ML15233A074

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SPRA Relief - Information to Support Reconsideration of Hatch U1 for Inclusion in SPRA Relief Due to Seismic Robustness and Similarities to Hatch U2
ML15233A074
Person / Time
Site: Hatch  Southern Nuclear icon.png
Issue date: 08/10/2015
From: Giddens J
Southern Nuclear Operating Co
To:
Japan Lessons-Learned Division
DiFrancesco N, NRR/JLD, 415-1115
References
Download: ML15233A074 (45)
v • d • e


Text

HATCH UNIT 1 AND 2 SPRA RELIEF Information to Support Reconsideration of Hatch U1 for Inclusion in SPRA Relief due to Seismic Robustness and Similarities to Hatch U2 BACKGROUND

  • NRC will be providing SPRA relief for 11 1/2 sites. Hatch Unit 2 is the 1/2 site.
  • SNC agrees with NRCs opinion that Hatch Unit 2 should receive SPRA relief.
  • This document contains additional information for NRCs consideration to also provide SPRA relief to Hatch Unit 1.

TECHNICAL POINTS AND DISCUSSION

1. Technical Point: Both DBEs anchored at 0.15g.

Discussion: Unit 1 Design Basis Earthquake (DBE) is a Housner spectral shape, Unit 2 DBE is a Modified Newmark spectral shape. Both are anchored at 0.15g. [See Reference 1 and Attachment 1]

2. Technical Point: Units 1 and 2 are basically the same plant.

Discussion: Both units are GE Boiling Water Reactors Type 4g with Mark I containments and the drywell/pressure suppression concept is used. The Reactor Buildings are reinforced-concrete structures that act as the secondary containment. Hatch Units 1 and 2 are the same site, common Control Building, common Control Room, common Intake Structure, common Diesel Generator Building.

3. Technical Point: The U1 and U2 In-Structure Response Spectra (ISRS) used to design/qualify equipment are very similar.

Discussion: Though the spectral shapes are different, the U1 and U2 ISRS used to design/qualify equipment are very similar. In many cases, the U1 ISRS are higher than U2 equivalent ISRS (for sister unit buildings, elevations). [See Reference 2 and Attachment 3]

4. Technical Point: The two Units have similar ISRS.

Discussion: For all shared structures, Hatch Unit 1 seismic analysis produces similar ISRS to those calculated for Hatch Unit 2 in peak spectral amplitude and frequency range. This demonstrates that even though the Unit 1 DBE spectral shape accelerations are less than the Unit 2 DBE accelerations, the resulting seismic demand used to design and qualify Unit 1 and Unit 2 safety related Structures, Systems, and Components (SSCs) are essentially the same. The Hatch Unit 1 DBE by itself cannot be used as an indicator of the Unit 1 seismic robustness. Also it can then be expected that the seismic robustness of both units would be similar.

Conclusion:

No significant difference between the seismic demands calculated and used for design between Hatch Unit 1 and Hatch Unit 2; essentiality the seismic designs are the same.

Page 1 of 3

Plant Hatch Unit 1 and 2 SPRA Relief Information for NRC

5. Technical Point: Previous Seismic Margin Assessments Discussion: An additional demonstration of the Hatch Unit 1 seismic robustness or seismic margin was provided by implementing the full EPRI Seismic Margin Assessment (SMA) methodology as a pilot implementation project. The Hatch Unit 1 SMA demonstrated a High Confidence of a Low Probability of Failure (HCLPF) of at least 0.3g; where the review level earthquake (RLE) ground motion exceeded the Hatch Unit 1 DBE by a factor of 2 or more. It should be noted the Hatch Unit 1 SMA also showed that the Unit 1 NSSS has at least a HCLPF of 0.3g. For IPEEE-seismic a reduced scope SMA of Hatch Unit 2 was performed that demonstrated a plant HCLPF of 0.3g. No seismic issues were identified that were unique just to Hatch Unit 1.

Conclusion:

Hatch Unit 1 has significant seismic margin as demonstrated by the SMA as was also demonstrated for Hatch Unit 2; and no seismic issues were found that were Hatch Unit 1 unique. [See References 7 and 8, Attachments 2 and 4]

a. The maximum GMRS/DBE ratio for either unit is less than 2
b. The maximum HCLPF/U2 DBE ratio is 2.6
c. The maximum HCLPF/U1 DBE ratio is 3.388
6. Technical Point: NTTF 2.3 Seismic verified SMA modifications.

