ML20134F372
| ML20134F372 | |
| Person / Time | |
|---|---|
| Site: | Farley  |
| Issue date: | 02/03/1997 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20134F364 | List: |
| References | |
| NUDOCS 9702070406 | |
| Download: ML20134F372 (3) | |
Text
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UNITED STATES g
j NUCLEAR REGULATORY COMMISSION 2
WASHINGTON, D.C. 2006tM001 o%...../
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.123 TO FACILITY OPERATING LICENSE NO. NPF-2 AND AMENDMENT NO. 118 TO FACILITY OPERATING LICENSE NO. NPF-8 SOUTHERN NUCLEAR OPERATING COMPANY. INC.
JOSEPH M. FARLEY NUCLEAR PLANT. UNITS 1 AND 2 DOCKET NOS. 50-348 AND 50-364
1.0 INTRODUCTION
By letter dated November 15, 1996, the Southern Nuclear Operating Company, Inc., et al. (the licensee), submitted a request for changes to the Joseph M.
Farley Nuclear Plant, Units 1 and 2, Technical Specifications (TS). The requested changes would replaco the Containment System TS 3.6.2.2 for the Spray Additive System with a new Emergency Core Cooling System (ECCS) TS 3.5.6 for the ECCS Recirculation Fluid pH Control System. This action is to support a planned plant modification that would eliminate the containment spray additive system for Units 1 and 2.
The planned plant modifications will be made on Unit I during the refueling out49e in the spring of 1997 and on Unit 2 during the refueling outage in the spring of 1998.
2.0 EVALUATION The containment spray system (CSS) is an engineered safety feature system that functions to reduce reactor containment building pressure and temperature and the quantity of airborne fission products in the containment atmosphere during the initial injection and subsequent recirculation pnases after a loss-of-coolant accident (LOCA).
In the original design, liquid sodium hydroxide (NaOH) is added to the containment spray water to increase the pH in order to enhance absorption of the airborne fission product iodine, retain the lodine in the containment sump solution, minimize hydrogen production, and inhibit stress corrosion cracking of mechanical systems and components.
During the LOCA injection phase, the licensee has proposed to operate the containment spray system with a boric acid (2300 to 2500 ppm) solution from the refueling water storage tank (RWST), which has a pH of approximately 4.5.
Recent results, documented in Revision 2 of the Standard Review Plan (SRP),
Section 6.5.2, " Containment Spray As A Fission Product Cleanup System" addressing iodine removal, demonstrate that a low pH value would not affect the removal rate of the elemental and particulate iodine from the post-LOCA containment atmosphere, 9702070406 970203 PDR ADOCK 05000348 P
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' l These rates are determined by the first-order removal coefficients whicle, for elemental iodine removal by spray water and deposition on the containment walls, are independent of pH and therefore are not affected by elimination of the pH controlling additive. The same applies to the removal coefficients for particulate iodine, which is controlled by the hydrodynamic characteristics of the spray.
During the recirculation spray phase, coolant from the sump will contain dissolved iodine removed from the containment atmosphere during the injection phase.
In a radiation environment this iodine could be desorbed from the water and released to the containment atmosphere if the pH of the sump solution is too low. Since the long-term pH of the ECCS solution should be no less than 7.0, a chemical additive must be utilized to raise the pH of the solution in the containment building sump.
The licensee has proposed to control the pH above a level of 7.5 by the addition of the ECCS recirculation fluid pH control system. This is a passive system that consists of crystalline trisodium phosphate (TSP) stored in three baskets located in the containment sump g)rea with a total minimum TSP loading of approximately 10,000 pounds (185 feet The TSP baskets are designed to Seismic Category 1 standards and would be anJured to the filler slab at an elevation of 105 feet - 6 inches.
In accorduce with the proposed ECCS recirculation fluid pH control system TS, the licensee has proposed to verify, during each refueling outage, that the three storage baskets (a) are in place, (b) have maintained their integrity, and (c) are filled with TSP compound such that the level is between the indicated fill marks on the baskets.
The licensee plans to selectively leave in place or remove the components associated with the spray additive system. The blind flanges installed in the educator lines will meet ASME Code,Section III, Class 3 requirements. The containment spray piping will continue to meet the plant seismic and ASME Code,Section III, Class 3 requirments. The level and flow indicators and hand switches associated with these components will be removed from the main control board and replaced with cover plates.
The sump water must also be maintained in the alkaline condition in order to minimize corrosion of metallic surfaces. Chloride-induced stress corrosion cracking of austenitic stainless steel components is considerably reduced if the pH of the solution is maintained above 7.
During the injection phase, the TSP will begin to dissolve and the pH of the ECCS sump solution will be raised from 4.5 into tlee range of 7.5 to 10.5.
The surfaces sprayed during the injection will be resprayed during the recirculation phase with a high pH solution.
Control of the sump pH is also required to minimize hydrogen generation by l
corrosion of aluminum and zinc on galvanized surfaces and in the organic l
coatings on containment surfaces. The propo;ed change will affect the pH by l
introducing an initial pH of 4.5 (borated water spray) followed by a pH range
c.re of 7.5 to 10.5 using TSP. The proposed lowering of the pH for the spray will have no significant effect on the corrosion of aluminum as long as the pH remains above 4.5.
The corrosion of zine and zinc-based paints will produce hydrogen. However, the results of NRC-sponsored studies performed by Sandia National Laboratory demonstrate that with a controlled pH the corrosion rate will be low and no significant amounts of hydrogen would be produced. The operating conditions proposed by the licensee would preclude any unfavorable conditions.
TSP is being used in similar passive systems at several operating nuclear power plants. The proposed pH levels have been determined to hava no significant effect on the removal of elemental and particulate iodine f rom the post-LOCA containment atmosphere. Also, the potential for stress corrosion and hydrogen generation has been evaluated and dismissed as credible threats to the plant components by study of the pH levels.
The staff has reviewed the proposed changes and finds the proposed TS changes acceptable.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the State of Alabama official was notified of the proposed issuance of the amendments. The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
The amendments change 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 amendments involve 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 amendments involve no significant hazards consideration, and there has been no public coment on such finding (61 FR 66718 dated December 18,1996).
Accordingiy, the amendments meet 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 amendments.
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 amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
J. Zimmerman Date:
February 3, 1997
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