NOC-AE-16003369, Applicability of Application Supplement 1 Correspondence to Supplement 2 to STP Risk-Informed GSI-191 Licensing Application

Applicability of Application Supplement 1 Correspondence to Supplement 2 to STP Risk-Informed GSI-191 Licensing Application

ML16176A148
Person / Time
Site:	South Texas
Issue date:	06/09/2016
From:	Connolly J South Texas
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
GSI-191, NOC-AE-16003369, TAC MF2400, TAC MF2401
Download: ML16176A148 (51)

Text

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June 9, 2016 NOC-AE-16003369 10 CFR 50.12 10 CFR 50.90 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555-0001 South Texas Project Units 1 & 2 Docket Nos. STN 50-498, STN 50-499 Applicability of Application Supplement 1 Correspondence to Supplement 2 to STP Risk-Informed GSl-191 Licensing Application

<TAC NOs MF2400 and MF2401)

References:

1. Letter, G. T. Powell, STPNOC, to NRC Document Control Desk, "Supplement 1 to Revised STP Pilot Submittal and Requests for Exemptions and License Amendment for Risk-Informed Approach to Resolving Generic Safety Issue (GSl)-191 ," November 13, 2013, NOC-AE-13003043, ML13323A183

2. Letter, G. T. Powell, STPNOC, to NRC Document Control Desk, "Supplement 2 to STP Pilot Submittal and Requests for Exemptions and License Amendment for a Risk-Informed Approach to Address Generic Safety Issue (GSl)-191 and Respond to Generic Letter (GL) 2004-02," August 20, 2015, NOC-AE-15003241, ML 15246A12ff

3. Letter, G. T. Powell, STPNOC, to NRC Document Control Desk, "Response to Request for Additional Information re Use of RELAP5 for Analyses for Risk-Informed GSl-191 Licensing Application," January 9, 2014, NOC-AE-13003057, ML14029A533 (Response to ML14009A307) .

4. Letter, G. T. Powell, STPNOC, to NRC Document Control Desk, "First Set of Responses to April 14, 2014, Requests for Additional Information Regarding STP Risk-Informed GSl-191 Licensing Application- Revised," May 22, 2014, NOC-AE-14003103, ML14149A434 (Response to ML14087A075)

5. Letter, G. T. Powell, STPNOC, to NRC Document Control Desk, "Second Set of Responses to April 14, 2014, Requests for Additional Information Regarding STP Risk-Informed GSl-191 Licensing Application," June 25, 2014, NOC-AE-14003101, ML14178A481 (Response to ML14087A075)

6. Letter, G. T. Powell, STPNOC, to NRC Document Control Desk, "Third Set of Responses to April 14, 2014, Requests for Additional Information Regarding STP Risk-Informed GSl-191 Licensing Application," July 15, 2014, NOC-AE-14003105, ML14202A045 (Respol'lse to ML14087A075)

7. Letter, G. T. Powell, STPNOC, to NRC Document Control Desk, "Description of Revised Risk-Informed Methodology and Responses to Round 2 Requests for Additional Information Regarding STP Risk-Informed GSl-191 Licensing Application," March 25, 2015, NOC-AE-15003220, ML15091A440 (Response to ML14357A171)

Reference 2 revised the methodologies used and described in Reference 1. References 3 - 7 responded to NRC RAls on Reference 1 and portions of those responses are no longer relevant to the STPNOC application as described in Reference 2. The attachments identify the information that is no longer relevant and the basis for the determination.

too r STl34306886

Jilt.

NOC-AE-16003369 Page 2 of 3 STPNOC's process for evaluating the applicability of the RAls focused primarily on whether the response to the RAI was relevant to the revised methodology; i.e., whether a reviewer could cite it in a safety evaluation. If the RAI for a "not applicable" response appeared still be relevant to the revised methodology and there is a docketed submittal describing how the revised methodology applies, STPNOC called the response "not applicable" and identified that reference. However, STPNOC did not revise responses .for apparently relevant questions if the response was "not applicable" and there is no docketed reference. A determination that a response is "not applicable" does not mean that the response is not correct. It only means that it does not apply for the current methodology.

STPNOC also reviewed Supplement 1 to the risk-informed GSl-191 application (Ref. 1) for applicability. The results of the review are tabulated at relatively high level for each enclosure to Ref. 1.

There are no commitments in this submittal.

If there are any questions, please contact Mr. Wayne Harrison at 361-972-877 4.

I declare under penalty of perjury that the foregoing is true and correct.

Executed on:

(}~ Cf', :Joi{/,

James Connolly Site Vice President awh Attachments:

1. Applicability of Supplement 1

2. Applicability of RAI Responses regarding Supplement 1

• 3. Definitions and Acronyms

NOC-AE-16003369 Page 3 of 3 cc:

(paper copy) (electronic copy)

Regional Administrator, Region IV Morgan. Lewis & Bockius LLP U. S. Nuclear Regulatory Commission Steven P. Frantz, Esquire 1600 East Lamar Boulevard Arlington, TX 76011-4511 U. S. Nuclear Regulatory Commission Lisa M. Regner Lisa M. Regner Senior Project Manager NRG South Texas LP U.S. Nuclear Regulatory Commission Chris O'Hara One White Flint North (08H04) Jim van Suskil 11555 Rockville Pike Skip Zahn Rockville, MD 20852 CPS Energy NRC Resident Inspector Kevin Pollo U. S. Nuclear Regulatory Commission Cris Eugster P. 0. Box 289, Mail Code: MN116 L. D. Blaylock Wadsworth, ~X 77 483 Crain Caton & James. P.C.

Peter Nemeth City of Austin Elaina Ball John Wester Texas Dept of State Health Services Helen Watkins Robert Free

NOC-AE-16003369 Attachment 1 Attachment 1 Applicability of Supplement 1

NOC-AE-16003369 Attachment 1 Page 1 of 3 The table below addresses the applicability of Supplement 1 to STPNOC's Risk-Informed GSl-191 pilot licensing application (Reference 1 in the cover letter).

The methodology change described in Supplement 2 (Reference 2 in the cover letter) revises the method of risk quantification from a detailed analysis in which conditional failure probabilities were calculated using correlations and applied in the STP PRA, to a simplified approach with a deterministic element based on plant specific testing and a risk-informed element for conditions not bounded by the testing. As a result of the methodology change, the risk quantifications in Supplement 1 are superseded by those in presented in Supplement 2. Methods using correlations and associated RAls no longer apply. STPNOC has also revised aspects of the requests for exemption such that the descriptions in Supplement 2 and later correspondence are the appropriate references. '

Enclosure Title Applicability Basis 1 STP Piloted Risk- Not applicable Enclosure is based on detailed analysis approach Informed Approach to which has been superseded by the Rovero method GSl-191 described in Supplement 2.

2-1 Request for Exemption Not applicable Exemption has been revised to be from from 10CFR50 .46( a)( 1) 10CFR50.46(b)(5) 2-2 Request for Exemption Not applicable The specific applicability and scope of the exemptions from GOC 35 have changed due to the Rovero methodology. The 2-3 Request for Exemption Not applicable burden impact described in Supplement 1 is still from GOC 38 accurate, and is presented with less detail in 2-4 Request for Exemption Not applicable Supplement 2.

from GOC 41 3 License Amendment Not applicable. Superseded by LAR in Supplement 2. Methodology Request for STP change substantially changes the licensing basis and Piloted Risk-Informed its description in the UFSAR. Addition of change to Approach to GSl-191 the TS also supersedes the TS Bases changes in Supplement 1.

4-1 Volume 1: Project Not applicable The Rovero description in the August 20, 2015 Summary supplement as updated by subsequent RAI responses provides the necessary elements of the oroiect description.

NOC-AE-16003369 Attachment 1 Page 2 of 3 Enclosure Title Applicability Basis 4-2 Volume 2: Probabilistic Information regarding the history The Rovero approach described in the August 20, Risk Analysis and configuration control of the 2015 supplement does not incorporate debris-related STP PRA is applicable. conditional failure probabilities or revise the STP base Information regarding the basis for model PRA.

the current STP PRA model of record is applicable.

Information regarding incorporation of conditional failure probabilities for the risk-informed GSl-191 application is Not Applicable.

