ML17333A332

DC Cook Nuclear Plant Boric Acid Concentration Reduction.

ML17333A332
Person / Time
Site:	Cook
Issue date:	07/31/1995
From:	AMERICAN ELECTRIC POWER SERVICE CORP.
To:
Shared Package
ML17333A331	List: ML17333A330 ML17333A332 ML17334B575
References
NUDOCS 9603110157
Download: ML17333A332 (91)

Text

DONALD C. COOK NUCLEAR PLANT BORIC ACID CONCENTRATION REDUCTION JULY 1995 AMERICAN ELECTRIC POWER SERVICE CORPORATION COLUMBUS, OHIO ee03<<0X57 9SO2i9 PDR ADQCK 05000315 p PDR

,i

,II

TABLE OF CONTENTS Introduction and Definition of Terms ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 1 1.1 Introduction 1.2 Definition of Terms Boration S stem Technical S ec fication . 3 2.1 Problem Description 2.2 Problem Solution Safet Anal sis Concerns ~ ~ ~ ~ 6 3' Large Break LOCA 3.2 Small Break LOCA 3.1 Steam Line Break 3.4 Long Term Core Cooling 3.5 Reactivity Consideration Reactivit Calculations ~ ~ ~ ~ ~ ~ 9 4.1 Design Requirements 4.2 Cooldown Shutdown Margin Requirement 4.3 Analysis Method 4.4 Reactor Trip from Full Power, Equilibrium Xenon Conditions 4.5 Reactor Trip from Full Power, Peak Xenon Conditions 4.6 Normal Shutdown 4.7 Flow Rate Verification 4.8 Shutdown Boration Requirements (Modes 5 & 6) 4,9 Applicability for Future Cycles 0 erational Anal sis ~ ~ ~ ~ ~ ~ ~ ~ 21 5.1 Response to Emergency Situation 5.2 Normal Boration 5.3 Technical Specification Changes 5.4 Modification to the Plant 5.5 Implementation

~Summar 25 Re ere ces ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 26

INTRODUCTION AND DEFINITION OF TERMS 1.1 Introduction The Donald C. Cook Nuclear Plant, constructed and operated by the American Electric Power Corporation, is located along the eastern shore of Lake Michigan in Bridgman, Berrien County, Michigan. The reactor is a closed-cycle, pressurized, light water moderated and cooled system, which uses slightly enriched uranium oxide fuel. The Unit 1 reactor is designed to produce 3250 MW<>,~,~ and Unit 2 is designed to produce 3411 MW~~,~,~. This report describes results of the analyses performed to modify the boration system technical specifications.

1.2 Definition of Terms The following list of symbols, terms and abbreviations will be used consistently throughout this report:

BOL Beginning of Life MOL Middle of Life EOL End of Life MWD/MTU Megawatt days per metric tonne of uranium metal (represents burnup of fuel)

RCCA Rod Cluster Control Assemblies (type of control rods used)

T/S Technical Specification RTP Rated Thermal Power

hp Change in reactivity (hp ln(kq/k2) where kz and k2 are eigenvalues obtained from two calculations) pcm Percent mille (a reactivity change of 1 pcm equals a reactivity change of 10 hp) step A unit of control rod travel equal to 0.625 inch ppm Parts per million by weight (specifies chemical shim boron concentration)

HFP Hot Full Power HZP Hot Zero Power RCS Reactor Coolant System CVCS Chemical and Volume Control System Residual Heat Removal System BAST Boric Acid Storage Tank (High Boron Concentration Storage Tank)

RWST Refueling Water Storage Tank (Low Boron Concentration Storage Tank)

LBLOCA Large Break Loss of Coolant Accident SBLOCA Small Break Loss of Coolant Accident SLBA Steam Line Break Accident PC-NDR Personal Computer based Nuclear Design Report. Provides the user with reactivity coefficients, power distributions and contains procedures to determine shutdown boron / estimated critical positions.

BORATION SYSTEM TECHNICAL SPECIFICATION 2.1 Problem Descri tion The current Technical Specifications (T/S) require a boric acid storage tank (BAST) containing "

borated water at concentration between 20,000 ppm and 22,500 ppm of boron.

This concentration and the current minimum BAST borated water volume of 5641 gal for Unit 1 and 4905 gal for Unit 2 are based on the ability to borate the reactor coolant system (RCS) to the required cold shutdown concentration through the feed and bleed process. Prior to commencing the cooldown, the RCS is borated to a concentration required to provide a shutdown margin of 1000 pcm at 68 F. In addition, the BAST water volume must provide blended makeup to compensate for coolant contraction that occurs during cooldown. RCS boron concentration is maintained constant during the cooldown process.

Since the concentration of borated water in the BAST is very high, the solution has to be kept at a high temperature of 145'F. This is accomplished through heat tracing of all associated tanks and pipes, This high concentration presently creates two major operational problems in the chemical and volume control system (CVCS). First, the high boric acid concentration causes accelerated Boric Acid Transfer Pump seal wear which requires additional maintenance and can result in pump inoperability. The heat tracing associated with the high

boric acid concentration also contributes to higher maintenance requirements through temperature degradation of the diaphragm valves associated with the boric acid system piping. In addition, the heat trace itself requires significant maintenance to keep it fully operational and much of this activity results in radiation exposure to the maintenance personnel. If a heat trace failure is undetected, the possibility of pipe blockage due to boric acid precipitation may render one of the flow paths inoperable, thus impacting safety system availability.

