RA-21-0009, Request for License Amendment - Standby Liquid Control (SLC) System Boron Solution Storage Tank Volume

Request for License Amendment - Standby Liquid Control (SLC) System Boron Solution Storage Tank Volume

ML21054A197
Person / Time
Site:	Brunswick
Issue date:	02/23/2021
From:	Krakuszeski J Duke Energy Progress
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RA-21-0009
Download: ML21054A197 (21)

Text

John A. Krakuszeski Vice President Brunswick Nuclear Plant 8470 River Rd SE Southport, NC 28461 o: 910.832.3698 February 23, 2021 Serial: RA-21-0009 10 CFR 50.90 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001

Subject:

Brunswick Steam Electric Plant, Unit Nos. 1 and 2 Renewed Facility Operating License Nos. DPR-71 and DPR-62 Docket Nos. 50-325 and 50-324 Request for License Amendment - Standby Liquid Control (SLC) System Boron Solution Storage Tank Volume Ladies and Gentlemen:

Pursuant to 10 CFR 50.90, Duke Energy Progress, LLC (Duke Energy), is submitting a request for an amendment to the Technical Specifications (TS) for the Brunswick Steam Electric Plant (BSEP), Unit Nos. 1 and 2. The proposed change increases the minimum boron solution storage tank volume requirements of Figure 3.1.7-1, "Sodium Pentaborate Solution Volume Versus Concentration Requirements," for the Standby Liquid Control (SLC) system.

The enclosure provides a description and assessment of the proposed change. Attachments 1 and 2 to the enclosure provide the existing TS pages, for Units 1 and 2, respectively, marked-up to show the proposed change. Attachments 3 and 4 provide revised (i.e., typed) TS pages for Units 1 and 2, respectively. The existing Unit 1 TS Bases page, marked-up to show corresponding changes, is provided in Attachment 5 for information only.

Duke Energy request approval of the proposed amendment by March 10, 2022, to support startup of Unit 1 from the 2022 refueling outage. Once approved, the Unit 1 amendment shall be implemented prior to startup from the 2022 Unit 1 refueling outage and the Unit 2 amendment shall be implemented prior to startup from the 2023 Unit 2 refueling outage.

In accordance with 10 CFR 50.91, Duke Energy is providing a copy of the proposed license amendment to the designated representative for the State of North Carolina.

This document contains no new regulatory commitments. Please refer any questions regarding this submittal to Mr. Art Zaremba, Director - Nuclear Fleet Licensing, at (980) 373-2062.

U.S. Nuclear Regulatory Commission Page 2 of 2 I declare, under penalty of perjury, that the foregoing is true and correct. Executed on February 23, 2021 Sincerely, John A. Krakuszeski MAT/mat

Enclosure:

Description and Assessment of the Proposed Change Attachment 1: Proposed Technical Specification Changes (Mark-Up)- Unit 1 Attachment 2: Proposed Technical Specification Changes (Mark-Up)- Unit 2 Attachment 3: Revised (Typed)Technical Specification Page - Unit 1 Attachment 4: Revised (Typed)Technical Specification Page - Unit 2 Attachment 5: Technical Specification Bases Page (Mark-Up)- Unit 1 (For Information Only) cc:

Ms. Laura Dudes, Regional Administrator, Region II Mr. Andrew Hon, Project Manager Mr. Gale Smith, NRC Senior Resident Inspector Chair - North Carolina Utilities Commission Mr. W. Lee Cox, Ill Section Chief, Radiation Protection Section, NC DHHS

RA-21-0009 Enclosure Page 1 of 7 Description and Assessment of the Proposed Change

Subject:

Request for License Amendment - Standby Liquid Control (SLC) System Boron Solution Storage Tank Volume

1.

