ML18010A744
| ML18010A744 | |
| Person / Time | |
|---|---|
| Site: | Harris  |
| Issue date: | 09/02/1992 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML18010A743 | List: |
| References | |
| NUDOCS 9209100146 | |
| Download: ML18010A744 (5) | |
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UNITEDSTATES CLEAR REGULATORY COMMISSIO WASHINGTON, D. C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.
30 TO FACILITY OPERATING LICENSE NO. NPF-63 CAROLINA POWER 5 LIGHT COMPANY SHEARON HARRIS NUCLEAR POWER PLANT UNIT 1 DOCKET NO. 50-400
- 1. 0 INTRODUCTION By letter dated March 10,
- 1992, as revised Hay 11,
- 1992, and July 10,
- 1992, the Carolina Power
- 5. Light Company (CP&L or the licensee) submitted a request for changes to the Shearon Harris Nuclear Power Plant, Unit 1, (Shearon Harris) Technical Specifications (TS).
These changes would:
(1) increase the limits for boron concentration in the refueling water storage tank (RWST) and the safety injection system (SIS) accumulators from 2000-2200 ppm to 2400-2600 ppm (TS Sections
- 3. 1.2.5.b.2,
- 3. 1.2.6.b.2, 3.5. l.c, 3.5.4.b and Figure
- 3. 1-1, Shutdown Margin versus RCS (reactor coolant system)
Boron Concentration; (2) increase the specified volume (level) of NaOH in the spray additive tank (SAT) from 2736-2912 gallons to 3268-3964 gallons and add the level range, 92-96 percent (TS Section 3.6.2.2.a.);
(3) change the minimum level in the boric acid tank (BAT) from 60 percent (21,400 gallon) to 74 percent (24, 150 gallons) in Modes 1-4, and from 17 percent (7100 gallons) to 21 percent (6650 gallons)
(the minimum volume for the 21 percent indicated tank level is lower than the volume for the previous 17 percent indicated tank levels because of increased uncertainties applied to the indicated leve'1 of 21 percent) in Modes 5-6 (TS Sections
- 3. 1.2.5.a.
1 and 3. 1.2.6.a. 1);
and (4) provide for specification of the boron concentration in the RCS and refueling canal via the Core Operating Limits Report (COLR),
(TS Section 3.9. l.a and associated ACTION Statements 6.9. 1.6. 1 and 6.9. 1.6.2).
Additionally, the proposed changes were to standardize and clarify the TS wording used for the BAT, the safety injection accumulator, and the
- SAT, and to clarify the relationship between volume and level in the TS Bases.
2.0 BACKGROUND
Currently the operation of the Shearon Harris plant requires the use of wet annular burnable absor bers (WABAs) and other burnable poisons (BPs).
By increasing the boron concentrations in the RWST and the safety injection accumulators, as well as adjusting BAT and SAT levels, the WABAs and many of the other BPs can be eliminated.
Similar changes have previously been approved by the NRC for a number of other plants (Surry and Indian Point 3).
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- 3. 0 EVALUATION The licensee has evaluated the effect of the proposed increased boron concentration limits on each of the Chapter 15 transients presented in the Shearon Harris FSAR.
Increasing the maximum boron concentration in the RWST to 2600 ppm required reanalysis of the boron dilution accident, pos't-LOCA hot leg to cold leg switch over time, and post-LOCA containment sump pH after the RWST water mixes with RCS coolant and other water volumes.
In the letter dated July 10, 1992, the licensee stated that changing the RWST boron concentration does not affect the calculation of peak cladding temperature or the percentage of zirconium-water reaction analyzed in FSAR section 15.6.5.
In the relatively short period covered by this calculation, the negative reactivity needed to shutdown power production in the core is provided by other means:
void formation for, large breaks and control rod insertion for small breaks.
Reanalysis of the boron dilution accident for Modes 3, 4, and 5 resulted in a
slightly revised TS Figure 3. 1-1 to ensure a minimum of 15 minutes for operator action prior to a loss of shutdown margin in a dilution accident and to ensure that all shutdown margin criteria satisfy all TS Bases.
CP&L has found that the current analysis result for the inadvertent boron dilution event in Nodes 1, 2, and 6 remains valid.
- Also, an inadvertent boron dilution event in Node 6 is precluded by administrative procedures.
The boron dilution event is sensitive to core design and is evaluated by CP&L in the reload safety evaluation (RSE) for each cycle.
A reanalysis of the post-LOCA cold leg to hot leg switchover time to ensure protection against boron precipitation (with 4 weight percent margin) in the RCS resulted in a change from 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to 6.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />.
This change is attributed, in part, to an improved, more conservative plant-specific model and partially to the increase in boron concentration.
