ML17222A290

Safety Evaluation Supporting Amend 94 to License DPR-67

ML17222A290
Person / Time
Site:	Saint Lucie
Issue date:	06/06/1988
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML17222A289	List: ML17222A288 ML17222A290
References
NUDOCS 8806210278
Download: ML17222A290 (8)

Text

~y,s asst c>

0 Cy

• 0O lg 9

r

~ /p IP ++*++

i UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT N0.94 TO FACILITY OPERATIIIG LICENSE NO.

DPR-67 FLORIDA POWER 8( LIGHT COMPANY ST.

LUCIE PLANT UNIT NO.

1 DOCKET NO. 50-335

1.0 INTRODUCTION

By letter dated January 22, 1988, the Florida Power and Light Company (FPSL, the licensee) requested Technical Specification changes for the St. Lucie Plant, Unit No.

1.

The proposed changes would revise the requirements of the boric acid makeup system such that the boric acid concentration would be lowered, the water volume would be increased, and heat tracing of the circuits would no longer be required.

A minor decrease in sodium hydroxide concentration for the spray additive system was also proposed due to the above changes.

The decrease is necessary to ensure proper pH range of solutions under loss of coolant accident conditions.

The licensee also submitted Combustion Engineering report number CEN-353(F) entitled "Boric Acid Concentration Reduction Effort, Technical Bases and Operational Analysis," to serve as the technical basis for the proposed changes.

The licensee provided additional information by letter dated April 6, 1988.

The additional information did not, in any way, alter the staff's proposed no significant hazards consideration determination.

2. 0 DISCUSSION The proposed changes would modify the requirements for the boric acid makeup (BAMU) system, which is used to provide an adequate volume of borated water in the reactor coolant system (RCS) to assure that the shutdown margin is met in all modes of reactor operation.

The boron contained in the BAMU system is not taken credit for inreactivity control during transients and accidents.

Thus, the plant's accident analysis basis is not changed as a result of the proposed changes to the requirements of the BAMU system.

Presently, the minimum required boric acid concentration in water is 8 percent.

This requires the minimum water temperature to be approximately 105'F.

In

practice, the boric acid concentration has operational range, i.e.,

8 to 12 weight percent in this case.

Twelve weight percent boric acid concentration requires a water temperature of approximately 135'F.

If the minimum water temperature is not maintained for a given boric acid concentration, the boron in the boric acid wi 11 precipitate out of solution and solidify at the bottom of tanks and piping.

If the boron starts to precipitate, the BAMU system cannot be called upon to meet shutdown margin requirements.

Thus, the water c

ssosssos7s ssoso+

PDR ADOCK 05000335Ii P

~ temperature in the BAMU system is continually being maintained by electrical means called heat tracing.

The boric acid concentration can be lowered to an extent that heat tracing is not necessary, but other compensatory measures would also have to be taken.

The licensee proposed to delete the heat tracing requirement for the BAMU system.

In order to do so, the licensee proposed to decrease the required boric acid concentration and increase the required borated water volume to offset the reduced concentration.

The range of boric acid concentration is proposed to be reduced from 8.0 to 12.0 weight percent to 2.5 to 3.5 weight percent.

This reduction in boric acid concentration will prevent boron precipitation at ambient temperatures in the auxiliary building after the heat tracing is removed.

For

example, the minimum water temperature necessary to keep the boron in solution is only 50'F.

The range of borated water volume in a boric acid makeup tank is proposed to be increased from the approximate range of 6,600 - 7,900 gallons to the range of 8,350 - 13,300 gallons for Modes I through 4, and at least 3,650 gallons (assumes 2.5 weight percent concentration) for Modes 5 and 6.

The following Technical Specifications would be changed to effect the above described changes:

TS 3/4. 1.2. 1, Boration Systems

- Flow Paths

- Shutdown; TS 3/4.1.2.2, Boration System - Flow Paths - Operation; TS 3/4.1.2.7, Borated Water Sources-Shutdown; and TS 3/4 1.2.8, Borated Water Sources

- Operating.

The licensee also proposed to make a minor change to the sodium hydroxide (NAOH) concentration in the chemical storage tank, associated with the spray additive system.

The spray additive system is used during a large-break loss of coolant accident to maintain the pH range of post-accident solutions.