2.2 Problem Solution Information regarding solubility of boric acid in water versus temperature of the solution for temperatures between 32 F and 160'F was obtained from reference 1. The solubility temperature of the solution with 4 weight percent (6990 ppm) boric acid is 58 F. Assuming a measurement uncertainty/conservatism of 5 F, solution temperature of 63 F is required to prevent precipitation. At or below a concentration of 4.0 weight percent, the normal ambient temperature in the auxiliary building will be sufficient to preclude precipitation within the boric acid makeup system.

By reducing the concentration in the BAST to between 6550 ppm and 6990 ppm (between 3.5 and 4.0 weight percent), heat tracing problems can be avoided.

-4.-

The reduction in BAST boron concentration is achieved by relying on both the BAST and the RWST for cooldown.

Specifically, the BAST borated water is used for increasing the RCS boron concentration at hot conditions and the RWST borated water is used for overcoming coolant contraction.

After reactor shutdown, boration through feed and bleed operation using BAST borated water is completed to satisfy the hot zero power shutdown margin requirement. This negative reactivity is introduced to compensate for the decrease in power and xenon decay. Water from the refueling water storage tank (RWST) is then used for coolant contraction.

Calculations were performed to determine the maximum volume of borated water required in the BAST to accomplish core boration to compensate for the above mentioned effects. To compensate for the reduced concentration, calculations were also performed to determine the minimum delivery volume flow rate from the BAST. For further cooldown, the RCS shrinkage mass is obtained from a second BAST, batching tank, or a combination of the two. In lieu of the boric acid storage tank system, the refueling Water Storage Tank (RWST) borated water can also be used for RCS boration for plant shutdown and cooldown. Calculations were performed to determine the amount of RWST borated water to compensate for the above mentioned reactivity effects'5-

t f'

3. SAFETY ANALYSIS CONCERNS 3.1 Lar e Break LOC The current Large Break Loss-of-Coolant Accident (LBLOCA) analysis of record for Cook Nuclear Plant was performed using the NRC approved Westinghouse ECCS Evaluation Model. The proposed reduction in the boron concentration in the BAST will not adversely affect the LBLOCA because the evaluation model codes used in analyzing the large break do not take credit for boron concentration in the BAST.

3.2 Small Break LOCA The current Small Break Loss-of-Coolant Accident (SBLOCA) analysis of record for Cook Nuclear Plant was performed using NRC-approved SBLOCA ECCS evaluation model with NOTRUMP. The proposed reduction in the boron concentration in the BAST will not adversely affect the SBLOCA because the evaluation model codes used in analyzing the small break do not take credit for boron concentration in the BAST.

3.3 Steam Line Break The steam line break accident (SLBA) was the only original design basis event that could have been significantly affected by the proposed reduction of the high concentration in the BAST, since the highly concentrated borated water initially found in the boron in)ection tank (BIT) was recirculated with t'

the borated water in the BAST. Reanalysis of the SLBA, however, was performed in 1991 using an NRC approved methodology to eliminate the BIT for high concentration boric acid in]ection. That is, pure water is currently assumed to be in the BIT. This reanalysis was submitted to the NRC on March 26, 1991 via letter AEP:NRC:1140. The NRC safety evaluation was obtained on November 20,1991 (amendment 158 for unit 1 and 142 for unit 2). As a result, the current SLBA is not affected by the proposed reduction in the BAST boron concentration.

3.4 Lon Term Core Coolin Since the solution stored in the BAST is not pumped into the RCS by the Emergency Core Cooling System during a Design Basis Accident, the change in BAST concentration will have no effect on this issue.

3.5 Reactiv t Consideratio The Reactivity Holddown Capability Criterion in the UFSAR states: "The reactivity control systems provided shall be capable of making the core subcritical under credible accident conditions with appropriate margins for contingencies, and shall be capable of limiting any subsequent return to power such that there will be no undue risk to the health and safety of the public "

l~

j 3(

Ji

Normal reactivity shutdown capability is provided by control rods with boric acid injection used to compensate for long term xenon decay. Technical Specifications on BAST volume and boron concentration ensure that two flow paths and associated sources of borated water are available to maintain subcriticality. Therefore, calculations were performed to determine how much BAST and RWST water is required to counteract the reactivity increase due to reactor shutdown and subsequent xenon decay. Calculations were also performed to determine the required flow rate of the boric acid solution at the reduced boron concentration. The results of these calculations are presented in Section 4.0 of this report.

II 4.0 REACTIVITY CALCULATIONS Several cooldown scenarios were investigated for both units and for several operating cycles (Reference 3 and 4). The purpose of the investigation was to determine the amount of boric acid in the BAST required to counteract positive reactivity addition due to reactor shutdown and xenon decay. For this, shutdown from a full power equilibrium xenon condition and shutdown from a 100X RTP, peak xenon condition were investigated to determine if the reduced concentration boric acid in the BAST was sufficient to keep the reactor subcritical at hot conditions even after xenon decay. Next, the rate of boron addition required to counteract xenon decay after reactor shutdown and to counteract xenon burnout during power operation after a startup at peak xenon were investigated. Finally, the boration requirements for cooldown below 200'F was investigated.

