ML13038A603
| ML13038A603 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 02/25/2013 |
| From: | Wang A Plant Licensing Branch IV |
| To: | Entergy Operations |
| Wang A | |
| References | |
| TAC MF0343 | |
| Download: ML13038A603 (8) | |
Text
't\\{J)J OFFICIAL USE ONLY - PROPRIETARY INFORMATION UNITED STATES.
NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555*0001 February 25, 2013 Vice President, Operations Entergy Operations, Inc.
Grand Gulf Nuclear Station P.O. Box 756 Port Gibson, MS 39150
SUBJECT:
GRAND GULF NUCLEAR STATION. UNIT 1 - REQUEST FOR ADDITIONAL INFORMATION REGARDING ENTERGY'S FINAL REPORT FOR REPLACEMENT STEAM DRYER (TAC NO. MF0343)
Dear Sir or Madam:
By letter dated September 8.2010 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML102660409), Entergy Operations, Inc. (Entergy. the licensee),
submitted an extended power uprate (EPU) license amendment request for Grand Gulf Nuclear Station, Unit No.1 (GGNS). The proposed amendment requested an increase in the maximum steady-state power level at GGNS from 3898 megawatts thermal (MWt) to 4408 MWt. This represented an approximate 13 percent increase above the current licensed thermal power or an approximate 15 percent increase above the original licensed thermal power.
By letter dated July 18,2012 (ADAMS Accession No. ML121210023), the U.S. Nuclear Regulatory Commission (NRC) issued Amendment No. 191 to Entergy approving the EPU for GGNS to increase the maximum reactor core power operating limit from 3898 to 4408 MWt. As part of this approval, the NRC staff required several license conditions including the submittal of a final report for the replacement steam dryer which was to provide a final load definition and stress report of the steam dryer. including the results of a complete re-analysis using the GGNS-specific bias and uncertainties and transfer function. This report was to be submitted to the NRC within 90 days of achieving the EPU power level. By letter dated December 6, 2012 (ADAMS Accession No. ML123420255), Entergy submitted the final report for the replacement steam dryer for NRC staff review.
The NRC staff has determined that additional information is needed for the NRC staff to complete our review of this report. This enclosed request for additional information (RAI) pertaining to the final report for the replacement steam dryer was discussed with Mr. Guy Davant of your staff on January 28, 2013, and it was agreed that a response would be provided within 60 days of receipt of this request. The NRC staff's proprietary version of the RAI is provided in Enclosure 1 and a non-proprietary version is provided in Enclosure 2.
NOTICE: Enclosure 1 to this letter contains Proprietary Information. Upon separation from : this letter is decontrolled.
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- 2 If circumstances result in the need to revise the requested response date, please contact me at (301) 415-1445 or via e-mail at Alan.Wang@nrc.gov.
Sincerely, Alan B. Wang, Proje tanager Plant licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-416 cc w/Encl2: Distribution via Listserv
Enclosures:
- 1. Request for Additional Information (proprietary)
- 2. Request for Additional Information (non-proprietary)
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OFFICIAl US. ONb¥ PROPRIETARY INFORMATION
ENCLOSURE 2 (NON-PROPRIETARY)
REQUEST FOR ADDITIONAL INFORMATION FINAL REPORT FOR REPLACEMENT STEAM DRYER GRAND GULF NUCLEAR STATION. UNIT NO.1 EXTENDED POWER UPRATE LICENSE AMENDMENT REQUEST ENTERGY OPERATIONS, INC.
DOCKET NO. 50-416
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OFFIOIAL USE ONLY PROPRIETARY INFORMATION REQUEST FOR ADDITIONAL INFORMATION NRC REVIEW OF FINAL REPORT FOR REPLACEMENT STEAM DRYER GRAND GULF NUCLEAR STATION, UNIT 1 ENTERGY OPERATIONS, INC.
DOCKET NO. 50-416 By letter dated September 8, 2010 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML102660409), Entergy Operations, Inc. (Entergy, the licensee),
submitted an extended power uprate (EPU) license amendment request for Grand Gulf Nuclear Station, Unit NO.1 (GGNS). The proposed amendment requested an increase in the maximum steady-state power level at GGNS from 3898 megawatts thermal (MWt) to 4408 MWt. This represented an approximate 13 percent increase above the current licensed thermal power (CL TP) or an approximate 15 percent increase above the original licensed thermal power (OLTP).
By letter dated July 18, 2012 (ADAMS Accession No. ML121210023), the U.S. Nuclear Regulatory Commission (NRC) issued Amendment No. 191 to Entergy approving the EPU for GGNS to increase the maximum reactor core power operating limit from 3898 to 4408 MWt. As part of this approval, the NRC staff required several license conditions including the submittal of a final report for the replacement steam dryer (RSD) which was to provide a final load definition and stress report of the steam dryer, including the results of a complete re-analysis using the GGNS-specific bias errors and uncertainties (B&U) and transfer function. This report was to be submitted to the NRC within 90 days of achieving the EPU power level. By letter dated December 6,2012 (ADAMS Accession No. ML123420255), Entergy submitted the final report for the replacement steam dryer for NRC staff review.
The NRC staff has determined that the following additional information is needed for the staff to complete the review of this report.
- 1)
Please explain why the dryer stresses are dominated by ((
))
response, as it is not intuitive considering the ((
)) safety relief valve (SRV) tones in the plant.
- 2)
The NRC staff notes that the results Un" in Table 12 demonstrate that for high stress locations, ((
)) and the maximum stress projections ranged from ((
)) at full EPU power.