A lowering of the BAMU system boric acid concentration will change the pH of the solutions.

The licensee proposed to change the range from 30-32K to 28.5-30.5%

by weight NAOH solution.

The applicable Technical Specification is TS 3.6.2.2.a

- Spray Additive System.

3. 0 EVALUATION The proposed changes to the requirements for the BAMU system, the associated Technical Specifications

changes, and the calculated results associated with the Combustion Engineering report are evaluated below.

The NAOH concentration change is also addressed.

3.1 Boration Ca acit The methodology and analytical results to support the request for the Technical Specifications changes are documented in Combustion Engineering report number CEN-353(F),

and include two distinct series of calculations for the required and available boron concentration in the RCS to maintain a safe shutdown margin.

Both are employed at each time of interest in the plant cooldown conditions.

3. 1. I Evaluation of Anal sis for Re uired Boron Concentration According to the licensee, the analysis for the required boron concentration is based on the shutdown requirements of Branch Technical Position

5. I, entitled "Design Requirements for the Residual Heat Removal System" (SRP Section 5.4.7).

Specifically, the shutdown margin requirements are consistent with those specified in Technical Specifications

3. l. 1.1 and 3. 1.1.2 for operating Modes I through 4, and 5 through 6, respectively.

Reasonable core physics parameters were used to calculate the boron concentration required to be present in the RCS for the shutdown margins required by the Technical Specifications.

. In the analysis, the analytical and measurement uncertainties were included to ensure that the upper bound boron requirements were predicted.

The uncertainties include

-10% in scram worth,

+10% in moderator temperature

feedback,

+5% in Doppler reactivity feedback, and the time constant of 26 hours3.009259e-4 days <br />0.00722 hours <br />4.298942e-5 weeks <br />9.893e-6 months <br /> for xenon decay to maximize the xenon poison effect.

The staff has reviewed the licensee's analysis for required boron concentration and finds the analysis acceptable.

3.1.2 Evaluation of Anal sis for Available Boron Concentration The licensee specified that the calculated method to determine the available boron concentration is based on a steady-state mass balance for boron in the entire RCS.

It is assumed that the borated water added to the RCS is equal to the fluid volume contraction due to the cooldown while the pressurizer water level is maintained constant.

In the analysis (CEN-353(F)), various core condi-tions were considered to minimize the available boron reactivity effect.

The limiting core conditions identified and used in the analysis were (1) end-of-cycle conditions with initial RCS concentrations at zero ppm boron, (2) the core with the most reactive control rod fully stuck out, (3) plant power at 100% with 100% equilibrium xenon prior to initiation of plant shutdown, (4) a slow plant cooldown rate of 12.5'F/hr.,

(5) end-of-cycle moderator cooldown effects, and (6) beginning-of-cycle boron reactivity worths.

These assumptions are conservative with respect to minimizing the boron reactivity effects since assumptions (1) and (2) minimize the existing boron within the core and available scram worth, assumptions (3) and (4) maximize the xenon poison

effect, and assumptions (5) and (6) maximize the boration requirements due to moderator cooldown effects.

The use of a cooldown rate of 12.5'F/hr. is consistent with the plant test pro-cedures for the boron mixing test performed during a natural circulation test at another Combustion Engineering plant.

Included in CEN-353(F) is an analysis that demonstrates that the boration requirements for the fastest cooldown rate of 100'F/hr.,

as allowed by Technical Specifications, is bounded by the case when the cooldown rate was limited to 12.5'F/hr.

The report (CEN-353(F)) uses a conservative method to calculate the required boron concentration necessary to maintain the shutdown margin required by Technical Specifications 3.1.1. 1 and 3. 1.1.2 during a safe shutdown scenario.

A conservative RCS makeup scenario was used to demonstrate that the proposed boron concentration and volume requirements for the BAMU tanks will maintain the safe shutdown margins required by the Technical Specifications.

The staff agrees with the above licensee

analysis, showing that the available boron meets the required boron concentration requirements, and finds it acceptable.

3.2 Transient and Accidents The licensee addressed off-normal operations as follows.

As stated in Section 2.6 of CEN-353(F), credit is not taken for boron addition to the RCS from the boric acid makeup tanks for the purpose of reactivity control in the accidents analyzed in Chapter 15 of the plant's Final Safety Analysis Report.