4.1 esi Re u rements

~ The amount of boric acid in the BAST must be sufficient to maintain the reactor subcritical by 1600 pcm at hot conditions following a reactor trip from all credible operating conditions. [Note that the control rods provide at least a shutdown margin of 1600 pcm (k,ff 0.984) immediately following a reactor trip from full power conditions assuming that the most reactive RCCA is fully withdrawn]. Or, in other words, sufficient borated water in the BAST must be available to compensate for

xenon decay.

~ The flow rate of boric acid from the BAST must be sufficient to follow the highest burnout rate of xenon following reactor startup from peak xenon conditions.

4.2 Cooldown Shutdown Mar in Re uirement To protect against the consequences of postulated increased steam loads with safeguards blocked below P-ll and P-12 (RCS temperature of approximately 541 F), it is a requirement at Cook Nuclear Plant that the RCS be borated to cold (68 F) shutdown boron conditions prior to cooldown below 541'F.

Therefore, feed and bleed operation will be started at hot conditions before commencing cooldown. Once the required boron concentration is achieved in the RCS, then RWST'water at 2400 ppm will be added for contraction makeup of the RCS mass due to cooldown. Calculations were performed to show that the addition of RWST water maintains the necessary shutdown boron concentration in the RCS.

Also, an inadvertent boron dilution event while shutdown and operating on the RHR system is of concern. Therefore, RCS boron concentration is increased (boron dilution penalty) to provide the operator sufficient time to identify and terminate the event. This boron dilution penalty is included in the shutdown boron values provided in the PC-NDR computer program (Reference 2).

[Note that these requirements are not T/S requirements but are administrative controls.)

The amount of BAST boric acid required to increase the RCS boron concentration from critical boron concentration to hot shutdown boron concentration (i.e., boron concentration at 547 F with no xenon) by feed and bleed operation was calculated using the equation Cz~ = C x e ' C~(1-e ')

where C - initial boron concentration C~ - final boron concentration after feed and bleed operation Cs~q- boron concentration in BAST M mass of water The amount of source water used for feed and bleed operation was calculated using the equation Vms =

pcs x

>assr x Rcs 1n[ C~

Cmsr Co C<>

] (2) where V~> - volume of BAST water used for feed

and bleed operation.

pcs volume of RCS v~s specific volume of RCS water

'>~> - specific volume of BAST water After feed and bleed operation to obtain the cold shutdown boron concentration, RWST water is added to the RCS to compensate for contraction due to cooldown. Final RCS concentration is calculated using the equation CfS = Cfb x V +Vr CR WST(1 vr )

Vf where Cfg - final RCS boron concentration Cqwsq boron concentration in RWST specific volume of RCS water before cooldown v~ - specific volume of RCS water after cooldown The mass of make-up water required was then calculated for cooldown to 350 F, 200 F and 68'F using the following equation M = V ( 1 Vr 1

) (4) where M, - Shrinkage mass

V~cs volume of RCS The volume of make-up water was then calculated as follows.

V = M x vz~ x (7.4805gal/Zt')

where V, - shrinkage volume in gallons 4.4 Reactor Tri from Full Power E u librium Xenon Conditions In this calculation, it is assumed that the reactor is shutdown from full power, equilibrium conditions. All control and shutdown rods except the most reactive rod are assumed to be in the core. Shutdown boron values for no xenon conditions are obtained from the PC-NDR computer program. Shutdown boron calculated by the PC-NDR program include 100 ppm for conservatism and a Boron -10 depletion allowance. It should be noted that, in this calculation, T/S shutdown margin requirements are met; but other requirements noted in section 4.2 are not taken into account since additional administrative requirements are not needed to keep the reactor subcritical.

The amount of boric acid solution from the BAST (6550 ppm) required to increase the RCS critical boron concentration to HZP shutdown boron concentration was then calculated. To show that there is enough RWST water available for further cooldown, calculations were performed using RWST water at a i

iJ I(

lj

lower boron concentration (2400 ppm) to compensate for shrinkage. The resulting RCS boron concentration due to the addition of RWST water was then calculated.

Results for Unit 1, Cycle 14 (BOL, MOL and EOL) are shown in tables 4.4.-1 through 4.4-3. Results for Unit 2, Cycle 10 (BOL, MOL and EOL) are shown in tables 4.4.-4 through 4.4-6.

Values for Unit 2, cycle 10 are shown to be limiting compared to other cycles analyzed [Note that three cycles per unit were analyzed and the limiting cases are presented here). Review of the data shows that, for any credible incident requiring reactor shutdown, the amount of boric acid solution available in the BAST should be 2939 gallons. There is also sufficient RWST water available in the event that cooldown is required.

4.5 eactor Tri from Full Power Peak Xenon Conditions In this case, it was assumed that the reactor is tripped from a peak xenon condition. That is, the reactor was assumed to be at full power approximately 8 hrs after a previous trip.