4-3 Volume 3: Engineering Not applicable The Rovero approach described in the August 20, (CASA Grande) Information regarding the following 2015 supplement does not use any of these aspects Analysis aspects is no longer applicable: of the detailed analysis described in the November

• Time dependence of debris 13, 2013 supplement.

generation and transport The relevant descriptions from this volume have been

• Use of correlations for NPSH incorporated as needed into the current application.

• Use of correlations for chemical effects

• Calculation of conditional failure probabilities, including distributions Although information regarding other applications of CASA Grande may still apply, the relevant parts have been incorporated in the current Rovero methodology.

NOC-AE-16003369 Attachment 1 Page 3 of 3 Enclosure Title Applicability Basis 5 Response to NRC Information regarding the following The Rovero approach described in the August 20, Supplemental aspects is no longer applicable: 2015 supplement does not use any of these aspects Information Items:

• Time dependence of debris of the detailed analysis described in the November generation and transport 13, 2013 supplement.

• Use of correlations for NPSH The regulatory basis for the exemptions has been

• Use of correlations for chemical revised. The UFSAR changes are superseded by the effects current descriptions that reflect the Rovero

• Calculation of conditional failure methodology. The current application includes a probabilities, including change to the ECCS and CSS Technical distributions Specifications.

• Regulatory descriptions regarding exemptions, UFSAR changes and TS changes.

6 Changes to June 19, Not applicable Per STPNOC letter dated 11/21/2013 2013 Submittal (ML13338A165), Supplement 1 superseded the June 19, 2013 letter, so the June 19 letter is not relevant for the submittal.

NOC-AE-16003369 Attachment 2 Attachment 2 Applicability of RAI Responses Regarding Supplement 1

NOC-AE-16003369 Attachment 2 Page 1 of 40 Table 1 describes the applicability of the responses to Round 1 RAls. Table 2 describes applicability of the responses to Round 2 RAls.

Most of the Table 2 responses are applicable because they were submitted at the time of the change to the Rovero methodology.

Table 1 Applicability of Responses to Round 1 RAls (ML14087A075)

Applicability and Letter RAI Applicability Basis Comments Reference for

Response

Not applicable APLAB, CASA Grande - The uncertainty quantification process requires General: Question 1a, 1b, characterization of parameter distributions used ML14202A045 1c in sampling strategies for estimating and (Cover Letter propagating physical model responses. Rovero Ref.6) instead uses a test designed to bound the uncertainty associated with Emergency Core Cooling System (ECCS) strainer head losses.

NOC-AE-16003369 Attachment 2 Page 2 of 40 Not applicable APLAB, CASA Grande - In order to comprehensively estimate the Plant Configuration: Reactor Containment Building (RCB) and ML14202A045 Questions 1a, 1b, 2a, 2b Reactor Coolant System (RCS) responses to (Cover Letter different break scenarios and plant states Ref.6) (pumping combinations), several thermal-hydraulic simulations are required to estimate the temperature and pressure histories in the RCB and RCS using coupled models of the RCB and RCS. The current Rovero methodology relies on the existing The STP Nuclear Operating Company (STPNOC) license-basis RCB analysis for strainer performance parameters; bounding test data and bounding thermal-hydraulic analysis to ensure adequate core cooling. The pump states are bounded for fiber penetration and collection (single train and two or more trains considered).

NOC-AE-16003369 Attachment 2 Page 3 of 40 Applicability and Letter RAI Applicability Basis Comments Reference for

Response

Not applicable APLAB, CASA Grande - In order to support the many possible ECCS Plant Configuration: and Containment Spray System (CSS)

ML14202A045 Question 3a, b, c configurations, the PRA needed to have several (Cover Letter top events added. The necessary fidelity and Ref.6) concomitant model support detail needed to accurately represent all possible configurations is relatively complex. The current application applies the Rovero methodology, which avoids extensive reliance on the PRA and uses what could effectively be thought of as a "LOCA Debris" initiating event frequency as a bounding CDF rather than detailed modeling in the PRA.

Similarly, the PRA model of record is used to evaluate the LERF using the ratio of LERF conditional on ECCS sump screen failure for Large Break Loss of Coolant Accident (LLOCA) and CDF conditional on sump screen failure in LLOCA.

Not applicable APLAB, CASA Grande, The most accurate modeling of failure likelihood LOCA Frequencies: (Loss of Coolant Accident (LOCA)) at any given ML14149A434 Question 1a, 1b location in the RCS pressure boundary would (Cover Letter take into consideration failure mechanisms Ref.4) based on causal modeling of the underlying phenomena thereby producing probabilities for each location. Theoretically, such values could be used in sums to estimate the (preferentially) frequency (or likelihood) of a LOCA of any particular size in a plant. The STP 2013 LAR used a weighting scheme that attempted to preserve the NUREG 1829 frequencies but additionally

.. takinQ into account in- service data

NOC-AE-16003369 Attachment 2 Page 4 of 40 Applicability and Letter RAI Applicability Basis Comments Reference for Response ,-

where cracks were observed and some consideration of the type of service. In Rovero, a bounding method, called top-down, was adopted that avoids the need to account for weighting by relying on the fact that locations where debris amounts exceed tested levels have been mitigated. That is, the problematic or "risk" locations have been mitigated and only the non "risk" locations have not been. The Rovero methodology ignores the mitigation improvements and equally weights the NUREG 1829 exceedance frequencies for all locations thereby bounding local effects.

Applicable APLAB, CASA Grande - The STP 2013 LAR estimated breaks of any LOCA Frequencies: size that could be supported by a given pipe ML14178A481 Question 2 diameter. This requires assuming a continuum Cover Letter of break sizes up to the pipe diameter and Ref. 5 gives the most complete picture of possible breaks that could be used in a risk-based application. The NUREG 1829 elicitation report can be interpreted to indicate only Double Ended Guillotine Breaks (DEGBs) can occur.

Both attribution and frequency must be considered in any interpretation. In the Rovero methodology, the continuum break model is compared to the DEGB-only model of interpretation and it automatically includes a (conservative) interpretation of attribution (spherical Zone Of Influence (ZOI) for all d" locations).

NOC-AE-16003369 Attachment 2

\..

Page 5 of 40 Applicability and Letter RAI Applicability Basis Comments Reference for

Response

Not applicable APLAB, CASA Grande, All the elicited exceedance frequency quantiles Also, the current STPNOC LOCA Frequencies: and means aggregated in NUREG 1829 application does not use Ref. 7 ML14149A434 Questions *3 & 4 decrease rapidly with size of break. As a (KNF)

(Cover Letter consequence, sampling must be done very Ref.4) carefully to ensure the "long tails" of the distributions are captured. This was done in CASA Grande as described in the STP 2013 LAR using stratified sampling techniques and ensuring that the OEGB break size was sampled in each quantification. The Rovero methodology avoids the need to perform sampling, in the way required for Monte Carlo quantification, by assuming all break sizes larger than the smallest break size producing more debris than was tested at the location are assumed to be failure. This is a conservative estimate that also avoids the possibility of

, inadequate sampling of long tails.

Not applicable APLAB, CASA Grande, to The STP 2013 LAR estimates fiber mass PRA Interface - General: distribution in the RCB pool, the reactor core, ML14149A434 Questions 1a & 1b and the ECCS strainers. The method used in (Cover Letter the STP 2013 LAR performs estimates for the Ref.4) pump configurations assumed and calculates head loss based on collection of particulates (fiber, paint, chemical precipitates). The Rovero methodology performs a similar calculation however, instead of looking at all possible pumping configurations, Rovero looks at

'expected' and 'extreme' cases to ensure the in-vessel effects are not limiting. Head loss computation is not done in Rovero. Instead, re-

NOC-AE-16003369 Attachment 2 Page 6 of 40 Applicability and Letter RAI Applicability Basis Comments Reference for

Response

suits of testing on an STP ECCS strainer module are used. Any fine fiber loading that exceeds the tested amount is assumed to lead to core damage.

Not applicable APLAB, CASA Grande to All the elicited exceedance frequency quantiles PRA Interface-General: and means aggregated in NUREG 1829 ,_

ML14202A045 Question 2a decrease rapidly with size of break. As a (Cover Letter consequence, sampling must be done very Ref.4) carefully to ensure the "long tails" of the distributions are captured. This was done in CASA Grande as described in the STP 2013 LAR using stratified sampling techniques and ensuring that the DEGB break size was sampled in each quantification. The Rovero methodology avoids the need to perform sampling, in the way required for Monte Carlo quantification, by assuming all break sizes larger than the smallest break size producing more debris than was tested at the location are assumed to be failure. This is a conservative estimate that also avoids the possibility of inadequate sampling of long tails.