The response of an operator, therefore, to such events as steam line break, overcooling, boron dilution, etc., will not be affected by a reduction in boric acid makeup tank (BAHT) concentration.

In particular, the action statements associated

~ with Technical Specification 3.1.1.2 require that boration be commenced at greater than 40 gallons per minute using a solution of at least 1720 ppm boron in the event that shutdown margin is lost.

Such statements are conservatively based upon the refueling water tank concentration and are therefore independent of the amount of boron in the BANTs. It should be noted that even after reducing the boron concentration in the BAHT, the minimum boron concentration in these tanks is higher than 1720 ppm.

Similar to the Technical Specification action steps in the event of a loss of shutdown margin, the operator guidance in Combustion Engineering's Emergency Procedure Guidelines (EPGs),

CEN-152, Rev. 2, are also independent of specific boron concentration within the boric acid makeup tanks.

Specifically, the acceptance criteria developed for the reactivity control section of the Functional Recovery Guidelines of CEN-152 are based upon a boron addition rate from the chemical and volume control system of 40 gallons per minute without reference to a particular boration concentration.

Therefore, the reduction in boron concentration within the boric acid makeup tanks has no impact on, and does not change, the guidance contained in the EPGs.

The staff agrees with the above licensee analysis and finds it acceptable.

3.3 ~di tl d ld The licensee proposed changing the concentration of sodium hydroxide in the chemical storage tank from a concentration range of 30K-32K to 28.5%-30.5%

by weight.

This change is necessary because of a reduction of the boric acid concentration in the boric acid makeup tanks.

The staff did not audit the licensee's calculations to confirm the ling concentration reduction, nor did the staff perform independent calculations to confirm the reduction.

The staff agrees that a slight reduction is in order.

The licensee's discussion of this matter in the April 6, 1988 submittal is appropriate and the proposed 15%

reduction appears reasonable.

On this basis, the change is acceptable.

3.4 Technical S ecification Chan es The Technical Specification changes and the reasons for their acceptability are provided blow.

Technical S ecification 3/4.1.2.1 Boration S stems Flow Paths - Shutdown The proposed change to the Technical Specifications eliminates the requirements for heat tracing of the BANU system.

The design purpose of heat tracing of the BANU system is to maintain the temperature of fluid in the BANU tanks and the boration flowpaths high enough to prevent the boric acid from precipitating.

The proposed changes to TS 3/4.1.2.7 and TS 3/4.1.2.8 (explained later) reduce the concentration in the BANU tanks to a maximum concentration of 3.5 weight percent boric acid, which will not precipitate at a borated water temperature higher than 55'F.

Chemical analyses have shown that a 3.5 weight percent solution of boric acid will remain dissolved (i.e., will not precipitate or "plate out") at solution temperatures above 50'F.

The proposed changes also include a surveillance requirement to ensure that the borated water source is operable by verifying that the temperature in the BANU is above 55'F whenever the auxiliary building temperature is below 55'F.

The 55'F requirement provides a 5'F margin, since the boron will remain in solution down to 50'F.

Consistent with the new surveillance requirement

above, the old surveillance requirement to verify the flow path temperature above the temperature limit line on Figure 3.1-1 will be deleted.

4

. The licensee specified that the auxiliary building temperature will be monitored at the Boric Acid Makeup Station.

Therefore, the Technical Specification change is acceptable.

Technical S ecification 3/4.1.2.2 Flow Paths - 0 eratin Currently, the Technical Specifications require two out of the following three flow paths for boron injection into the RCS:

(1) a BAMU tank gravity feed path and associated heat tracing, (2) a BANU tank path via a boric acid makeup pump and associated heat tracing, or (3) flow path from the refueling water tank.

The proposed change requires a flow path from any credited source of water (refueling water storage tank and/or BAMU tank (or tanks)) to be operable.

These changes are consistent with the assumptions used in CEN-353(F).

The proposed change to the Technical Specifications eliminates the requirement for heat tracing of the BANU system.

As in Technical Specification 3/4.1.2.1, deletion of the requirement to heat trace the BANU system is consistent with the ability of the boric acid to remain in solution at temperatures above 50'F.

