ML20038A626
| ML20038A626 | |
| Person / Time | |
|---|---|
| Site: | Midland |
| Issue date: | 11/12/1981 |
| From: | Jackie Cook CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| 14835, NUDOCS 8111160065 | |
| Download: ML20038A626 (4) | |
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and Constrssctson General offices: 1945 West Parnali Road. Jackson. MI 49201 * (517) 788 0453 November 12, 1981 p\\Y
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'I Harold R Denton, Director p
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US Nuclear Regulatory Commission Washington, DC 20555 MIDLAND PROJECT
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,s MIDLAND DOCKET NOS 50-329, 50-330 RESPONSE TO OPEN ITEMS OF PRELIMINARY DRAFT SER SECTIONS 3.6.1 AND 10.4.9 FILE:
0505.805 SERIAL:
14835 ENCLOSURE:
RESPONSE TO OPEN ITEMS OF PRELIMINARY DRAFT SER SECTIONS 3.6.1 AND 10.4.9 We have reviewed the preliminary draft sections of the NRC Staff's Safety Evaluation Report 3.6.1, " Plant Design for Protection Against Postulated Piping Failures in Fluid Systems Outside Containment" and 10.4.9, " Auxiliary Feedwater System."
Enclosed are our responses / comments to the open items contained within these draft sections.
With the response provided in the letter we believe Open Item 1 can be closed out by the Staff and Open Item 3 can be made a confirmatory item.
As noted in our response to Open Item 2, we have requested a meeting with the Staff to resolve our differences.
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CC RJCook, Midland Resident Inspector DSHood, US NRC ODParr, US NRC l
DBMiller, Midland Construction (3) h S
RWHuston, Washington
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d ENCLOSURE PLANT DESIGN FOR PROTECTION AGAINST POSTULATED PIPING FAILURES IN FLUID SYSTEMS OUTSIDE CONTAINMENT - DRAFT SER 3.6.1 OPEN ITEM 1.
Open Item - The applicant has n ' identified in the FSAR the environmental conditions for which essential e.ipment, within the protective structure around the main steam line break telusion zone has been qualified.
In discussions, the applicant has inu cated that the equipment within the protective structure around the ma steam line break exclusion zone has d
4 been qualified only for the ambient environment. We require that the applicant perform a subcompartment environmental analysis and assure that the essential equipment in this area is qualified to withstand the re-sulting environmental effects for an assumed main steam line crack equivalent to the flow area of one square foot.
Response - The essential equipment within the tornado shielded area on the auxiliary building roof has been qualified for ambient conditions that would exist. The equipment was not qualified for non-mechanistic breaks of the main steam line within the break exclusion zone. The break exclusion zone was designed in accordance with Branch Technical Position MEB 3-1, Rev 0, dated 11/24/75, and as a result breaks need not be postulated. The NRC agreed with this position in a meeting on September 13, 1978.
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2 AUXILIARY FEEDWATER SYSTEM - DRAFT SER 10.4.9 OPEN ITEMS 2.
Open Item - In accordance with present licensing criteria as interpreted in SRP 10.4.9, an Auxiliary FeeA ater System (AFWS) should have an
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unreliability in the range of 10 to 10 per demand to be acceptable with respect to the heat transfer and redundancy requirements of General Design Criterion 44 The Midland AFWS unreliability is unacceptably high.
We require that the applicant provide a third AFW pump for each unit capable of providing at least the minimum flow necessary to the steam generators for decay heat removal during a loss of offsite power condition.
Response - The 10~
to 10' unreliability range referenced in the open item comes from a recent revision (July 1981) of the Standard Review Plan.
Since the basis for this range and methodology is not provided, CP Co is unable to assess the acceptability of the overall Midland design against this goal. CP Co's AFV availability study used both conservative assu=p-tions and methods (propagation of uncertainty), and demonstrates that our AFW system is adequate and comparable in availability to other systems licensed or under review. This AFW design, when combined with an alter-nate mode of decay heat removal, results in an overall unavailability that meets the SRP goal and thus provides an acceptable alternative. Due to the construction status of the Midland Plant, the addition of a third AFW pump as required by the Staff's position would impose a severe hardship on our schedule. CP Co has requested a meeting with the Staff to discuss this issue.
3.
Open Item - Switchover of the auxiliary feedwater pump suction from the normal non-safety grade water source to the safety grade service water system is accomplished using two-out-of-four low pump suction pressure logic concurrent with the presence of an auxiliary feedwater actuation signal. We require that the applicant assure that the AFW pumps can survive the low suction pressure condition for the approximately seven seconds required to effect the water source transfer. We are also awaiting the applicants evaluation of the need for installation a low suction pressure pump trip to protect the AFW pumps in the event that the normal non-safety grade water source is lost while the AFWS is operating in a manual mode (ie, pumps running without the presence of an auxiliary feedwater actuation signal).
Response - CP Co has completed the evaluation of the need for installing a low suction pressure pu=p trip in the absence of an AFWAS. We are incorporating this feature into the Midland design. The sensors used will be the existing Class 1E suction pressure devices which will trip the respective pump on low suction conditions without AFWAS. The detailed design is underway and the FSAR will be updated to reflect this change.
The possibility of pump damage during switchover is currently under evaluation by our A/E and the AFW pump vendor. Following completion of this evaluation, we will take whatever measures that may be necessary to ensure that the pumps will not be damaged during automatic suction l
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switchover. Any system modifications resulting from the evaluation will be documented in the FSAR.
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