ML22307A317

Proposed License Amendment Request Removal of Refueling Water Chemical Addition Tank and Replacement of Containment Sump

ML22307A317
Person / Time
Site:	North Anna
Issue date:	11/03/2022
From:	James Holloway Virginia Electric & Power Co (VEPCO)
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
22-239
Download: ML22307A317 (1)

Text

V IRGI N IA E LECTRIC AND P OWER C OMPANY RICHMOND, VIRGINIA 2 3 2 61

November 3, 2022

U. S. Nuclear Regulatory Commission Serial No.: 22-239 Attention: Document Control Desk NRA/SS: RO Washington, DC 20555 -0001 Docket Nos.: 50 - 338/339 License Nos.: NPF -4/7

V IRGI NIA EL ECT R IC A ND POW ER CO MP ANY ( D OMINI O N E NERG Y VI RG IN IA )

NO R TH ANN A POW ER STAT IO N UN IT S 1 AND 2 P R O POSED LIC ENSE A ME N DMENT RE QU ES T REM OV A L O F RE FU ELI NG WA T ER C HEM IC AL ADD ITIO N T ANK AND REP LA C EMEN T OF CO NTAI NMEN T S U MP B U FFER Pursuant to 10 CFR 50.90, Virginia Electric and Power Company (Dominion Energy Virginia) requests amendments to North Anna Power Station (NAPS), Units 1 and 2, Renewed Facility Operating License Numbers NPF-4 and NPF-7, respectively, in the form of a change to the Technical Specifications (TS). The proposed amendment would revise the NAPS, Units 1 and 2, TS to eliminate the Refueling Water Chemical Addition Tank (CAT) and allow the use of sodium tetraborate decahydrate (NaTB) to replace sodium hydroxide (NaOH) as a chemical additive (buffer) for Containment sump pH control.

A description and summary technical evaluation supporting the proposed a mendment are provided in Attachment 1. Current a nd modified configurations of the Quench Spray Subsystem are shown in Attachment 2. The location of the proposed NaTB baskets in Containment are shown in Attachment 3. Marked-up TS pages and typed TS pages indicating the proposed change are provided in Atta chments 4 and 5, respectively.

Marked-up TS Bases pages are provided in Attachment 6, for information only.

The proposed amendment request does not involve a significant hazards consideration as defined in 10 CFR 50.92. The basis for this determination is included in Attachment 1.

The proposed change will not result in any significant increase in the amount of effluents that may be released off-site or any significant increase in individual or cumulative occupational radiation exposure. Therefore, the proposed amendment is eligible for categorical exclusion from an environmental assessment as set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment is needed in connection with the approval of the proposed change.

Serial No.: 22-239 Docket Nos.: 50-338/339 Page 2 of 4

Dominion Energy Virginia requests approval of the proposed TS change by August 31, 2023. The typical time frame for implementing license amendments is 30 days after issuance. However, installation of the Na TB buffer will occur during a different outage for each unit necessitating a different implementation schedule for NAPS, Units 1 and 2.

Additionally, CAT removal may not occur during the same outage as the NaTB buffer installation for the respective unit. The CAT will be isolated during the outage that NaTB buffer installation occurs and will remain non-operational after the baskets are installed until their final removal. Consequently, Dominion Energy Virginia requests implementation of the proposed TS changes to coincide with the completion of the spring 2024 refueling outage (RFO) for NAPS Unit 1 and the fall 2023 RFO for NAPS Unit 2.

If you have any questions or require additional information, please contact Mr. Shayan Sinha (804) 273-4687.

Sincerely,

James E. Holloway Vice President - Nuclear Engineering & Fleet Support Dominion Energy Virginia

COMMONWEAL TH OF VIRGINIA }

}

COUNTY OF HENRICO }

The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today by Mr. James E. Holloway, who is Vice President - Nuclear Engineering & Fleet Support, of Virginia Electric and Power Company. He has affirmed before me that he is duly authorized to execute and file the foregoing document in behalf of that company, and that the statements in the document are true to the best of his knowledge and belief.

Acknowledged before me this 3 r~ day of Nov '21>>\\:be r ' 2022.

My Commission Expires: 12 /31 / z.'{-

CRAIG D SLY Notary Public

Commonwealth of Virginia Reg.# 7518653 Notary Public Mt Co mm lssl<ln Expires December 31, 2ff!..

Serial No.: 22-239 Docket Nos.: 50-338/339 Page 3 of 4

Commitments made in this letter: None.

Attachments:

1. Discussion of Change

2. Quench Spray Subsystem Showing Current and Modified Configurations

3. Plan View of Reactor Containment Elevation 216'-11" Showing Na TB Basket Locations

4. Marked-up Technical Specifications Pages

5. Proposed Technical Specifications Pages

6. Marked-up Technical Specifications Bases Pages (for information only)

Serial No.: 22-239 Docket Nos.: 50-338/339 Page4 of4

cc: Regional Administrator, Region II U. S. Nuclear Regulatory Commission Marquis One Tower 245 Peachtree Center Avenue, NE, Suite 1200 Atlanta, Georgia 30303-1257

Mr. G. Edward Miller Senior Project Manager - North Anna Power Station U.S. Nuclear Regulatory Commission Mail Stop 09 E-3 One White Flint North 11555 Rockville Pike Rockville, Maryland 20852-2738

Mr. L. John Klos Senior Project Manager - Surry Power Station U. S. Nuclear Regulatory Commission Mail Stop 09 E-3 One White Flint North 11555 Rockville Pike Rockville, Maryland 20852-2738

NRC Senior Resident Inspector North Anna Power Station

Old Dominion Electric Cooperative R-North-Anna-Correspondence@odec.com

State Health Commissioner Virginia Department of Health James Madison Building - 7th Floor 109 Governor Street, Suite 730 Richmond, Virginia 23219 Serial No.: 22-239 Docket Nos.: 50-338/50-339

ATTACHMENT 1

Discussion of Change

NORTH ANNA POWER STATION UNITS 1 AND 2 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION ENERGY VIRGINIA)

Serial No.: 22-239 Docket Nos.: 50-338/50-339 Attachment 1 Page 1 of 26

TABL E OF CONT EN T S

1.0

SUMMARY

DESCRIPTION 2.0 DETAILED DESCR IPTION 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 3.0 TECHNICAL EVALUATION 3.1 Calculation and Plant Analysis 3.1.1 Required Amount of NaTB 3.1.2 Radiological Consequences 3.1.3 Chemical Effects 3.1.4 Corrosion of Containment Materials 3.1.5 Hydrogen Generation 3.1.6 Environmental Qualification (EQ) of Equipment 3.2 Design Solution 3.2.1 NaTB Basket Design 3.2.2 CAT Isolation and Removal 4.0 REGULA TORY EVALUATION 4.1 Applicable Regulatory Requirements/Criteria 4.2 Precedent 4.3 No Significant Hazards Consideration 4.4 Conclusions 5.0 EN VIRONMENTAL CONSIDERATION

REFERENCES Serial No.: 22-239 Docket Nos.: 50-338/50-339 Attachment 1 Page 2 of 26

DISCUSSION OF CHANG E

1.0

SUMMARY

DESCRIPTION In accordance with 10 CFR 50.90, Virginia Electric and Power Company (Dominion Energy Virginia) requests an amendment to Renewed Facility Operating License Nos.

NPF-4 and NPF-7 in the form of changes to the Technical Specifications (TS) for North Anna Power Station (NAPS), Units 1 and 2, respectively.

The proposed amendment would revise both unit's TS to eliminate the Refueling Water Chemical Addition Tank (CAT) and allow the use of sodium tetraborate decahydrate (NaTB) to replace sodium hydroxide (NaOH) as a chemical additive (buffer) for Containment sump pH control in each unit. This change will eliminate the need to perform inspections of the CAT and the attendant risk of personal injury associated with performing maintenance activities due to the caustic nature of the NaOH solution.

Additionally, active components from the Quench Spray (QS) subsystem will be removed.

2.0 DETAILED DESCRIPTION 2.1 System Design and Operation The Containment Depressurization System ensures the integrity of the containment structure and consists of two (2) separate, but parallel Quench Spray (QS) subsystems, each rated at 100% capacity, and four (4) separate, but parallel Recirculation Spray (RS) subsystems, each rated at approximately 50% capacity. The design functions of the Containment Depressurization System consist of the following:

1) Cool and depressurize the Containment atmosphere to less than 2.0 psig in one ( 1) hour and to subatmospheric pressure in less than six (6) hours following a loss of coolant accident (LOCA);

2) Reduce the concentration of radioactive iodine in the Containment atmosphere quickly so that for any outleakage during the time the Containment is above 1.0 atm pressure, the resulting dose meets General Design Criteria (GDC) 19 and is within the limits specified in 10 CFR 50.67; and

3) Provide the Emergency Core Cooling System (ECCS) with water for effective core cooling on a long-term basis after a LOCA.

Serial No.: 22-239 Docket Nos.: 50-338/50-339 Attachment 1 Page 3 of 26

Each QS subsystem contains an electric motor-driven QS pump capable of supplying 1,600 to 2,000 gpm of borated water to a separate 360-degree QS ring header located in the dome of the Containment structure. The QS subsystem transfers heat from the Containment atmosphere to the quench spray, which is collected in the Containment sump. This subsystem draws water from the refueling water storage tank (RWST) which is maintained between 40°F and 50°F. NaOH solution is added to the QS subsystem water by a balanced gravity feed from the CAT. The CAT has an operating volume of between 4,800 and 5,500 gallons and is located in close proximity to the RWST. The CAT and the RWST are connected by a pipe that conveys the NaOH solution from the bottom of the CAT through a 6-inch diameter opening to the volume within a weir in the RWST. There it mixes with the borated water flowing to the QS subsystem and flows through two (2) 10-inch diameter openings located symmetrically on either side of the 6-inch inlet. The effect caused by the combination of various flow directions creates turbulence within the weir and enhances mixing. The mixture is then discharged under turbulent flow conditions to the QS pumps where the pump impeller supplies final mixing. The NaOH solution enhances iodine removal from the containment atmosphere and provides Containment sump pH control. Two (2) parallel, redundant motor-operated valves are located in the piping between the CAT and the RWST. The valves are closed during normal unit operation to prevent mixing of the NaOH solution with the water in the RWST.

Each RS subsystem consists of a motor-driven RS pump, a RS cooler, and a 180-degree spray ring header located above the operating floor of the Containment structure. Two (2) of the RS pumps and motors are located inside the Containment structure, and two (2) pumps and motors are located outside the Containment structure.

The outside RS pumps are rated at 3700 gpm and the inside pumps at 3300 gpm. The RS subsystem transfers heat, via the RS coolers, from the water collected on the containment structure floor and from the Containment atmosphere to the Service Water System. The RS subsystem is capable of maintaining a subatmospheric pressure inside the Containment structure following a LOCA.