The proposed change includes a surveillance requir ement to assure that the borated water source is operable by verifying that the temperature in the BAMU is above 55'F whenever the auxiliary building temperature is below 55'F.

As in Technical Specification 3/4.1.2.1, the old surveillance requirement for temperature verification of the flow. path from the boric acid makeup tanks has been deleted.

The Technical Specification change is. acceptable.

Technical S ecification 3/4.1.2.7 Borated Water Sources

- Shutdown The existing Technical Specification requires that one of the two BANU tanks and its associated heat tracing be operable with the tank containing 8 weight percent boron and a minimum content of 1660 gallons.

The proposed changes will delete the heat tracing operability requirement, lower the boric acid concentration to a range of 2.5 to 3.5 weight percent, change the minimum BAMT content to 3650 gallons (assumes a minimum of 2.5 weight percent boric acid concentration),

and modify the surveillance requirement to verify that the BAMU tank temperature is above 55'F whenever the auxiliary building temperature is below 55'F.

As in Technical Specification 3/4.1.2. 1, the old surveillance requirement to verify the temperature of the flow path from the boric acid makeup tanks has been deleted.

These changes are consistent with the analysis presented in CEN-353(F), which demonstrates adequate boration capability at the lower boric acid concentrations and the ability for boric acid to remain in solution at these concentrations at temperatures above 50'F.

Therefore, the Technical Specification changes are acceptable.

Fi ure 3.1-1 (for 0 eratin Modes 1 throu h 4)

The existing figure specifies the minimum required BANU water volume and temperature as a function of stored boric acid concentration for the various plant operating modes.

The existing figure is applicable to any one of the two BANU tanks, each having a maximum capacity of 9700 gallons (only 9450 gallons assumed to be useable).

The revised figure specifies the minimum required water volume (contained in one or both BANU tanks) as a function of boric acid concentration in the BAMU tank.

This curve was generated in report CEH-353(F) for a minimum refueling water tank boron concentration of 1720 ppm boron.

This curve conservatively bounds BANU tank minimum required water volumes for conditions when the refueling water tank boron concentration is greater than 1720 ppm (a Technical Specification requirement).

The range of

~'

boron concentration in the BANU tank will be reduced from 8.0 to 12.0 weight percent boric acid to 2.5 to 3.5 weight percent.

The upper range of the required borated water volume will increase from 7,900 gallons (8 weight percent) to 13,300 gallons (2.5 weight percent).

The lower range of the required borated water volume will increase from 6,600 gallons (12 weight percent) to 8,350 gallons (3.5 weight percent).

Tl>e revised Figure 3.1-1 is consistent with the analytical results of CEN-353(F) for plant conditions at Operating Nodes 1 through 4 to maintain the required safe shutdown margin.

The temperature versus BANT concentration curve has been removed from the Technical Specifications since it is no longer required.

The revised figure is acceptable.

Technical S ecification 3.1.2.8 Borated Water - 0 eratin The current Technical Specification requires that at least one BANU tank and its associated heat tracing be operable with the contents of boric acid in the tank to be consistent with the existing Figure 3.1-1.

The existing Figure 3.1-1 specifies the volume of boric acid of 7,900 gallons at a minimum concentration of 8.0 weight percent to be maintained in the BANU tank.

The proposed changes are to provide a

new range of boric acid concentra-tion of 2.5 to 3.5 weight percent for one or both of the BAMU tanks.

The revised volumes of Figure 3.1-1 raise the minimum water volume to 8,350 gallons.

Oeletion of the requirement to heat trace the BANU system is consistent with the ability to maintain 2.5 to 3.5 weight percent boric acid in solution at tempera-tures above 50'F.

The revised surveillance requirements delete verifying the BANU tank temperature unless the auxiliary building temperature is below 55'F.

For conservatism, this verification of temperature is done more frequently (24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> versus 7 days) and the old surveillance requirement has been deleted.

Since the borated water source can be made up of one BANU tank (1A or 1B) per the proposed Technical Specifications, and considering that one tank has a

maximum capacity of 9700 gallons, a minimum concentration of boric acid needs to be specified.

The minimum weight percent boric acid is specified as 3.2 weight percent under these conditions.

The proposed Technical Specification changes are acceptable.