SUMMARY

DESCRIPTION

2. DETAILED DESCRIPTION 2.1 System Design and Operation 2.2 Current Technical Specification Requirements 2.3 Reason for the Proposed Change 2.4 Description of the Proposed Change

3. TECHNICAL EVALUATION

4. REGULATORY EVALUATION 4.1 Applicable Regulatory Requirements/Criteria 4.2 Precedent 4.3 No Significant Hazards Consideration Determination Analysis 4.4 Conclusions

5. ENVIRONMENTAL CONSIDERATION

6. REFERENCES ATTACHMENTS:

1. Proposed Technical Specification Changes (Mark-Up) - Unit 1

2. Proposed Technical Specification Changes (Mark-Up) - Unit 2

3. Revised (Typed) Technical Specification Pages - Unit 1

4. Revised (Typed) Technical Specification Pages - Unit 2

5. Technical Specification Bases Pages (Mark-Up) - Unit 1 (For Information Only)

RA-21-0009 Enclosure Page 2 of 7

1.

SUMMARY

DESCRIPTION Pursuant to 10 CFR 50.90, Duke Energy Progress, LLC (Duke Energy), is submitting a request for an amendment to the Technical Specifications (TS) for the Brunswick Steam Electric Plant (BSEP), Unit Nos. 1 and 2. The proposed change increases the minimum boron solution storage tank volume requirements of Figure 3.1.7-1, "Sodium Pentaborate Solution Volume Versus Concentration Requirements," for the Standby Liquid Control (SLC) system.

2. DETAILED DESCRIPTION 2.1 System Design and Operation The SLC system is designed to provide the capability of bringing the reactor, at any time in a fuel cycle, from full power and minimum control rod inventory, which is at the peak of the xenon transient, to a subcritical condition with the reactor in the most reactive, xenon free state without taking credit for control rod movement. The SLC System satisfies the requirements of 10 CFR 50.62, "Requirements for reduction of risk from anticipated transients without scram (ATWS) events for light-water-cooled nuclear power plants."

The SLC system consists of a sodium pentaborate (SPB) solution storage tank, two positive displacement pumps, two explosive valves that are provided in parallel for redundancy, and associated piping and valves used to transfer the SPB solution from the storage tank to the reactor pressure vessel (RPV). The borated solution is discharged near the bottom of the core shroud, where it then mixes with the cooling water rising through the core.

The SLC system is used in the event that enough control rods cannot be inserted to accomplish shutdown and cooldown in the normal manner. The SLC System injects borated water into the reactor core to add negative reactivity to compensate for all of the various reactivity effects that could occur during plant operations.

Although not required by TSs, the SLC System is also used to maintain suppression pool pH level above 7 following a loss of coolant accident (LOCA) involving significant fission product releases. Maintaining suppression pool pH levels greater than 7 following an accident ensures that iodine will be retained in the suppression pool water as reflected in the LOCA dose analysis.

2.2 Current Technical Specification Requirements To comply with 10 CFR 50.62, BSEP uses a SPB solution with boron enriched to 92 atom-percent with boron-10 (B-10) isotope. The current volume versus concentration limits in Figure 3.1.7-1 are established to ensure that the SLC system injects a quantity of boron which produces a concentration of 720 ppm equivalent of natural boron in the reactor coolant at 70°F with normal reactor vessel water level. The current Figure 3.1.7-1 was established with issuance of the amendments approving implementation of Maximum Extended Load Line Limit Analysis Plus (MELLLA+) for BSEP (i.e., Reference 1).

2.3 Reason for the Proposed Change To accommodate core reload flexibility, the assumed 720 ppm equivalent of natural boron is being increased to 925 ppm. This increase in boron concentration will add significant margin to the SLC shutdown margin analysis which will sufficiently bound future advancements in core

RA-21-0009 Enclosure Page 3 of 7 designs without impacting operation. While recent core designs have shown a reduction in SLC shutdown margin, reloads beginning in 2022 (i.e., BSEP Unit 1) will require >720 ppm to achieve the required design margin.