The cold leg to hot leg switchover time and the NaOH level are independent of the fuel design and are not reevaluated in the RSg unless necessitated by "other; non-fuel'rel'ated,. modifications.,
Reanalysis of the post-LOCA containment sump pH after mixing with RCS coolant and other water volumes showed that the NaOH volume in the SAT must be increased to maintain a
sump pH between 8.5 and 11.0.
This pH range minimizes iodine evolution and chloride and caustic stress corrosion in the components
and systems needed for post-LOCA operations (TS Bases 3/4. 1.2).
To maintain sump pH between 8.5 and 11.0, the licensee proposed to increase the volume of the NaOH solution in the SAT to the range of 3268-3964 gallons.
This range is 92-96 percent of the indicated level (about 50X of the tank's full capacity).
These changes are presented in TS Section 3.6.2.2.a.
The tank and structural supports were seismically qualified based on a full tank assuming a
NaOH concentration of 30 percent and remain qualified with the proposed increase of NaOH solution volume in the tank.
The higher boron concentration in the RCS causes a very small increase in tritium production in the coolant but does not contribute significantly to offsite doses or to personnel doses.
The post-LOCA hydrogen production may increase by about 3.5 percent because of higher boron concentration but this increase is considered insignificant.
The minimum and maximum boron concentration (2400 ppm-2600 ppm) required for the SIS accumulators is consistent with that required for the RWST and is given in TS Section 3.5. l.c for Modes 1 and 2, and Mode 3 if RCS pressure is greater than 1000 psig.
The minimum volume of boric acid in the BAT for Modes 1 to 4 was increased from 21,400 gallons to 24, 150 gallons based on a minimum analytical limit together with the total unmeasurable channel uncertainty.
The proposed new tank level, 74 percent, is based on the minimum analytical limit together with total indicated channel uncertainty.
These changes are presented in TS Section 3. 1.2.6.a. 1.
The tank and structural supports were seismically qualified assuming the tank was filled.
The minimum volume of boric acid in the BAT for Modes 5 and 6 was decreased from 7,100 gallons to 6650 gallons based on a minimum analytical limit together with the unmeasurable ch'annel uncertainty.
The proposed new tank
- level, 21 percent, is based on the minimum analytical limit together with total uncertainty in the indicator channel used for surveillance.
These changes are presented in TS Section 3. 1.2.5.a. l.
Although the proposed new specifications have margin for anticipated variation of future core designs, the shutdown margin requirements for Modes 5 and 6 will be verified each cycle using approved methodology.
CP&L has determined that:
(1) the higher boron concentration in the
and RCS will have no adverse affect on the stainless steel container material, despite the slightly lower pH level at 2600 ppm than at 2200 ppm; (2) there is no danger of boron precipitation; and (3), corrosion of carbon steel by leakage of the more highly borated water will
not be increased significantly because the pH change is small and remains in the range where the corrosion rate is nearly independent of pH level.
- Also, although the volume of NaOH solution is increased, the concentration will not change.
Therefore, equipment integrity remains unchanged.
To ensure a Keff equal or less than 0.95 during refueling operations (Mode 6),
as required in TS Section 3.9. l.a, the minimum boron concentration as calculated each cycle will be provided in the COLR.
The TS will require the more restrictive of either the value in the COLR or 2000 ppm.
4.0
SUMMARY
The staff has reviewed the effects of the proposed increased boron concentration limits on the Chapter 15 transients, the time to switchover between cold and hot leg recirculation following LOCA, the post-LOCA containment sump pH, and the equipment qualification requirements, and concludes that all pertinent safety criteria are satisfactorily met.
Therefore, based on the above, the licensee's request to increase the specified boron concentration from 2000-2200 ppm to 2400-2600 ppm in the RWST and SIS accumulators; increase the specified volume of NaOH solution in the SAT from 2736-2912 gallons to 3268-3964 gallons and to add the indicated level range of 92-96 percent is acceptable.
Also, the licensee's request to change the level of the BAT from 60 percent (21,400 gallons) to 74 percent (24, 150 gal'lons) in Modes 1-4, and from 17 percent (7100 gallons) to 21 percent (6650 gallons) in Modes 5 and 6 and reference the COLR for determining the necessary RCS and refueling canal boron concentrations is acceptable.
5.0 STATE CONSULTATION
In accordance with the Commission,'s regulations, the State of North Carolina official was notified of the proposed issuance of the amendment.
The State official had no comments.
- 6. 0 ENYIRONMENTAL CONSIDERATION The amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20.
The NRC 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 issued a proposed finding that the amendment involves no significant hazards consideration, and there has been no public comment on such finding (57 FR 13128 and 57 FR 34580).
Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9) and (c)(10).
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.
7.0 CONCLUSION
The Commission has concluded, based on the considerations discussed
- above, that:
(I) 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.
Principal Contributor:
H. Balukjian Date:
September 2,
1992