which an Enercon strainer DBE has formed a debris bed. Jn addition, the assertion that the DBE results in a more uniform debris bed on the top hat sUilace is contrary to observations made by Alion during most similar tests.

The response also stated that during non-chemical testing, two Microtherm tests were performed with relatively similar results, thereby showing test repeatability. Jn addition, the response stated that Min-K isfabricatedfrom the same constituents as Microtherm and therefore should behave similarly. However, the staffnoted that the response to RAJ 14 pointed out significant differences between the percentages ofeach constituent making up the two types ofinsulation; therefore, the staffbelieves that the chemical effects tests conducted with the two different materials should not be compared.

The staffconcludes that there is not enough information to justify that the full difference between test 3 and test 4 was due solely to the absence ofthe DBE in test 4. Further information may be available to assist in this justification, and is requested in order for the staffto complete its review. For example, the licensee could provide higher resolution test traces ofhead loss during debris addition to provide additional insight. The licensee could also provide details ofindustry experience for other problematic debris tests both with and without the DBE installed in Enercon strainers.

Page 5 of 11

SHEARON HARRIS NUCLEAR POWER PLANT. UNIT NO.1 DOCKET NO. 50-400fRENEWED LICENSE NO. NPF-63 DRAFT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING SUPPLEMENTAL RESPONSES TO GENERIC LETTER 2004-02 For use in Category 1 Meeting scheduled for February 22, 2010 HNP Response:

HNP will be replacing the encapsulated Min-K insulation on the pressurizer PORV and SRV loop seal piping with an alternate insulation material that is less problematic from a strainer head loss standpoint. HNP will either perform additional strainer head loss testing with the replacement material or demonstrate that the debris transported to the strainer due to a break of the pressurizer PORV or SRV piping is bounded by the debris generated by another tested break.

Head loss testing will be consistent with the guidance in "NRC Staff Review Guidance Regarding Generic Letter 2004-02 Closure in the Area of Strainer Head Loss and Vortexing" (ADAMS Accession No. ML080230038). In order for the additional testing to be more representative of the final installed HNP strainer design, these additional tests will be conducted without the use of Debris Bypass Eliminator mesh.

NRC Request 14:

The RAJ raised questions regarding the repeatability ofthe Alion testing based on the results of HNP test cases using Min-K and Microtherm [microporous insulation]. Specifically, given that Min-K and Microtherm are composed essentially ofthe same base materials (silicon dioxide and titanium dioxide), and given that the amounts ofMin-K and Microtherm in the material-specific testing were close to the same (11.6 cubic feet (ft3) and 12. J.fi3, respectively), the staff askedfor the basis for why these two similar materials had significantly different head loss results in the tests with the DEE mesh installed. Although the final HNP strainer configuration does not contain a DEE mesh, this observation demonstrates the potential for a lack ofrepeatability in the head loss test results.

The supplemental response stated that although the materials are composed ofthe same constituents, the percentage ofeach constituent is sufficiently different, such that the head loss from tests ofthe two materials would be expected to be different. The staffunderstands that there are differences in the amount ofeach constituent in the insulation. However, the information provided does not remove doubt about the consistency oftest results attained during the strainer testing.

The staffnoted the following during its review: 1) the fibrous portion ofthe microporous debris should not be a large contributor to any differences due to the other fibrous debris (latent) included in the test; 2) the amount offumed silica in each test was approximately the same,' 3) the titanium dioxide was significantly higher in the Microtherm test, yet this test had lower head loss,' and 4) unless the titanium dioxide is a contributor to reduced head loss, or the fibrous debris added to the test(s) for latent debris was not prepared properly as fines, it is difficult to understand how the test results are consistent. Therefore, please address the above stated staff concerns regarding test repeatability.

Page 6 of 11

SHEARON HARRIS NUCLEAR POWER PLANT, UNIT NO.1 DOCKET NO. 50-400/RENEWED LICENSE NO. NPF-63 DRAFT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING SUPPLEMENTAL RESPONSES TO GENERIC LETTER 2004-02 For use in Category 1 Meeting scheduled for February 22, 2010 HNP Response:

HNP will perfonn additional strainer head loss testing for the Microthenn break consistent with the guidance in "NRC Staff Review Guidance Regarding Generic Letter 2004-02 Closure in the Area of Strainer Head Loss and Vortexing" (ADAMS Accession No. ML080230038).

Additional Min-K testing will not be conducted as HNP has opted to replace the Min-K insulation on the pressurizer PORV and SRV loop seal piping with an alternate insulation material that is less problematic from a strainer head loss standpoint.

NRC Request 15:

The RAJ requested the fibrous debris size distribution usedfor testing. as well as a comparison to the size distribution predicted by the transport evaluation.