In this condition, the RCS boron concentration will be at a minimum due to the xenon buildup from the earlier trip. Once the RCS is at this low boron concentration, the reactor is again assumed to trip, requiring RCS boron concentration to be increased to the no xenon, HZP shutdown boron concentration.

Shutdown boron values for no xenon conditions are obtained from the PC-NDR computer program. Shutdown boron calculated

,I C

by PC-NDR program include 100 ppm for conservatism and a Boron

-10 depletion allowance. It should be noted that in this calculation T/S shutdown margin requirements are met; but no other requirements, such as that noted in section 4.2, are taken into account since additional administrative requirements are not needed to keep the reactor subcritical.

The amount of BAST boric acid solution at 6550 ppm required to increase the boron concentration to hot shutdown boron concentration by feed and bleed operations was then calculated. Finally, the amount of RWST water at 2400 ppm required for shrinkage due to cooldown to 68'F was calculated.

Results for Unit 1, cycle 14 (BOL, MOL and EOL) are shown in tables 4.5-1 through 4.5-3. Results for Unit 2, cycle 10 (BOL, MOL and EOL) are shown in tables 4.5-4 through 4.5-6.

Review of the data shows that, even for a reactor trip from peak xenon conditions, the maximum amount of boric acid in the BAST required to keep the reactor at hot conditions with no xenon in the core is 6017 gallons. There is also sufficient RWST water available in the event that cooldown is required.

4.6 ormal Shutdown The purpose of this section is to show that, for all expected normal shutdown scenarios, there is enough BAST borated water volume available to increase the RCS boron concentration by feed and bleed operation to cold shutdown boron concentration.

II j,r Iq

During a normal shutdown, the RCS boron is first increased to the shutdown boron concentration (i.e., shutdown boron corresponding to 547'F) by feed and bleed operation. Next, if a cooldown is to be conducted, the RCS boron concentration is increased to the cold shutdown boron concentration (i.e.,

shutdown boron corresponding to 68 F) via feed and bleed operation before blocking safeguards below P-11 and P-12 (i.e., before cooling below 541'F).

For normal shutdown, the pre-trip boron concentration will be that corresponding to the equilibrium xenon critical boron concentration for 100X RTP. This value is higher than that assumed for the peak xenon conditions. As a result, the RCS needs to be borated to a lesser extent than that described in section 4.5. Therefore, using available BAST borated water, RCS boron can be increased to that required for cold shutdown while staying at hot conditions. The required boron concentration at the cold condition is higher compared to that given in previous sections due to the boron dilution penalty which was discussed in section 4.2. [In the cases described in sections 4.4 and 4.5, cooldown to HZP T,, was considered for shutdown margin requirements. Further cooldown calculations in sections 4.4 and 4.5 were performed to show that the volume of the RWST water is sufficient for coolant contraction and to keep the reactor subcritical.]

t 0

For cooldown below 541'F, the contraction volume is filled with water from the RWST and the resulting RCS boron concentration was checked to see that the RCS boron concentration is always above the required boron concentration.

Results for Unit 1, cycle 14 (BOL, MOL and EOL) are shown in Tables 4.6-1 through 4.6-3. Results for Unit 2, cycle 10 (BOL, MOL and EOL) are shown in Tables 4.6-4 through 4.6-6.

From these tables, it can be seen that 7498 gallons of boric acid in the BAST is enough for borating the core to meet shutdown margin requirements. This calculation provides a rough idea of how much BAST boric acid solution will be used during normal operation.

4.7 Flow Rate Verification Due to the reduction of the boric acid concentration in the BAST, calculations were performed to determine the BAST flow rate needed to counteract the xenon decay following shutdown.

For this calculation, the reactor is assumed to be tripped from an equilibrium xenon condition. Table 4.7-1 shows the xenon decay rate for BOL, MOL and EOL for unit 2, cycle 10

[Note that calculations were performed for units 1 and 2 and only the worst case results are presented in this section].

From this, table, it can be seen that the maximum decay rate is If Ii

183 pcm/hr. To counteract this xenon decay, it was found that the core has to be borated at approximately 24 ppm/hr. The flow rate necessary to increase RCS boron at this rate is approximately 6 gpm of BAST boric acid at 6550 ppm.

Xeno Burnout Due to the reduced boric acid concentration in the BAST, calculations were also performed to determine the rate of BAST boric acid solution addition required to counteract xenon burnout. In this scenario, reactor startup is assumed 8 hrs after a previous trip.

For conservatism, a step jump to full power was assumed and the xenon that was built up due to the initial trip begins to burnout. The burnout rate for Unit 2 for cycle 10 is shown in Table 4.7-2 [Note that calculations were performed for units 1 and 2 and only the worst case results are presented in this section].

The maximum boration rate is approximately 137 ppm/hr. This translates to approximately 33 gpm of boric acid addition from BAST. Therefore, a conservative value of 34 gpm flow requirement is chosen.

4.8 Shutdown Boration Re uirements Modes 5 6 Current technical specifications require us to maintain a lC shutdown margin of 1600 pcm down to a temperature of 200'F and a shutdown margin of 1000 pcm below RCS temperature of 200OF.