2.2 Current Technical Specification Requirements NAPS TS 3.6.8, "Chemical Addition System," Limiting Condition for Operation (LCO) states that, "the Chemical Addition System shall be operable," in Modes 1, 2, 3, and 4.

The associated surveillance requirements (SRs) apply to the CAT, NaOH solution, valves, and flow path that are currently contained within this system.

Serial No.: 22 - 239 Docket Nos. : 50-338/50 -339 Attachment 1 Page 4 of 26

2.3 Reason for the Propo se d Change As part of the subsequent license renewal for NAPS, the CATs are required to be inspected to identify aging effects that could impair the ability of the tank to perform its intended function, and to demonstrate that these effects will be adequately managed during the period of extended operation. NUREG-2191, "Generic Aging Lessons Learned for Subsequent License Renewal (GALL -SLR) Report," [Reference 1] Section XI.M29, "Outdoor and Large Atmospheric Metallic Storage Tanks," specifies a one-time visual inspection of interior surfaces or a volumetric inspection from the outside surface capable of precisely determining wall thickness of at least 20% of the inside surface.

Due to the hazardous environment internal to the CAT caused by the NaOH solution and the risk of causing damage by removing external insulation to perform the required inspections in support of NUREG-2191,Section XI.M29, it is desired to remove the CAT along with its associated caustic piping and equipment. Buffering agent baskets containing a chemical additive (buffer) for Containment sump pH control will be installed in each unit's Containment. Because the use of trisodium phosphate (TSP) can result in more precipitates in the post-accident sump pool, NaTB has been selected to replace NaOH as the buffer.

2.4 Description of the Proposed Change The proposed change will revise the Unit 1 and Unit 2 TS Section 3.6.8, "Chemical Addition System," as well as TS Bases Sections B 3.3.2, "Engineered Safety Feature Actuation System (ESFAS) Instrumentation," B 3.6.6, "Quench Spray System," B 3.6.7, "Recirculation Spray System," and B 3.6.8, "Chemical Addition System". The revision to TS Section 3.6.8 will require verification that the NaTB baskets are unobstructed, in place and intact, collectively contain between 16,013 lbm and 22,192 lbm of NaTB, and that the NaTB contained in the baskets provides adequate pH adjustment of borated water. The associated SRs will be revised as follows:

• SR 3.6.8.1 will require verification that each NaTB basket is unobstructed, in place and intact;

• SR 3.6.8.2 will require verification that the NaTB baskets collectively contain between 16,013 lbm and 22,192 lbm of NaTB;

• SR 3.6.8.3 will require verification that a sample from the NaTB baskets provides adequate pH adjustment of borated water; and

• SR 3.6.8.4 and SR 3.6.8.5 will be deleted.

Markups of the affected TS pages are provided in Attachment 4.

Serial No.: 22-239 Docket Nos.: 50-338/50-339 Attachment 1 Page 5 of 26

3.0 TECHNICAL EVALUATION The proposed change replaces the NaOH solution in the CAT with granular NaTB in baskets located in the lower level of the Containment basement (EL. 216'-11"). The NaOH solution flows from the CAT to the RWST under hydrostatic head. It is then delivered to the QS spray rings via the QS pumps. The QS spray water, buffered with NaOH, is atomized and dispersed into the Containment atmosphere and ultimately collects in the Containment sumps. After the initial spray down of Containment, the granular NaTB mixes with the RWST water collecting in the lower levels of Containment. Both NaOH and NaTB are considered acceptable buffering agents to raise the pH levels of the RWST water and enhance removal of iodine from Containment. The CAT and associated caustic piping and equipment will be permanently isolated from the RWST and removed.

3.1 Calculation and Plant Analysis 3.1.1 Required Amount of NaTB The amount of NaTB buffer required is the amount to ensure that the sump pool will remain at a pH greater than 7.0 from the time (t) when recirculation spray is credited for iodine removal (40 minutes) to 30 days while also ensuring that the pH does not exceed the design limit of 9.0 (t s 20 minutes) and 8.5 (t > 20 minutes). A minimum of 16,013 lbm of NaTB is required to maintain the sump pH above 7.0. The maximum amount of buffer which will be installed in Containment is 22,192 lbm. This mass results in a maximum long-term (t ;?: 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />) sump pH below 8.5. The required mass of NaTB accounts for chemical equivalence variations and the required volume accounts for chemical density variations.

The maximum time it takes the buffer to dissolve is determined for both single-train and full Engineered Safety Feature (ESF) conditions using conservative inputs. The maximum dissolution time is determined based on the minimum rate at which the water level rises and the bounding minimum temperature profile. The post-LOCA pH analysis is based on steady-state conditions and considers all species in the Containment sump solution to be in equilibrium. The Containment sump pH is computed using guidance from NUREG/CR-5950 [Reference 7].

The concentration of negatively charged species (anions) must equal the concentration of positively charged species (cations) for electroneutrality in the Containment sump solution. The sum of negative charges for the charge balance is determined from the molal concentrations of anions [B(OH)4J-, [B2(OH)1]-, [83(QH)10]-, [84(QH)14]2-or

[Bs(OH)1a]3-, OH-, NQ3-, c1-, and 1-. The sum of positive charges for the charge balance Serial No.: 22-239 Docket Nos.: 50-338/50-339 Attachment 1 Page 6 of 26

is determined from the concentrations of H+, Na+, Cs+, and u+. The ionic activity product constant of water is modeled using the Marshall-Frank correlation.

Boric acid speciation is based on the temperature dependent molal-equilibrium quotients reported by Palmer [Reference 9]. The concentration of boron in solution based on the total mass of boric acid and NaTB must be equal to the concentration based on the contribution of all boric acid species.

Equilibrium sump conditions are determined using an analytical model which was benchmarked to site-specific buffer testing using the same buffer as will be installed.

Different inputs are utilized based on whether the calculation is determining: 1) solution pH based on buffer quantity, or 2) buffer quantity based on desired solution pH. The model iterates boric acid speciation, and either NaTB mass or pH until convergence is achieved for the boron mass balance and charge balance equations.

The following inputs were used to determine the NaTB required to ensure the minimum required Containment sump pH at the time when recirculation spray is credited for iodine removal and at 30 days for a single train of ESF and full ESF cases:

• Containment sump pH= 7.0

• Maximum mass of boron/boric acid in the Containment sump at time of interest for the ESF scenario being investigated

• Minimum lithium concentration in the Reactor Coolant System (RCS)

• Hydrochloric acid generation due to cable irradiation at time of interest (biased high)

• Nitric acid generation due to water irradiation at time of interest (biased high)

• Maximum core iodine release at time of interest

• Minimum core cesium release at time of interest

• Minimum NaTB chemical equivalence These inputs conservatively bias high the quantities of acids and bias low the quantities of bases. The acids (non-boric acid) and bases considered in the post-LOCA pH analysis are listed in Tables 1 and 2, respectively. The mass and boron concentration in the Containment sump are based on the maximum mass and boron concentration of each borated water source listed in Table 3. The analytical model used to determine the buffer quantity was validated via comparison to buffer test results from plant specific testing.

The maximum Containment sump pH following an accident is determined based on the maximum dissolved quantity of NaTB at select times early in the post-LOCA transient and the maximum anticipated installed mass of granular NaTB to ensure that the maximum allowable pH of 9.0 (ts 20 minutes) and 8.5 (t > 20 minutes) is not exceeded.

Se rial No.: 22-239 Docket Nos.: 50 -338/50 - 339 Attachm e nt 1 Pa g e 7 of 26

The maximum Containm e nt sump pH is dete rmined using the same analytical mod e l bas ed on the inputs below to determine the maximum containment sump pH at sele ct times for a single train of ESF and full ESF cases:

• Maximum Na TB mass at time of interest

• Minimum mass of boron/boric acid in the Containment sump at time of interest for the scenario being investigated

• Maximum lithium concentration in the R CS

• No hydrochloric acid generation due to cable irradiation

• No nitric acid gener a tion due to water irradiation

• No core iodine release

• Maximum core cesium release at time of interest

• Maximum NaTB chemical equivalence These inputs conservatively bias high the quantities of b a ses a nd bia s low the q ua ntities of acids. The sump mass and boron concentration in the sump are based on the minimum mass and boron concentration of each borated water source listed in Table 3.

T ab le 1. (Non-Boric) Acids included in post-LOCA pH analysis

A ci d S ourc e Referen c e ( s )

Nitric acid Irradiation of water §2.2.4 of NUREG/CR - 5950

Hydrochloric acid Irradiation of §2.2.5.2 of NUREG/CR-5950 chloride bearing cables

• ORIGEN in SCALE 6.2.3 Hydriodic acid Released core inventory * §3.2 of R eg Guide 1.183

• §2.2.2 of NUREG/CR - 5950 Serial No.: 22-239 Docket Nos.: 50-338/50-339 Attachment 1 Page 8 of 26

Table 2. Bases included in post-LOCA pH analysis

Base Source Reference( s)

• ORIGEN in SCALE 6.2.3 Cesium hydroxide Released core inventory * §3.2 of Reg Guide 1.183

• §2.3.1 of NUREG/CR-5950

Lithium hydroxide RCS water Plant Chemistry Procedure

Table 3. Borated water sources

1. I Parameter Units Minimum Maximum

Refueling Water Storage Tank (RWST)

Volume gal 436,898 496,689 Boron Concentration ppm 2,574 2,828

Reactor Coolant System (RCS)

Volume gal 65,375 70,229 Boron Concentration ppm 0 2,828 Safety Injection Accumulators Including Associated Piping (SIAs)

Volume gal 22,633 23,376 Boron Concentration ppm 2,475 2,828

SI Piping (sum of a/13 loops)

Volume gal 154 154 Boron Concentration ppm 0 2,828 Boron Injection Tank (BIT)

Volume gal 900 900 Boron Concentration ppm 12,821 15,908 Casing Cooling Tank (CCT)

Volume gal 90,000 108,877 Boron Concentration ppm 2,574 2,828 Serial No.: 22-239 Docket Nos.: 50-338/50-339 Attachment 1 Page 9 of 26

Various margins are incorporated into the maximum dissolution time analysis including a reduction in the minimum water level, an increased clearance between the bottom of the basket and the Containment floor, and a reduction in the open area of the sides and bottom of the basket. These margins result in a slower exposure of the buffer in the baskets to the sump water as well as a reduced dissolution rate. Likewise, the previously noted margins are reversed and incorporated in the minimum dissolution time analysis. The results of the analyses show that even with the conservatisms and margin, a pH greater than 7.0 is acquired from the time when recirculation spray is credited for iodine removal up to 30 days and that the upper pH limit of 9.0 (t :5 20 minutes) and 8.5 (t > 20 minutes) is not exceeded.