The supplemental response provided additional information on the fibrous debris sizing. The test debris was stated to be within size classes 1-4 as defined by NUREGICR-6808, "Knowledge Basefor the Effect ofDebris on Pressurized Water Reactor Emergency Core Cooling Sump Performance, " and deemed to be readily transportable. However, the response provided neither a predicted size distribution for the debris at the strainer nor a comparison to the size distribution used during the testing.

Based on the percentage offiber calculated to be available for the crossover leg break, the use of size class 1-4fibers is likely conservative for the test corresponding to that break. However, this size distribution is not representative oftypical latent debris. For the hot-leg and pressurizer cubicle break, all fiber should have been size class 1-3, with a relatively low percentage ofsize 3 fibers because almost all fibers for these breaks are latent (treated as individual fibers).

Based on the response to RAJ 15, the staffcould not determine that the fibrous debris usedfor the pressurizer and hot-leg breaks was representative oflatent debris which wouldprovide a conservative test condition for these breaks. Further information may be available to assist in this determination, and is requested in orderfor the staffto complete its review.

HNP Response:

HNP will perform additional strainer head loss testing consistent with the guidance in "NRC Staff Review Guidance Regarding Generic Letter 2004-02 Closure in the Area of Strainer Head Loss and Vortexing" (ADAMS Accession No. ML080230038). This will ensure that the fibrous debris size distribution used in the test is representative of typical latent debris.

Page 7 of 11

SHEARON HARRIS NUCLEAR POWER PLANT, UNIT NO.1 DOCKET NO. 50-400/RENEWED LICENSE NO. NPF-63 DRAFT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING SUPPLEMENTAL RESPONSES TO GENERIC LETTER 2004-02 For use in Category 1 Meeting scheduled for February 22, 2010 NRC Request 16:

This RAJ requested details ofthe debris addition procedures used.

The supplemental response stated that the debris was mixed with water into a homogeneous slurry using 5 gallon buckets prior to introduction into the test flume. About 1-3 pounds ofdebris.

was added to each bucketfor mixing with water. Stirring was used as necessary to ensure that a majority ofthe debris was transported to the strainer. The response stated that the addition methods resulted in thorough mixing and dispersion ofthe debris and lack ofagglomeration while allowing the debris to transport to the strainer.

The description provided by the response indicates that the debris introduction was conducted in a manner that would prevent agglomeration. Additionally, the response indicated that stirring prevented excessive debris settlement and that mixing ofthe debris typically occurredjust prior to addition to the test tank.

However, during a trip to Alion to observe testing, the staffidentified issues regarding debris preparation and introduction that could affect head loss and tramport during testing (refer to the trip report located at ADAMS Accession No. ML071230203j. The staffnoted that these issues were likely more important for tests with low fibrous loads.

Therefore, for HNP the debris preparation and introduction issues would have the most impact on the Min-K and Microtherm tests. The staffconsiders it likely that the debris addition practices for the HNP testing were similar to those used during the testing that the staffobserved. Based these observations ofsimilar testing, the HNP testing may not have used a conservative debris introduction process.

Accordingly, please address the above staffconcerns and demonstrate that the HNP testing led to prototypical or conservative results for the strainer head loss.

HNP Response:

HNP will perform additional strainer head loss testing consistent with the guidance in "NRC Staff Review Guidance Regarding Generic Letter 2004-02 Closure in the Area of Strainer Head Loss and Vortexing" (ADAMS Accession No. ML080230038). This includes ensuring the representative debris tested is prepared and introduced in a manner consistent with NRC guidance.

NRC Request 19:

This RAJ requested information to show that a valid thin bed test was conducted such that: (1) fibrous debris preparation and introduction would result in prototypical tramport and bed Page 8 of II

SHEARON HARRIS NUCLEAR POWER PLANT, UNIT NO. ]

DOCKET NO. 50-400/RENEWED LICENSE NO. NPF-63 DRAFT RESPONSE TO REQUEST FOR ADDrTIONAL INFORMATION REGARDING SUPPLEMENTAL RESPONSES TO GENERIC LETTER 2004-02 For use in Category 1 Meeting scheduled for February 22, 2010 formation (note that the staffconsiders that the most transportable debris will reach the strainer first); (2) jlow conditions. including any stirring used during testing, would allow prototypical bedformation; (3) the installation ofthe DEE would not change the prototypicality ofbed formation on the strainer, or ver(fication that testing was conducted with the same top hat arrangement (i.e., no DEE) installed in the plant; and (4) various incremental amounts offiber were used in conjunction with limiting particulate debris loads during thin bed testing.

The supplemental response provided additional iriformation on how head loss testing was conducted with respect to acceptable thin bed test practices. The iriformation provided answered some areas adequately. The re:-.ponse regardingjlow conditions (item 2) was acceptable overall.

However, the other items were not addressed satisfactorily.