Not applicable APLAB, CASA Grande to The STP 2013 LAR included timing PRA Interface-General: considerations and many different break sizes ML14202A045 Question 2b and orientations. Rovero only requires that the (Cover Letter amounts of failed coatings assumed in the test

~ef.4) are appropriately conservative (accepted to exceed amounts expected) or are otherwise bounded. As a consequence, no modelinQ of

\

/

NOC-AE-16003369 Attachment 2 Page 7 of 40 Applicability and Letter RAI Applicability Basis Comments Reference for

Response

failure size or timing is required in the Rovero methodology.

Not applicable APLAB, CASA Grande, to RAI pertains to how pump states relate to PRA Interface - General: conditional failure probability which is not a ML14149A434 Question 3 feature of Rovero. Rovero discussion of ECCS (Cover Letter single-train adequately addresses bounding Ref.4) pump state.

Not applicable APLAB, CASA Grande, to In order to support the many possible ECCS PRA Interface - General: and Containment Spray System (CSS)

ML14149A434 Questions 4a, 4b, 4c configurations, the PRA needed to have several (Cover Letter top events added. The necessary fidelity and Ref.4) concomitant model support detail needed to accurately represent all possible configurations is relatively complex. The Rovero methodology avoids extensive reliance on the PRA and uses what could effectively be thought of as a "LOCA Debris" initiating event frequency as a bounding CDF rather than detailed modeling in the PRA.

Similarly, the PRA model of record is used to evaluate the LERF using the ratio of LERF conditional on ECCS sump screen failure for Large Break Loss of Coolant Accident (LLOCA) and CDF conditional on sump screen failure in LLOCA.

Not applicable APLAB, CASA Grande, to Rovero evaluation has shown that all relevant PRA Interface - General: breaks are LLOCA ML14149A434 Question 5

NOC-AE-16003369 Attachment 2 Page 8 of 40 Applicability and Letter RAI Applicability Basis Comments Reference for

Response

(Cover Letter Ref.4)

Not applicable APLAB, CASA Grande, to All the elicited exceedance frequency quantiles PRA Interface - General: and means aggregated in NUREG 1829 ML14149A434 Question 6a, 6b, 6c decrease rapidly with size of break. As a (Cover Letter consequence, sampling must be done very Ref.4) carefully to ensure the "long tails" of the distributions are captured. This was done in CASA Grande as described in the STP 2013 LAR using stratified sampling techniques and ensuring that the OEGB break size was sampled in each quantification. The Rovero methodology avoids the need to perform sampling, in the way required for Monte Carlo quantification, by assuming all break sizes larger than the smallest break size producing more debris than was tested at the location are assumed to be failure. This is a conservative estimate that also avoids the possibility of inadequate sampling of long tails.

Applicable APLAB, STP PRA Model- These RAls and their responses generally Although the STP at- power PRA General: Questions 1, 2, address the adequacy of the peer review is suitable for the Rovero Response 1, 3: 3 performed for the STP PRA and the application as stated in ML14202A045 conclusions made from those reviews. Although ML14202A045, Attachment 1, (Cover Letter the PRA plays a less complex part in the Page 47 of 67 does not apply as Ref. 6) Rovero methodology, the assessment of its the PRA used in Rovero is not Response 2: capability is still relevant. modified as described. Rovero ML14178A481 simply relies on reports from the (Cover Letter at-power PRA to obtain: the Ref. 5)

NOC-AE-16003369 Attachment 2 Page 9 of 40 Applicability and Letter RAI Applicability Basis Comments Reference for

Response

LERF and OeltaLERF results; and the single train frequencies.

Not applicable APLAB, STP PRA Model- The 2013 LAR showed no in-core blockage that Success Criteria: resulted in loss adequate core cooling.- While ML14202A045 Question 1 these conclusions have not changed, the (Cover Letter STPNOC T-H analyses have been simplified in Ref. 6) the Rovero approach. The changes are described in the responses to the SNPB Round 3 RAls.

Not applicable APLAB, STP PRA Model- Rovero incorporates a bounding T-H analysis Success Criteria:

ML14202A045 Question 2a (Cover Letter Ref. 6)

Not applicable APLAB, STP PRA Model- Rovero incorporates a bounding T-H analysis Success Criteria:

ML14202A045 Question 2b (Cover Letter Ref. 6)

Applicable APLAB, STP PRA Model- The response provides information relevant to Success Criteria: the application of LOCAOM to STP. However, ML14202A045 Question 2c Rovero relies on the existing The STPNOC (Cover Letter license-basis RCB analysis for strainer Ref. 6) performance parameters; bounding test data and bounding thermal-hydraulic analysis to ensure adequate core cooling. The pump states are bounded for fiber penetration and collection

NOC-AE-16003369 Attachment 2 Page 10 of 40 Applicability and Letter RAI Applicability Basis Comments Reference for

Response

(single train and two or more trains considered)

Not applicable APLAB, STP PRA Model- Rovero does not apply time dependence. The Success Criteria: Rovero methodology avoids extensive reliance ML14202A045 Questions 3a, 3b on the PRA and uses what could effectively be (Cover Letter thought of as a "LOCA Debris" initiating event Ref. 6) frequency as a bounding CDF rather than detailed modeling in the PRA. Similarly, the PRA model of record is used to evaluate the LERF using the ratio of LERF conditional on ECCS sump screen failure for Large Break Loss of Coolant Accident (LLOCA) and CDF conditional on sump screen failure in LLOCA.

Applicable APLAB, STP PRA Model- PRA safe, stable state does not change with Success Criteria: application of Rovero methodology.

ML14202A045 Question 3c (Cover Letter -

Ref. 6)

Not applicable APLAB, STP PRA Model- Question refers to the CASA-PRA interface.

Success Criteria: The Rovero methodology does not rely on ML14202A045 Question 3d mission times for the calculation of Delta CDF, (Cover Letter CDF or Delta LERF, LERF. Also, Rovero Ref. 6) methodology does not calculate conditional failure probabilities.

Not applicable APLAB, STP PRA Model Human reliability analysis is required for the This basis applies to all the HRA

- Human Reliability various actions assumed in the detailed plant RAls.

Response to RAI Analysis: Question 1 model (pump operation, for example). The 1, 2, 4a, 4b, 6: human reliability analysis included in the PRA

NOC-AE-16003369 Attachment 2 Page 11 of 40 Applicability and Letter RAI Applicability Basis Comments Reference for

Response

ML14149A434 model of record already includes human (Cover Letter reliability analysis required for initiating events Ref.4) other than the debris event (which, when strainer success criteria are exceeded assumes Response to RAI core damage).

3a, 3b, 3c: In the STP 2013 LAR, the PRA required some ML14202A045 modifications to accommodate the several new (Cover Letter ECCS strainer and in-vessel failure modes.

Ref. 6) Rovero creates, in effect, a new initiating event for debris failure and the initiating event Response to RAI frequency is directly used as the in- crease in 5: GDF (the GDF). In this way, the STP PRA does ML14178A481 not require modification since any information (Cover Letter needed can be obtained directly from the STP Ref. 5) PRA.

Applicable APLAB, STP PRA Model Seismic LOCA frequencies still need to be

- PRA Scope: Question 1 incorporated, if necessary. The response to this ML14149A434 RAI is still applicable.

(Cover Letter Ref.4)

Applicable APLAB, STP PRA Model- Seismic LOCA frequencies still need to be PRA Scope: Question 2 incorporated, if necessary. The response to this ML14202A045 RAI is still applicable.

(Cover Letter Ref. 6 Not applicable APLAB, Results The Rovero methodology avoids extensive Interpretation - reliance on the PRA and uses what could ML14149A434 Quantification: Questions effectively be thought of as a "LOCA Debris" (Cover Letter 1a & 1b, 2 initiating event frequency as a bounding GDF Ref.4) rather than detailed modelinq in the PRA.

