ML20198F469
| ML20198F469 | |
| Person / Time | |
|---|---|
| Site: | Waterford  |
| Issue date: | 12/21/1998 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20198F466 | List: |
| References | |
| NUDOCS 9812280129 | |
| Download: ML20198F469 (3) | |
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4 UNITED STATES s
j NUCLEAR REGULATORY COMMISSION
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WASHINGTON, D.C. 30EeH001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.147' TO FACILITY OPERATING LICENSE NO. NPF-38 ENTERGY OPERATIONS. INC.
WATERFORD STEAM ELECTRIC STATION. UNIT 3 4
DOCKET NO. 50-382
1.0 INTRODUCTION
- By application dated August 12,1998, Entergy Operations, Inc. (the licensee), submitted a request for changes to the Waterford Steam Electric Station, Unit 3 ( Waterford 3), Technical Specifications (TSs). The requested changes would increase the maximum boron concentration in the Safety injection Tanks (SITS) and the Refueling Water Storage Pool (RWSP) from 2300 ppm to 2900 ppm.
The proposed change will allow operators greater flexibility for refueling activities without challenging the minimum boron concentration necessary to ensure adequate shutdown margin in the event of an accident. The licensee has considered several factors associated with the proposed change including: corrosion and iodine retention concerns associated with a pH decrease in the sources of borated water, volume changes in the Boron Acid Makeup Tank (BAMT), pH control of recirculated water with Trisodium Phosphate Dodecahydrate (TSP), and timing limits for Emergency Core Cooling System (ECCS) injection.
2.0 EVALUATION The licensee has requested a change to TS 3.1.2.8,3.5.1,3.5.4, Figure 3.1-1 and Bases 3/4.5.2, The change entails increasing the maximum boron concentration in the SITS and RWSP from 2300 ppm to 2900 ppm.
The licensee has analyzed the increase of boron concentration for the possibility of corrosion and iodine retention concems during a loss of coolant accident (LOCA). In the event of an accident, the reactor coolant system (RCS) will experience a decrease in pH due to the injection of a higher concentration of boric acid into the system from the SITS. However, the increased acidity in the RCS is short-lived. As the borated water flows through the core and out into containment through the pipeline break, it mixes with the TSP contained in open baskets located on the containment floor. During the ECCS recirculation phase, the borated water is pumped through the core at a pH above 7.0 due to the TSP addition. By maintaining the borated water at a pH greater than 7.0, the chances of dissolved radioactive iodine escaping into the containment and subsequently released into the environment are minimized.
9812280129 981221 PDR ADOCK 05000382 P
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The failures due to corrosion are a long term process and therefore, the carbon steel components in containment will not be affected by the brevity of this decreased pH of borated water. The boric acid in the SITS and RWSP is a relatively weak acid due to the low temperatures and pressures present in these systems. In addition, these systems are lined with austenitic stainless steel such that an increase in boron concentration will not result in an increase of corrosion problems.
Figure 3.1-1," Required Stored Boric Acid Volume as a Function of Concentration," defines the acceptable regions of operation for the available volume in the BAMT as a function of the boric acid concentration. As indicated in the figure for the RWSP concentration of 2300 ppm, the volume needed in the BAMT to ensure adequate shutdown margin increases with decreasing boric acid concentration. The plot for an RWSP concentration of 2900 ppm will lie below tra plot for a boric acid concentration of 2300 ppm indicating that, for each boric acid concentraten in the BAMT, less volume from the BAMT is needed to ensure adequate shutdown margin due to the increased availability of boron. The licensee proposes to use the plot of the RWSP boric acid concentration of 2300 ppm as the limit for boric acid concentrations greater than and equal to 2300 ppm. This change conservatively bounds the proposed increase of boric acid concentration of 2900 ppm in the RWSP.
The licensee's analysis assumes an average sump boron concentration of 3011 ppm for maximum volumes from each of the following water sources: RWSP, SITS, RCS and BAMT.
The RWSP and SITS are assumed to each have a boron concentration of 2949 ppm, the RCS of 2500 ppm, and the BAMT of 6125 ppm. Based on these assumptions, the amount of TSP currently available in the sump bounds the proposed boron concentration change of 2900 ppm to ensure that a minimum borated water pH of 7.0 is still attainable in the event of an accident.
The precipitation of boron out of solution during ECCS is a concern since the deposition of the material on fuel cladding can cause cooling channels to be blocked. The blockage of the cooling channels will lead to a reduction in heat transferred from the fuel and increase the Ilkelihood of radioactive material release to the environment. The licensee's previous analysis assumed the following boron concentrations: RWSP, SITS, and RCS each at 3000 ppm and the BAMT at 6125 ppm. Based on these assumptions, the solubility limit was set at 27.6 wt%
corresponding to an RCS pressure of 14.7 psia at RCS saturation temperature. The minimum precipitation time with no flushing flow was determined to be 7.87 hours0.00101 days <br />0.0242 hours <br />1.438492e-4 weeks <br />3.31035e-5 months <br />. The effective flushing flow was calculated at 1.4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> but conservatively set at 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. The effective flushing flow time assures that the hot leg steam velocity drops below the critical gas velocity for the onset of entrainment. The maximum start time for simultaneous injection is conservatively set at four hours, which is prior to the time when the assumed HPSI flow to one side of the core exceeds the core boil off rate. The minimum required HPSI flow to either side of the core to avoid precipitation was determined to be 275 gpm or a total of 550 gpm (assuming a 50% flow split between hot and cold sides). The HPSI flow currently available is 777 gpm at 0 psia. Based on the analysis presented, the increased concentration of boron to 2900 ppm in the SITS and RWSP will not lead to boron precipitation during a LOCA.
Based on its evaluation, the staff finds that the licensee has adequately addressed the following consequences to changes in the boroa concentration in the SITS and RWSP: corrosion and iodine retention concerns associated with a pH decrease in the sources of borated water, volume changes in the DAMT, pH control of recirculated water with TSP, and timing limits for the ECCS injection. These concerns have been addressed and analyzed with results
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- c indicating that the capability to ensure adequate shutdown margin in the event of a LOCA is not challenged. The staff concludes, therefore, that the increased concentration of boron in the SITS and RWSP from 2300 ppm to 2900 ppm is acceptable. The corresponding changes in Bases are also acceptable.
3.0 STATE CONSULTATION
in accordance with the Commission's regulations, the Louisiana State official was notified of the proposed issuance of the amendment. The State official had no comments.
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4.0 ENVIRONMENTAL CONSIDERATION
The amendment changes a requirement "ith respect to installation or use of a facility d
component located within the restricted area as defined in 10 CFR Part 20 and changes surveillance requirements. The Nuclear Hegulatory Commission 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 (63 FR 56249). 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.
5.0 CONCLUSION
The Commission has 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, (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: C. Lauron, EMCB/DE Date: December 21, 1998 I
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