To ensure that the chemical composition, and hence buffering ability, of the buffer does not change over time, testing of the buffer will be required to be performed during each refueling outage (RFO) per the TS. A Na TB buffer sample will be taken from each of the eight (8) baskets during each RFO. Using the sample, a known quantity of buffer will be added to a known quantity/concentration of borated water. The test will be satisfactory provided the resultant solution pH is 7.0 or greater. The mass of the Na TB added to the test is based on the initial prototypical pH adjustment/buffer testing that was previously performed in support of the buffer replacement. As part of the buffer SRs, the NaTB in the baskets will be checked to ensure the chemical remains in the desired loose consistency and is not clumped due to the Containment environment.

3.1.2 Radiological Consequences The present method of buffer addition is to add NaOH from the CAT to the RWST and ultimately to the quench spray during the initial injection phase of the LOCA. The Na OH is mixed with water from the RWST prior to being sprayed into the Containment atmosphere. The proposed change to replace this method with granular NaTB stored in baskets inside Containment will eliminate buffer addition to the quench spray during the initial injection phase; therefore, the quench spray mixture will consist of a boric acid solution. The quench spray pH during the injection phase may be as low as 4.25.

As indicated in NUREG-0800, Standard Review Plan (SRP), Section 6.5.2, "Containment Spray as a Fission Product Cleanup System" [Reference 2], fresh sprays (i.e., sprays with no dissolved iodine) are effective at scrubbing elemental iodine and thus a spray additive (used to increase sump pH) is unnecessary during the initial injection phase when the spray solution is being drawn from the RWST. As described in the SRP, experiments [Reference 3] have shown that elemental iodine can be effectively scrubbed from the atmosphere with borated water, even at low pH (less than 7). For example, experiment "Run C-1" from Reference 3 used a boric acid solution with Serial No.: 22-239 Docket Nos.: 50-338/50-339 Attachment 1 Page 10 of 26

a pH of 5. It should also be noted that the PSICO 10 experiments [Reference 4] indicate that, "The elemental iodine removal half-times obtained by spraying service water do not differ greatly from those found by spraying thiosulfate solution."

Based on these experiments, the SRP provides an equation for calculating a first-order removal coefficient for elemental iodine that is not dependent on a spray additive for pH control but is chiefly based on the rate at which fresh-solution surface area is introduced into the containment building atmosphere [Equation 1].

A _ 6KgTF [Equation 1]

S - VD

where

.J.5 = removal coefficient K9 = gas phase mass transfer coefficient T = time of fall of the drops F = volume flow rate of the spray pump V = containment building net free volume D = mass mean diameter of the spray drops

Therefore, the use of Equation 1 for determining the elemental iodine spray removal coefficients during the injection phase (pH as low as 4.25) is considered a valid approach for modelling elemental iodine removal in Containment during a LOCA event.

It should also be noted, per the SRP, that Equation 1 is valid for As values equal to or greater than 10 per hour and that As must be limited to 20 per hour for fresh solution to prevent extrapolation beyond the existing data this equation is based on. For As values less than 10 per hour, the SRP recommends using an analysis with a more sophisticated expression.

Based on the above, the current radiological consequences associated with a LOCA which has quench spray buffered with NaOH during initial injection remains unchanged with the use of NaTB stored in baskets inside Containment and results in the quench spray during initial injection having a pH as low as 4.25. The NaTB buffers the Containment sump water to ensure that the pH of the sump water will remain greater than 7.0 from the time when recirculation spray is credited for iodine removal.

Serial No.: 22-239 Docket Nos.: 50-338/50-339 Attachment 1 Page 11 of 26

3.1.3 Chemical Effects WCAP-16596, "Evaluation of Alternative Emergency Core Cooling Buffering Agents"

[Reference 5], documents the evaluation of alternative ECCS buffering agents relative to traditional NaOH and TSP buffers. This evaluation was performed as part of Generic Safety Issue (GSI) 191 [Reference 1 O] and Generic Letter (GL) 2004-02 [Reference 11]

to provide plants with options to potentially reduce their chemical precipitate source term. NaTB was recommended as an alternative to TSP since both are solids that dissolve in the post-LOCA sump and are not stored in solution. NaTB is also less likely to result in significant amounts of precipitate than TSP. In particular, calcium precipitates are more likely with TSP than with Na TB.

The impact to the resolution of GSl-191/GL 2004-02 provided by NAPS as a result of changing the buffer from NaOH to Na TB was assessed based on both industry literature and utilizing the existing chemical effects models to predict aluminum dissolution following buffer replacement. Post-LOCA sump buffering with NaTB will not result in any different precipitates than those that form with a NaOH buffer (i.e., only aluminum-based precipitates are expected with NaTB and NaOH). Calcium based precipitates will not form with a NaTB buffer. Given that the precipitates formed with NaTB and NaOH are the same and that less precipitate is expected with Na TB, it is also expected that the time of precipitate formation in the post-LOCA sump would be the same or greater especially when considering that Na TB also enhances aluminum solubility.

The amount of insulation that dissolves in the post-LOCA sump is not expected to change significantly with a NaTB buffer since this debris is submerged in the pool (not sprayed) and the design pool pH will remain the same with NaTB (except for a short -

term initial increase). Slight increases in the amount of dissolved aluminum from insulation could occur since the corrosion rate for insulation debris has a dependence on the concentration of aluminum in the pool (which will be lower overall, hence increasing the aluminum release from insulation) per WCAP-16530 [Reference 6].

However, the increases in aluminum released from insulation would be more than offset by the reduction in total dissolved aluminum.

The dissolved aluminum expected in the long term post-LOCA sump can be predicted based on the Atomic Energy of Canada Limited (AECL) correlation for aluminum dissolution. The maximum allowable 30-day aluminum loading determined via the AECL strainer head loss testing was specified to be 5,020 grams in the Updated Supplemental Response to GL 2004-02 for NAPS (Reference 21), but this limit was subsequently revised to 6,830 grams to address a strainer fin area error. The predicted dissolved aluminum quantities with NaTB are approximately 60% of the updated limit. When compared to an NaOH buffer, an NaTB buffer results in less aluminum dissolved in the Serial No.: 22-239 Docket Nos.: 50-338/50-339 Attachment 1 Page 12 of 26

post-LOCA environment. As such, the margin between the allowable dissolved aluminum and expected post-LOCA dissolved aluminum will increase with an NaTB buffer since less aluminum will dissolve in the Containment sump following buffer replacement, therefore resulting in lower strainer head losses (although the head loss reduction is not credited as part of this design change). This reduction in dissolved aluminum is due to the unsubmerged (sprayed) aluminum being subject to a much lower initial pH spray solution. Therefore, the design basis strainer head loss tests will remain applicable following NaOH replacement with Na TB.

3.1.4 Corrosion of Containment Materials As stated in NRC Branch Technical Position 6-1, "pH for Emergency Coolant Water for Pressurized Water Reactors," [Reference 19] to reduce the probability of stress corrosion cracking of austenitic stainless steels components, the pH of the recirculation solution should have a minimum pH of 7.0. The amount of NaTB specified in the proposed TS change will achieve a long-term sump pH between 7.0 and 8.5, consistent with the current licensing basis.

For the proposed change, the pH of the spray solution during the post-LOCA injection phase will be acidic. The Containment coating materials have been evaluated for a spray pH of 4.0, with an exposure time of eight (8) hours. The coating materials were determined to be acceptable for the proposed change since these materials exhibit fair to good resistance to chemical exposure of stronger acids, and the low pH exposure is for a relatively short (less than 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />) duration. The gradual increase in pH minimizes the potential for coating degradation due to acid exposure.

3.1.5 Hydrogen Generation The amount of post-accident hydrogen generation resulting from corrosion of materials exposed to water is influenced by the pH value of the water. With the replacement of NaOH with NaTB, the pH of the recirculation spray is maintained between 7.0 and 8.5 during the long-term post-accident period which is the same as the current design pH range. Therefore, post-LOCA hydrogen concentration will not increase as a result of the proposed change.

3.1.6 Environmental Qualification (EQ) of Equipment The EQ program at NAPS meets the requirements of 10 CFR 50.49, "Environmental Qualification of Electrical Equipment Important to Safety for Nuclear Power Plants."

Serial No.: 22-239 Docket Nos.: 50-338/50-339 Attachment 1 Page 13 of 26

NAPS is licensed to implement the requirements of 10 CFR 50.49 per NRC Division of Operating Reactors (DOR) Guidelines [Reference 20], IEEE Standard 323-1974

[Reference 16] and NUREG-0588 [Reference 17], as codified by 10 CFR 50.49.

In the current design, the QS solution is alkaline due to the direct addition of NaOH to the borated solution in the RWST. Equipment in the EQ Program is qualified for a chemical spray with a pH range of 8.5 to 10.5 for the first four (4) hours and a pH range of 7.0 to 8.5 from four (4) hours to 120 days. In the proposed design, the QS solution during the injection mode would be acidic, consisting of borated solution from the RWST only. The components in Containment subject to the EQ Program have been identified and evaluated for the effects of a spray with a pH ranging from 4.0 to 9.0 for the first 20 minutes, a pH range of 4.0 to 8.5 from 20 minutes to 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, and a pH range of 7.0 to 10.5 from four (4) hours to 120 days. A pH of 10.5 was used for the equipment qualification to retain the qualification at the existing high end of the pH range. The evaluation considered the chemical resistance of organic materials, the corrosive effects of metallic materials exposed to the spray, and the duration of the initial acidic spray followed by the longer-term alkaline spray. The method used for the EQ evaluations relied on available industry and technical/research data regarding the chemical resistance of materials for acidic and alkaline sprays, as well as the corrosion rate from the spray composition for the enclosures that house parts of the equipment. The physical installation was evaluated to determine what parts of the component would be subjected to the direct spray. Credit is taken for junction boxes, conduit, and seals. The evaluations concluded that EQ equipment located in the Containment is qualified for the revised Containment and recirculating sprays without the need for additional protection from spray.

3.2 Design Solution 3.2.1 NaTB Basket Design A total of eight (8) Na TB baskets will be located in each Unit's Containment. Each Na TB basket has a nominal size of 5 feet (60 inches) by 6 feet (72 inches) by 1.83 feet (22 inches). A one-inch clearance from the bottom of the baskets to the Containment floor provides additional surface area to dissolve the NaTB in sump water and avoids loss of NaTB due to any inadvertent water spillage or leakage on the floor. The NaTB baskets are fabricated of stainless steel (Type 304 SS) and have a frame with a 100-mesh screen lining the interior. External support is provided by perforated plate on the sides and bottom. The baskets are designed with four (4) caster wheels (Type 304 SS and 2205 Duplex SS) to facilitate the movement of the baskets during outages, if required. A Serial No.: 22-239 Docket Nos.: 50-338/50 -339 Attachment 1 Page 14 of 26

removable cover with a drip edge is provided to ensure that accumulated leaks and condensation above the baskets are directed away from the Na TB inside the basket.