NOC-AE-16003369 Attachment 2 Page 12 of 40 Applicability and Letter RAI Applicability Basis Comments Reference for

Response

Similarly, the PRA model of record is used to evaluate the LERF using the ratio of LERF conditional on ECCS sump screen failure for Large Break Loss of Coolant Accident (LLOCA) and CDF conditional on sump screen failure in LLOCA.

Not applicable APLAB, Results The STP 2013 LAR included timing Uncertainties are addressed in Interpretation-U ncertai nty considerations and many different break sizes the relevant sections of Ref. 2 to ML14202A045 Analysis: Question 1a and orientations. Rovero only requires that the the cover letter.

(Cover Letter amounts of failed coatings assumed in the test Ref. 6) are appropriately conservative (accepted to exceed amounts expected) or are otherwise bounded. No modeling of failure size or timing is required in the Rovero methodology.

Consequently, key sources of uncertainty, particularly for correlations, identified in this response do not apply for Rovero.

Not applicable APLAB, Results The list of assumptions applies to the CASA Interpretation-Uncertainty Grande analysis. The Rovero methodology has ML14202A045 Analysis: Question 1b different assumptions due to the deterministic (Cover Letter element.

Ref. 6)

Not applicable APLAB, Results The Rovero methodology avoids extensive Interpretation-Uncertainty reliance on the PRA and uses what could ML14202A045 Analysis: Question 1c effectively be thought of as a "LOCA Debris" (Cover Letter initiating event frequency as a bounding CDF Ref. 6) rather than detailed modeling in the PRA.

Similarly, the PRA model of record is used to evaluate the LERF using the ratio of LERF conditional on ECCS sump screen failure for

NOC-AE-16003369 Attachment 2 Page 13 of 40 Applicability and Letter RAI Applicability Basis Comments Reference for

Response

Large Break Loss of Coolant Accident (LLOCA) and COF conditional on sump screen failure in LLOCA.

Applicable APLAB, Results STPNOC's evaluation regarding applicability of Because the PRA community Interpretation - the geometric mean still represents the most generally adopts the ML14149A434 Uncertainty Analysis: STPNOC position that it is the appropriate geometric mean aggregation and (Cover Letter Question 2 metric. it represents a more realistic Ref.4) estimate, the STPNOC adopted the geometric mean aggregation.

The Rovero methodology provides estimates of both aggregations.

Applicable APLAB, Results STPNOC's evaluation of the effect of operating Interpretation-Uncertainty life on the risk evaluation still represents the ML14202A045 Analysis: Question 3 current STPNOC position regarding the use of (Cover Letter NUREG 1829 25 service year values. However, Ref. 6) the table of COF and LERF is not applicable because it was based on CASA Grande frequencies.

Not applicable APLAB, Results The LOCA frequency distributions described in Interpretation-Uncertainty the 2013 LAR and associated RAls are not ML14202A045 Analysis: Questions 4a, used in the Rovero methodology.

(Cover Letter 4b, 4c, 4d Ref. 6) In Rovero, a bounding method, called top-down, was adopted that avoids the need to account for weighting by relying on the fact that locations where debris amounts exceed tested levels have been mitigated. That is, the problematic or "risk" locations have been mitigated and only the non "risk" locations have not been. The Rovero methodology ignores the

NOC-AE-16003369 Attachment 2 Page 14 of 40 Applicability and Letter RAI Applicability Basis Comments Reference for

Response

mitigation improvements and equally weights the NUREG 1829 exceedance frequencies for all locations thereby bounding local effects.

In the Rovero methodology, the continuum break model is compared to the OEGB-only model of interpretation and it automatically includes a (conservative) interpretation of attribution (spherical ZOI for all locations).

The Rovero methodology avoids the need to perform sampling, in the way required for Monte Carlo quantification, by assuming all break sizes larger than the smallest break size producing more debris than was tested at the location are assumed to be failure. This is a conservative estimate that also avoids the possibility of inadequate sampling of long tails.

Not applicable APLAB, Results Section 1.2, Item 4 Interpretation-Uncertainty ML14202A045 Analysis: Question 5 (Cover Letter Ref. 6 Not applicable APLAB, Results Section 1.2, Item 4 Interpretation-Uncertainty ML14202A045 Analysis: Question 6 (Cover Letter Ref. 6)

ARCBRAls**

NOC-AE-16003369 Attachment 2 Page 15 of 40 Applicability and Letter RAI Applicability Basis Comments Reference for

Response

Not applicable ARCB: Questions 1, 3 The response that STPNOC made no changes See comments on SCVB RAls.

(M~ 14015A045) to the UFSAR design basis is correct. However, Study calculation provides ML14086A385 the study calculation referenced for this RAI support for defense-in-ML14086A386 and RAI 3 (ML14086A386) is not applicable to depth/safety margin.

the Rovero methodology. Per the draft 10CFR50.46c rule change, dose need not consider debris effects if risk evaluation is acce tabl small.

Applicable ARCB: Question 2 RAI addresses resolution completion status of a ML14086A385 (ML14015A045) design issue. Response described the resolution and is still a licable.

. . E.MCB R;A.ls Applicable EMCB, Questions 1, 2 Strainer mechanical unchanged by Rovero ML14015A311 methodology.

ML14202A045 (Cover Letter Ref. 6)

. * :'.EPNB HAis:

Not applicable EPNB, Questions 1, 2, 3, See basis for APLAB, Results Interpretation-4,5 Uncertainty Analysis: Questions 4a, 4b, 4c, 4d ML14202A045 above. Break distribution and aggregation (Cover Letter methods in the previous LAR application are Ref. 6) not used in the Rovero methodology.

Not applicable EPNB, Question 6a Although Rovero maintains the NUREG 1829 LOCA frequencies, the distribution ML14202A045 methodology is different from that described in (Cover Letter in the RAI response. The conclusion of the Ref. 6

NOC-AE-16003369 Attachment 2 Page 16 of 40 Applicability and Letter RAI Applicability Basis Comments Reference for

Response

response still applies, but the premise has chan ed.

Not applicable EPNB, Question 6b The statement regarding the basis statistical difference is correct for Rovero; however, the ML14202A045 references in the RAI response are not (Cover Letter consistent with Rovero. The conclusion of the Ref. 6) response still applies, but the premise has chan ed.

E=sGs *. RA1s" Not applicable ESGB, Chemical Effects: The STP 2013 LAR estimates fiber mass Question 1a, 1b, 1c, 1d, distribution in the RCB pool, the reactor core, Responses to 2, 3, 4, 5, 6, 7, 8, 9, 10, and the ECCS strainers. The method used in RAls 1, 2, 4, 5, 11a the STP 2013 LAR performs estimates for the 6, 8, 9, 10: pump configurations assumed and calculates ML14202A045 head loss based on collection of particulates (Cover Letter (fiber, paint, chemical precipitates). The Rovero Ref. 6) methodology performs a similar calculation however, instead of looking at all possible Responses to pumping and debris configurations, Rovero RAIS 3, 7, 11: looks at 'expected' and 'extreme' cases to ML14178A481 ensure the in-vessel effects are not limiting.

(Cover Letter Head loss computation is not done in Rovero.

Ref. 5) Instead, results of testing on an STP ECCS strainer module are used. Any fine fiber loading that exceeds the tested amount is assumed to lead to core damage.

NOC-AE-16003369 Attachment 2 Page 17 of 40 Applicability and Letter RAI Applicability Basis Comments Reference for

Response

Not applicable ESGB, Chemical Effects: The RAI pertains to bump-up factors, which are Question 11 b not applicable to the Rovero methodology. Tin ML14178A481 powder was used as a surrogate for zinc in (Cover Letter plant-specific testing.

Ref. 5)

Not applicable ESGB, Chemical Effects: These RAI and responses are applied in the Although the STP deterministic Question 12, 13a, 13b, context of supporting chemical effects on head testing that supports Rovero was ML14149A434 13c loss. The 2013 LAR process requires not addressed in the responses, (Cover Letter characterization of parameter distributions used The test results show nothing Ref.4) in sampling strategies for estimating and that affects the conclusions of the propagating physical model responses and for Rovero deterministic testing.

development of correlations. Rovero instead uses a test designed to bound the uncertainty associated with Emergency Core Cooling System (ECCS) strainer head losses.