Discussion: The NTTF 2.3 seismic walk downs verified modifications resulting from the Hatch Unit 1 SMA, used as the IPEEE-seismic response, are fully implemented.

Conclusion:

Under the 2.3 seismic it was verified that SMA modifications remain in place for both units which supports the expectation that both the Hatch Unit 1 and Unit 2 seismic margins remain at their previous HCLPF values. [See References 3 and 4]

7. Technical Point: NTTF 2.1 ESEP documented U1 ESEL components have HCLPFs of at least 0.3g.

Discussion: The Hatch Unit 1 ESEP provided documentation that the Unit 1 ESEL components have HCLPFs of at least 0.3g using the same SMA ground motion used for the Hatch Unit 1 SMA and the Unit 2 SMA. This SMA ground motion is called the review level earthquake ground motion which exceeds the Hatch Unit 1 DBE by a factor of 2 or more. (See Attachments 1 and 2).

The only exception is the CST which is surface mounted where the Hatch GMRS was used as the input motion. No modifications were identified. Similar ESEP results were found for Unit 2.

Conclusion:

The ESEP assessment further demonstrates the significant seismic margin above the Hatch Unit 1 DBE as was also demonstrated for Hatch Unit 2. [See References 5 and 6]

8. Technical Point: NRC GI-199 SCDF is same for both units.

Discussion: The NRC GI-199 Safety/Risk Assessment indicates that no concern exists regarding adequate protection and that the current seismic design of operating reactors provides a safety margin to withstand potential earthquakes exceeding the original design basis. The site hazard is the same for both units, the HCLPF is the same for both units.

Conclusion:

The estimated point estimate SCDF would be the same for both Unit 1 and Unit 2.

9. Technical Point: Enveloping curves are used for design/qualification.

Discussion: Since the mid 90's seismic design and qualification for components for both Units have used an envelope of the Hatch Unit 1 and Unit 2 ISRS of record and 1/2 the SMA ISRS. This is a conservative practice, but it demonstrates the use of later seismic analysis results with design basis results to assure conservative design and qualification. This points out that any new design changes reflect all the latest seismic analyses.

Conclusion:

Hatch Unit 1 and Unit 2 both Page 2 of 3

Plant Hatch Unit 1 and 2 SPRA Relief Information for NRC are incorporating the latest seismic results with the original design basis for new design changes; therefore, both Units are being maintained to the same standard IN CONCLUSION SNC agrees with the NRC that Hatch Unit 2 should receive SPRA relief. The Technical Points and Discussion above illustrate that the seismic designs, loads, etc. are essentially the same for Hatch Unit 1 and that the seismic margin of 0.3g for both units has been demonstrated several times. No unique seismic issues have been identified between Unit 1 and Unit 2; and all new design changes for both units incorporate later seismic analyses. It can be concluded based on the above that the seismic robustness of Hatch Unit 1 is similar to Hatch Unit 2; and therefore based on the relief from a SPRA granted to Unit 2, a relief from a SPRA should also be granted to Unit 1.

REFERENCES

1. Edwin I. Hatch Units 1 and 2, Seismic Hazard and Screening Report for CEUS Sites, March 31, 2014, NL-14-0343, Sections 2.0 and 3.1
2. Edwin I. Hatch Nuclear Power Plant Units 1 and 2, Seismic Floor Response Spectra of Record, Rev. 1 dated July 31, 1987
3. Hatch Unit 1, Staff Assessment of the Seismic Walkdown Report Supporting Implementation of Near-Term Task Force Recommendation 2.3 Related to the Fukushima Dai-Ichi Nuclear Power Plant Accident (ML14155a361)
4. Hatch Unit 2, Staff Assessment of the Seismic Walkdown Report Supporting Implementation of Near-Term Task Force Recommendation 2.3 Related to the Fukushima Dai-Ichi Nuclear Power Plant Accident (ML14079a355)
5. Memo: Diane Jackson to Mohamed Shams, July 7, 2015, Hatch Units 1 and 2, Technical Review Checklist Related to Interim ESEP Supporting Implementation of NTTF R 2.1, Seismic (ML15190A131)
6. NRC to Mr. C. R Pierce, July 22, 2015, Hatch Units 1 and 2 - Staff Review of Interim Evaluation Associated with Revaluated Seismic Hazard implementation of Near-Term Task Force Recommendation 2.1 (ML15201A474)
7. A Methodology for Assessment of Nuclear Power Plant Seismic Margin (Revision 1), EPRI NP-6041-SL, August 1991, Appendix S Lessons Learned from Hatch Nuclear Plant Seismic Margin Assessment
8. Seismic Margin Assessment of the Edwin I. Hatch Nuclear Plant, Unit 2, EPRI NP-7217s-M, October 2008.