Each basket has a mark indicating the minimum acceptable level of NaTB as a visual aide for NaTB addition in the field. The basket's minimum acceptable level indication is conservatively higher than the level associated with the minimum buffer mass specified in TS to ensure sufficient buffer is installed in Containment. A fully assembled empty basket weighs approximately 1,465 pounds and approximately 4,450 pounds when loaded with NaTB.

The granular NaTB is procured as Safety Related and can perform its design function without the presence of the baskets; therefore, the purpose of the baskets is to contain the NaTB. The baskets are classified as Non-safety Quality (NSQ) based on not being functionally safety-related, but are required to be seismically anchored to prevent damage to nearby safety-related equipment. The baskets are also required to remain functional (i.e., some of or all their passive functions must remain intact) during and/or after a Design Basis Event (DBE). Therefore, the baskets are designed to meet Seismic 11/1 requirements and maintain their structural integrity during a DBE.

The design loads for the baskets are generated by combining the unfactored load effects of dead loading, chemical pressure loading, and seismic loading. The NaTB baskets were evaluated to maintain their structural integrity during an Earthquake DBE concurrent with post-LOCA elevated temperature conditions. Thermal expansion and Containment pressurization as a result of increased temperature and pressure during a LOCA event were considered in the basket design, which was determined to be acceptable in maintaining its structural integrity. The basket members and connections are analyzed to meet applicable licensing and design basis requirements in the NAPS Updated Final Safety Analysis Report (UFSAR) for Unit 1 and Unit 2 and Dominion Energy Nuclear Engineering Standard (ONES) DNES-VA-CE-0046, American Institute of Steel Construction (AISC) 9th Edition, "Manual of Steel Construction" [Reference 12].

In accordance with the AISC 9th Edition and UFSAR Section 3.7, Seismic Design, allowable stresses for members may be increased by 1/3 for earthquake loading using the applicable load combinations. When considering the 1/3 increase for earthquake loading, the maximum member interaction for members, connections, welds, wheels, bolts, and anchor bolts is less than the required 1.0. While not required, additional checks were conservatively performed on the members and connections using American Society of Civil Engineers (ASCE) 8-90, "Specification for the Design of Cold Formed Stainless Steel Structural Members" [Reference 13], ASCE 7-88, "Minimum Design Loads for Buildings and Other Structures" [Reference 14], and Design Guide 24, "Hollow Structural Section Connections" [Reference 15]. In all cases, the additional checks determined that code requirements were satisfied.

Serial No.: 22-239 Docket Nos.: 50-338/50-339 Attachment 1 Page 15 of 26

The baskets will be installed on the 216' -11" elevation of the NAPS Unit 1 and Unit 2 Containments near the annulus, near the lncore Instrumentation Room, and near the 2C Safety Injection Accumulation Tank and Iodine Filtration Fan (Unit 2 only). The planned installation locations of the baskets in the NAPS Units 1 and 2 Containments are shown in Attachment 3. It is noted that the basket locations may be adjusted during the design change implementation process due to unforeseen installation issues. The basket locations have been selected such that they are not adversely affected by or adversely affect the Containment sump strainers due to the effects of High Energy Line Break (HELB). Protection against the effects of blowdown jet forces and pipe whip resulting from a postulated pipe rupture of the Reactor Coolant, Pressurizer, Main Steam, or Feedwater System piping is provided by a combination of distance, restraints, and barriers. Specifically, high energy piping is protected/isolated by missile barriers and restrained to limit pipe whip. The baskets located in the containment annulus area are protected by the crane wall. Baskets that are not protected by the crane wall are located so that the impingement pressure from a HELB would not affect the baskets, except for three (3) baskets, such that the ability of the NaTB buffer to perform its design function would not be impeded based on the zone of influence (ZOI) radius.

Three (3) baskets located in the Unit 2 Containment are in close proximity to pressurizer spray lines. The portions of these lines do not contain postulated breaks based on the break location criteria outlined in the NAPS Units 1 and 2 UFSAR. Therefore, the baskets are either sufficiently protected from the effects of HELBs using barriers, restraints, and distance, or the lines which are located in close proximity to the baskets are not susceptible to a postulated break.

The granular NaTB *is retained in the baskets until dissolved by the Containment sump water, and therefore does not become a particulate debris source.

The proposed installation of NaTB baskets will result in a minor decrease in net free volume of the Containment. This decrease has been reviewed for effects on the Containment peak pressure analysis. The proposed change will not affect the calculated post-accident Containment peak pressure or the Containment pressure profile.

Additionally, the proposed installation of NaTB baskets will increase the containment passive metal heat sink inventory. A Containment heat sink evaluation has been performed and determined that this increase is acceptable.

3.2.2 CAT Isolation and Removal The CAT (01 (02)-QS-TK-2) will be isolated from the RWST and drained. The CAT, caustic addition piping, with exception of portions of buried pipe, and associated equipment will be removed permanently up to a location near the connection with the Serial No.: 22-239 Docket Nos.: 50-338/50-339 Attachment 1 Page 16 of 26

RWST. The portions of the associated piping that remain in place will be capped. shows the current configuration of the QS subsystem and the proposed change to permanently isolate and remove the CAT and associated piping and equipment. The proposed change will not alter the seismic classification of the remaining QS subsystem (Seismic Class I). The associated instrumentation, indications, and controls will be disconnected and removed.

Isolation and removal of the CAT eliminates the CAT liquid inventory from the post accident Containment sump water inventory. However, the minimum liquid flood level used in the low head safety injection (LHSI) and RS pump net positive suction head (NPSH) analysis conservatively ignores the volume in the CAT. Therefore, removal of the CAT does not adversely impact the NPSH at the minimum flood level. The maximum liquid flood level analysis does credit volume from the CAT. The impact of the total basket volume, including NaTB, on the maximum flood level was evaluated. This evaluation accounts for the removal of the credited volume from the CAT as well as the volume of water displaced by the addition of the NaTB baskets and it was determined the maximum flood level remains below the design basis value after buffer replacement.

4.0 REGULATORY EVALUATION

4.1 Applicable Regulatory Requirements/Criteria 10 CFR 50, Appendix A, "General Design Criteria for Nuclear Power Plants" Prior to May 21, 1971, applications for construction permits for water-cooled power plants under 10 CFR 50.34 contained principal design criteria that defined the necessary design, fabrication, construction, testing, and performance requirements for structures, systems, and components (SSCs) important to safety. The regulations in 10 CFR 50, Appendix A, that became effective on May 21, 1971, established General Design Criteria that defined the minimum requirements to meet the principal design criteria.

The Construction Permits for NAPS Units 1 and 2 were issued prior to May 21, 1971; consequently, NAPS Units 1 and 2 were not subject to current GDC requirements in Appendix A [Reference 18]. During the initial plant licensing of NAPS Units 1 and 2, it was demonstrated that the QS and RS Systems met the regulatory requirements in place at that time.

Section 3.1 of the NAPS Unit 1 and Unit 2 UFSAR discusses the design of NAPS relative to the design criteria published in 1971, and the UFSAR discussion demonstrates that NAPS Units 1 and 2 meet the intent of the GDC in Appendix A.

Serial No.: 22-239 Docket Nos.: 50-338/50-339 Attachment 1 Page 17 of 26

The following GDC are applicable to the proposed change:

• Criterion 1 - Quality Standards and Records "Structures, systems, and components important to safety shall be designed, fabricated, erected, and tested to quality standards commensurate with the importance of the safety functions to be performed. Where generally recognized codes and standards are used, they shall be identified and evaluated to determine their applicability, accuracy, and sufficiency, and shall be supplemented or modified as necessary to ensure a quality product in keeping with the required safety function. A quality assurance program shall be established and implemented in order to provide adequate assurance that these structures, systems, and components will satisfactorily perform their safety functions. Appropriate records of the design, fabrication, erection, and testing of structures, systems, and components important to safety shall be maintained by or under the control of the nuclear power unit licensee throughout the life of the unit."

SSCs of importance are designed, fabricated, erected, and tested to quality standards commensurate with the importance of the safety functions to be performed.

The Quality Assurance Program was established to provide assurance that safety-related structures, systems, and components satisfactorily perform their intended safety functions.

Therefore, the proposed change will not impact the ability of NAPS to comply with the requirements of Criterion 1.

• Criterion 19 - Control Room

'~ control room shall be provided from which actions can be taken to operate the nuclear power unit safely under normal conditions and to maintain it in a safe condition under accident conditions, including LOCAs. Adequate radiation protection shall be provided to permit access and occupancy of the control room under accident conditions without personnel receiving radiation exposures in excess of 5 rem TEDE for the duration of the accident. Equipment at appropriate locations outside the control room shall be provided (1) with a design capability for prompt hot shutdown of the reactor, including necessary instrumentation and controls to maintain the unit in a safe condition Serial No.: 22 -239 Docket Nos.: 50- 338/50 -339 Attachment 1 Page 18 of 26

during hot shutdown, and (2) with a potential capability for subsequent cold shutdown of the reactor through the use of suitable procedures."

Calculated post-accident control room doses for the proposed change are within 10 CFR 50.67 limits.

Therefore, the proposed change will not impact the ability of NAPS to comply with the requirements of Criterion 19.

• Criterion 38 - Containment Heat Removal "A system to remove heat from the reactor containment shall be provided. The system safety function shall be to reduce rapidly, consistent with the functioning of other associated systems, the containment pressure and temperature following any LOCA and maintain them at acceptably low levels.

Suitable redundancy in components and features, and suitable interconnections, leak detection, isolation, and containment capabilities shall be provided to assure that for onsite electric power system operation (assuming offsite power is not available) and for offsite electric power system operation (assuming onsite power is not available) the system safety function can be accomplished, assuming a single failure."

Two (2) as subsystems, each 100 percent capacity, and four (4) separate RS subsystems, each rated at approximately 50 percent capacity, remove heat from the Containment following a LOCA. Each subsystem contains a separate pump and spray header, and each RS subsystem contains a separate cooler. Two (2) electrical buses, each connected to both offsite and onsite power, feed the pump motors and the necessary valves. Redundant remote-reading water level indication is provided in the Safeguards area for leak detection of Safeguards equipment. Containment isolation valves separate a ll outside components from the Containment penetrations.

The ability of the as and RS subsystems to cool the reactor core and return the containment to subatmospheric pressure and m aintain it at subatmospheric pressure is not affected by the proposed change. Additionally, the redundancy, interconnections, leak detection, isolation, and containment capabilities of these subsystems discussed above are not affected.

Therefore, the proposed change will not impact the ability of NAPS to comply with the requirements of Criterion 38.

Serial No.: 22 - 239 Docket Nos.: 50 -338/50-339 Attachm e nt 1 Page 19 of 26

• Criterion 4 1 - Containment Atmosphere Cleanup "Systems to control fission products, hydrogen, oxygen, and other substances that may be released into the reactor containment shall be provided as necessary to reduce, consistent with the functioning of other associated systems, the concentration and quality of fission products released to the environment following _postulated accidents, and to control the concentration of hydrogen or oxygen and other substances in the containment atmosphere following postulated accidents to ensure that containment integrity is maintained.

