ML20236C973
| ML20236C973 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 03/10/1989 |
| From: | Musolf D NORTHERN STATES POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 8903220398 | |
| Download: ML20236C973 (2) | |
Text
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Northern States Power Company 414 NicJiet Mall Minneapolis, Minnesota 55401 Telechone (612) 330 5500 March 10, 1989 10 CFR Part 50 Section 50.90 Director of Nuclear Reactor Regulation U S Nuclear Regulatory Conaission Attn:
Document Control Desk Washington, DC 20555 PRAIRIE ISLAND NUCLEAR GENERATING PLANT Docket Nos. 50 282 License Nos. DPR-42 50 306 DPR-60 l
Supplemental Information License Amendment Request Dated July 18, 1988 Digital Feedwater Control System The pu: pose of this letter is to provide additional information re-quested by the NRC Staff related to a planned upgrade of the feedwater control system at the Prairie Island Nuclear Generating Plant.
This information supplements our License Amendment Request dated July 18, 1988.
l Isolation Devices 1
The isolation devices in the Reactor Protection System that provide 4
the steam generator narrow range level signal to the advanced digital I
feedwater control system are Foxboro Model 66 BC-0 Style C current i
repeaters. The applicable test reports are Westinghouse Topical Reports WCAP-7685 and WCAP-7508.
i The maximum voltage level that exists in the new control system is 120 l
l VAC. This voltage is within the voltage ranges at which these devices l
were tested (250 VDC and 480 VAC). Therefore, these isolators are I
satisfactory for preventing a control fault from propagating back to I
the protection system.
j Median Signal Selector The three level channels enter the new feedwater control system via three separate analog-to-digital converter cards which are physically distributed among three separate input card crates.
Each input card also provides isolation through a transformer between the analog input and the digital portion of the system. A digital input / output bus transfers the digital signal value to the control processing unit 8903220398 890310 PDR ADOCK 05000282 l
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Director of NRR I
Narch 10, 1988 Northem States Power Company Page 2 l
card, which performs the Median Signal Selector (MSS) function as well-as other control functions. An over-range signal that may damage an input card will not propagate through to the control processing ur.it and affect the MSS function.
The normal signal range of the input to the median aignal selector from the steam generator narrow range level channel isolators is 10;to 4
50 ma.
The new feedwater control system assigns a status of " bad" data when the signal is out-of range (greater than 50.2 ms or less than 9.8 ma).
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Single channel failures, both.in the normal range and out-of-range, were tested as to their effect on the control system.
Tests showed l
that the control system functioned satisfactorily.with a single chan-
)
nel failure. The anaximum credible over-range signal. from the protec-l tion system current repeater isolator'is 105'ma.
Westinghouse has i
type tested an' input card used in the Prairie Island control system at i
an input current level of 106~ma for one hour.
The. result of this i
test showed that the MSS function continued,to select the appropriate H
value.
l Please contact us if you have any questions related to the information-we.have provided, l
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D d bw.d David Musolf Manager Nuclear Support Services 1
c: Regional Administrator III, NRC Sr Resident Inspector, NRC Project Manager, NRC MPCA Attn:
Dr J V Ferman G Charnoff
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