ATTACHMENTS Att 1 - Figure/Plot - Hatch U1 DBE, Hatch U2 DBE, Hatch GMRS, Hatch HCLPF Spectrum (SMA)

Att 2 - Table - Hatch Response Spectra Comparison (Ratios: GMRS to DBE, HCLPF to DBE)

Att 3 - Table/Word Doc - Hatch Comparison of U1 to U2 ISRS Similar Bldgs/Elevations DBE Att 4 - Excerpt from Hatch SMA, Sections 1 through 5 Att 5 - Excerpt from Hatch IPEEE Response, Section 4.9 Third-Party Audit Page 3 of 3

Attachment 1 - Hatch Units 1 and 2 0.8 Hatch HCLPF Spectrum (SMA)

Hatch GMRS 0.7 Hatch Unit 2 DBE Hatch Unit 1 DBE 0.6 5% Damping Spectral Acceleration (g) 0.5 0.4 0.3 0.2 0.1 0.0 0.10 1.00 10.00 100.00 Frequency [Hz]

ATTACHMENT 2 - HATCH RESPONSE SPECTRA COMPARISON GMRS H1 DBE H2 DBE HCLPF Spectrum Freq Spectral GMRS/U1 DBE GMRS/U2 DBE HCLPF/U2 DBE HCLPF/U1 DBE Spectral Accel Spectral Accel (Hz) Acceleration Ratio Ratio Ratio Ratio (g) Accel (g) (g)

(g) 0.1 0.015 0.007 0.14 0.015 0.125 0.0203 0.167 0.0346 0.2 0.0437 0.22 0.036 1.21 0.3 0.058 0.33 0.051 0.05 0.4 0.0737 0.5 0.1113 0.069 1.61 0.08 1.39 0.15 1.875 2.174 0.6 0.1452 0.67 0.092 0.7 0.1696 0.11 1.54 0.8 0.2009 0.9 0.2171 1 0.2206 0.128 1.72 0.16 1.38 0.3 1.875 2.344 1.11 0.133 1.25 0.2654 0.15 1.77 0.2 1.33 1.43 0.165 1.5 0.2844 0.24 1.19 1.67 0.178 2 0.3158 0.206 1.53 0.32 0.99 0.637 1.991 3.092 2.22 0.216 2.5 0.3096 0.221 1.40 0.32 0.97 2.86 0.225 3 0.3029 0.32 0.95 3.33 0.221 4 0.308 0.221 1.39 0.32 0.96 5 0.3118 0.216 1.44 0.32 0.97 6 0.3203 0.32 1.00 6.67 0.206 7 0.3164 7.7 0.26 8 0.3142 0.188 1.67 0.637 2.600 3.388

ATTACHMENT 2 - HATCH RESPONSE SPECTRA COMPARISON GMRS H1 DBE H2 DBE HCLPF Spectrum Freq Spectral GMRS/U1 DBE GMRS/U2 DBE HCLPF/U2 DBE HCLPF/U1 DBE Spectral Accel Spectral Accel (Hz) Acceleration Ratio Ratio Ratio Ratio (g) Accel (g) (g)