Each system shall have suitable redundancy in components and features, and suitable interconnections, leak detection, isolation, and containment capabilities to assure that for onsite electric power system operation (assuming offsite power is not available) and for offsite electric power system operation (assuming onsite power is not available) its safety function can be accomplished, assuming a single failure."

The use of NaTB does not change the current radiological consequences associated with a LOCA. During initial injection, quench spray has a pH as low as 4.25 as a result of the NaTB being stored in baskets inside Containment. The NaTB buffers the Containment sump water to ensure that the pH of the sump water will remain greater than 7.0 from the time when recirculation spray is credited for iodine removal. The pH of the Containment sump fluid is maintained between 7.0 and 8.5 during the long-term post-accident period, which is the same as the current design p H range.

Therefore, the proposed change will not impact the ability of NAPS to comply with the requirements of Criterion 41.

• Criterion 42 - Inspection of Containment Atmosphere Cleanup Systems "The containment atmosphere cleanup systems shall be designed to permit appropriate periodic inspection of important components, such as filter frames, ducts, and piping to ensure the integrity and capability of the systems."

The design of QS and RS subsystems to permit appropriate periodic inspection of the important components is not affected by the proposed change. The design of NaTB baskets allows for periodic inspection and inspection of the contained NaTB chemical.

Serial No.: 22-239 Docket Nos.: 50-338/50-339 Attachment 1 Page 20 of 26

Therefore, the proposed change will not impact the ability of NAPS to comply with the requirements of Criterion 42.

• Criterion 43 - Testing of Containment Atmosphere Cleanup Systems "The containment atmosphere cleanup systems shall be designed to permit appropriate periodic pressure and functional testing to assure (1) _ the structural and leaktight integrity of its components, (2) the operability and performance of the active components of the systems, such as fans, filters, dampers, pumps, and valves, and (3) the operability of the systems as a whole and, under conditions as close to design as practical, the performance of the full operational sequence that brings the systems into operation, including operation of applicable portions of the protection system, the transfer between normal and emergency power sources, and the operation of associated systems."

The design of QS and RS subsystems to permit periodic pressure and functional testing of their components is not affected by the proposed change.

Therefore, the proposed change will not impact the ability of NAPS to comply with the requirements of Criterion 43.

10 CFR 50.49, "Environmental Qualification of Electrical Equipment Important to Safety for Nuclear Power Plants" An evaluation of environmentally qualified components concluded that all components analyzed will remain capable of performing their safety functions under the short-term and long-term post-accident Containment pH conditions.

10 CFR 50.67, "Accident Source Term" and 10 CFR 100, "Reactor Site Criteria" The proposed buffer change from NaOH to NaTB maintains the post-LOCA offsite radiological consequences at the Exclusion Area Boundary (EAB), the Low Population Zone (LPZ), and the Control Room in compliance with 10 CFR 50.67 and 10 CFR 100.

10 CFR 50, Appendix B, "Quality Assurance Criteria for Nuclear Power Plants and Fuel Reprocessing Plants" Quality assurance criteria in 10 CFR 50, Appendix B, that apply to the systems and components pertinent to the proposed change include: Criteria Ill, V, XI, XVI, and XVII.

Serial No.: 22 - 239 Dock et No s.: 50-338/50 -339 Attachm e nt 1 Pag e 21 of 26

• Criteria Ill and V require measures be established to assure that applicable regulatory requirements and the design basis, as defined in 10 CFR 50.2, "Definitions," and as specified in the lice nse application, ar e correctly tran slated into controlled specifications, drawings, procedur es, and instructions;

• Criterion XI requires a test program to ensure that the subject syste ms will perform satisfactorily in service and requires that test results be document e d and evaluated to ensure that test requirements have been satisfied;

• Criterion XVI requires measures to ensure that conditions a dverse to quality, such as failures, malfunctions, deficiencies, deviations, defective material and equipment, and nonconformances, are promptly identified and corrected, and that significant conditions adverse to quality are documented and reported to management; and

• Criterion XVII requires maintenance of records of activities affecting qu a lity.

4.2 P recede n ts Many operating U.S. PWR power plants have replaced either NaOH or TSP as the buffer used for Containment sump pH control following a LOCA with NaTB. Th e following plants have replaced NaOH with NaTB:

• Beaver Valley Power Station Units 1 and 2 (ML111510646 and ML082730716)

• Indian Point Nuclear Generating Unit 3 (ML081140142)

• Surry Power Station Units 1 and 2 (ML22193A295)

Additional plants have replaced TSP with NaTB:

• Arkansas Nuclear One Unit 2 (ML072890085)

• Calvert Cliffs Nuclear Power Plant Units 1 and 2 (ML082480671)

• Indian Point Nuclear Generating Unit 2 (ML082480671)

• Palisades Nuclear Plant (ML071830385)

4.3 No S ig ni fica n t Hazards C o n s ide rat io n In accordance with 10 CFR 50.90, "Application for amendment of license, construction permit, or early site permit," Dominion Energy Virginia proposes a change to the NAPS Units 1 and 2 TS to allow the use of NaTB to replace NaOH as a chemical additive (buffer) for Containment sump pH control following a LOCA.

Serial No.: 22-239 Docket Nos.: 50-338/50-339 Attachment 1 Page 22 of 26

Dominion Energy Virginia has evaluated whether or not a significant hazards consideration is involved with the proposed change in accordance with the standards set forth in 10 CFR 50.92, "Issuance of Amendment," as discussed below.

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

Response: No.

Use of NaTB in place of NaOH would not involve a significant increase in the probability of a previously evaluated accident because the Containment spra y additive is not an initiator of any analyzed accident. The NaTB would be stored and delivered by a passive method that does not have potential to affect plant operations. Any existing portion of the NaOH delivery system that remains in place will meet existing seismic requirements. Therefore, the change in chemical additive and removal of existing NaOH equipment from service would not result in any failure modes that could initiate an accident.

The chemical additive is used to mitigate the long-term consequences of a LOCA. Use of NaTB as an additive in lieu of NaOH would not involve a significant increase in the consequences of a previously evaluated accident because the amount of NaTB specified in the proposed TS would achieve a sump pH of 7.0 or greater, consistent with the current licensing basis. This pH is sufficient to achieve long-term retention of iodine by the Containment sump fluid for the purpose of reducing accident-related radiation dose following a LOCA.

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

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

Response: No.

Regarding the proposed use of NaTB in place of NaOH, the NaTB would be stored and delivered by a passive method that does not have potential to affect plant operations. Any existing portion of the NaOH delivery system that remains in place will meet existing seismic requirements. The design basis strainer head loss tests remain applicable following NaOH replacement with NaTB. The granular NaTB is retained in the baskets until dissolved by the Containment post accident water, and therefore does not become a particulate debris source.

Hydrogen generation will not be significantly impacted by the change. No new Serial No.: 22-239 Docket Nos.: 50 -338/50-339 Attachment 1 Page 23 of 26

failure mechanisms, malfunctions, or accident initiators would be introduced by the proposed change.

Therefore, the proposed change does not create the possibility of a new or different kind of accident from any previously evaluated.

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

Response: No.

Since the quantity of NaTB specified in the amended TS would reduce the potential for undesirable chemical effects debris loading while achieving radiation dose consequences, corrosion control and hydrogen generation effects that are comparable to NaOH, the proposed change does not involve a significant reduction in a margin of safety. The primary function of a chemical additive is to reduce long-term LOCA consequences by reducing the amount of iodine fission products released to the Containment atmosphere. Because the amended TS would achieve a sump pH of 7.0 or greater using NaTB, dose related safety margins would not be significantly reduced. Use of NaTB reduces the potential for undesirable chemical effects that could interfere with recirculation flow through the sump strainers. Any existing portion of the NaOH delivery system that remains in place would meet existing seismic requirements and would not interfere with operation of the existing Containment or containment spray system.

Therefore, the proposed change does not involve a significant reduction in a margin of safety.

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

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 Commission's 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.

Serial No.: 22 -239 Docket Nos.: 50- 338/50 -339 Attachm e nt 1 Pag e 24 of 26

5.0 EN VI R O NMENTA L CONS IDERA TI ON 10 CFR 51.22, "Criterion for categorical exclusion; identification of lice nsing and regulatory actions eligible for categorical exclusion s or otherwise not requiring environmental review," addr esses requirements for submitting environm e ntal assessments as part of licensing actions. 10 CFR 51.22, paragraph (c)(9) states that a categorical exclusion applies for Part 50 license amendm e nts that meet the following criteria:

i. No significant hazards consideration (as defined in 10 CFR 50.92(c));

ii. No significant change in the types or significant increase in the amounts of any effluents that may be released offsite; and

iii. No significant increase in individual or cumulative occupational radiation exposure.

As demonstrated above, the proposed TS change does not involve a significant hazards consideration. The reviews and evaluations performed to support the proposed ch a nge concluded that all plant systems will continue to function as designed. Also, performance requirements for these systems have been evaluated and determined to be a cceptable. No new accident scen a rios, failure mechanisms, or limiting single failures are introduced a s a result of the proposed change. Operation of the plant with the proposed change does not involve a significant reduction in a margin of safety.

The proposed change to revise the TS to allow the use of NaTB to replace NaOH as a buffer for Containment sump pH control following a LOCA does not result in a significant change in types or amounts of effluents that may be released offsite. The use of NaTB as an additive in lieu of NaOH results in a long-term sump pH of 7 or greater, not exceeding 8.5, consistent with the current licensing b a sis. This pH is sufficient to achieve long-term retention of iodine by the containment sump fluid for the purpose of reducing accident-related radiation dose following a LOCA.

There is no significant increase in individual or cumulative occupational radiation exposure with the proposed change.

Accordingly, the proposed amendment meets the eligibility criterion for categorical exclusion set forth in 10 CFR 51.22, paragraph (c)(9). Therefore, pursuant to 10 CFR 51.22, paragraph (b), no environmental impact statement or environmental assessment needs to be prepared in connection with the proposed amendment.

Serial No.: 22 -239 Docket Nos.: 50-338/50-339 Attachment 1 Page 25 of 26

REFERENCES

1. NUREG-2191, "Generic Aging Lessons Learned for Subsequent License Renewal (GALL-SLR) Report," July 2017. (ADAMS Accession No. ML17187A031 (Vol. 1) and ML16274A399 (Vol. 2))

2. NUREG-0800, NRC Standard Review Plan, Section 6.5.2, "Containment Spray as a Fission Product Cleanup System," Revision 4. (ML092330826)

3. BNP-100, Pacific Northwest Laboratories Report, "Iodine Removal from Containment Atmospheres by Boric Acid Spray," July 1970.

