ML11216A263

Summary of Telephone Conference Call Held on July 28, 2011, Between the U.S. NRC and STP Nuclear Operating Company, Concerning RAI Pertaining to the South Texas Project, LRA

ML11216A263
Person / Time
Site:	South Texas
Issue date:	08/23/2011
From:	Tam Tran License Renewal Projects Branch 2
To:	South Texas
Tran T, 415-3617
References
Download: ML11216A263 (8)

Text

,,~p.~ REaU, _ UNITED STATES vCJ '"'{>>

o,~. _01>" NUCLEAR REGULATORY COMMISSION t:! (> WASHINGTON, D.C. 20555-0001

< 0 t;  ;

~ ~ A~gust23, 2011

~ ~

'S-" ~o

• • • • -¥ LICENSEE: STP Nuclear Operating Company FACILITY: South Texas Project SUB~IECT:

SUMMARY

OF TELEPHONE CONFERENCE CALL HELD ON JULY 28, 2011, BETWEEN THE U.S. NUCLEAR REGULATORY COMMISSION AND STP NUCLEAR OPERATING COMPANY, CONCERNING REQUESTS FOR ADDITIONAL INFORMATION PERTAINING TO THE SOUTH TEXAS PROJECT LICENSE RENEWAL APPLICATION The U.S. Nuclear Regulatory Commission (NRC or the staff) and representatives of STP Nuclear Operating Company held a telephone conference call on July 28,2011, to discuss and clarify the applicant's responses to the staff's requests for additional information (RAls) concerning the South Texas Project license renewal application. The telephone conference call was useful in clarifying the needs for follow-up RAls.

Enclosure 1 provides a listing of the partiCipants and Enclosure 2 contains a listing of the clarifications for RAI responses that were discussed with the applicant, including a brief description of the status of the items.

The applicant had an opportunity to comment on this summary.

-'l~'~

Tam Tran, Project Manager Projects Branch 2 Division of License Renewal Office of Nuclear Reactor Regulation Docket Nos.: 50-498 and 50-499

Enclosures:

1. List of Participants

2. List of RAI cc w/encls: Listserv

TELEPHONE CONFERENCE CAll SOUTH TEXAS PRO~IECT LICENSE RENEWAL APPLICATION LIST OF PARTICIPANTS JULY 28, 2011 PARTICIPANTS AFFILIATIONS Tam Tran Nuclear Regulatory Commission (NRC)

Jerry Dozier NRC Travis Tate NRC Donnie Harrison NRC Steve Short Pacific Northwest National laboratory (PNNl)

Bruce Schmidt PNNl Arden Aldridge South Texas Project (STP)

Chet Mcl ntyre STP Shawn Rodgers STP Mary Ann Billings STP Don Macleod Engineering and Research, Inc. (ERIN)

ENCLOSURE 1

REQUESTS FOR ADDITIONAL INFORMATION LICENSE RENEWAL APPLICATION JULY 2S, 2011 The U.S. Nuclear Regulatory Commission (NRC or the staff) and representatives of STP Nuclear Operating Company held a telephone conference call on July 2S, 2011, to discuss and clarify the following responses to requests for additional information (RAls) concerning the license renewal application (LRA), listed in ML11140A015.

A RAJ response supplements are needed for additional clarification RAI 1.d: The response to this RAI states that a reduced set of sequences was used for the uncertainty analysis and the results scaled so that the mean of the distribution was scaled to match the mean of the CDF point estimate or 6.39E-06 per year. It is unclear how this scaling of the CDF distribution impacts the 95th percentile multiplier of 1.6 used in the uncertainty analysis.

Provide the mean and 95th percentile CDF from the Monte Carlo distribution and the ratio of this 95 th percentile CDF to the point estimate CDF for the reduced set of sequences. If the resulting ratio is greater than 1.6, consider the impact on the SAMA cost benefit analysis provided in the environmental report (ER) and in response to RAls. Also, confirm that all CDF and release frequency values provided in the ER and in RAI responses are point estimates based on mean basic event values.

RAI 1.f: The total CDF for STP _REV4 is given in Table 1-3 of the RAI response as 1.17E-05 per year. Section F.2 of the ER and page 9 of Attachment 1 to STPNOC's 2/2S/07 RMTS submittal give the total as 9.0SE-06 per year.

Explain this difference and/or indicate the necessary corrections in the submittals.

RAI 2.c: The response to this RAI states that an additional initiator with a large contribution to LERF, HWIND2, that was not included in the IPE was added to the PRA later. ER Table F.2-1 does not include the HWIND2 initiator, only the HWIND initiator.

Discuss the difference between the HWIND and HWIND2 initiators, their contributions to CDF and LERF, and identify the version of the PRA model to which the HWIND2 initiator was first added.