(g) 8.3 0.24 9 0.3111 10 0.3039 0.169 1.798 0.21 1.447 0.54 2.571 3.195 11.11 0.163 0.2 12.5 0.2744 0.156 1.76 0.18 1.52 0.45 2.500 2.885 14.29 0.15 14.3 0.165 15 0.2469 16 0.15 16.67 0.15 0.15 20 0.2027 0.15 1.35 0.15 1.35 0.3 2.000 2.000 22.22 0.15 0.15 25 0.179 0.15 1.19 0.15 1.19 28.67 0.15 0.15 30 0.166 0.15 1.11 0.15 1.11 33 0.3 2.000 2.000 33.33 0.15 0.15 35 0.1583 0.15 1.06 0.15 1.06 40 0.1532 0.15 1.02 0.15 1.02 45 0.1508 0.15 1.01 0.15 1.01 50 0.1478 0.15 0.99 0.15 0.99 60 0.1452 0.15 0.97 0.15 0.97 70 0.1438 0.15 0.96 0.15 0.96 80 0.1427 0.15 0.95 0.15 0.95 90 0.1422 0.15 0.95 0.15 0.95 100 0.1422 0.15 0.95 0.15 0.95 0.3 2.000 2.000 Comments:

1. Unit 1 max GMRS/U1DBE ratio occurs at 10hz and is less than 2 (ratio is 1.798)
2. Unit 2 max GMRS/U2DBE ratio occurs at 12.5hz, and is less than 2 (ratio is 1.52)
2. Unit 2 max GMRS/U2DBE ratio between 1 and 10 hz is less than 2 (ratio is 1.447)

- Comparison of Hatch Unit 1 and 2, Similar Buildings/elevations/Horizontal ISRS DBE 5% critical damping Plant Hatch Unit 1 Unit 1 Plant Hatch Unit 2 Unit 2 Peak (__gs @ __ hz) zpa(gs) Peak (__gs @ __hz ) zpa (gs)

Control Bldg 130 N-S 0.781g @ ~6 - 8hz 0.1680g 0.792g @ ~5.5 - 7hz 0.2110g Control Bldg 130 E-W 1.051g @ ~6 - 8hz 0.1800g 0.745g @ ~5.5 - 7hz 0.2140g Control Bldg 164 N-S 1.245g @ ~6 - 8hz 0.2560g 1.073g @ ~5.5 - 7hz 0.2850g Control Bldg 164E-W 1.458g @ ~6 - 8hz 0.2520g 0.919g @ ~ 5.5 - 8hz 0.2640g Reactor Bldg 130 N-S 0.660g @ ~ 3.8 - 5hz 0.1610g 0.875g @ ~ 2.9 - 3.8hz 0.1810g Reactor Bldg 130 E-W 0.773g @ ~3.8 - 5hz 0.1650g 0.799g @ ~ 3.1 - 4hz 0.2070g Reactor Bldg 158 N-S 0.906g @ ~ 3.8 - 5hz 0.1850g 1.228g @ ~3 - 4hz 0.2300g Reactor Bldg 158 E-W 1.047g @ ~ 3.8 - 5hz 0.1840g 1.116g @ ~3.5 - 4.8hz 0.2490g Intake Structure 111 N-S 0.795g @ ~8 to 10hz 0.2000g 0.680g @ ~7.5 - 9.5hz 0.1960g Intake Structure 111 E-W 1.438g @ ~5.8 - 8hz 0.2550g 1.963g @ ~5.9 - 8hz 0.3440g Intake Structure 128 N-S 0.888g @ ~8 - 12hz 0.2230g 0.743g @ ~ 7.5 - 9.5hz 0.2090g Intake Structure 128 E-W 1.753g @ ~6 - 8hz 0.3020g 2.373g @ ~ 6.0 - 8hz 0.4100g Diesel Gen Bldg 130 N-S 1.241g @ 2.5 - 5 hz 0.2250g 0.876g @ ~2.8 - 5hz 0.2010g Diesel Gen Bldg 130 E-W 1.235g @ 2.5 - 5 hz 0.2240g 0.889g @ ~2.8 - 5hz 0.2000g

Reference:

Edwin I. Hatch Nuclear Power Plant Units 1 and 2, Seismic Floor Response Spectra of Record, Rev. 1 dated July 31, 1987 NOTE: Highlighted text/values indicate the higher acceleration between the two ISRS

- Excerpts from Hatch SMA

- Hatch IPEEE Third Party Audit Information

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