ML20115H812
| ML20115H812 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 04/18/1985 |
| From: | Daltroff S PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | Thompson A Office of Nuclear Reactor Regulation |
| References | |
| GL-84-23, NUDOCS 8504230272 | |
| Download: ML20115H812 (2) | |
Text
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4 PHILADELPHIA ELECTRIC COMPANY 2301 MARKET STREET P.O. BOX 8699 PHILADELPHIA, PA.19101 SHIELDS L. DALTROFF stsc'inic rn som April 18, 1su5 Docket Nos. 50-277 50-276 Mr. Hugh L. Thompson, Jr., Director Division of Licensing U.S. Nuclear Regulatory Commission Udshington, D.C.
20555
SUBJECT:
Peach Bottom Atomic Power Station Reactor Vessel Water Level Instrumentation In BWR's (Generic Letter No. 84-23)
REFERENCE:
Correspondence dated December 5, 1984, S. L. Daltroff, Philadelphia Electric Company to D. G. Eisenbut, NRC
Dear Mr. Thompson:
This letter requests a revision in the schedule proposed in the referenced correspondence for implementing one of the reactor vessel water level instrument modifications on Peach Bottom Unit 2.
Generic Letter No. 84-23, dated October 26, 1984, requested modifications to reduce level indication errors caused by high drywell temperature, and the replacement of mechanical type reactor water level transmitters with analog transmitters.
In the referenced December 5, 1984 letter, Philadelphia Electric Company informed the NRC that previous modifications satisfy the second improvement category regarding analog transmitters, and committed to a modification to reduce the vertical reference legs in the drywell in response to the concern regarding indication errors.
The schedule proposed for the modification was the current Unit 2 outage for the replacement of the reactor recirculation piping, and the first Unit 3 outage requiring draining of the reactor vessel.
8504230272 850418 PDR ADOCK 05000277 P
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.Mr. Hugh L. Thompson, Jr.
March 18, 1985 Page 2 The current Unit 2 outage was selected because the' planned modification required the reactor vessel to be drained to a level approximately 175 inches below instrument zero to permit rework of piping which is connected directly to the reactor pressure vessel.
It had been our intention to perform the modification.during the recently completed. recirculation p'"'
replacement modification while the fuel was off loaded and c e vessel drained.
However, during a review of the design with the Plant Operations Review Committee, a concern was identified regarding the performance of the proposed configuration under normal operating conditions.
The design involved the replacement of temperature - compensated reference columns with uncompensated chambers, and the reroute of the reference leg piping to limit the vertical drop inside the drywell to no more than three feet.
The PORC review identified potentially undesirable human factors relating to instrument error at-low pressure and discrepancies among various control room indicators.
Additionally, at normal level during low pressure conditions, the error in the wide range level instrumentation would render the HPCI and RCIC systems inoperable (trip condition due to a high level signal).
As a result of these concerns, it was decided to delay implementation of this modification to permit an evaluation of alternative designs that address these problems.
Our plans are to complete the engineering by early 1986 which would. support implementation during the subsequent refueling outage on each unit, provided plant outage conditions permit.
In the event outage repair: activities, such as replacement of recirculation piping requite fuel off-loading and vessel drainage, the level instrumentation modification would be implemented concurrently with these activities.
If future outage plans do not include fuel off loading, we will investigate the feasibility of performing the modification with fuel in the reactor vessel.- In any case we will identify our plans 90 days prior to the refueling outages scheduled af ter January 1,1986.
Should you have any questions regarding this matter, please do not hesitate to contact us.
Very truly yours,
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P. Johnson, Resident Site Inspector