The response regarding item i stated thatfibrous debris was prepared such that a range of individualfibers through -i-inch tufts was represented in the testing. For the Nukon case, which was the only case for which a thin bed test needed to be conducted, the fibrous debris should have been added such that the fine fibrous debris was introduced before the smallfibrous debris, and the particulate debris should have been addedprior to anyfibrous debris. This position is documented in the "NRC StaffReview Guidance Regarding Generic Letter 200402 Closure in the Area ofStrainer Head Loss and Vortexing" (ADAMS Accession No. ML080230038).

However, this was not the case for the HNP testing, as all the debris was mixed together.

The response to item 3 indicated that the installation ofthe DEE results in a more uniform debris bed, and would therefore result in a higher likelihood ofthin bedformation. However, this statement is in conflict with iriformation that has been provided to the staffduring discussions with Alion. According to Alion, the installation ofthe DEE is likely to result in a less uniform bed. Testing with the DEE installed appears, therefore, to be non-conservative for thin bed considerations when compared to the strainer installed in the plant (i.e., no DEE).

With respect to item 4, the re:-.ponse stated that for the Min-K and Microtherm tests, batching of

.fiber is not required due to the low amounts ofjibrous debris created by the break. The staff considers this acceptable. However, for the Nukon break, the two amounts offiber tested would result in i /8-inch and -3/4-inch theoretical bed thicknesses. These two test points do not include the likely limiting thin bed thickness for the strainers used during Alion testing. The NRC staffguidance document cited above recommends that debris be batched in small increments to determine the limiting thin bed.

Eased on the above, the staffconcludes that a valid thin bed test may not have been conducted.

Therefore, please address the above concerns regarding the adequacy ofthin bed testingfor HNP.

Page 9 of 11

SHEARON HARRIS NUCLEAR POWER PLANT, UNIT NO. ]

DOCKET NO. 50-400/RENEWED LICENSE NO. NPF-63 DRAFT RESPONSE TO REQUEST FOR ADDITJONAL INFORMATJON REGARDING SUPPLEMENTAL RESPONSES TO GENERIC LETTER 2004-02 For use in Category 1 Meeting scheduled for February 22, 2010 HNP Response:

fThlP will perform additional strainer head loss testing to include thin bed testing consistent with the guidance in "NRC Staff Review Guidance Regarding Generic Letter 2004-02 Closure in the Area of Strainer Head Loss and Vortexing" (ADAMS Accession No. ML080230038). This includes ensuring the representative debris tested is prepared and introduced in a manner consistent with NRC guidance. In order for the additional testing to be more representative of the final installed HNP strainer design, these additional tests wilJ be conducted without the use of Debris Bypass Eliminator mesh.

NRC Request 21:

The original submittal stated that the vortexing evaluation was completed w;ing a residual heat removal (RHR) pump runout flow (4500 gallons per minute (gpm)). It was not clear to the staff whether containment sprayflow was included in the evaluation. It was also not clear whether either testing or the clean strainer head loss calculation included the containment spray/low.

The staffrequested additional information regarding the pump flows that were used to furnish inputsfor head loss scaling, as well as the bases for these flows.

The supplemental response provided additional information that clar(fied the flow rates usedfor both the test scaling and clean strainer head loss calculations. The response for the clean strainer head loss portion ofthe question is acceptable. However, based on the response, the staffcould not determine why the vortexing evaluation was conducted at RHR runoutflow (4500 gpm) versus maximum sump flow (5754 gpm).

The response implies that only the RHR or the containment !'pray pump can take suctionfrom the sump at any given time, but this is not how the flow through the sump is described in the initial supplemental response (see page AI-3I), which indicates that the RHR and containment spray pumps both take suction through the same strainer. In addition, the installation ofa vortex suppressor over the strainer, as described in the initial supplemental response, indicates that a vortex from the sump pool sUI/ace is ofconcern.

Accordingly, please provide information to justifY that the vortexing evaluation should only consider the RHRflow, and not the containment sprayflow, since both pumps take suction through the strainer surface during recirculation..

HNP Response:

Each sump is arranged in two halves separated by a concrete divider wall. The RHR pump suction is on one side of the wall and the containment spray pump suction is on the other with a flow-balancing opening at the bottom. Due to this arrangement, a limiting case for vortexing would be one that considers the maximum flow that could be directed through one half of a Page 10 of 11

SHEARON HARRIS NUCLEAR POWER PLANT, UNIT NO.1 DOCKET NO. 50-400/RENEWED LICENSE NO. NPF-63 DRAFT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING SUPPLEMENTAL RESPONSES TO GENERIC LETTER 2004-02 For use in Category 1 Meeting scheduled for February 22, 2010 sump's strainer screen area. Since the RHR pump runout flow of 4,500 gpm bounds the maximum flow rate of 1,863 gpm from the sump to a containment spray pump, 4,500 gpm was selected as the flow rate to use in the vortexing evaluation. The maximum flow rate through the RHR half of the sump strainer would actually be less than 4,500 because the flow-balancing opening allows a portion ofthe RHR pump flow to be drawn through the containment spray half ofthe sump strainer screen.