Bases - 3/4 1.2 Boration S stems The Technical Specifications define the required components for the.boron injection system, which ensures that negative reactivity is available during each mode of operation, and define the boric acid concentration and volume requirements for the BANU tank and refueling water tank (RMT).

Since heat tracing will no longer be required, the deletion of the heat tracing system, as part of the boron injection system components, will be deleted from the bases statements.

This change is acceptable.

The permissible range of boric acid concentration and associated water volumes needs to be changed in the bases statements.

The bases statement for Nodes 1

through 4 will now read "This range is bounded by 8,350 gallons of 3.5 weight percent (6119 ppm boron boric acid from the 8AIITs and 14,000 gallons of 1720 ppm borated water from the RIIT to 13,300 gallons of 2.5 weight percent (4371 ppm boron) boric acid from the BANTs and 9,000 gallons of 1720 ppm borated water from the RWT."

The Combustion Engineering report, Table 2-34,

~

~

age 2-66, specified 7 317.1 gallons of 3.5 weight percent boric acid and

$,271.2 gallons of 2.( weight percent boric acsd for Nodes 1 through 4.

~ The relationship between these values and the Technical Specification values is explained on page 2-21 of the Combustion Engineering report.

Each value was rounded up to the nearest 50 gallons and 1,000 gallons was added to provide water for auxiliary spray for RCS depressurization purposes.

For example, 12,271.2 gallons was rounded to 12,300 gallons, and adding an additional 1,000 gallons yields 13,300 gallons.

Therefore, the proposed changes are acceptable.

The base statement for Modes 5 and 6 specifies 3,650 gallons of 2.5 to 3.5 weight percent boric acid solution.

The 3,650 gallon calculation in the Combustion Engineering report assumed 2.5 weight percent boric acid solution.

Thus, any concentration greater than 2.5 weight percent, up to and including 3.5 weight percent, is conservative.

In addition, the 3,650 gallon value is made up of the following components.

The Combustion Engineering report on page 2-ft specifies that 3,114.8 gallons of 2.5 weight percent boric acid solution is the required value per analysis.

An additional 500 gallons was added to this figure for conservatism.

Finally, the 3,614.8 gallon number was rounded up to the nearest 50 gallon value of 3,650 gallons.

Therefore, the proposed changes are acceptable.

Technical S ecification 3.6.2.2 S ra Additive S stem The current Technical Specification requires a sodium hydroxide (NAOH) concentration range of 30-32% by weight in the spray additive tank.

Because of the boric acid concentration reduction, the new NAOH concentration range is 28.5-30.5%

by weight.

The licensee's discussion supports this new range.

It should be noted that the chemical storage tank discussed in the above evaluation is the same as the spray additive tank discussed in the Technical Specification.

Thus, the proposed change is acceptable.

3.5

SUMMARY

The staff has reviewed the proposed changes to the St. Lucie Plant, Unit No.

1 Technical Specifications involving reduction in boric acid concentration and volume requirements for the BAMU system, and deletion of the requirement for heat tracing in the BAMU system.

The staff concludes that the proposed changes are acceptable since the changes of boric acid requirements for the BAMU system do not reduce shutdown margin, below the required values specified in Technical Specifications 3.1.1.1 and 3.1.1.2.

Because the concentration of boric acid in the BAMU system has been reduced to a value which will not cause precipitation at ambient temperatures for the BAMU system, heat tracing'n the BAMU system is not required.

The proposed Technical Specifications are acceptable since they are consistent with the proposed changes to require-ments for the BAMU system and are supported by the analytical results.

The staff has also reviewed the proposed Technical Specification change in sodium hydroxide concentration range for the chemical storage tank.

The new range is reasonable and is acceptable.

'NVIRONMENTAL CONSIDERATION This amendment involves a change in the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 or a

change to a surveillance requirement.

The staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that

~ there is no significant increase in individual or cumulative occupational radiation exposure.

The Commission has previously published a proposed finding that the amendment involves no significant hazards consideration and ther e has been no public comment on such finding.

Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).

Pursuant to 10 CFR 51.22(b),

no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.

CONC LUS ION Ne have concluded, based on the considerations discussed above, that (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed

manner, and (2) such activities will be conducted in compliance with the Commission's regulations, and the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.

Date:

June 6, 1988 Princi al Contributor:

E. Tourigny