RS-21-082, Attachment 2 - Technical Basis for NSAL-09-5 Revision 1 and Applicability to Byron, Braidwood, and R.E. Ginna Non-Proprietary Version for NRC

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Attachment 2 - Technical Basis for NSAL-09-5 Revision 1 and Applicability to Byron, Braidwood, and R.E. Ginna Non-Proprietary Version for NRC
ML21225A008
Person / Time
Site: Byron, Braidwood, Ginna  Constellation icon.png
Issue date: 08/13/2021
From:
Exelon Generation Co
To:
Office of Nuclear Reactor Regulation
Shared Package
ML21225A005 List:
References
RS-21-082
Download: ML21225A008 (4)
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ATTACHMENT 2 Technical Basis for NSAL-09-5 Revision 1 and Applicability to Byron, Braidwood, and R.E. Ginna Non-Proprietary Version for NRC (NON-PROPRIETARY) 3 pages follow contains Proprietary Information. Withhold from public disclosure under 10 CFR 2.390. When separated from Attachment 3, this document is decontrolled.

Westinghouse Non-Proprietary Class 3 CE-20-392 Revision 1, Attachment 3 Page 1 of 3 Technical Basis for NSAL-09-5 Revision 1 and Applicability to Byron, Braidwood, and R.E. Ginna

References:

1. NSAL-09-5, Revision 1, Relaxed Axial Offset Control FQ Technical Specification Actions
2. TSD-20-008 (Westinghouse letter NF-CB-20-129), NSAL-09-5 Justification Letter for Byron, Braidwood, Ginna
3. NUREG-1431, Revision 4, Vol. 1, Standard Technical Specifications Westinghouse Plants
4. CN-GEN-MISC-230, Evaluation of Interim Action Statement for Transient FQ Violations in RAOC Plants
5. WCAP-17661-P-A, Revision 1, Improved RAOC and CAOC FQ Surveillance Technical Specifications
6. RESPONSE TO PRESSURIZED WATER REACTOR OWNERS GROUP LETTER REGARDING NON-CONSERVATIVE TECHNICAL SPECIFICATIONS AND TIMELY SUBMITTAL OF A LICENSE AMENDMENT REQUEST, (Accession Number ML103210497).
7. WCAP-10217-A, Relaxation of Constant Axial Offset Control
8. WCAP-8403, Topical Report Power Distribution Control and Load Following Procedures Exelon is exploring the implementation of the Reference 1 Recommended Actions in the Technical Specifications (TS) of Byron, Braidwood, and R.E. Ginna units. Reference 1 addressed a deficiency in the Westinghouse Standard Technical Specifications (STS), Reference 3, which is representative for the R.E. Ginna TS. Reference 3 would have also been representative for Byron and Braidwood when the Power Distribution Monitoring System (PDMS) is inoperable if the STS were implemented without modifications into the Byron/Braidwood TS. This letter provides the technical basis for the Recommended Actions in Reference 1, as requested in Reference 2.

Background:

While the Byron, Braidwood, and R.E. Ginna plants implemented the same Relaxed Axial Offset Control (RAOC) methodology, there were differences among these plants in the implementation of the Required Actions for Limiting Condition for Operation (LCO) 3.2.1 Condition B. In addition, Byron and Braidwood also concurrently implemented other TS changes accommodating the BEACON TM Core Monitoring System.

The R.E. Ginna LCO 3.2.1 Action B.1 (Amendment 94) followed Reference 3 by implementing a 1% Axial Flux Difference (AFD) reduction for each 1% of FQW(z) violation. In contrast, Byron (via Amendment 116) and Braidwood (via Amendment 110) implemented for LCO 3.2.1 Required Action B.1 a thermal power reduction of 1% for each 1% that FQW(z) exceeds the limit, without an Axial Flux Difference (AFD) reduction.

For Byron, Braidwood, and R.E. Ginna, LCO 3.2.1 Required Actions B.2 and B.3 implemented reductions of Power Range Neutron Flux High, and Overpower T trip setpoints; note however, that for R.E. Ginna this occurs only if the AFD limits reduction translates into a power reduction (consistent with Reference 3), whereas for Byron and Braidwood the magnitude of trip setpoints adjustment derives directly from the thermal power reduction. The R.E. Ginna LCO 3.2.1 also shows Required Action B.4 (consistent with Reference 3), but the Byron/Braidwood LCO 3.2.1 does not.

In Reference 1 (issued after the above-mentioned TS Amendments), Westinghouse determined that the Required Actions for Condition B of TS 3.2.1B in Reference 3 for plants that have implemented the RAOC methodology may not be sufficient to assure that the peaking factor basis assumed in the licensing basis analysis is maintained under all conditions if the transient heat flux hot channel factor (FQ) limit is not met. In order to maintain the BEACON is a trademark or registered trademark of Westinghouse Electric Company LLC, its Affiliates and/or its Subsidiaries in the United States of America and may be registered in other countries throughout the world. All rights reserved. Unauthorized use is strictly prohibited. Other names may be trademarks of their respective owners.

      • This record was final approved on 8/6/2021 1:14:16 PM. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 CE-20-392 Revision 1, Attachment 3 Page 2 of 3 intent of Reference 3 LCO 3.2.1B Required Action B.1 to restore the measured transient heat flux hot channel factor to within the limiting condition for operation (LCO) limit, Westinghouse recommended that conservative interim actions be administratively implemented in addition to those required for Condition B of the FQ TS 3.2.1B from Reference 3.