2.4 Description of the Proposed Change The proposed change increases the minimum boron solution storage tank volume requirements of Figure 3.1.7-1. This is accomplished by shifting the left boundary of the Acceptable region of Figure 3.1.7-1 to the right. The existing minimum volume at a concentration of 10.5 weight percent SPB is increased from 1084 gallons to 1393 gallons. The existing minimum volume at a concentration of 8.5 weight percent SPB is increased from 1353 gallons to 1738 gallons. No additional Technical Specification changes are required to support the increase in boron concentration from 720 ppm is to 925 ppm.

The Applicable Safety Analysis section of the TS 3.1.7 Bases currently refers to 720 ppm equivalent of natural boron in the reactor coolant at 70°F. This is being updated to the new value of 925 ppm. The existing Unit 1 TS Bases page, marked to show this change, is provided for information only.

3. TECHNICAL EVALUATION The minimum amount of SPB to inject into the reactor vessel (i.e., left boundary of Figure 3.1.7-1) results in an equivalent concentration of natural boron (i.e., concentration used in the SLC SDM calculation) in the reactor coolant based on SPB concentration and B-10 enrichment. The quantity of reactor coolant is based on water, at 70°F, in the reactor vessel at normal vessel level, the recirculation loops, and the Shutdown Cooling portion of the Residual Heat Removal (RHR) System. To account for imperfect mixing, leakage, and additional water volume found in small piping connected to the reactor vessel, the minimum amount of SPB is then increased by 25 percent.

Increasing the boron concentration of equivalent natural boron to 925 ppm results in an increase in the minimum acceptable SPB solution volume reflected in the revised Figure 3.1.7-1. Since there are no changes to the SPB concentration range (i.e., 8.5 to 10.5 weight percent), SPB B-10 enrichment (i.e., 92 atom-percent) or the reactor coolant volume, the increase in SPB minimum volume is directly proportional to the increase in boron concentration. This is demonstrated below for the high SPB concentration limit (i.e., 10.5 weight percent):

925

= = 1084 = 1393 720 The proposed change is more restrictive than the current Acceptable region in Figure 3.1.7-1 and does not allow SLC tank concentration and volume combinations outside the currently approved range. In addition, no plant modifications are required based on recent surveillances of SLC tank level (SR 3.1.7.1).

RA-21-0009 Enclosure Page 4 of 7

4. REGULATORY EVALUATION 4.1 Applicable Regulatory Requirements/Criteria The requirements for ATWS are specified in 10 CFR 50.62, "Requirements for reduction of risk from anticipated transients without scram (ATWS) events for light-water-cooled nuclear power plants," which requires, in part, that:

(4) Each boiling water reactor must have a standby liquid control system (SLCS) with the capability of injecting into the reactor pressure vessel a borated water solution at such a flow rate, level of boron concentration and boron-10 isotope enrichment, and accounting for reactor pressure vessel volume, that the resulting reactivity control is at least equivalent to that resulting from injection of 86 gallons per minute of 13 weight percent sodium pentaborate decahydrate solution at the natural boron-10 isotope abundance into a 251-inch inside diameter reactor pressure vessel for a given core design.

The current compliance with 10 CFR 50.62 is based on an equivalency equation from Section 9.3.4.6 of the BSEP UFSAR, shown below.

(Q/86)*(M251/M)*(C/13)*(E/19.8) must be 1.E Where:

Variable Description Value Q Design flow rate 43 gpm M251 Reference plant (with 251-inch diameter vessel) 628,300 lbs mass of dilution water M Mass of BSEP dilution water at reference 485,500 lbs conditions C Sodium pentaborate chemical concentration. 8.5 weight percent E Minimum boron-10 enrichment. 92 atom percent When solved for the above values:

(43/86)*(628300/485500)*(8.5/13)*(92/19.8) = 1.966 None of the variables in this equation (i.e., flow rate, vessel water mass, SPB concentration and B-10 enrichment) are impacted by this change. Therefore, the requirements of 10 CFR 50.62 continue to be satisfied with the same margin established with the approval of Reference 1.

