ML20079L208
| ML20079L208 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 02/18/1983 |
| From: | Hukill H GENERAL PUBLIC UTILITIES CORP. |
| To: | Stolz J Office of Nuclear Reactor Regulation |
| References | |
| 5211-83-039, 5211-83-39, NUDOCS 8302230175 | |
| Download: ML20079L208 (2) | |
Text
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GPU Nuclear Corporation
. Nuclear
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Middletown, Pennsylvania 17057 717 944-7621 TELEX 84-2386 Writer"s Direct Dial Number:
February 18, 1983 5211-83-039
\\
Office of Nuclear Reactor Regulation Attn: John F. Stolz, Chief Division of Licensing U.S. Nuclear Regulatory Commission Washington, D.C.
20555
Dear Sir:
Three Mile Island Nuclear Station, Unit 1 (TMI-1)
Operating License No. DPR-50 Docket No. 50-289 Saturation Temperature Margin Alarm Section 2.1.1.6.4.3 of the Restart Report concerning the subject alarm states:
"The modification will provide continuous indication of Tsat margin to the operator. The design will use existing reliable plant inputs.
The new instrumentation will be solid state, seismically qualified, safety grade equipment."
A similar statement is also in SER Section 2.1.3b (Page C8-18). This modification was installed as safety grade seismically qualified system with the exception of the digital readouts. The new instrumentation referred to above consists of signal conditioning equipment which provides output to the panel mounted digital indica-tors in the control room. The signal conditioning equipment is safety grade and seismically qualified. The digital indicators are the best quality industrial grade available. GPUN attempted to find individually seismically qualified digital indicators, however, was unable to do so.
A contract has been placed with a manufacturer to have a digital indicator qualified. This c.>ntract was terminated when it became evident that the program would not be successful. GPUN was unable to find another manufacturer who had a qualified device or was willing to quality one.
Use of a qualified analog indicator was considered but was judged to be unacceptable because of functional and human factors considerations. GPU intends to continue tc explore the availability of a qualified digital indicator.
It should be noted that the existing plant inputs for the indicator are reliable but not safety grade (ref: SER Section 2.1.36, Page C8-18).
It is further stated in the referenced SER that the exception to safety grade input is exceptable be-cause the pressure measurement is obtained from two seismic and environmentally qualifiy sensors and the temperature measurement is obtained from four TH channels, two in each reactor loop. Redundancy is provided by computing a saturation margin indonendently for each loop.
8302230175 830218 f
PDR ADOCK 05000289 i
P PDR GPU Nuclear Carporation is a subsidiary of the General Pubhc Utihties Corporation
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Mr. John F. Stolz ~ 5211-83-039-
~
In the event of a digital indicator being unavailable, adequate redundancy and diversity exist to ensure that-T, e margin can be determined.in the control room
-- of TMI.using any_ of the following, alternate means.
1.
There.are separate T,,e margin measurements-for each loop.
If one indicator is inoperable, the-other. loop measurement.can be used.
22 A portable indicator can be substituted for the digit' indicator.
3.
The plant computer provides an independent calculation'of Tsat. margin.
4.
Tsat. margin can be manually computed using steam. tables ~ (available in.
the control room) and primary pressure and temperature readings, which are safety grade.
GPUN will develop the procedure to obtain the Tsat margin measurements by alternate means. The deviation from the original design specification, for the digital readouts does not significantly diminish the installed Tsat'-
monitoring capability. Adequate redundancy and diversity exist to ensure that Tsat margin can be determined in the control room at TMI-1.
Sincerely, Director, TMI-l' HDH:MI:vj f -
cc:
R. C. Haynes J. Van Vliet i
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