Not applicable ESGB, Chemical Effects: RAI was directed toward chemical effects Question 14a, 14b, 14c testing associated with CASA Grande ML14202A045 correlations. The Rovero methodology is based (Cover Letter on accepted deterministic testing .

.Ref. 6)

Not applicable ESGB, Chemical Effects: See response above for ESGB Chemical Question 15 Effects RAI 12, 13a, 13b, 13c ML14202A045 (Cover Letter Ref. 6)

Not applicable ESGB, Chemical Effects: See response above for ESGB Chemical Question 16 Effects RAI 12, 13a, 13b, 13c.

ML t 4202A045

NOC-AE-16003369 Attachment 2 Page 18 of 40 Applicability and Letter RAI Applicability Basis Comments Reference for

Response

(Cover Letter Response to RAI addresses variations in pH Ref. 6) and amounts of LOFG from different break sizes. Those variations are not required for the Rovero deterministic testinQ.

Not applicable ESGB, Chemical Effects: The RAI and response relate to correlations Question 17 and chemical effects "bump up" factors which ML14178A481 are not used in the Rovero methodology.

(Cover Letter Ref. 5)

Not applicable ESGB, Chemical Effects: Testing credited in Rovero methodology used Response also indicates that the Question 18a WCAP-16530 process. information cited in the RAI was ML14202A045 not used in the 2013 LAR (Cover Letter analyses.

Ref. 6)

Not applicable ESGB, Chemical Effects: The RAI and response supports evaluation of Question 18b the CASA Grande modeling and and ML14202A045 correlations which are not used in the Rovero (Cover Letter methodology. Rovero looks at 'expected' and Ref. 6) 'extreme' cases to ensure the in-vessel effects are not limiting. Head loss computation is not done in Rovero. Instead, results of testing on an STP ECCS strainer module are used. Any fine fiber loading that exceeds the tested amount is assumed to lead to core damage.

Not applicable ESGB, Chemical Effects: Although the response clarifies a typographical Question 18c error, the information in the affected graphics ML14202A045 related to the CASA Grande analyses that are (Cover Letter not used in the Rovero methodology. See Ref. 6) response to 18b above.

NOC-AE-16003369 Attachment 2 Page 19 of 40 Applicability and Letter RAI Applicability Basis Comments Reference for

Response

Not applicable ESGB, Chemical Effects: See response to ESGB RAI 18b above.

Question 19 ML14149A434 (Cover Letter Ref.4)

Not applicable ESGB, Chemical Effects: The RAI and response relate to correlations Question 20 and chemical effects "bump up" factors which ML14178A481 are not used in the Rovero methodology.

(Cover Letter Ref. 5)

Applicable ESGB, Chemical Effects: See ESGB RAl-33 in Round 2 (Table 2 below)

Question 21 ML14202A045 (Cover Letter Ref. 6)

Not applicable ESGB, Chemical Effects: The CHLE test program is not applicable to the This basis is generally applicable Question 22a, 22b Rovero methodology or associated plant- to RAls and responses regarding ML14178A481 specific test. the CHLE testing. As stated in (Cover Letter the response to ESGB Chemical Ref. 5) Effects RAI 22b, "The objective of the CHLE testing program was to generate experimental data to support an overall risk-informed approach to the resolution of GSl-191, while also conducting a manageable number of tests."

Although the CHLE tests and results can provide insight with respect to margin in the deterministic testinq that supports

NOC-AE-16003369 Attachment 2 Page 20 of 40 Applicability and Letter RAI Applicability Basis Comments Reference for

Response

Rovero, the Rovero methodology and STPNOC LAR does not rely on them.

Applicable ESGB, Coatings: Original response and response to RAI SSIB Question 1 6 in ML16082A507 address epoxy coatings Not applicable ESGB, Coatings: IOZ quantified differently for the Rovero Question 2 evaluation ML14149A434 (Cover Letter Ref.4)

Applicable ESGB, Coatings: Unqualified coatings are assumed to fail at Question 3 100%

ML14149A434 (Cover Letter Ref.4)

Not applicable ESGB, Coatings: The STP 2013 LAR included timing Questions 4, 5, 6a, 6b, 6c considerations and many different break sizes Responses to and orientations. Rovero only requires that the RAls 4, 5: amounts of failed coatings assumed in the test ML14149A434 are appropriately conservative (accepted to (Cover Letter exceed amounts expected) or are otherwise Ref.4) bounded. As a consequence, no modeling of failure size or timing is required in the Rovero Response to RAI methodology.

6a, 6b, 6c:

ML14202A045 (Cover Letter Ref. 6)

NOC-AE-16003369 Attachment 2 Page 21 of 40 Applicability and Letter RAI Applicability Basis Comments Reference for

Response

Applicable ESGB, Coatings: Coatings program description is still applicable Question 7 for the Rovero methodology ML14149A434 (Cover Letter Ref.4 SCVBRAl's' Applicable SCVB, Question: 1a Exemption to CSS still required for Rovero The SCVB RAls are relevant to the STPNOC application. The ML14178A481 pre-Rovero responses provided (Cover Letter in ML14178A481 (A485 rR:-:--ef_._ 5 ' - - - : " : - - - - + - : : : - - - - - - - - - + - - - - - - - - - - - - - - - - - - - i attachment) are updated by Not applicable SCVB, Question: 1b See comment. STPNOC changed single failure responses provided in response in ML15246A126 ML15091A440 dated March 25, ML14178A481 2015 as revised in Attachment 1-(Cover Letter 6 to Supplement 2 of the Ref. 5 t--:--:--'-:-:------t--c:c-::----,---,------t---------------------J STPNOC submittal Applicable SCVB, Question: 2a Exemption to CSS still required for Rovero (ML15246A128) to reflect the Rovero methodology changes.

ML14178A481 (Cover Letter Also, in accordance with the Ref. 5 proposed 10CFR50.46c rule r--~-----+------------+--------------------1 Not applicable SCVB, Question: 2b See comment. STPNOC changed single failure change, "The NRC approval of response in ML15246A126 an entity's risk-informed ML14178A481 approach allows the enity to (Cover Letter exclude the effects of debris in its Ref. 5) analysis of long-term cooling ... ".

rA~p_p_l-ic~a~bl-e----t--S-C_V_B_,_Q_u_e_s_ti_on_:_3_a----t--G-e_n_e-ra-l-ly_a_p_p_lic_a_b_le-,-b-u_t_o_rig_i_n_a_Ir-e-~-r-e-nc_e_----J In addition, the NRCappliedthe document has been revised to references same rationale to the relationship ML14178A481 shown in comment. of 10CFR50.46c to other (Cover Letter regulations; i.e., GOC 35, 38 and Ref. 5 41. Since STPNOC met those

NOC-AE-16003369 Attachment 2 Page 22 of 40 Applicability and Letter RAI Applicability Basis Comments Reference for

Response

Not applicable SCVB, Question: 3b See comment. The description is superseded requirements by showing that the by Rovero. effects of debris are small in ML14178A481 accordance with RG 1.174 (Cover Letter (considering COF, LERF, safety Ref. 5) margin and defense-in-depth),

Applicable SCVB, Question: 3c Generally applicable, but original reference the CLB design basis for document has been revised to references containment need not be revised.

ML14178A481 shown in comment.

(Cover Letter Ref. 5)

Applicable SCVB, Question: 4a Generally applicable, but original reference document has been revised to references ML14178A481 shown in comment.

(Cover Letter Ref. 5)

Applicable SCVB, Question: 4b Rovero methodology has no impact on response.

ML14178A481 (Cover Letter Ref. 5)

Applicable SCVB, Question: 4c Generally applicable, but original reference document has been revised to references ML14178A481 shown in comment.

(Cover Letter Ref. 5)

Not applicable SCVB, Question: 5 See comment. Rovero does not use time-dependent containment analyses, and does not ML14178A481 change the CLB containment analysis (Cover Letter Ref. 5)

NOC-AE-16003369 Attachment 2 Page 23 of 40 Applicability and Letter RAI Applicability Basis Comments Reference for

Response

Applicable SCVB, Question: 6 See comment. Rovero does not change the containment analysis (current LB calculation is ML14178A481 used).

(Cover Letter Ref. 5 Applicable SCVB, Question: 7 The response still applies with respect to how Rovero is used to assess debris effects.