4. WCAP-14542-NP, "Evaluation of the Radiological Consequences from a Loss of Coolant Accident at Indian Point Nuclear Generating Station Unit No. 2 Using NUREG-1465 Source Term Methodology," July 1996. (ML100470750)

5. WCAP-16596-NP, Revision 0, "Evaluation of Alternative Emergency Core Cooling Buffering Agents," July 2006.

6. WCAP-16530-NP, "Evaluation of Post-Accident Chemical Effects in Containment Sump Fluids to Support GSl-191," March 2008. (ML081150379)

7. NUREG/CR-5950, "Iodine Evolution and pH Control," December 1992.

(ML063460464)

8. Regulatory Guide 1.183, "Alternative Radiological Source Terms for Evaluating Design Basis Accidents at Nuclear Power Reactors," July 2000. (ML003716792)

9. Palmer, D. A., Benezeth, P., and D. J. Wesolowski, "Boric Acid Hydrolysis: A New Look at the Available Data," Power Plant Chemistry, v. 2(5), pp. 261-264, 2000.

10. SER Package, GSl-191, "Assessment of Debris Accumulation on Pressurized Water Reactor (PWR) Sump Performance," dated December 6, 2004.

(ML043280641)

11. NRC Generic Letter 2004-02, "Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors,"

September 13, 2004. (ML042360586)

12. AISC Manual of Steel Construction, 9th Edition.

13. ASCE-8-90, Specification for the Design of Cold-Formed Stainless Steel Structural Members.

14. ASCE 7-88, Minimum Design Loads for Buildings and Other Structures.

15. AISC Design Guide 24, 1st Edition, "Hollow Structural Section Connections."

Serial No.: 22-239 Docket Nos.: 50-338/50-339 Attachment 1 Page 26 of 26

16. IEEE Standard 323-1974, "IEEE Standard for Qualifying Class IE Equipment for Nuclear Power Generating Stations."

17. NUREG-0588, "Interim Staff Position on Environmental Qualification of Safety Related Electrical Equipment," Revision 1. (ML031480402)

18. SECY-92-223, "Resolution of Deviations Identified During the Systematic Evaluation Program," dated September 18, 1992. (ML122568290)

19. NUREG-0800, Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants: LWR Edition - Engineered Safety Features, Chapter 6, NRC Branch Technical Position 6-1, "pH for Emergency Coolant Water for Pressurized Water Reactors," Initial Issuance, March 2007. (ML063190011)

20. DOR Guidelines: "Guidelines for Evaluating Qualification of Class IE Electrical Equipment in Operating Reactors," November 13, 1979. (ML032541214)

21. Letter from Virginia Electric and Power Company to USNRC, "North Anna Power Station Units 1 and 2, Updated Supplemental Response to NRC Generic Letter 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation During Design Bases Accidents at Pressurized-Water Reactors," dated February 27, 2009.

(ML090641038)

Serial No.: 22-239 Docket Nos.: 50-338/50-339

ATTACHMENT 2

Quench Spray Subsystem Showing Current and Modified Configurations

NORTH ANNA POWER STATION UNITS 1 AND 2 VIRGINIA ELEC TRIC AND POWER COMPANY (DOMINION ENERGY VIRGINIA)

SPRAY

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CAT RtCIRCll..ATIDN RW ST R£CIRCLI..ATIDH PUWS C NTAJl'I MEN T rl.ltlP Laaend CAT CHEMICAL ADDmON TANK OS QUENCH SPRAY FIWST REFUEUN GWATERSTORAGETANK RS RECIRC SPRAY

S STRAINER PUMPS OS ~ MOTOR OPERATED VALVE MOV

QUENCH SPRAY SUBSYSTEM - CURRENT CONFIGURATION

Page 1 of 2 SPRAY

RWST RINGS

RW ST CllOLERS RU'R JGERATlDN RIJS1 UN11

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Caustic addition line capped RCClRCULA1JON RWS1 CONTAINMENT near the RWST PU MPS

QS QUENCH SPRAY RWST REFU ELING WA TER STORAGE AS AECIACSPAAY TANK

S STRAINER QS A MOTOR OPl!RATED VALVI!

PUMPS MOY

QUENC H SPRAY SUBSYSTEM - MODIFIED CONF I GURA TI ON

Page 2 o f 2 Serial No.: 22-239 Docket Nos.: 50-338/50-339

ATTACHMENT 3

Plan View of Reactor Containment Elevation 216'-11" Showing NaTB Basket Locations

NORTH ANNA POWER STATION UNITS 1 AND 2 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION ENERGY VIRGINIA)

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Page 2 of2 Se ria l No.: 22-239 Do c ket Nos.: 50-338 / 5 0-339

ATTACHMENT 4

Marked-up Tech nica l Spec ifications Pages

NORT H ANNA POWER STAT ION U NITS 1 AND 2 VI RG INIA ELECTR IC AND POWER COMPAN Y (DOMIN ION ENERG Y VIRG IN IA )

Chemical Addition System 3.6.8

3.6 CONTAINMENT SYSTEMS 3.6.8 Chemical Addition System

LCO 3.6.8 The Chemical Addition System shall be OPERABLE.

APPLICABILITY: MODES 1, 2, 3, and 4.

ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME

A. Chemical Addition A.1 Restore Chemical System inoperable. Addition System to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> OPERABLE status.

B. Required Action and B.1 Be in MODE 3. associated Completion 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> Time not met. AND -

B.2 Be in MODE 5. 84 hours9.722222e-4 days <br />0.0233 hours <br />1.388889e-4 weeks <br />3.1962e-5 months <br />

SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY

SR 3.6.8.1 manual, power operated, and automatic valve Verify each Chemical Addition System with the In accordance in the flow path that is not locked, Surveillance sealed, or otherwise secured in position is Frequency in the correct position. Control Program

tion In accordance

~ 4800 gal and~ 5500 gal. with the Surveillance Ver ify that the sod ium tetraborate decahydrate ogram baskets co llectively conta in~ 16,013 lbm and

- --~---------1 s 22, 192 lbm of sod ium tetraborate decahydrate.

Verify that each sod ium tetraborate decahydrate basket is unobstructed, in p lace and intact. REPLACE North Anna Units 1 and 2 3.6.8-1 262/243 REPLACE Chemical Addition System 3.6.8 V erify tha t a sa mple from the sodium tetra bor a te SURVEILLANCE REQUIREMENTS d e c a hydr a te b as kets provides a dequ a te pH

______________ __ a djustm e nt of bor a ted w a ter.

SURVEILLANCE FREQUENCY

SR 3.6.8.3 Verify chemical addition tank NaOH solution In accordance concentration is~ 12% and~ 13% by with the weight. Surveillance Frequency Control Program

Verify each Chemical Addition System In accordance automatic valve in the flow path that is with the not locked, sealed, or otherwise secured in Surveillance position, actuates to the correct position Frequency on an actual or simulated actuation signal. Control Program

SR 3.6.8.5 Verify Chemical Addition System flow from In accordance each solution's flow path. with the Surveillance Frequency Control Program

RE MOV E

North Anna Units 1 and 2 3. 6. 8-2 Amendments 262/243 Serial No.: 22-239 Docket Nos.: 50-338/50-339

ATTACHMENT 5

Proposed Technical Specifications Pages

NORTH ANNA POWER STATION UNITS 1 AND 2 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION ENERGY VIRGINIA)

Chemical Addition System 3.6.8

3.6 CONTAINMENT SYSTEMS 3.6.8 Chemical Addition System

LCO 3.6.8 The Chemical Addition System shall be OPERABLE.

APPLICABILITY: MODES 1, 2, 3, and 4.

ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME

A. Chemical Addition A.1 Restore Chemical System inoperable. Addition System to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> OPERABLE status.

B. Required Action and B.1 Be in MODE 3. associated Completion 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> Time not met. AND -

B.2 Be in MODE 5. 84 hours9.722222e-4 days <br />0.0233 hours <br />1.388889e-4 weeks <br />3.1962e-5 months <br />

SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY

SR 3.6.8.1 Verify that each sodium tetraborate In accordance decahydrate basket is unobstructed, in with the place and intact. Surveillance Frequency Control Program

SR 3.6.8.2 Verify that the sodium tetraborate In accordance decahydrate baskets collectively contain with the

~ 16,013 lbm and ~22,192 lbm of sodium Surveillance tetraborate decahydrate. Control Program Frequency

North Anna Units 1 and 2 3.6.8 - 1 Amendments Chemical Addition System 3.6.8

SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY

SR 3.6.8.3 Verify that a sample from the sodium In accordance tetraborate decahydrate baskets provides with the adequate pH adjustment of borated water. Surveillance Frequency Control Program

North Anna Units 1 and 2 3.6.8-2 Amendments Serial No.: 22-239 Docket Nos.: 50-338/50-339

ATTACHM E NT 6

Marked-up Technical Specification Bases Pages (For Information Only)

NORTH ANNA POWER STATION UNITS 1 AND 2 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION ENERGY VIRGINIA)

ESFAS Instrumentation B 3.3.2

No ch a nge - provided for context only BASES

APPLICABLE 1. Safety Injection (continued)

SAFETY ANALYSES, LCO, f. g. Safety Injection - High Steam Flow in Two Steam Lines AND Coincident With Tav9-Low Low or Coincident With Steam APPLICABILITY Line Pressure-Low lCOntinued)

With the transmitters located inside the containment (Tavg) or near the steam lines (High Steam Flow), it state environmental conditions during an SLB event. is possible for them to experience adverse steady The trip setpoint reflects only steady state instrument uncertainties.

This Function must be OPERABLE in MODES 1, 2, and 3 (above P-12) when a secondary side break or stuck open valve could result in the rapid depressurization of the steam line(s). This signal may be manually blocked by the operator when below the P-12 setpoint.

Above P-12, this Function is automatically unblocked.

This Function is not required OPERABLE below P-12 because the reactor is not critical, so steam line break is not a concern. SLB may be addressed by Containment Pressure High (inside containment) or by High Steam Flow in Two Steam Lines coincident with Steam Line Pressure-Low, for Steam Line Isolation, followed by High Differential Pressure Between Two Steam Lines, for SI. This Function is not required to be OPERABLE in MOD E 4, 5, or 6 because there is insufficient energy in the secondary side of the unit to cause an accident.

2. Containment Spray Systems The Containment Spray Systems (Quench Spray (QS) and Recirculation Spray (RS)) provide four primary functions:

1. Lowers containment pressure and temperature after an HELB in contain ment;

2. Reduces the amcontainment at mount of radioactive iodine in the osphere;

3. Adjusts the pH of the water in the containment sump after a large break LOCA; and

4. Remove heat from containment.

North Anna Units 1 and 2 B 3.3.2 - 13 Revision 31 ESFAS Instrumentation B 3.3.2

BASES APPLICABLE 2. Containment Spray Systems (continued)

SAFETY ANALYSES, LCO, These functions are necessary to:

AND

• Ensure the pressure boundary integrity of the APPLICABILITY containment structure;

• Limit the release of radioactive iodine to the environment in the event of a failure of the containment structure; and

REPLACE

• Minimize corrosion of the components and systems inside containment following a LOCA.