During a normal shutdown, the RCS boron concentration is first increased to the hot shutdown boron concentration (i.e.,

shutdown boron corresponding to 547'F) by feed and bleed operation. Next, if a cooldown is to be conducted, the RCS boron concentration is increased to the cold shutdown boron concentration (i.e., shutdown boron corresponding to 68 F) via feed and bleed operation before blocking safeguards below P-ll and P-12 (i.e., before cooling below 541 F). Because of this fact, there is no need for additional core boration for cooldown from 200 F to 68'F. The maximum amount of BAST water necessary for blending to compensate for the resulting shrinkage from 200'F to 68 F is 900 gallons. The maximum amount of RWST water necessary to compensate for the resulting shrinkage from 200'F to 68'F is 3264 gallons.

In Mode 6, with the reactor vessel head detensioned or removed, a boron concentration sufficient to ensure the more restrictive of the following reactivity conditions must be maintained: a k,~~ of 0.95 or less, or 2400 ppm. With the high boric acid concentration in the RCS, the reactivity addition due to any postulated dilution accident is slow enough to allo~ the operator to determine the cause of the dilution and take corrective action before shutdown margin is

4.9 A licabi it for Futu e C cles Calculations were performed for Unit 1 cycles 12, 13 and 14 and for Unit 2 cycles 8, 9 and 10. These are representative of the cycles for Units 1 and 2 ~ It should be noted that the required shutdown margin (as specified in the current T/S reference 5 and 6) for these 6 cycles was 1600 pcm. New changers safety analysis for both units shows that only 1300 pcm is required and the T/S are being amended to reflect this Therefore, the calculations presented have a 300 pcm (- 30 ppm) margin built into the analysis. This margin will take care of uprating or cycle length increase planned for the future. Also, for added conservatism the minimum amount of boric acid solution required has been increased from 6017 gallons to 8500 gallons for hot shutdown requirements. [It is also noted that 8500 gallons is sufficient to borate the RCS to cold shutdown (68 F) boron conditions with the BAST, should the operator choose to do this for normal shutdown situations.] Requirement for Modes 5 and 6 is increased from 900 gallons to 5000 gallons. These conservatisms are enough to conclude that future cycles of both units are enveloped with this analysis'20-

5.0 0 erational Anal sis The impact on plant operations from a reduction in the boron concentration in the BAST is presented in this section.

5.1 es onse to Emer enc Situation Return to criticality during the cooldown following a Steam Line Break Accident (SLBA) or a Steam Generator Tube Rupture (SGTR) event, Following a SLBA or SGTR, the plant procedures and instructions direct the operators to borate the RCS to maintain shutdown margin.

The boration is to be performed from either the RWST or the BAST. Therefore, emergency procedures directing blender control settings will be modified to reflect the reduction in the BAST boron concentration.

5.2 Normal Bo atio During a feed-and-bleed operation performed to increase the system boron concentration, the charging pumps are used to inject concentrated boric acid into the RCS.

The rate of increase in boron concentration at any given point in time is proportional to the difference between the system concentration and the concentration of the charging fluid. Therefore, the normal operating procedures will be changed to reflect the reduction in the BAST boron concentration.

I jI Ij I

I'

5.3 Technical S ecification Chan es The technical specification (3.1.2.8) on borated water sources is changed to require 8500 gal of boric acid at a boron concentration between 6550 ppm and 6990 ppm.

The calculations discussed in section 3.5 justify the changes in volume and concentration of borated water.

The technical specifications for modes 1, 2, 3 and 4 were also changed to include a note for the BAST volume requirement stating that the volume of borated water is not required once the reactor is tripped and the borated water is injected into the RCS for boron concentration increase. The amount (8500 gal) of BAST ~ater is required only in modes 1 6 2 in anticipation of a reactor shutdown and subsequent increase in reactivity due to xenon decay and cooldown. For modes 5 and 6, a lower amount (900 gal) is required to counteract volume shrinkage. This value is conservatively increased to 5000 gallons. Therefore, technical specification 3.1.2.7 is changed to reflect the change in volume and concentration.

The rate at which the borated water is injected into the RCS is increased from 10 gpm to 34 gpm. The calculations discussed in section 3.5 justify the acceptability of the change to the higher flow rate.

4 IP

The requirement for heat tracing of the flow paths from the BAST is deleted and replaced with a requirement to monitor the ambient air temperature of the rooms containing the flow path components from the boric acid tank to the blending tee. The area temperature is to be greater than 63'F and is to be monitored once per 7 days' new flow rate surveillance requirement is introduced in T/S 3.1.2.2. Once per 18 months, the flow rate is to be verified to be greater than 34 gpm.

5.4 Modification to the Plant The flow diagram for the boron makeup portion of the CVCS depicting the normal and emergency boration paths is shown in figure 5.4-1 (Unit 1) and figure 5.4-2 (Unit 2). Since the flow rate requirements (34 gpm) are higher at the reduced boron concentration, calculations were performed to determine whether the normal boration flow path (1" line) could tolerate the increased flow.

The investigation showed high pressure drop at the control valve 1-QRV-411 (Unit 1) and 2-QRV-421 (Unit 2).

These valves will, therefore, be modified to accommodate the increased flow rate. Other modifications to install area temperature monitoring will be also performed.