ML14178A481 (Cover Letter Ref. 5 Not applicable SCVB, Question: 8 RELAP5 screening cases have changed and are being reviewed by SNPB.

ML14178A481 (Cover Letter Ref. 5 Applicable SCVB, Question: 9a Rovero methodology still requires exemption to GOC 35.

ML14178A481 (Cover Letter Ref. 5 Not applicable SCVB, Question: 9b See comment. STPNOC changed single failure response in ML15246A126 ML14178A481 (Cover Letter Ref. 5 Applicable SNPB Questions: 1a, 1b, Used by NRC for their thermal-hydraulic review 1c, 1d, 1e, 1f, 1g, 1h, 1i, ML14178A481 1j, 1k, 11, 1m, 2a, 2b, 2c, (Cover Letter 2d,3,5 Ref. 5

NOC-AE-16003369 Attachment 2 Page 24 of 40 Applicability and Letter RAI Applicability Basis Comments Reference for

Response

Not applicable SNPB, Question 4 STP BAP LB calculation has been revised since this STPNOC responded to this RAI and ML14202A045 was the subject of an NRC audit.

(Cover Letter Ref. 6)

Applicable SNPB, Question: 5 STP BA concentration is not calculated in the ML14178A481 Rovero methodology (Cover Letter Ref. 5 Applicable SRXB, Question 1 NRC review of RELAP5 documentation These also address the applicability of Reference 3 of the ML14202A045 cover letter.

(Cover Letter Ref. 6 Not applicable SRXB, Question 2 Not using 30 capability of RELAP5 30 ML14202A045 (Cover Letter Ref. 6 Applicable SRXB, Question 3 NRG review of RELAP5 documentation ML14202A045 (Cover Letter Ref. 6 Applicable SRXB, Question 4 NRC review of RELAP5 documentation ML14202A045 (Cover Letter Ref. 6

NOC-AE-16003369 Attachment 2 Page 25 of 40 Applicability and Letter RAI Applicability Basis Comments Reference for

Response

Not applicable SRXB, Question Sa Limiting values used in Rovero methodology ML14149A434 (Cover Letter Ref.4)

Not applicable SRXB, Question Sb Table not used Not using CASA Grande to calculate these values.

ML14149A434 (Cover Letter Ref.4)

Not applicable SRXB, Question Sc Rovero uses different assumptions for the calculation.

ML14149A434 (Cover Letter Ref.4)

Not applicable SRXB, Question 6 Part of input for conditional failure probabilities, which are not being used in Rovero Applicable SRXB, Question 7a, 7b HLSO procedure is not changed for Rovero methodology ML14149A434 (Cover Letter Ref.4)

Not applicable SRXB, Question 8 Rovero applies bounding sensitivities for ECCS flow ML14149A434 -

(Cover Letter Ref.4)

Applicable SRXB, Question 9 Flow combination definitions still apply ML14149A434

NOC-AE-16003369 Attachment 2 Page 26 of 40 Applicability and Letter RAI Applicability Basis Comments Reference for

Response

(Cover Letter Ref.4 Applicable SSIB, ZOI: Question 1 Debris transport in CASA still required ML14149A434 (Cover Letter Ref.4 Applicable SSIB, Debris Debris transport in CASA still required Characteristics: Question ML14149A434 2 (Cover Letter Ref.4 Not applicable SSIB, Debris Not using head loss correlation Characteristics: Question 3

Applicable SSIB, Transport: Debris transport in CASA still required Question 4 Not applicable SSIB, Transport: Supplement 2 establishes transport fraction for Question 5 pool fill at 5%.

ML14149A434 (Cover Letter Ref.4 Applicable SSIB, Transport: Debris generation and transport models are not Question 6a, 6b, 6c, 6d, changed.

ML14202A045 6e, ?a, 7b, 7c, 7d, 7e (Cover Letter Ref. 6)

NOC-AE-16003369 Attachment 2 Page 27 of 40 Applicability and Letter RAI Applicability Basis Comments Reference for

Response

Applicable, SSIB, Transport: RAI was an editorial correction Question 7f ML14202A045 (Cover Letter Ref. 6)

Applicable SSIB, Transport: STPNOC assumes no credit for hold up of Question 8a, Sb, Sc, Sd, partially submerged debris on the concrete of ML14202A045 Se the operating deck.

(Cover Letter Ref. 6)

Not applicable SSIB, Transport: The revised methodology holds up and erodes Question 9 smalls instead of transporting them.

ML14149A434 (Cover Letter Ref.4)

Applicable SSIB, Transport: Discussion of no transport after sprays are Question 10 secured is still valid.

ML14202A045 (Cover Letter Ref. 6)

Not applicable SSIB, Transport: Correlations are not used in Rovero Question 11 a ML14149A434 (Cover Letter Ref.4)

Not applicable SSIB, Transport: Correlations are not used in Rovero Question 11 b ML14149A434 (Cover Letter Ref.4)

Applicable SSIB, Transport: Basis is not changed for Rovero Question 11 c

NOC-AE-16003369 Attachment 2 Page 28 of 40 Applicability and Letter RAI Applicability Basis Comments Reference for

Response

ML14149A434 (Cover Letter Ref.4)

Not applicable SSIB, Transport: Correlations are not used in Rovero Question 11 d ML14149A434 (Cover Letter Ref.4)

Not applicable SSIB, Transport: Correlations are not used in Rovero Question 11 e ML14149A434 (Cover Letter Ref.4)

Applicable SSIB, Transport: Transport model not changed Question 12 Applicable SSIB, Transport: Micro-Therm still transports as fines in current Question 13 methodology.

ML14149A434 (Cover Letter Ref.4)

Not applicable SSIB, Head Loss and Head loss correlations are not used in Rovero Chemical Effects Bump ML14202A045 Up: Question 14 (Cover Letter Ref. 6)

Not applicable SSIB, Head Loss and Head loss correlations are not used in Rovero Chemical Effects Bump ML14202A045 Up: Question 15a, 15b, (Cover Letter 15c, 15d, 16a, 16b, 16c, Ref. 6) 16d, 17a, 17b, 17c, 17d, 17e, 17f, 18a, 18b, 18c,

NOC-AE-16003369 Attachment 2 Page 29 of 40 Applicability and Letter RAI Applicability Basis Comments Reference for

Response

18d, 18e, 19,20,21a, 21b,21c,21d,22,23,24 Not applicable SSIB, Head Loss and Head loss correlations are not used in Rovero Chemical Effects Bump-ML14178A481 up: Questions 25a, 25b, (Cover Letter 26a,26b,26d,26e,26f Ref. 5 Applicable SSIB, Head Loss and Strainer loading related to actual performance Chemical Effects Bump- compared to test ML14178A481 up: Question 26c (Cover Letter Ref. 5 Applicable SSIB, Head Loss and Strainer LB NPSH Chemical Effects Bump ML14202A045 Up: Question 27 (Cover Letter Ref. 6)

Not applicable SSIB, Head Loss and Head loss correlations are not used in Rovero Chemical Effects Bump ML14202A045 Up: Question 28 (Cover Letter Ref. 6)

Applicable SSIB, NPSH and Strainer NPSH Not a CASA Grande calculation Oegasification: Question for current application; however, ML14149A434 29 STP Engineering calculation (Cover Letter includes the same considerations Ref.4)

NOC-AE-16003369 Attachment 2 Page 30 of 40 Applicability and Letter RAI Applicability Basis Comments Reference for

Response

Not applicable SSIB, NPSH and NPSHR is now a different calculation that Degasification: Question credits accident pressure. Response is ML14178A481 30 superseded by response to SSIB Follow up (Cover Letter RAls 33 and 34.

Ref. 5 Applicable SSIB, NPSH and Strainer LB NPSH Portions of the response related Degasification: Question to use of CASA Grande are not ML14178A481 31 applicable (Cover Letter Ref. 5 Applicable SSIB, NPSH and Strainer LB NPSH STP Engineering calculation Degasification: Question instead of CASA Grande ML14178A481 32 calculation.

(Cover Letter Ref. 5 Not applicable SSIB, NPSH and Not done with CASA Grande methodology for Degasification: Question current LAR supplement. This was done in the ML14178A481 33 deterministic calculation by Enercon.