The containment spray actuation signal starts the QS Water is initially drawn from pumps_and aligns the discharge of the pumps to the the RWST by the QS pumps.

Pressure-High High, the RS pumps receive a start signal.

The outside RS pumps start immediately and the inside RS pumps start after a 120 - second delay. Water is drawn from the containment sump through heat exchangers and discharged to the RS nozzle headers. When the RWST reaches the low low level setpoint, the Low Head Safety Injection pump suctions are shifted to the containment sump. Containment spray is actuated manually or by manually or by RWST Level - Low coincident with Containment Pressure-High High signal. RS is actuated Containment Pressure-High High.

a. Containment Spray-Manual Initiation The operator can initiate containment spray at any time from the control room by simultaneously turning two containment spray actuation switches in the same train. Because an inadvertent actuation of containment spray could have such serious consequences, two switches must be turned simultaneously to initiate containment spray. There are two sets of two switches each in the control room. (continued)

North Anna Units 1 and 2 B 3.3.2 - 14 Revision 31 QS System B 3.6.6

B 3.6 CONTAINMENT SYSTEMS B 3.6.6 Quench Spray (QS) System

BASES

BACKGROUND The QS System is designed to provide containment atmosphere cooling to limit post accident pressure and temperature in containment to less than the design values. The QS System, System, is designed to cool and depressurize the containment operating in conjunction with the Recirculation Spray (RS) structure to less than 2.0 psig in 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and to subatmospheric pressure within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> following a Design Basis Accident (DBA). Reduction of containment pressure and the iodine removal capability of the spray limit the release of fission product radioactivity from containment to the environment in the event of a DBA.

The QS System consists of two separate trains of equal capacity, each capable of meeting the design bases. Each train includes a spray pump, a dedicated spray header, nozzles, valves, and piping. Each train is powered from a water storage tank (RWST) supplies borated water to the QS separate Engineered Safety Features (ESF) bus. The refueling System.

The QS System is actuated either automatically by a containment High - High pressure signal or manually. The QS System provides a spray of cold borated water into the upper regions of containment to reduce the containment pressure provides adequate spray coverage to meet the system design and temperature during a DBA. Each train of the QS System requirements for containment heat and iodine fission product removal. The QS System also provides flow to the Inside RS pumps to improve the net positive suction head available.

REMOVE The Chemical Addition System supplies a sodium hydroxide the spray enhances the ability of the spray to scavenge (NaOH) solution into the spray. The resulting alkaline pH of iodine fission products from the contain ment atmosphere. The solution recirculated in the contain mNaOH added to the spray also ensures an alkaline pH for the ent su mp. The alkaline pH of the containment sump water mini mizes the evolution of iodine and minimizes the occurrence of chloride and caustic stress corrosion on mechanical systems and components f]..

(continued)

North Anna Units 1 and 2 B 3.6.6-1 Revision 31 QS System B 3.6.6

BASES

LCO During a OBA, one train of the QS System is required to

R EMOV E

. Therefore, in the event of an accident, at wo safety related, independent th is requirement is least one train of QS will operate, assuming that the worst case single active failure occurs.

header, nozzles, valves, piping, instruments, and controls Each QS train includes a spray pump, a dedicated spray R E PLAC E to ensure an OPERABLE flow path capable of taking suction from the RWST.

APPLICABILITY radioactive material to containment and an increase in In MODES 1, 2, 3, and 4, a OBA could cause a release of containment pressure and temperature requiring the operation of the QS System.

events are reduced due to the pressure and temperature In MODES 5 and 6, the probability and consequences of these limitations of these MODES. Thus, the QS System is not required to be OPERABLE in MODE 5 or 6.

ACTIONS A.1 OPERABLE status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. The components available in If one QS train is inoperable, it must be restored to this degraded condition are capable of providing 100% of the heat removal and iodine removal needs after an accident. The 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> Completion Time was developed taking into account the redundant heat removal and iodine removal capabilities afforded by the OPERABLE train and the low probability of a OBA occurring during this period.

B.1 and B.2 not met, the unit must be brought to a MODE in which the LCO If the Required Action and associated Completion Time are does not apply. To achieve this status, the unit must be brought to at least MODE 3 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and to MODE 5 (continued)

North Anna Units 1 and 2 B 3.6.6-4 Revision 31 RS System B 3.6.7

B 3.6 CONTAINMENT SYSTEMS B 3.6.7 Recirculation Spray (RS) System

BASES

BACKGROUND The RS System, operating in conjunction with the Quench Spray (QS) System, is designed to limit the post accident pressure and temperature in the containment to less than the

.---------------. to less than 2.0 psig in 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and to subatmospheric design values and to depressurize the containment structure spray pH adjusted In addition, the RS System, with pressure within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> following a Design Basis Accident by the (DBA). The reduction of containment pressure and the removal contents of the sodium of i o ne from the containment atmosphere by the spray limit tetra borate decahydrate baskets, the el ease of fission product radi oact co ain ment to the environment in the event of a DBA. i vi ty from is required to scavenge iodine fission products from the The RS System consists of two separate trains of equal containmentatmosphereand capacity, each capable of meeting the design and accident ensuretheirretentioninthe analysis bases. Each train includes one RS subsystem outside

..__------.- -------~ subsystem consists of one approximately 50% capacity spray containment sump water. containment and one RS subsystem inside containment. Each pump, one spray cooler, one 180° coverage spray header, nozzles, valves, piping, instrumentation, and controls. Each outside RS subsystem also includes a casing cooling pump INSERT with its own valves, piping, instrumentation, and controls.

The two outside RS subsystems* spray pumps are located outside containment and the two inside RS subsystems* spray pumps are located inside containment. Each RS train (one inside and one outside RS subsystem) is powered fro m a separate Engineered Safety Features (ESF) bus. Each train of the RS System provides adequate spray coverage to meet the system design requirements for containment heat and iodine fission product removal. Two spray pumps are required to provide 360° of containment spray coverage assumed in the accident analysis. One train of RS or two outside RS subsystems will provide the containment spray coverage and required fl ow.

The two casing cooling pumps and common casing cooling tank are designed to increase the net positive suction head (NPSH) available to the outside RS pumps by injecting cold water into the suction of the spray pumps. They are also beneficial to the containment depressurization analysis. The casing cooling tank contains at least 116,500 gal of chilled and borated water. Each casing cooling pu mp supplies one outside spray pump with cold borated water from the casing (continued)

North Anna Units 1 and 2 B 3.6.7-1 Revision 31 RS System B 3.6.7

BASES

BACKGROUND (continued) of the outside RS subsystems. Each casing cooling pump is cooling tank. The casing cooling pumps are considered part powered from a separate ESF bus.

The inside RS subsystem pump NPSH is increased by reducing the temperature of the water at the pump suction. Flow is diverted from the QS system to the suction of the inside RS pump on the same safety train as the quench spray pump supplying the water.

The RS System provides a spray of subcooled water into the upper regions of contain ment to reduce the containment pressure and temperature during a DBA. Upon receipt of a High-High containment pressure signal, the two casing cooling pumps start, the casing cooling discharge valves open, and the RS pump suction and discharge valves receive an open signal to assure the valves are open. Refueling water storage tank (RWST) Level-Low coincident with Containment Pressure-High High provides the automatic start signal for the inside RS and outside RS pumps. Once the coincidence logic is satisfied, the outside RS pumps start immediately and the inside RS pumps start after a 120-second delay. The delay time is sufficient to avoid simultaneous starting of the RS pumps on the same emergency diesel generator. The coincident trip ensures that adequate water inventory is present in the containment sump to meet the RS sump strainer functional requirements following a loss of coolant accident (LOCA). The RS system is not required for steam line break containment sump and discharge through their respective (SLB) mitigation. The RS pumps take suction from the spray coolers to the spray headers and into the containment atmosphere. Heat is transferred from the containment sump water to service water in the spray coolers.

The Chemical Addition System supplies a sodium hydroxide (NaOH) solution to the RWST water supplied to the suction of the QS System pumps. The NaOH added to the QS System spray ensures an alkali e H fo he lut* n ire 1 te in e containment sump. e resu 1ng a a 1ne p o e spray ump) enhances the ability of the spray to scavenge iodine fission products from the containment minimizes the evolution of iodine and minimizes the atmosphere. The alkaline pH of the containment sump water mechanical systems and components exposed to the fluid. occurrence of chloride and caustic stress corrosion on (continued)

The Chemi ca l Add ition Sy stem cons ists of baskets located on the conta inment floor conta ining sod ium tetraborate deca hydrate ( NaTB ). The NaTB is d isso lved into the conta inment sump water wh ic h ensures an a lka line pH for the so lutio n recircu lated in the conta inment su mp.

North Anna Units 1 and 2 B 3.6.7-2 Revision 31 Chemical Addition System B 3.6.8

INSERT B 3.6 CONTAINMENT SYSTEMS B 3.6.8 Chemical Addition System during recirculation from the sump

BASES

BACKGROUND 1 SSl 0 passive system consisting of from a Design - ---~ resulti n eight baskets containing Basis Accident (OBA). REMOVE sodium tetraborate Radioiodine in its various forms is the fission product of decahydrate (NaTB) that ass ist primary concern in the evaluation of a DA. It is absorbed by the spray from the containment atmosph e. To enhance the The NaTB is stored in baskets iodine absorption capacity of the spray, the spray solution located on the containment floor. is adjusted to an alkaline pH that promotes iodine The initial quench spray is acidic hydrolysis, in which iodine is converted to nonvolatile since it is a boric ac id solution forms. a o ts a t w n po a 10 vated temperature, sodium hydroxide (Na0H) is the from the Refueling Water Storage ensures a pH value of between 7.0 and 8.5 of the solution preferred spray additive. The Na0H added to the spray also Tank (RWST). As the in itial spray recirculated from the containment sump. This pH band solution, and subsequently the minimizes the evolution of iodine as well as the occurrence recirculation solution, comes in of chloride and caustic stress corrosion on mechanical contact with the NaTB, the NaTB s stems and com onents.

dissolves, raising the pH of the The Chemical Addition System consists of one chemical sump so lut ion. addition tank, two parallel redundant motor operated valves

.---------------- refueling water storage tank (RWST), instrumentation, and a.__ _____ ~ in the line between the chemical addition tank and the The design of the Na TB baskets to recirculation pump. The Na0H solution is added to the spray faci litate dissolution of the Na TB water by a balanced gravity feed from the chemical addition into the containment sump water tank through the connecting piping into a weir within the and the collective amount of NaTB RWST. There, it mixes with the borated water flowing to the spray pump suction. Because of the hydrostatic balance between 16,013 lbm and 22,192 between the two tanks, the flow rate of the Na0H is lbm ensure a long-term (t.:: 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />) controlled by the volume per foot of height ratio of the two containment sump pH of.:: 7.0 and tanks. This ensures a spray mixture pH that is~ 8.5 and

~ 8.5. Th is pH band ensures the s; 10.5.

continued iodine retention he uencn Spray ystem actuation signa opens e va ves effectiveness of the sump water from the chemical addition tank to the spray pump suctions or during the recirculation phase of the quench spray pump start signal opens the valves from the spray operation and also minimizes chemical addition tank after a 5 minute delay. The 12% to 13% Na0H solution is drawn into the spray pump suctions. The the occurrence of ch lor ide induced chemical addition tank capacity provides for the addition of stress corrosion cracking of the Na0H solution to all of the water sprayed from the RWST into sta inless stee l recirculation piping. con ainment. Te rce solution nd olu of olution Ma inta ining the long-term sump (continued) fluid pH less than or equal to 8.5 ensures that there is adequate NPSH ava il ab le to the ECCS and RSS and 2 B 3.6.8-1 Revision 36 pumps with post-LOCA debris and chem ica l precipitant load ing on the L - -------- 7REPLACE containment sump strainer.

