ML20094B736
| ML20094B736 | |
| Person / Time | |
|---|---|
| Issue date: | 11/24/1975 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| References | |
| NUREG-75-087, NUREG-75-087-06.1.3, NUREG-75-87, NUREG-75-87-6.1.3, SRP-06.01.03, SRP-6.01.03, NUDOCS 9511010238 | |
| Download: ML20094B736 (3) | |
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NUREG 75/087 lpa Ktog'o l
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4 STANDARD REVIEW PLAN l
OFFICE OF NUCLEAR REACTOR REGULATION l
l SECTION 6.1.3 POST-ACCIDENT CHEMISTRY REVIEW RESPONSIBILITIES Primary - Accident Analysis Branch (AAB)
Secondary - Materials Engineering Branch (MTEB) 1.
AREAS OF REVIEW The methods and procedures used to control the chemical composition of solutions recirculated within containment after design basis accidents (DBA) are reviewed to assure that adverse chemical reactions or inadequate solution mixing will not occur.
II.
ACCEPTANCE CRITERIA The procedures and methods which the applicant proposes to use to raise or maintain the pH of the solutions expected to be recirculated within containment after a DBA should be straight-forward and reliable. The chemistry of the post-accident environment in the containment should not result in significant deterioration of engineered safety features.
Ill.
REVIEW PROCEDURES The purpose of controlling the pH is to reduce the probability of chloride stress corrosion cracking leading to equipment failure or loss of containment integrityt and to ensure low volatility of dissolved radioiodines. These purposes are met by maintaining a high pHe at least 7 (Ref. I and 2), but not high enough to cause any substantial attack on aluminum fittings. A number of plants have used NaOH added to the containment spray solution, or solid trisodium phosphate placed in baskets on the containment lower level where it can dissolve in the recirculated water in the event of a DBA.
Guidance as to allowable pH histories should be obtained from the Materials Engineering Branch. At present, available information indicates optimum pH control consists of stabilizing pH between 7 and 8 within four hours (Ref. 3).
The reviewer examines the paths which solutions would follow in the containment from sprays and emergency core cooling systems to the sump, for both injection and recirculation phases e to verify that no areas accumulate very high or low pH solutions and that any assumptions regarding pH in the modeling of containment spray fission product removal are valid (see Standard Review Plan 6.5.2).
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EVALUATION FINDINGS The reviewer verifies that sufficient information has been provided and the review and cal-culations support conclusions of the following type, to be included in the staff's safety evaluation report:
"The methods and procedures for controlling the pH of solutions expected to be recircu-lated in containment following dtsign basis accidents have been found adequate. The proposed control provides assurance that the pH will be maintained at a level which
- minimizes the possibility of stress corrosion cracking of mechanical systems and components."
Y.
REFERENCES 1.
D. D. Whyte and L. F. Picone, " Behavior of Austenitic Stainless Steel in Post Hypothetical Loss of Coolant Environments," WCAP-7798-L (proprietary) Westinghouse Electric Corporation, November 1971.
2.
J. C. Greiss and G. E. Creek, " Design Considerations of Reactor Containment Spray Systems - Part X. The Stress Corrosion Cracking of Types 304 and 316 Stainless Steel in Boric Acid Solutions," ORNL-TM-2412, Oak Ridge National Laboratory, May 1971.
3.
R. Zavaccski, " Stress Corrosion Cracking a d pH for the Fort Calhoun Station,"
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- regulatory staff memorandum to K. Goller, April 7.1972.
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