RAI 6.b: The ER discussion of the modeling of SAMA 12 appears to indicate that the only sequences impacted and credited in the cost benefit analysis are those involving leakage from the primary system. The conservative modeling discussed involves hydrogen generation for non-leakage sequences. The response to the RAI states sequences involving this conservative ENCLOSURE 2

-2 modeling are included in the assessment of the impact of this SAMA. Describe how these conservatively modeled sequences are included in the SAMA evaluation.

Discussion: The applicant indicated that the questions are clear. The applicant will provide an RAI supplement by August 19, 2011. In addition, during the discussion, the applicant provided clarification that the information in the ER for RAI 2.c is correct; hence, the staff withdraws this question (RAI 2.c).

B. Resolution path is needed on the use of best available methodology or data for evaluation in DSEIS RAI 3.b: The response to this RAI simply indicates that a review of the NUREG/CR-6850 will be performed in the future. However, the recent research and guidance reported in NUREG/CR 6850, specifically in the areas of hot short probabilities, fire ignition frequencies, and non suppression probabilities, indicate that the fire analysis methodologies utilized for the IPE may underestimate fire risk.

Provide assurance that consideration of this new information is not expected to impact the selection of cost beneficial SAMAs for STP.

Discussion: The applicant indicated that the question is clear. The applicant will provide a proposed resolution by August 19, 2011.

RAI 3.c: The response to this RAI did not provide the requested updated seismic CDF results instead citing IN 2010-18. While this Information Notice concluded that the US plants had adequate safety margin, it did indicate that the seismic CDF for South Texas could be as high as 3E-06 per year (for spectral accelerations of 5 hz and 10hz). This is 40 times the total seismic CDF given in the ER. Also note that the STP IPE gives a seismic CDF using the LLNL hazard curve of 1.7E-05 per year which is over 200 times the value used in the PRA. Since the seismic CDF was determined using point estimates, the seismic CDF for STP _REV6, based on the LLNL hazard curve, can be obtained from the LLNL seismic frequencies from Table 3.4.4-9 of the IPEIIPEEE and the CCDPs from Table F.2-1 of the ER. The result is a SCDF of 8.7E-06 per year.

Comparing the USGS hazard curves for the STP site with the EPRI hazard curves indicates that the frequency for the USGS curves is 60 to 150 times those for the EPRI curves over the range of 0.4 to 0.6 g which is the range for the largest contributors to STP seismic CDF. Furthermore, the USGS hazard curve is higher than the LLNL hazard curve by a factor of 1.5 to 2 over the same range.

Using the above method for determining the CDF for SEIS3 and SEIS4 initiators gives seismic CDFs of 4E-06 and 5E-06 per year, respectively. This indicates that applying the LLNL hazard curves or the 2008 USGS hazard curves to the SEIS3 and SEIS4 initiators could lead to CDF contributions of about 60 to 150% of the STP _REV6 total CDF.

-3 Provide an assessment of the seismic CDF contribution due to the updated USGS hazard curves and the potential for cost beneficial SAMAs.

Discussion: The applicant indicated that the question is clear. The applicant's experts are having discussion with the industry on the use of USGS hazard curves, but this effort may not meet the license renewal schedule. The difficulty for the applicant's experts is that the use of LLNL or the USGS hazard curves may not provide consistently realistic results requiring extensive peer-reviews. The applicant is working on a proposed resolution by August 19, 2011.

... ML11216A263 *concurred via email OFFICE LA:DLR* PM:RPB2:DLR BC:RPB2:DLR NAME IKing TTran DWrona DATE 8/10/11 8/18/11 8/23/11 Memorandum to STP Nuclear Operating Company from T. Tran dated August 23, 2011

SUMMARY

OF TELEPHONE CONFERENCE CALL HELD ON JULY 28, 2011 BETWEEN THE U.S. NUCLEAR REGULATORY COMMISSION AND STP NUCLEAR OPERATING COMPANY, CONCERNING REQUESTS FOR ADDITIONAL INFORMATION PERTAINING TO THE SOUTH TEXAS PROJECT, LICENSE RENEWAL APPLICATION DISTRIBUTION:

E-MAIL:

PUBLIC (or NON-PUBLIC if appropriate)

RidsNrrDlr Resource RidsNrrDlrRpb1 Resource RidsNrrDlrRpb2 Resource RidsNrrDlrRerb Resource RidsNrrDlrRpob Resource RidsNrrDraApla Resource RidsOgcMailCenter JDaily TTran ICouret, OPA BSingal, DORL NO'Keefe GPick, RIV JDixon, RIV VDricks, RIV WMaier, RIV AVegel, RIV SGraves, RIV