Chemical Addition System B 3.6.8

REMOVE BASES

BACKGROUND sprayed into containment ensures a long term containment (continued) su mp pH of~ 7.0 and~ 8.5. This ensures the continued iodine retention effectiveness of the sump water during the recirculation phase of spray operation and also minimizes the occurrence of chloride induced stress corrosion cracking of the stainless steel recirculation piping. Maintaining the sump fluid pH less than or equal to 8.5 ensures that there is adequate NPSH available to the ECCS and RSS pumps with post LOCA debris and chemical precipitant loading on the containment sump strainer.

APPLICABLE The Chemical Addition System is essential to the removal of SAFETY ANALYSES airborne iodine within containment following a DBA.

Following the assumed release of radioactive materials into containment, the containment is assumed to leak at its analysis value volume following the accident. The plant accident dose calculations use an effective contain ment coverage of 70% of the contain ment volume. The contain ment safety analyses implicitly assume that the containment atmosphere is so turbulent following an accidental release of high energy fluids inside containment that, for heat

>~ completely covered by spray. removal purposes, the containment volume is effectively I In sert A -- he A response t1me assumed or ne he mical Act ition System is based on the Chemical Addition System isolation valves beginning to open 5 minutes after a QS pump start.

Insert B The DBA analyses assume that one train of the Quench Spray System is inoperable and that the entire chemical addition tank volume is added through the remaining Quench Spray S stem flow ath.

REPLACE The Chemical Addition System satisfies Criterion 3 of 10 CFR 50.36(c)(2)(ii).

LCO The Chemical Addition System is necessary to reduce the release of radioactive material to the envi

til the Quench Spray System has completed pumping water to raise

eight sod ium tetra borate decahydrate baskets must be unobstructed, in place and intact (i.e.,

• nued) having no re levant component removed, destroyed or damaged such that th e basket cannot perform its function), collectively contain between 16,013 lbm and 22,192 lbm of sodium tetra borate decahydrate and be capable of providing th e required pH adjustment.

36 Insert A-page B 3.6.8-2

Quench spray consists of a boric acid solution with a spray pH as low as 4.25. As indicated in Reference 1, fresh sprays (i.e., sprays with no dissolved iodine) are effective at scrubbing elemental iodine and thus a spray additive is unnecessary during the initial injection phase when the spray solution is being drawn from the RWST. As described in the Reference 1, research has shown that elemental iodine can be scrubbed from the atmosphere with borated water, even at low pH. Reference 1 also provides guidance for calculating a first-order removal coefficient for elemental iodine that does not depend on a spray additive for pH control but is primarily based on the rate at which fresh-solution surface area is introduced into the containment building atmosphere. Therefore, quench spray can be credited for scrubbing elemental iodine during the initial injection phase having a pH as low as 4.25.

Insert B - page B 3.6.8-2

Since long-term use of a plain boric acid spray could increase the potential for elemental iodine re-evolution during the recirculation phase of the LOCA, the equilibrium sump solution pH is increased by adding Na TB. Reference 2 guidance indicates that if the sump water pH is 7 or greater, then a licensee does not need to evaluate re-evolution of iodines for dose consequences. In accordance with the current licensing basis, the dose analysis need not address iodine re-evolution if the sump water pH of 7 or greater is achieved within 40 minutes after the LOCA and is maintained for the duration of the accident. The Chemical Addition System provides a passive safeguard with eight baskets of Na TB located in the containment.

The basket contents dissolve as the sump fills, raising pH to the required value and maintaining it at or above that value throughout the accident.

Chemical Addition System B 3.6.8 REMOVE

average spray solution pH to a level conducive to iodine maximizes the effectiveness of the iodine removal mechanism removal, namely, to between 8.5 and 10.5. This pH range without introducing conditions that may induce caustic stress corrosion cracking of mechanical system components.

Addition System flow paths are properly positioned and that In addition, it is essential that valves in the Chemical automatic valves are capable of activating to their correct positions.

APPLICABILITY In MODES 1, 2, 3, and 4, a OBA could cause a release of of the Chemical Addition System. The Chemical Addition radioactive material to containment requiring the operation System assists in reducing the iodine fission product inventory prior to release to the environment.

events are reduced due to the pressure and temperature In MODES 5 and 6, the probability and consequences of these System is not required to be OPERABLE in MODE 5 or 6. limitations in these MODES. Thus, the Chemical Addition

REPLACE ACTIONS A.1 If the Chemical Addition System is inoperable, it must be rec ircu lation spray so lut ion for 1--~ :..~~~~~~~r:r-P-f-. w *~-v'i-~ u r. *odine removal enhancement rs. The pH adjustment of corrosion protection and e enc pry Sys em woula sti be avai able and would emove some iodine from the The 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> Comp let ion Time containment atmosphere in the event of a OBA. The 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> takes into account that the Completion Time takes into account the ability of the Quench cond it ion wh ich caused the Spray System to remove iodine at a reduced capability using the redundant Quench Spray flow path capabilities and the inoperable system would most low probability of the worst case OBA occurring during this li kely all ow this passive system to e. d.

continue to prov ide some B.1 and B.2 capability for pH adjustment and iodine remova l, the Containment If the Chemical Addition System cannot be restored to Spray System wou ld sti ll be OPERABLE status within the required Completion Time, the ava ilab le and wou ld remove some unit must be brought to a MODE in which the LCO does not iod ine from the containment apply. To achieve this status, the unit must be brought to at atmosphere in the event of a DBA, least MODE 3 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and to MODE 5 within 84 hours9.722222e-4 days <br />0.0233 hours <br />1.388889e-4 weeks <br />3.1962e-5 months <br />.

and the low probabili ty of the The allowed Completion Time of 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> is reasonable, based worst case DBA occurring during REPLACE (continued) t hi s period.

North Anna Units 1 and 2 B 3.6.8-3 Revision 36 Chemical Addition System B 3.6.8

BASES

ACTIONS B.1 and B.2 (continued) on operating experience, to reach MODE 3 from full power Th is SR prov ides visua l conditions in an orderly manner and without challenging unit systems. The extended interval to reach MODE 5 allows ver ification that the eight 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> for restoration of the Chemical Addition System in sodium tetraborate MODE 3 and 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> to reach MODE 5. This is reasonable when decahydrate baskets are considering the reduced pressure and temperature conditions unobstructed, in place Reactor Coolant System. in MODE 3 for the release of radioactive material from the and intact. Th is ensures no re levant component has been removed, SR 3.6.8.1 destroyed or damaged er, ying t e correct a ignment o C emica Addition System such that the basket anual, power operated, and automatic valves in the chemical cannot perform its ddition flow path provides assurance that the system is function. ble to provide additive to the Quench Spray System in the Th is SR prov ides visua l ocked, sealed, or otherwise secured in position, since vent of a DBA. This SR does not apply to valves that are verification that the eight hese valves were verified to be in the correct position sod ium tetraborate equire any testing or valve manipulation. Rather, it rior to locking, sealing, or securing. This SR does not decahydrate baskets involves verification, through a system walkdown, that those co ll ective ly contain ~ valves outside contain ment and capable of otentiall bein 16,013 lbm ands 22,192 isP.ositioned are in th correct osi *on. e urv 1 lbm of NaTB. This amount reliability, and plant risk and is controlled under the requency 1s ase on operating experience, equipment of Na TB is sufficient to Surveillance Frequency Control Program.

ensure that the recirculat ion so lut ion SR 3.6.8.2 fo ll ow ing a LOCA is at the correct pH level. Each be an ine solution. Si WST contents are basket has indication ally acidic, the volume of th ical addition tank marks, based on NaTB t provide a sufficient volume y additive to adjust density and basket for all water injected. This S rformed to verify t * * * *

• n in th volume, wh ich are used to ency 1s visua ll y verify that the, ability, and plant risk NaTB is at an acceptable and is controlled under the Surveillance Frequency Control level corresponding to the Program.

requ ired mass range. SR 3.6.8.3

This SR provides verification, by chemical analysis, of the NaOH concentration in the chemical addition tank and is sufficient to ensure that the spra solution bein in*ected This SR ver ifies via samp li ng that the sod ium tetra borate decahydrate contained in the NaTB baskets prov ides adequate adjustment of containment sump borated water. The Surveill ance Frequency is based on operat ing experience, equ ipment re li ab ility, and plant risk and is controll ed under the Surveill ance Frequency Control Program.

North Anna Units 1 and 2 B 3.6.8-4 Revision 46 Chemical Addition Syste m B 3.6.8 REMOVE

SURVEILLANCE REQUIREMENTS SR 3.6.8.3 (continued) into containment is at the correct pH level. The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is controlled under the Surveillance Frequency Control Program.

SR 3.6.8.4 This SR provides verification that each automatic valve in the Chemical Addition System flow path actuates to its correct position. This Surveillance is not required for valves that are locked, sealed, or otherwise secured in the required position under administrative controls. The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is controlled under the Surveillance Frequency Control Program.

SR 3.6.8.5 To ensure that the correct pH level is established in the borated water solution provided by the Quench Spray System, flow from the Chemical Addition System is verified draining solution from the RWST and chemical addition tank through the drain lines in the cross-connection between the tanks.

This SR provides assurance that the correct amount of NaOH will be metered into the flow path upon Quench Spray System initiation. The Surveillance Frequency is based on operating experience, equipment reliability, and plant risk and is controlled under the Surveillance Frequency Control Program.

1. NUR EG -0800, Section 6.5.2, Rev. 4.

2. Regulatory Guide 1.183, Rev. 0. REPLACE

North Anna Units 1 and 2 B 3.6.8-5 Revision 46