The NRC staff also notes that the margin in the dryer stress has significantly dropped compared to the predictive design analysis (minimum alternating stress ratio or MASR of ((
))).
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- 2 Please explain how the final stress assessment of the RSD based on the changes in core flow (due to static pressure variations) is performed. Please clarify if the worst-case conditions from these figures are utilized.
Also, provide an explanation of ((
evidence of these increases) and ((
(Figure 99 shows ((
))).
)) (see Figures in Appendix B for
))
- 3)
Figures 94 and 96 in Appendix -B of the report show strong VPF response at A5 and S1 sensor locations. Please explain how the VPF stresses are accounted for in the final stress analysis of the steam dryer.
- 4)
Please confirm whether the end-to-end B&Us presented in the report are only for the GGNS-specific steam dryer evaluation and not for any future EPU applications or new reactor designs.
- 5)
During the start-up and power ascension testing at GGNS, data was obtained for the RSD at 100 percent, 105 percent, 110 percent, and 113 percent of the previous licensed thermal power (PL TP). However, the ((
)). The 90-day report should include the B&Us for all measured power levels explaining that a conservative envelope of all cases should be used as the appropriate B&Us for the PBLE methodology.
- 6)
The 90-day report utilizes a ((
attributes the changes in steam dryer stresses to the "((
)). The report
))." Although this approach sheds some light on the trends of these effects, the licensee is requested to provide an explanation regarding the involved physical mechanism.
- 7)
The licensee employs the PBLE Method 1 to predict the pressures on the entire steam dryer using the measured pressure results. At CL TP, when all the pressure sensors were working, it uses ((
))
as an input to the PBLE Method 1 to predict the pressures on the entire dryer surface (See Figures 82-96 in proprietary Attachment to GNRO-2012-00075 dated July 5,2012 (ADAMS Accession No. ML12192A113)). The measured and predicted pressures at ((
)) compare well and the pressures at other locations are generally ((
)).
However, at EPU, when ((
)) pressure sensors ((
uses the measured pressures at ((
]) had failed, it
)) to estimate the OFFICIAL USE ONLY PROPRIETARY INFORMATION
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- 3 pressures on the entire dryer surlace (See Figures 19-32 in Attachment to GNRO-2012/00150). In contrast to the comparisons at CL TP. [I II and, in addition, the PBLE Method 1 ((
)) the pressures. For example, the comparison of measured and predicted pressures at one of the pressure transducer location (P6) is presented in Figure 23 of the report. At several frequencies, there is a ((
1] results for P6. For example, ((
]). Please provide an explanation for these differing comparisons between measured and predicted pressures at CL TP and EPU.
- 8)
Table 2 of the report provides the maximum half-range of strains for the GGNS strain gages S1, S2, and S7. Please provide the following additional information:
(a)
Please describe how the maximum stress locations associated with these strain gages may be identified and the maximum stresses may be estimated.
(b)
Please provide the maximum stress locations associated with these strain gages.
(c)
Please provide the maximum half ranges of strains for these maximum stress locations. Please confirm whether the normalized histograms presented for the GGNS strain gages S1, S2, and S7 in Figure 1 also represent the histograms for the corresponding high-stress locations?
- 9)
Please explain how the pressure regulator set point for the high pressure turbine changes as power is increased from CL TP to EPU. Also. please describe how the pressure regulator set point is changed (incrementally or in one step).
- 10)
The GGNS EPU report estimates end-to-end B/U at EPU for PBLE Method 1.
However. two pressure sensors had failed and that ((
)). Please confirm whether the B/U thus determined would bound the BJU determined with no pressure sensor failures.
- 11)
In Section 4.2.3, the licensee stated that "((
ll." This statement implies that the pressure loads predicted by PBLE Method 2 may not be conservative. Please provide the following additional information:
(a)
The licensee is requested to provide information regarding the magnitudes of these non-acoustic sources.
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-4 (b)
The licensee is also requested to clarify whether the pressure loads predicted by PBLE Method 1 are also non-conservative.
- 12)
Please provide the following additional information:
a)
The licensee is requested to link the worst-case stress locations shown in Figures 73-77 to the dryer strain sensor locations indicated in the CLTP power ascension report GNRO 2012 00075 part 1, Appendix A.
b)
For these worst-case stress locations, the licensee is also requested to provide stress spectra and stress accumulation (total RMS stress accumulation as a function of frequency) plots before and after frequency dependent B/U are applied.
c)
The licensee is further requested to show that ((
)) is conservative compared to using localized B/U from linked nearby sensors. In particular, the licensee is requested to provide supporting information to substantiate the statement made on the bottom of page 124 of Section 5.4.1.2 of NEDC-33765 Supplement 4P (Attachment to GNRO-2012/00150) r... ((
)).")
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- 2 If circumstances result in the need to revise the requested response date, please contact me at (301) 415-1445 or via e-mail at Alan.Wang@nrc.gov.
Sincerely, IRA!
Alan B. Wang, Project Manager Plant Licensing Branch IV Division of Operating Reactor licensing Office of Nuclear Reactor Regulation Docket No. 50-416 cc w/Encl 2: Distribution via Listserv
Enclosures:
- 1. Request for Additional Information (proprietary)
- 2. Request for Additional Information (non-proprietary)
DISTRIBUTION:
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t d ML13038A603 OFFICIAL AGENCY RECORD II OFFICE NRRlDORUlPl4/PM NRR/DORlIlPl4/LA NRR/DElEMCBlBC NRRlDORUlPl4IBC NRRlDORUlPl4lPM I
[I NAME AWang JBurkhardt AMcMurtray MMarkley AWang II DATE 2125113
. 2/11/13 2115113 2125113 2125/13 Ii
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