It should be noted that the electric heaters in the BAST and steam heating of the boric acid batching tank will no longer be required for system functionality but they may be maintained for other operational considerations.

5.5 Im lementation The reduction in the boric acid concentration of the BAST will be implemented once the T/S changes are approved and the valve modifications discussed in the previous section are completed. The reduction in boron concentration can be accomplished while the units are operating since the emergency boration paths are still available.

I

'1 l

I(

6. 0 ~Summa Boration calculations were performed for Units l and 2.

Several cycles of operation was considered. The amount of borated water (at 6550 ppm) required to increase the RCS boron concentration to satisfy shutdown margin requirements was calculated. Also the required flow rate of the system was calculated.

I I

ill iI

'f

7.0 References

1) U.S. Borax tech data sheet IP-14 Boric Acid H>BO~ (Orthoboric Acid)

2) 'Personnel Computer D. C. Cook Operations Package user Manual, WCAP-10913

3) BAST Boron Concentration Reduction Project Calculation, FA-95-04

4) BAST Boron Concentration Reduction Project Calculation, FA-95-05

5) Technical Specification - Unit 1

6) Technical Specification - Unit 2

Table 4.4-1 Unit 1, Cycle 14 (BOL)

Feed & Bleed from BAST/Refill from RWST Reactor Trip from 100X RTP, Equilibrium Xenon Critical Boron - 1186 ppm RCS Tave ~F Required RCS Boron Source Boron Amount of Shutdown Concentration Concentration Source Boric Boron after Feed & ppm Acid Used Concentration Bleed/Refill Gal ppm ppm 547 1186 1186 6550(BAST) 0.0 350 1301 1376 2400(RWST) 12428 200 1318 1453 2400(RWST) 6820 68 1331 1485 2400(RWST) 3264 Total BAST volume used - 0.0 gal Total RWST volume used 22512 gal i(

Table 4.4-2 Unit 1, Cycle 14 (MOL)

Feed & Bleed from BAST/Refill from RWST Reactor Trip from lOOX RTP, Equilibrium Xenon Critical Boron - 624 ppm RCS Tave ~F Required RCS Boron Source Boron Amount of Shutdown Concentration Concentration Source Boric Boron after Feed & ppm Acid Used Concentration Bleed/Refill Gal ppm ppm 547 745 745 6550(BAST) 1383 350 932 1004 2400(RWST) 12428 200 958 1108 2400(RWST) 6820 68 979 1153 2400(RWST) 3264 Total BAST volume used 1383 gal Total RWST volume used 22512 gal II Table 4,4-3 Unit 1, Cycle 14 (EOL)

Feed & Bleed from BAST/Refill from RWST Reactor Trip from 100X RTP, Equilibrium Xenon Critical Boron 8 ppm RCS Tave ~F Required RCS Boron Source Boron Amount of Shutdown Concentration Concentration Source Boric Boron after Feed & ppm Acid Used Concentration Bleed/Refill Gal ppm ppm 547 57 57 6550(BAST) 504.

350 337 424 2400(RWST) 12428 200 393 572 2400(RWST) 6820 68 440 635 2400(RWST) 3264 Total BAST volume used 504 gal Total RWST volume used 22512 gal 0,

'I

Table 4.4-4 Unit 2, Cycle 10 (BOL)

Feed & Bleed from BAST/Refill from RWST Reactor Trip from 100X RTP, Equilibrium Xenon Critical Boron 1271 ppm RCS Tave ~F Required RCS Boron Source Boron Amount of Shutdown Concentration Concentration Source Boric Boron after Feed & ppm Acid Used Concentration Bleed/Refill Gal ppm ppm 547 1350 1350 6550(BAST) 1013 350 1424 1512 2400(RWST) 12264 200 1429 1579 2400(RWST) 6820 68 1429 1607 2400(RWST) 3264 Total BAST volume used - 1013 'gal Total RWST volume used 22348 gal Table 4.4-5 Unit 2, Cycle 10 (MOL)

Feed 6 Bleed from BAST/Refill from RWST Reactor Trip from 100X RTP, Equilibrium Xenon Critical Boron - 897 ppm RCS Tave ~F Required RCS Boron Source Boron Amount of Shutdown Concentration Concentration Source Boric Boron after Feed & ppm Acid Used Concentration Bleed/Refill Gal ppm ppm 547 1139 1139 6550(BAST) 2939 350 1284 1334 2400(RWST) 12264 200 1297 1414 2400(RWST) 6820

• 68 1307 1448 2400(RWST) 3264 Total BAST volume used 2939 gal Total RWST'olume used 22348 gal Table 4,4-6 Unit 2, Cycle 10 (EOL)

Feed & Bleed from BAST/Refill from RWST Critical Boron - 6 ppm RCS Tave ~F Required RCS Boron Source Boron Amount of Shutdown Concentration Concentration Source Boric Boron after Feed 6 ppm Acid Used Concentration Bleed/Refill Gal ppm ppm 547 185 185 6550(BAST) 1863 350 460 527 2400(RWST) 12264 200 512 667 2400(RWST) 6820 68 554 727 2400(RWST) 3264 Total BAST volume used 1863 gal Total RWST volume used 22348 gal Table 4,5-1 Unit 1, Cycle 14 (BOL)

