ML19289C994
| ML19289C994 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 01/12/1979 |
| From: | Reid R Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19289C995 | List: |
| References | |
| NUDOCS 7901290089 | |
| Download: ML19289C994 (7) | |
Text
UNITED STATES j
NUCLEAR REGULATORY COMMisslON y-WASHINGTON. D. C. 20555 s.._...,
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 2 TO FACILITY OPERATING LICENSE NO. DPR-51 ARKANSAS POWER AND LIGHT COMPANY ARKANSAS NUCLEAR ONE, UNIT N0. 1 00CXET NO. 50-313 Introduction By letters dated June 17, July 5, and December 6,1977, Arkansas Power and Light Company (the licensee) proposed an amendment to Section 3.3 and Tables 4.1-1 and 4.1-3 of the Technical Specifi-cations (TS) and changes to the Reactor Building Spray System (RBSS) for Arkansas Nuclear One, Unit 1 (ANO-1). These proposed changes would allow the deletion of the sodium thiosulfate from the RBSS, would allow the installation of an orifice in the line between the Sodium Hydroxide Tank (SHT) and the Borated Water Storage Tank (BWST),
and would specify a band of operating limits for the SHT and BWST water levels and chemical concentrations. The licensee has provided the basis for and additional infomation on this proposed amendment in his letters of June 17, December 6,1977, and December 13, 1978.
Discussion By letter dated May 8,1975, Babcock & Wilcox (B&W) identified a defi-ciency in the design performance of the RBSS of ANO-1. The letter stated that a computer analysis of the RBSS indicated that the SHT, sodium thiosulfate tank (STT), and BWST do not drawdown together under the calculated accident conditions. These tanks, which are a part of the RBSS, provide the boric acid and the chemical additives for the Emergency Core Cooling System (ECCS) and the RBSS during a loss-of-Coolant Accident (LOCA). Subsequently, the licensee submitted Unusual Event Report (UER) 50-313/75-2, dated June 25, 1975, based on the above B&W 1etter. The licensee stated that a computer analysis would be performed based on the ANO-1 as-built piping configuration.
By letter dated September 3,1975, the licensee submitted the results of the reanalysis of the uneven drawdown of RBSS tanks.
In a letter dated February 12, 1976, the licensee submitted a nonproprietary report, in support of a TS change, which contained data on a computer simulated drawdown test of the tanks in the ANO-1 RBSS. The licensee concluded in their September 3,1975 letter, that the perfomance of the as-built ANO-1 RBSS was adequate.
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In addition, by letter dated October 7, 1975, the licensee requested changes to Specifications 3.3.l(H) and 3.8.4(B) for ANO-1. These specifications specify the liquid level and chemical composition for the BWST, SHT and STT. The proposed specifications were to correct the present specifica-tions which refer only to minimum or specific values and to lower the con-centrations in the SHT and STT. A proprietary technical report, supporting these changes, was submitted in a letter dated December 22, 1975; a nonpro-prietary version of this report was submitted February 12, 1976.
We reviewed and evaluated the above data provided by,the licen--
see in his letters of September 3, October 7 and December 22, 1975, and February 12, 1976. He concluded that (1) additional information was needed from the licensee to complete our evaluation and (2) our initial analy-sis indicated that two problems could result frcm the uneven drawdown of and the proposed chemical composition specifications on the BWST,.SHT, and STT.
The two problems were that the potential consequences of the LOCA may exceed the guidelines of 10 CFR Part 100,and the chemistry of the spray water during the LOCA may be outside acceptable limits. The licensee was requested, in letters dated October 18 and November 19, 1976, to submit additional infor-mation to allow us to complete our review and evaluation of the RBSS.
The data and proposed specifications provided by the licensee in his letters dated June 27, July 5, and December 6,1977,were in response to our request for additional information to continue our review and evaluation of the RBSS. The proposed technical pecifications, the proposed installation of an orifice in the line betwen the SHT and BWST and the proposed de-
.letion of the STT are to correct deficiencies in the RBSS that might result in uneven drawdown of the tanks and unacceptable spray water chemistry dur-ing a LOCA.
Evaluation We have reviewed and evaluated the data provided by the licensee on the ANO-1 RBSS in his letters dated June 17, July 5, Decenter 6,1977 and December 13, 1978.
By letter dated July 5,1977, the licensee requested deletion of the STT from the ANO-1 RBSS 'because he has experienced difficulties operating ANO-1 with sodium thiosulfate in the STT.
There has been chloride stress corrosion cracking in engineered safety feature RBSS piping from chloride impurities in the sodium thiosulfate in the STT. There has also been an overflow of the STT.
The RBSS pipes which had corrosion cracking provide water for containment spray during a LOCA. Serious cracking of the pipes could impair the abil-ity of the RSSS to provide sufficient water spray to the containment to remove radiciodine and heat from the atmosphere. Removing the sodium thio-sulfate would significantly reduce the chances of corroa.on cracking in this piping.