The first recommended action in Reference 1 reduced thermal power by [ ]a,c FQW(Z) violation for surveillance performed above 75% RTP. The other three recommended actions are similar to Required Actions B.2 through B.4 from LCO 3.2.1B in Reference 3, with the distinction that the Reference 3 thermal power reduction is defined based on the AFD limits whereas the Reference 1 power reduction is driven by the first recommended action. Since the power reduction from the first recommended action in Reference 1 is always larger than the one implied by Action B.1 in LCO 3.2.1B of Reference 3, [

]a,c Hence, the effective recommendation of Reference 1 is to implement [

]a,c Taken together, these actions constitute a very conservative response to an FQ (Z) violation in order to bound all plants.

W Reference 1 was determined to be applicable for Byron and Braidwood despite the corresponding TS LCO 3.2.1 Action B.1 not following Reference 3 because these plants have a RAOC AFD specification (LCO 3.2.3) and because the FQW margin recovered with Reference 1 recommended actions is larger than the margin recovered using Byron/Braidwood LCO 3.2.1 Required Action B.1.

Technical Basis for NSAL-09-5 Revision 1 The Required Action B.1 in LCO 3.2.1B in STS (Reference 3) of AFD reduction proportional to FQW limit violation is sufficient to restore the measured transient heat flux hot channel factor to within the limiting condition for operation (LCO) limit if the most limiting elevation is away from the central region of the core (i.e. towards either the top or the bottom of the core). In such cases, the Condition 1 transients have the core operating near the RAOC AFD limits, therefore reduction of the AFD limits will [

]a,c If however the limiting FQ occurs in the middle elevations of the core, the reduction of the AFD limits could have W

only a limited efficiency in reducing the limiting FQW, and therefore be insufficient to restore the measured FQW(Z) within limits. In the remainder of this letter, middle-core elevations designate those elevations Z*

where a reduction of AFD limits is not effective in reducing the transient FQ(Z*).

For a plant and cycle when transient FQ occurred at a middle-core elevation for some of the burnup steps during the cycle, Reference 4 analyzed the adequacy of Reference 1 recommended actions for restoring FQW within limits. Specifically, a [ ]a,c FQW violation was postulated, followed by implementation of Required Actions consisting of a [ ]a,c thermal power reduction and a [ ]a,c AFD reduction. These actions are consistent with those required by Reference 1 for a plant that follows the standard TS (Reference 3). A [ ]a,c FQW violation was chosen, based on reload analyses validating [

]a,c The transient FQ margin improvement, when Reference 1 recommended actions are implemented, was calculated using [

]a,c Using this analysis procedure, Reference 4 showed that a [ ]a,c thermal power reduction and

[ ] a,c AFD limits reduction recovered more than [ ] of margin to the transient FQ in each of the analyzed a,c cases.

      • This record was final approved on 8/6/2021 1:14:16 PM. (This statement was added by the PRIME system upon its validation)

Westinghouse Non-Proprietary Class 3 CE-20-392 Revision 1, Attachment 3 Page 3 of 3 Since this is an issue only when the limiting FQW occurs at middle-core elevations, the efficiency of the actions recommended in Reference 1 in restoring FQW within limits [

]a,c Therefore, the choice of a given reactor core to demonstrate the adequacy of the Reference 1 recommended actions is [

]a,c The study performed in Reference 4 met this requirement and was therefore sufficient to support the applicability of the Reference 1 recommended actions to [ ]a,c including Byron, Braidwood, and R.E.

Ginna.

Another indirect validation of the conservatism of the Reference 1 recommended actions comes from the calculations that illustrated the methodology described in Reference 5. For a [

]a,c core, a [ ]a,c relative improvement in the transient FQ at the most limiting time in the cycle was obtained with a [ ] thermal power reduction and a [

a,c

]a,c AFD reduction. While the power and AFD reductions in the example presented in Reference 5 [

]a,c This example serves to further illustrate with a typical case that the thermal power reduction recommended in Reference 1 is conservative. The Reference 5 case discussed above also [ ]a,c of Action B.1 in the Byron/Braidwood LCO 3.2.1, since a [ ] power reduction (accompanied additionally by a,c an AFD reduction which is not requested by the Byron/Braidwood TS LCO 3.2.1 Condition B Actions) provides

[ ]a,c transient FQ improvement, which is [ ]a,c to restore the measured transient heat flux hot channel factor to within the LCO) limit following a [ ]a,c FQW violation.

In conclusion, the technical basis for Reference 1 (NSAL-09-5, Revision 1) is applicable to any RAOC plants, including Byron, Braidwood, and R.E. Ginna. The same technical basis supports the adequacy of the Reference 1 interim actions in addition to those required for Condition B of TS 3.2.1B in Reference 3. Further consistent with this conclusion, the NRC staff noted in Reference 6 that the Reference 1 approach provides reasonable assurance that the peaking factor basis assumed in the licensing basis analysis will be met.

Recommended Actions As detailed in the Background section, if it is determined that FQW(Z) is not within the LCO limit following a surveillance performed at 75% RTP, the following actions per Reference 1 will be sufficient to restore the FQW(Z) within the LCO limit for either Byron, Braidwood, or R.E. Ginna:

1. Reduce maximum allowable power by [ ]a,c FQW(Z) exceeds the limit, within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.

AND

2. Reduce AFD limits 1% for each 1% FQW(Z) exceeds the limit, within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />.

AND

3. Reduce Power Range Neutron Flux - High trip setpoints 1% for each 1% that the maximum allowable power is reduced within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

AND

4. Reduce the Overpower T trip setpoints 1% for each 1% that the maximum allowable power is reduced, within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

AND

5. Perform SR 3.2.1.1 and SR 3.2.1.2 prior to increasing the THERMAL POWER above the limit of action
1. Note that this action must be completed whenever the FQW(Z) limit is not met following a surveillance performed at 75% RTP.
      • This record was final approved on 8/6/2021 1:14:16 PM. (This statement was added by the PRIME system upon its validation)
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