ML20024G554
| ML20024G554 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 04/04/1974 |
| From: | Ziemann D Office of Nuclear Reactor Regulation |
| To: | Mayer L NORTHERN STATES POWER CO. |
| References | |
| NUDOCS 9102120653 | |
| Download: ML20024G554 (3) | |
Text
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APR
.i 1974 Docket No. 50-263 i
l Ziorthern States Power Cosipany j
ATTN. Mr. L. O. Mayer, Director of j
Nuclear Support Services 414 31 con et Ma u l
Minneapolis, Minnesota 55401 t
Gentlenen:
I r
By letters dated January 23, 1974, and supp1cuento dated March 8 and l
March 19,1974, you have described a Prompt Relief Trip System (PRT)
I and provided an analysis of plant behavior during abnormal transients.
using PRT to reduce the magnitude of pressure transients whenever i
reactor power level is above 70%. We have not completed our evaluation, but our preliminary review of the engineering drawings for the proposed design and installation of the PRT system in the Monticello plant has revealed that the design criterion "no more than one safety relief i
valve vin be inadvertently actuated" is not met.
A single event in the PRT cabinet can inadvertently actuate more than one safety relief valve.
Unless this concern is satisf actorily resolved, installation of the PRT i
cannot be approved, even though we can conclude that mere installation, j
but not actuation, of the PRT system can be made without degrading existing safety syr tems, i
In order for us to evaluate our additional concerns we have on the PRT, provide the following information:
i 1.
State the consequences of spurious or inadvertent trip (actuation) of the PRT system concurrent with the following evente:
a.
Loss of coolant accident.
b.
Steam line break accident.
c.
loss of of faite power.
d.
Identify other accidents and transients for which inadvertent
{
or spurious trip was analyzed.
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4 l
Northern States Power Company APR 4 19 g i
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Also, justify a PRT system whose functional response effects the reactor core and the reactor coolant pressure boundary i
l in ways similar to the Automatic Depressurization Systaan but does not incorporate the same protective permissives such i
as the ac interlocks.
I 2.
State your justification for a PRI design that is actuated unnecessarily 'esch time a loss of Reactor Protection System i
Voltage occurs.
i l
3.
Submit a Failure Mode Effects Analysis for the PRT system.
Specifically address the consequences of a single failure to (1) cause spurious PRT actuation and (2) prevent TRT l
actuation.
i 4.
Submit the results of the environmental and seismic qualifi-cation tests of equipnet employed in the PRT system.
Include j
the environmental qualification of the cabling and qualifil cation of terminals located within the drywell or other regious j
i where a high energy line break could occur.
t j
5.
The on-line testability provisions proposed by CE merely j
represent a continuity test and are not acceptable. Since
[
PRT is a new system, the Regulatory Guide 1.22-reconsaandations 4
should be considered in its design.
j 6.
Since full opening of five or six relief valves for short time intervals is necessary following some abnormal operating i
l trennsients to stay within fuel thermal design limits, describe i
the methods that are to be used by NSP to ascertain that the-system has operated according to design and that the relief j
valves passed sufficient steam following each PRT activation and before returning to power; i.e., what assurance will-be provided prior to returning to power that the core has not violated a design limit?
3 Your response to the concerns expressed above should be received no later than April 30, 1974, so that we can resolve these items prior to returning.
the Honticello facility to power.
j Since rely,
i.
I OHsna m uy Dennis L. 7Jemann Dennis L. Ziemann, Chief i
Operating Reactors Branch #2 t
Directorate of Licensing-omeeocl Sse nexg,pa ge g
1 1
4
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liorthern States Powcr Conpany 3-g Arthur tenquist, Esquire cc:
Vice President Law Northern Statco Power Co;;:pany i
414 Hicollet P.all i
Hinneapolis, Kinnesota 53401 Gerald Charnoff Shaw, Pittran, Potts, Trusbridge & Mcdden 910 - 17th Street, N. W.
Washington, D. C.
20006 110uard J. Vogel, Lsquire nnittle & Vogel 1154 East Grain Exchange Building 412 South 4th Street hinneapolis, Minnesota 55415
_Dintribution Steve Gadler. P. E.
rtf eket File 2120 Carter Avenue AEC PDR St. Paul, Minnesota 5510S L cal PDR Branch Reading lir. Danici L. Fickcr JRBuchanan, ORNL Ancistant City Attorney DJSkovholt, L:0R 647 City Hall TJCarter, L:0R St. Paul, liinnesota 55102 ACRS (16)
Ro (3)
Werren R. Lawson, M. D.
OGC Secretar/ 6 Executive Officer DLZiemann, L:0RB #2 State Department of Health JJShea, L:0RB #2 717 Delaware Street, S. E.
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Minneapolis, }!innesota 55440 RMDiggs, L:0RB #2 SVarga, L:RP Sandra S. Gardebring, Ecquire TIppolito, L:EICSB Minnesota Pollution Control Agency 1935 W. County Road B2 Poseville, Minnesota 55113 Ken Drugan Minnesota Pollution Control Agency 1935 U. County Road L2 Roseville, Minnesota 55113 Anthony Z. noistan, Lsquire Berlin, Roistr.an and Kessler 1712 H S tre c t, U. W.
Washington, D. C.
20036 Environmend
_ L. ORB.J2...[al Library efi Minnesota l
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L:0RB i X7403 JJShen:s h DLZi 1
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