10 CFR 50.67, "Accident source term," in part, sets limits for the radiological consequences of a postulated design-basis accident using an accident source term. The analytical methods described in Regulatory Guide 1.183, "Alternative Radiological Source Terms for Evaluating Design Basis Accidents at Nuclear Power Reactors," July 2000, and dose limits defined in 10 CFR 50.67 comprise the design basis for BSEP (i.e., Reference 2). The BSEP Alternate Source Term analyses credit the use of the SLC injection to maintain a Suppression Pool pH of 7 or greater. Maintaining this pH retains the iodine deposited in the Suppression Pool from a

RA-21-0009 Enclosure Page 5 of 7 design basis LOCA in solution. Therefore, if a design basis LOCA were to occur, the entire contents of the SLC tank are manually injected. The proposed change to increase the minimum boron solution storage tank volume requirements of Figure 3.1.7-1 does not adversely impact the ability to maintain the suppression pH at or above 7.0.

4.2 Precedent No precedent associated with increasing the minimum boron solution storage tank volume requirements was identified.

4.3 No Significant Hazards Consideration Determination Analysis Pursuant to 10 CFR 50.90, Duke Energy Progress, LLC (Duke Energy), is requesting an amendment to the Technical Specifications (TS) for the Brunswick Steam Electric Plant (BSEP),

Unit Nos. 1 and 2. The proposed change increases the minimum boron solution storage tank volume requirements of Figure 3.1.7-1, "Sodium Pentaborate Solution Volume Versus Concentration Requirements," for the Standby Liquid Control (SLC) system.

Duke Energy has evaluated whether a significant hazards consideration is involved with the proposed amendment(s) by focusing on the three standards set forth in 10 CFR 50.92, "Issuance of amendment," as discussed below:

1. Does the proposed change involve a significant increase in the probability or consequences of an accident previously evaluated?

Response: No The proposed change does not involve a physical alteration of the plant (i.e., no new or different type of equipment will be installed). The proposed change increases the minimum boron solution storage tank volume requirements included in Figure 3.1.7-1.

The plant response to design basis accidents does not change. Operation or failure of the SLC system is not assumed to be an initiator of any analyzed event in the Updated Final Safety Analysis Report (UFSAR) and cannot cause an accident. The proposed change conforms to NRC regulatory requirements regarding anticipated transients without scram (ATWS) and accident source term (AST).

Therefore, the proposed amendment does not involve a significant increase in the probability or consequences of an accident previously evaluated.

2. Does the proposed change create the possibility of a new or different kind of accident from any accident previously evaluated?

Response: No The proposed change increases the minimum boron solution storage tank volume requirements included in Figure 3.1.7-1. It does not require any physical modification to the plant and it does not alter the design configuration, or method of operation of plant equipment beyond its normal functional capabilities. The proposed change does not reduce or adversely affect the capabilities of any plant structure, system, or component in the performance of their safety function. Also, the response of the plant and the operators following design basis accidents is unaffected by the proposed change.

RA-21-0009 Enclosure Page 6 of 7 Therefore, the proposed amendment does not create the possibility of a new or different kind of accident from any accident previously evaluated.

3. Does the proposed change involve a significant reduction in a margin of safety?

Response: No The proposed change increases the minimum boron solution storage tank volume requirements included in Figure 3.1.7-1. The proposed changes conform to NRC regulatory requirements regarding ATWS and AST. To accommodate core reload flexibility, the assumed 720 ppm equivalent of natural boron is being increased to 925 ppm; which is accomplished by increasing the minimum boron solution storage tank volume requirements. This increase in boron concentration will add significant margin to the SLC shutdown margin analysis and will sufficiently bound future advancements in core designs without impacting operation. The proposed change conforms to NRC regulatory requirements regarding ATWS and AST.

Therefore, the proposed amendment does not result in a significant reduction in the margin of safety.

Based on the above, Duke Energy concludes that the proposed amendment presents no significant hazards consideration under the standards set forth in 10 CFR 50.92(c), and, accordingly, a finding of "no significant hazards consideration" is justified.