Feed & Bleed from BAST/Refill from RWST Rea'ctor Trip from 100X RTP; Peak Xenon Critical Boron 930 ppm RCS Tave ~F Required RCS Boron Source Boron Amount of Shutdown Concentration Concentration Source Boric Boron after Feed & ppm Acid Used Concentration Bleed/Refill Gal ppm ppm 547 1179 1179 6550(BAST) 3037 350 1301 1370 2400(RWST) 12428 200 1318 1447 2400(RWST) 6820 68 1331 1480 2400(RWST) 3264 Total BAST volume used 3037 gal Total RWST volume used - 22512 gal 1

4

~

<<,-p

Table 4.5-2 Unit 1, Cycle 14 (MOL)

Feed 6 Bleed from BAST/Refill from RWST Reactor Trip from lOOX RTP, Peak Xenon Critical Boron - 350 ppm RCS Tave ~F Required RCS Boron Source Boron Amount of Shutdown Concentration Concentration Source Boric Boron after Feed & ppm Acid Used Concentration Bleed/Refill Gal ppm ppm 547 745 745 6550(BAST) 4411 350 932 1004 2400(RWST) 12428 200 958 1108 2400(RWST) 6820 68 979 1153 2400(RWST) 3264 Total BAST volume used 4411 gal Total RWST volume used 22512 gal

~ .

0

Table 4.5-3 Unit 1, Cycle 14 (EOL)

Feed & Bleed from BAST/Refill from RWST Reactor Trip from 100% RTP, Peak Xenon Critical Boron - 8 ppm RCS Tave ~F Required RCS Boron Source Boron Amount of Shutdown Concentration Concentration Source Boric Boron after Feed 6 ppm Acid Used Concentration Bleed/Refill Gal ppm ppm 547 369 369 6550(BAST) 3804 350 369 687 2400(RWST) 12428 200 393 815 2400(RWST) 6820 68 440 870 2400(RWST) 3264 Total BAST volume used 3804 gal Total RWST volume used 22512 gal I

0 l

III Rl 4 j

Table 4,5-4 Unit 2, Cycle 10 (BOL)

Feed 6 Bleed from BAST/Refill from RWST Reactor Trip from 100X RTP, Peak Xenon Critical Boron 1044 ppm RCS Tave OF Required RCS Boron Source Boron Amount of Shutdown 'Concentration Concentration Source Boric Boron after Feed & ppm Acid Used Concentration Bleed/Refill Gal ppm ppm 547 1350 1350 6550(BAST) 3841 350 1429 1512 2400(RWST) 12264 200 1429 1579 2400(RWST) 6820 68 1429 1607 2400(RWST) 3264 Total BAST volume used - 3841 gal Total RWST volume used - 22348 gal 1

t

Table 4.5-5 Unit 2, Cycle 10 (MOL)

Feed & Bleed from BAST/Refill from RWST Reactor Trip from 100X RTP, Peak Xenon Critical Boron 632 ppm RCS Tave OF Required RCS Boron Source Boron Amount of Shutdown Concentration Concentration Source Boric Boron after Feed 6 ppm Acid Used Concentration Bleed/Refill Gal ppm ppm 547 1139 1139 6550(BAST) 6017 350 1284 1334 2400(RWST) 12264 200 1297 1414 2400(RWST) 6820 68 1307 1448 2400(RWST) 3264 Total BAST volume used 6017 gal Total RWST volume used 22348 gal 0

Table 4.5-6 Unit 2, Cycle 10 (EOL)

Feed & Bleed from BAST/Refill from RWST Reactor Trip from 100X RTP, Peak Xenon Critical Boron - 6 ppm RCS Tave ~F Required RCS Boron Source Boron Amount of Shutdown Concentration Concentration Source Boric Boron after Feed" & ppm Acid Used Concentration Bleed/Refill Gal ppm ppm 547 518 518 6550(BAST) 5473 350 518 808 2400(RWST) 12264 200 518 928 2400(RWST) 6820 68 554 979 2400(RWST) 3264 Total BAST volume used - 5473 gal Total RWST volume used - 22348 gal I

Table 4.6-1 Unit 1, Cycle 14 (BOL)

Feed & Bleed from BAST/Refill from RWST Reactor Trip from lOOX RTP, Equilibrium Xenon Cri.tical Boron - 1186 ppm RCS Tave ~F Required RCS Boron Source Boron Amount of Shutdown Concentration 'Concentration Source Boric Boron after Feed & ppm Acid Used Concentration Bleed/Refill Gal ppm ppm 547 1552 1552 6550(BAST) 4736 350 1552 1685 2400(RWST) 12428 200 1552 1738 2400(RWST) 6820 68 1552 1761 2400(RWST) 3264 Total BAST volume used 4736 gal Total RWST volume used 22512 gal

Table 4.6-2 Unit 1, Cycle 14 (MOL)

