ML19257B837
| ML19257B837 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 12/31/1979 |
| From: | Harold Denton Office of Nuclear Reactor Regulation |
| To: | Ahearne J, Gilinsky V, Kennedy R NRC COMMISSION (OCM) |
| References | |
| NUDOCS 8001210034 | |
| Download: ML19257B837 (2) | |
Text
/
h UNITED STATES NUCLEAR REGULATORY COMMISSION y
's e g
E WASHINGTON, D. C. 20555 s
]
Decembar 31, 1979 MEMORANDUM FOR: Chaiman Ahearne Commissioner Gilinsky Commissioner Kennedy Commissioner Hendrie Commissioner Bradford f^*
THRU:
Executive Director for Operations - W FROM:
Harold R. Denton, Director Office of Nuclear Reactor Regulation
SUBJECT:
P0 INT BEACH UNIT 1 - STEAM GENERATOR TUBE DEGRADATION In the Confirmatory Order for Modification of License dated November 30, 1979 (Order), certain requirements were made pertaining to the operation of Point Beach Unit 1.
In the Safety Evaluation appended to that Order, certain remedial actions were discussed. - Among these remedial actions we noted that the licensee planned to operate the facility at a reactor coolant pressure of 2000 psia rather than 2250 psia to reduce the internal pressure stresses by about 15% during operation ( Action No. 3, pp.15). This action was to be initiated upon NRC approval of an amendment request dai.ed November 2,1979, which requested pt..tnission to operate at that pressure.
In the same Safety Evaluation we discussed " Measures for Reducing the Rate of Degradation" on pp. 22 and 23. We indicated that the acceptability of this proposed operation would be addressed separately.
The Order of November 30, 1979, was based on infomation resulting from the steam generator tube inspection following the October 1979 leak. On De: ember 11, 1979, another steam generator leak occurred. An eddy current test was performed on both steam generators which resulted in eddy current indications below the tube sheet (in the tube crevice) in both steam generators.
Twenty tubes were plugged in steam generator A and fifteen tubes were plugged in steam generator B.
Since there appears to be evidence of continuing intergranular corrosion attack, the NRC staff has now found that it is not only desirable, but prudent and necessary, to take imediate action to require the reactor coolant pressure to be reduced from 2250 psia to 2000 psia since this will have the effect of substantially reducing the differential pressure across
.all tubes in both steam generators.
As explained below, operation of Unit 1 at a reactor coolant pressure of 2000 psia is acceptable from an accident analysis point of view. The applicable criteria for transient and accident are still satisfied.
Contact:
l//} Q D. G. Eisenhut X27672 8001210 hf
The^Comission December 31, 1979 Since the licensee's amendment request was for operation at either 2250 psia or 2000 psia, he has recently withdrawn his amendment request and has made a comitment to operate Unit 1 at a reactor coolant system pressure of 2000 psia. Sumary Evaluation Operating the facility at a reactor coolant pressure of 2000 psia rather than 2250 psia will reduce the internal pressure stresses during operation by about 157,. The systems perfomance aspects of this change was evaluated by the licensee. Two trip setting changes are required. These relate to DNBR protection and low reactor pressure protection. Several accidents were reanalyzed using standard Westinghouse methods. These included the LOCA and the Rod Ejection Accident. We have concluded that the appropriate reactor protection criteria continue to be met. Degraded Tubes Above the Tube Sheet Since our November 28, 1979 Comission meeting, the staff has learned of five degraded tubes, located at or above the surface of the tube sheet, that were detected and plugged during the October-November plant outage. The licensee have examined this infomation and detemined that it is not associatt. with intergranular corrosion attack, the phemonenon occurring in the tube sheet crevice. The staff discussed this experience with the licensee in late December, and concurred that this degradation was associated with the thinning, or wastage phenomenon occurring during the 1972-1975 time frame. Conclusion The staff proposes to issue a Confimatory Order, following the Comission briefing now scheduled for January 2,1980. P [ Y h.$0 Ul Harold R. De.1 on, Director Office of Nuc ear Reactor Regulation cc: SECY OPE OGC 1773 034}}