(Cover Letter Ref. 5 Not applicable SSIB, NPSH and Containment Spray flows are addressed in Degasification: Question FIDOE discussion in Attachment 1-3 to cover ML14178A481 34 letter Ref.2 (ML15246A126 cover /127 (Cover Letter attachment)

Ref. 5 Not applicable SSIB, NPSH and The CASA evaluation described in the RAI 35 Degasification: Question response used the equivalent diameter to ML14178A481 35 assign LOCA category. Rovero does not (Cover Letter assign LOCA categories based on equivalent Ref. 5 diameter.

NOC-AE-16003369 Attachment 2 Page 31 of 40 Applicability and Letter RAI Applicability Basis Comments Reference for

Response

Not applicable SSIB, NPSH and Superseded by information in Att. 1-2 p.56 Degasification: Question cover letter Ref. 2, (ML15246A126 cover ML14202A045 36 letter/A 127 attachment)

(Cover Letter Ref. 6)

Not applicable SSIB, In-Vessel and Boric See BAP discussion in Att. 1-3 to cover letter Acid Precipitation: Ref. 2, (ML15246A126 cover letter/A127 ML14178A481 Question 37 attachment)

(Cover Letter Ref. 5 Not applicable SSIB, NPSH and See FIDOE discussion in Att. 1-3 of cover letter Degasification: Question Ref. 2, (ML15246A126 cover letter/A127 ML14202A045 38 attachment)

(Cover Letter Ref. 6)

Applicable SSIB, Debris Bypass: Debris bypass is required for downstream Question 39a, 39b, 39c, analysis in Rovero.

ML14178A481 39d, 39e, 39f (Cover Letter Ref. 5 Not applicable SSIB, Defense In Depth See DID and Safety Margin in Att. 1-4 to cover References to earlier CDF and and Mitigative Measures: letter Ref. 2, (ML15246A126 cover/A127 LERF are not applicable, but ML14202A045 Question 40 attachment) qualitative discussion still applies.

(Cover Letter Ref. 6)

Not applicable SSIB, Defense in Depth Risk methodology has changed Discussion with regard to EOPs and Mitigative Measures: is applicable. Description of ML14178A481 Question 41 a application of risk methodology is (Cover Letter not applicable.

Ref. 5

NOC-AE-16003369 Attachment 2 Page 32 of 40 Applicability and Letter RAI Applicability Basis Comments Reference for

Response

Applicable SSIB, Defense in Depth DID and SM required by RG 1.174 and Mitigative Measures:

ML14178A481 Question 41 b (Cover Letter Ref. 5 Applicable SSIB, Defense in Depth DID and SM required by RG 1.174 and Mitigative Measures:

ML14178A481 Question 41 c (Cover Letter Ref. 5 Applicable SSIB, Defense in Depth DID and SM required by RG 1.174 and Mitigative Measures:

ML14178A481 Question 41 d (Cover Letter Ref. 5 Applicable SSIB, Defense In Depth DID and SM required by RG 1.174 and Mitigative Measures:

ML14202A045 Question 42 (Cover Letter Ref. 6

'STSBRAls.

Not applicable STSB: Question 1 Although response accurately describes application of RMTS, RMTS would not be ML14149A434 required for proposed 90-day completion time (Cover Letter Ref.4 Not applicable STSB: Question 2 Although response accurately describes application of RMTS, RMTS would not be ML14149A434 required for proposed 90-day completion time (Cover Letter Ref.4

NOC-AE-16003369 Attachment 2 Page 33 of 40 Applicability and Letter RAI Applicability Basis Comments Reference for

Response

Applicable STSB: Question 3 Engineering change control still manages quantities of material going into RCB ML14149A434 (Cover Letter Ref.4)

Table 2 Applicability of Responses to Round 2 RAls (ML14357A171)

Applicability (All responses RAI Applicability Basis Comments are in ML15091A440)

Applicable Question 1: Project Appropriate quality controls required for license Quality Assurance activities Not applicable Question 2: Project CASA Grande 1.7.2 is controlled in accordance Quality Assurance with the STPNOC SQA program Applicable Question 3: Project Appropriate quality controls required for license Quality Assurance activities Applicable Question 4: Project Appropriate quality controls required for license Quality Assurance activities

NOC-AE-16003369 Attachment 2 Page 34 of 40 Applicability (All responses RAI Applicability Basis Comments are in ML15091A440)

Applicable Question 1: Treatment of Appropriately refers to Rovero Unanalyzed Plant Conditions Applicable Question 7: Human Appropriately refers to Rovero Reliability Analysis Applicable Question 1 : Key Appropriately refers to Rovero Assumptions/Key Sources of Uncertainty Applicable Question 1: Validity of Appropriately refers to Rovero Assumption on Pump Configurations Applicable Question 7: CASA Appropriately refers to Rovero. The Grande to PRA Interface methodology now strictly looks for smallest break size below which tested fines amounts are not exceeded.

Applicable Question 1: Fidelity Appropriately refers to Rovero between RELAP Simulations and CASA Grande Applicable Question 1: State-of- Appropriately refers to Rovero. Rovero does Knowledge Correlation not calculate failure probabilities. Instead, Rovero calculates core damage frequencies come from direct evaluation of the NU REG 1829 quantiles and means.

NOC-AE-16003369 Attachment 2 Page 35 of 40

/

Applicability (All responses RAI Applicability Basis Comments are in ML15091A440)

Applicable Question 1 : Selection of Appropriately refers to Rover 0. Rovero Johnson Parameters evaluates calculates core damage frequencies from direct evaluation of the NU REG 1829 quantiles and means.

Applicable Question 2 Strainer mechanical must be met for Rovero. Also addressed in Att. 1-2 to cover letter Ref. 2, p. 81-82 (ML15246A126 cover letter/A 127 attachment)

.. .*.. :****:. <L '*!< . .*:  :.* . '::t. ;..:* ..... ;. **.*.* **o:-::**, './ .. ;:. :i'*c::.. *: ***.: . . '. *;;::i'.

.Es<3s:r~fo:1~r ).

' .," *,' , '; ,;_;:',' .... ~

• • ) "":' .'.- .  !>;.

.I*

• o*:;* .. >*'.\. :. .'"  ::: *... ...... .:;:;*~, ...... '; . ' *,:*:""  : .. :. ;:,: .*. ":: .... */*

Applicable Question 23: Chemical Appropriately refers to Rovero Effects Applicable Question 24: Chemical Appropriately refers to Rovero Effects Applicable Question 25: Chemical Appropriately refers to Rovero Effects Applicable Question 26: Chemical Appropriately refers to Rovero Effects Applicable Question 27: Chemical Appropriately refers to Rovero Effects Applicable [ML15091A440]Question Appropriately refers to Rovero.

28: Chemical Effects Applicable Question 29: Chemical Appropriately refers to Rovero.

Effects Applicable Question 30: Chemical Appropriately refers to Rovero.

Effects Applicable Question 31: Chemical Appropriately refers to Rovero.

Effects Applicable Question 32: Chemical Appropriately refers to Rovero.

Effects

NOC-AE-16003369 Attachment 2 Page 36 of 40 Applicability (All responses RAI Applicability Basis Comments are in ML15091A440)

Applicable Question 33: Chemical Response not affected by methodology change.

Effects Not applicable Question 34: Chemical Rovero does not use correlations to evaluate Response is applicable in that it Effects strainer head loss. provides the clarification re uested b the reviewer.

Applicable Question 8: Coatings All unqualified coatings were included in the STP 2008 strainer test used by Rovero. This is also addressed in Round 3 SSIB RAls.

Applicable Question 9: Coatings Response appropriately refers to Rovero Topic to be further addressed in response to Round 3 RAls sent in ML16082A507 Applicable Question 1O: Coatings Response appropriately refers to Rovero Topic to be further addressed in methodology. response to Round 3 RAls sent in ML16082A507 Not applicable Responses to SCVB Revised responses to each of these RAls were Also see evaluation of responses RAls 10 - 18 from NRC provided in Att. 1-6 to STPNOC's August 20, to initial SCVB RAls 1 - 9, above letter dated March 3, 2015, Supplement 2 to the application 2015(ML14357A171), as (ML15246A128) provided in STPNOC letter dated March 25, 2015 ML15091A440 .