Feed & Bleed from BAST/Refill from RWST Reactor Trip from 100X RTP, Equilibrium Xenon Critical Boron - 624 ppm RCS Tave ~F Required RCS Boron Source Boron Amount of Shutdown Concentration Concentration Source Boric Boron after Feed & ppm Acid Used Concentration Bleed/Refill Gal ppm ppm 547 1067 1067 6550(BAST) 5207 350 1067 1276 2400(RWST) 12428 200 1067 1360 2400(RWST) 6820 68 1067 1396 2400(RWST) 3264 Total BAST volume used 5207 gal Total RWST volume used 22512 gal h r Table 4.6-3 Unit 1, Cycle 14 (EOL)

Feed & Bleed from BAST/Refill from RWST Reactor Trip from 100X RTP, Equilibrium Xenon Critical Boron 8 ppm RCS Tave ~F Required RCS Boron Source Boron Amount of Shutdown Concentration Concentration Source Boric Boron after Feed & ppm Acid Used Concentration Bleed/Refill Gal ppm ppm 547 440 440 6550(BAST) 4578 350 440 747 2400(RWST) 12428 200 440 870 2400(RWST) 6820 68 440 923 2400(RWST) 3264 Total BAST volume used 4578 gal Total RWST volume used 22512 gal ll I l

g 4

Table 4,6-4 Unit 2, Cycle 10 (BOL)

Feed & Bleed from BAST/Refill from RWST Reactor Trip from lOOX RTP, Equilibrium Xenon Critical Boron - 1271 ppm RCS Tave ~F Required RCS Boron Source Boron Amount of Shutdown Concentration Concentration Source Boric Boron after Feed & ppm Acid Used Concentration Bleed/Refill Gal ppm ppm 547 1667 1667 6550(BAST) 5238 350 1667 1780 2400(RWST) 12264 200 1667 1827 2400(RWST) 6820 68 1667 1846 2400(RWST) 3264 Total BAST volume used - 5238 gal Total RWST volume used 22348 gal Table 4.6-5 Unit 2, Cycle 10 (MOL)

Feed & Bleed from BAST/Refill from RWST Reactor Trip from 100X RTP, Equilibrium Xenon Critical Boron - 897 ppm RCS Tave 'F Required RCS Boron Source Boron Amount of Shutdown Concentration Concentration Source Boric Boron after Feed 6 ppm Acid Used Concentration'pm Bleed/Refill Gal ppm 547 1494 1494 6550(BAST) 7498 350 1494 1634 2400(RWST) 12264 200 1494 1691 2400(RWST) 6820 68 1494 1716 2400(RWST) 3264 Total BAST volume used 7498 gal Total RWST volume used 22348 gal Table 4.6-6 Unit 2, Cycle 10 (EOL)

Feed 6 Bleed from BAST/Refill from RWST Reactor Trip from lOOX RTP, Equilibrium Xenon Critical Boron - 6 ppm RCS Tave ~F Required RCS Boron Source Boron Amount of Shutdown Concentration Concentration Source Boric Boron after Feed & ppm Acid Used Concentration Bleed/Refill Gal ppm ppm 547 554 554 6550(BAST) 5875 350 554 839 2400(RWST) 12264 200 554 956 2400(RWST) 6820 68 554 1006 2400(RWST) 3264 Total BAST volume used 5875 gal Total RWST volume used 22348 gal 4

Table 4.7-1 Unit 2 Reactor Trip from 100X hr., Equilibrium Xenon Xenon Decay Rate Reactivity Increase Required Boration

'4.

Cycle No./Burnup due to Xenon Decay - pcm/hr ppm/hr 10/BOL 145 19.

10/MOL 159 20.

10/EOL 183

Table 4.7-2 Unit 2 Reactor Startup at Peak Xenon Conditions BAST Boration Rate Cycle No./Burnup Reactivity Increase due Required Boration to Burnup pcm/hr ppm/hr 10/BOL 914 117 10/MOL 1079 127 10/EOL 1391 137 0

Fig 5.4-1 UNIT 1 CVCS (FLIjM DIAGRAMS 3.2 5131, 1 5129)

BORIC ACID TRANSFER BORIC ACID PUMP FILTER (PP-46) (QC-12)

Qt TO EMERGENCY BORATION NODE 1

I-CS487 PIPE I-QFC SEGMENT 4 CONTROL I-CS294 PIPE SEGHENT I FROM VOL TO CENTRIFUGAL CONTROL TANK CHARGING PUMPS 6'ODE 5 PIPE SEGMENT 2 PIPE SEGHENT 3 NODE 1-QR V-411 1-CS425N BORIC ACID BLENDER NODE (I-QP-21) 4 3 SYSTEM ENGINEERS J. SATIN SKETCHED . HANNIGAN

UNIT 2 CVCS (F LGV DIAGRAMS 12 5131, 2 5129)

BORIC ACID BORIC ACID TRANSFER FILTER PUMP (QC-12) (PP-46)

TO EHERGENCY BORA/ION NODE 6

2-CS486 2-QFC PIPE F LOg SEGMENT 8 CONTROL 2-CS294 PIPE SEGHENT S TO CENTRIFUGAL FROH VOL, CHARGING PUHPS CONTROL TANK PIPE NODE SEGHENT 6 10 PIPE NODE SEGMENT 7 6'-CS425S 2-QRV-421 BORIC ACID NODE NODE BLENDER 8 (2-QP-21>

SYSTEM ENGINEER< J. SATIN SKETCHED BYt B, HANNIGAN