4.4 Conclusion In conclusion, based on the considerations discussed above, (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commissions regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.

5. ENVIRONMENTAL CONSIDERATION A review has determined that the proposed amendment would change a requirement with respect to installation or use of a facility component located within the restricted area, as defined in 10 CFR 20, or would change an inspection or surveillance requirement. However, the proposed amendment does not involve (i) a significant hazards consideration, (ii) a significant change in the types or a significant increase in the amounts of any effluents that may be released offsite, or (iii) a significant increase in individual or cumulative occupational radiation exposure. Accordingly, the proposed amendment meets the eligibility criterion for categorical exclusion set forth in 10 CFR 51.22(c)(9). Therefore, pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment need be prepared in connection with the proposed amendment.

6. REFERENCES

1. Letter from the U.S. Nuclear Regulatory Commission to Mr. William R. Gideon, Brunswick Steam Electric Plant, Units 1 and 2 - "Issuance of Amendment Regarding Core Flow Operating Range Expansion (MELLLA+)," dated September 18, 2018, ADAMS Accession Number ML18172A258

RA-21-0009 Enclosure Page 7 of 7

2. Letter from the U.S. Nuclear Regulatory Commission to Mr. J. S. Keenan, Brunswick Steam Electric Plant, Units 1 and 2 - "Issuance of Amendment Re: Alternative Source Term," dated May 30, 2002, ADAMS Accession Number ML021480483

RA-21-0009 Enclosure Attachment 1 Proposed Technical Specification Changes (Mark-Up)

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Insert A RA-21-0009 Enclosure Attachment 3 Revised (Typed) Technical Specification Page Unit 1

SLC System 3.1.7 Brunswick Unit 1 3.1-23 Amendment No. 285

RA-21-0009 Enclosure Attachment 4 Revised (Typed) Technical Specification Page Unit 2

SLC System 3.1.7 Brunswick Unit 2 3.1-23 Amendment No. 313

RA-21-0009 Enclosure Attachment 5 Technical Specification Bases Page (Mark-Up) - Unit 1 (For Information Only)

SLC System B 3.1.7 B 3.1 REACTIVITY CONTROL SYSTEMS B 3.1.7 Standby Liquid Control (SLC) System BASES BACKGROUND The SLC System is designed to provide the capability of bringing the reactor, at any time in a fuel cycle, from full power and minimum control rod inventory (which is at the peak of the xenon transient) to a subcritical condition with the reactor in the most reactive, xenon free state without taking credit for control rod movement. The SLC System satisfies the requirements of 10 CFR 50.62 (Ref. 1) on anticipated transient without scram.

The SLC System is also used to maintain suppression pool pH level above 7 following a loss of coolant accident (LOCA) involving significant fission product releases. Maintaining suppression pool pH levels greater than 7 following an accident ensures that iodine will be retained in the suppression pool water (Ref. 2).

The SLC System consists of a boron solution storage tank, two positive displacement pumps, two explosive valves that are provided in parallel for redundancy, and associated piping and valves used to transfer borated water from the storage tank to the reactor pressure vessel (RPV). The borated solution is discharged near the bottom of the core shroud, where it then mixes with the cooling water rising through the core. A smaller tank containing demineralized water is provided for testing purposes.

APPLICABLE The SLC System is manually initiated from the main control room, as SAFETY ANALYSES directed by the emergency operating procedures, if the operator believes the reactor cannot be shut down, or kept shut down, with the control rods.

The SLC System is used in the event that enough control rods cannot be inserted to accomplish shutdown and cooldown in the normal manner.

The SLC System injects borated water into the reactor core to add negative reactivity to compensate for all of the various reactivity effects that could occur during plant operations. To meet this objective, it is necessary for SLC to inject a quantity of boron which produces a concentration of 720 925 ppm equivalent of natural boron in the reactor coolant at 70°F with normal reactor vessel water level. To allow for (continued)

Brunswick Unit 1 B 3.1.7-1 Revision No. 34