NRC Request 26:

The RAJ requested a description ofthe methodology used to compute the maximum pump jlows for the RHR and containment spray pumps. Although an adequate re.sponse was provided regarding the containment spray pumps, the staffconsiders the response concerning the RHR pumps to be inadequate because: (1) rather than describing the methodology used, the response merely identified the vendor that pe/jormed the calculation; and (2) the response indicated that thejlow rate usedfor the sump performance analysis was representative (e.g., as opposed to a bounding or calculated value).

Accordingly, please describe the methodology used to determine the RHR pump maximum jlow rate, as well as provide the basisfor considering thisjlow rate to be a conservative or prototypical input to the sump strainer pe/jormance ana~vsis.

HNP Response:

The methodology used by Westinghouse to derive the RHR pump flow rate for the limiting break case (3,891 gpm from one RHR pump providing flow to one CSIP during cold leg recirculation) involved developing a system resistance curve using Zebra software, which is the predecessor of the PEGISYS code, and identifying its intersection with a RHR pump performance curve. However, HNP is continuing to evaluate whether the RHR pump performance curve used in the original analysis was appropriate for application to this system configuration.

Page 11 of 11

Vaaler, Marlayna From:

Stacy, Kara [Kara.Stacy@pgnmail.com]

Sent:

Friday, February 19, 2010 12:57 PM To:

Scott, Michael Cc:

Vaaler, Marlayna

Subject:

HNP GL 2004-02 RAI In preparation for Monday's phone call, following is additional information for RAI 26.

NRC Request 26:

The RAI requested a description of the methodology used to compute the maximum pump flows for the RHR

.and containment spray pumps. Although an adequate response was provided regarding the containment spray pumps, the staff considers the response concerning the RHR pumps to be inadequate because: (1) rather than describing the methodology used, the response merely identified the vendor that performed the calculation; and (2) the response indicated that the flow rate used for the sump performance analysis was representative (e.g., as opposed to a bounding or calculated value).

Accordingly, please describe the methodology used to determine the RHR pump maximum flow rate, as well as provide the basis for considering this flow rate to be a conservative or prototypical input to the sump strainer performance analysis.

HNP Response:

The methodology used by Westinghouse to derive the RHR pump flow rate for the limiting break case (3,891 gpm from one RHR pump providing flow to one CSIP during cold leg recirculation) involved developing a system resistance curve using Zebra software, which is the predecessor of the PEGISYS code, and identifying its intersection with a RHR pump performance curve.

This flow rate was provided to HNP by Westinghouse as an appropriate RHR pump flow rate for the case where there is a single train failure resulting in one RHR pump providing flow to one CSIP and also for the purpose of designing the original sump suction screens. To ensure that this flow rate is conservative or prototypical for the current sump strainer performance analysis, HNP chose to perform a verification using a system resistance curve we developed along with pump performance curves generated using actual pre operational test data. The intersection of the curves for the 'B' RHR pump gave a flow rate of 3,901 gpm and the curve intersection for the 'A' RHR pump gave a flow of 3,893 gpm. Although these flow rates are higher they only represent a maximum increase from the Westinghouse value of 0.26%. Next, the vendor pump performance curves were compared to the HNP system resistance curve. This gave a 'B' RHR flow rate of 3,945 gpm and an 'A' RHR flow rate of 3,901 gpm. Taking the highest flow rate of 3,945 gpm RHR flow would result in a total sump flow for the single train failure case of 5,808 gpm. This represents less than a 1%

difference from the analyzed sump flow of 5,754 gpm. Given the small percentage difference between the Westinghouse supplied flow rate of 3,891 gpm and the flow rates determined by HNP from actual test data and vendor curves, HNP considers the flow rate of 3,891 gpm to be a prototypical input to the sump strainer performance analysis. The small difference that exists is offset by other conservatisms, such as not crediting Stokesian settling or debris hold-up on gratings, that will be included in the additional sump strainer head loss testing that HNP will perform.

1

- 3 Please direct any inquiries to me at 301-415-3178, or Marlayna.Vaaler@nrc.gov.

IRAI Marlayna Vaaler, Project Manager Plant Licensing Branch 11-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-400

Enclosures:

1. List of Attendees

2. Draft RAI Responses cc wtencis: Distribution via Listserv DISTRIBUTION:

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NAME MVaaler CSoia MScott DBroaddus/SNB for DATE 03/31/10 03/02/10 03/05/10 03/09/10 OFFICIAL RECORD COpy