Applicable Question 6 BAP must be met in Rovero BAP is also addressed in later RA ls Applicable Question 7 BAP must be met in Rovero BAP is also addressed in later RA ls

NOC-AE-16003369 Attachment 2 Page 37 of 40 Applicability (All responses RAI Applicability Basis Comments are in ML15091A440)

Applicable Question 8 BAP must be met in Rovero BAP is also addressed in later RA ls Applicable Question 9 BAP must be met in Rovero BAP is also addressed in later RA ls Applicable Question 10 Rovero does not rely on HLSO timing Note that statement that "Rovero analysis relies on current UFSAR hot leg switchover time" only means that Rovero does not do a calculation that depends on HLSO time. The Rovero analysis shows there is no effect of debris on BAP.

Applicable Question 43 Rovero uses debris generation and transport to find critical/ non-critical weld locations Applicable Question 44 Rovero uses debris generation and transport to find critical/ non-critical weld locations Not applicable Question 45 Fractions have changed from 11/2013 LAR Revised fractions are provided in response to Round 3 SSIB RAI-3.

Applicable Question 46 Rovero uses debris generation and transport to find critical/ non-critical weld locations Applicable Question 47 Rovero is appropriately referenced.

Applicable Question 48 Rovero is appropriately referenced.

Applicable Question 49 Rovero requires strainer performance calculation

NOC-AE-16003369 Attachment 2 Page 38 of 40 Applicability (All responses RAI Applicability Basis Comments are in ML15091A440)

Applicable Question 50 Rovero is appropriately referenced in the response and does not use correlations for head loss Applicable Question 51 Rovero requires strainer performance calculation and response appropriately refers to 2008 evaluations.

Applicable Question 52 Rovero requires strainer performance calculation and response appropriately refers to 2008 evaluations.

Not applicable Question 53 Rovero does not use probability distributions for performance modeling Applicable Question 54 Rovero requires strainer performance Round 3 RAls also address calculation flashing Applicable Question 55 Response provides clarification for implementation of backwash as defense-in-depth Applicable Question 55a Rovero does not use correlations for head loss Applicable Question 56 Rovero requires strainer penetration calculation Applicable Question 57(a) Rovero requires strainer penetration calculation Applicable Question 57(b) Rovero requires strainer penetration calculation Applicable Question 57(c) Rovero requires strainer penetration calculation Applicable Question 57(d) Rovero requires strainer penetration calculation

NOC-AE-16003369 Attachment 2 Page 39 of 40 Applicability (All responses RAI Applicability Basis Comments are in ML15091A440)

Applicable Question 57(e) Rovero requires strainer penetration calculation Applicable Question 57(f) Rovero requires strainer penetration calculation Not applicable Question 58 Although there are some parallels, Rovero uses a different sampling process.

Applicable Question 59 Rovero requires the CAD model and CASA Grande for debris generation and transport Applicable Question 60 Latent fiber and eroded fiber are required for Rovero Applicable Question 61 Rovero requires the CAD model and CASA Grande for debris generation and transport Applicable Question 62 Rovero does not use correlations for head loss Applicable Question 63 Rovero does not use correlations for head loss Applicable Question 64 Rovero does not use correlations for head loss Applicable Question 65 Rovero does not use correlations for head loss Applicable Question 66 Rovero addresses BAP as required by NRC Note that statement that "Rovero guidance analysis relies on current UFSAR hot leg switchover time" only means that Rovero does not do a calculation that depends on HLSO time. The Rovero analysis shows there is no effect of debris on BAP.

NOC-AE-16003369 Attachment 2 Page 40 of 40 Applicability (All responses RAI Applicability Basis Comments are in ML15091A440)

Applicable Question 4 Application to clarify use of risk information August 20, 2015, Supplement 2 proposed TS changes that are consistent with the description in this RAI. Further information will be provided in response to Round 3 RAI from STSB.

NOC-AE-16003369 Attachment 3 Attachment 3 Definitions and Acronyms

NOC-AE-14003101 Attachment 9 Page 1of2 Definitions and Acronyms ANS American Nuclear Society EOF Emergency Operations ARL Alden Research Laboratory Facility ASME American Society of EOP Emergency Operating Mechanical Engineers Procedure(s)

BA Boric Acid EPRI Electric Power Research BAP Boric Acid Precipitation Institute BC Branch Connection EQ Equipment Qualification BEP Best Efficiency Point ESF Engineered Safety Feature B-F Bimetallic Welds FA Fuel Assembly(s)

B-J Single Metal Welds FHB Fuel Handling Building BWR Boiling Water Reactor GDC General Design Criterion(ia)

CAD Computer Aided Design GL Generic Letter CASA Containment Accident GSI Generic Safety Issue Stochastic Analysis HHSI High Head Safety Injection CCDF Complementary Cumulative (ECCS Subsystem)

Distribution Function or HLB Hot Leg Break Conditional Core Damage HTVL High Temperature Vertical Frequency Loop ccw Component Cooling Water HLSO Hot Leg Switchover CDF Core Damage Frequency ID Inside Diameter CET Core Exit Thermocouple(s) IGSCC lntergranular Stress CHLE Corrosion/Head Loss Corrosion Cracking Experiments ISi In-Service Inspection CHRS Containment Heat Removal LAR License Amendment System Request CLB Cold Leg Break or Current LBB Leak Before Break Licensing Basis LBLOCA Large Break Loss of Coolant CRMP Configuration Risk Accident Management Program LCO Limiting Condition for cs Containment Spray Operability CSHL Clean Strainer Head Loss LDFG Low Density Fiberglass css Containment Spray System LERF Large Early Release (same as CS) Frequency eves . Chemical Volume Control LHS Latin Hypercube Sampling System LHSI Low Head Safety Injection OBA Design Basis Accident (ECCS Subsystem)

DBD Design Basis Document LOCA Loss of Coolant Accident D&C Design and Construction LOOP/LOSP Loss of Off Site Power Defects MAAP Modular Accident Analysis DEGB Double Ended Guillotine Program Break MAB/MEAS Mechanical Auxiliary Building DID Defense in Depth or Mechanical Electrical DM Degradation Mechanism Auxiliary Building ECC Emergency Core Cooling MBLOCA Medium Break Loss of (same as ECCS) Coolant Accident ECCS Emergency Core Cooling NIST National Institute of System Standards and Technology ECWS Essential Cooling Water NLHS Non-uniform Latin Hypercube System (also ECW) Sampling

NOC-AE-14003101 Attachment 9 Page 2 of 2 Definitions and Acronyms NPSH Net Positive Suction Head, RWST Refueling Water Storage (NPSHA - available, NPSHR Tank

- required) SBLOCA Small Break Loss of Coolant NRC Nuclear Regulatory Accident Commission SC Stress Corrosion NSSS Nuclear Steam Supply SI/SIS Safety Injection, Safety System Injection System (same as OBE Operating Basis Earthquake ECCS)

OD Outer Diameter SIR Safety Injection and PCI Performance Contracting, Recirculation Inc. SR Surveillance Requirement PCT Peak Clad Temperature SRM Staff Requirements PDF Probability Density Function Memorandum PRA Probabilistic Risk SSE Safe Shutdown Earthquake Assessment STP South Texas Project PWR Pressurized Water Reactor STPEGS South Texas Project Electric PW ROG Pressurized Water Reactor Generating Station Owner's Group STPNOC STP Nuclear Operating PWSCC Primary Water Stress Company Corrosion Cracking TAMU Texas A&M University QDPS Qualified Display Processing TF Thermal Fatigue System TGSCC Transgranular Stress RAI Request for Additional Corrosion Cracking Information TS Technical Specification( s)

RCB Reactor Containment TSB Technical Specification Building Bases RCFC Reactor Containment Fan TSC Technical Support Center Cooler TSP Trisodium Phosphate RCS Reactor Coolant System UFSAR Updated Final Safety RG Regulatory Guide Analysis Report RHR Residual Heat Removal UNM University of New Mexico RI-ISi Risk-Informed In-Service USI Unresolved Safety Issue Inspection UT University of Texas (Austin)

RMI Reflective Metal Insulation V&V Verification and Validation RMTS Risk Managed Technical VF Vibration Fatigue Specifications WCAP Westinghouse Commercial Rovero Risk over Deterministic Atomic Power Methodology ZOI Zone of Influence RVWL Reactor Vessel Water Level