ML20057D072

Forwards Response to NRC Bulletin 93-002, Debris Plugging of ECCS, Documenting Action Taken on Containment Purge Ventilation Sys After Discussions W/Members of Staff

ML20057D072
Person / Time
Site:	McGuire, Mcguire
Issue date:	09/20/1993
From:	Mcmeekin T DUKE POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
IEB-93-002, IEB-93-2, NUDOCS 9310010065
Download: ML20057D072 (5)

Text

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Duke 1%wr Company T C Manus M.-Gwre Nuclear Generation Department Vice President 12 :00 flaters ferry Road (MGotA)

(TN)Sf5 4800 fluntershile, NC 280?S E.985 (TMISTS-48(19 tax

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DUKEPOWER

.V.,

September 20, 1993 U.S. Nuclear Regulatory Commission Attn:

Document Control Desk Washington, DC 20555

Subject:

McGuire Nuclear Station, Units 1 and 2 Docket Nos. 50-369 and 50-370 NRC Bulletin No. 93-02 Debris Plugging of Emergency Core Cooling Suction Strainers Gentlemen:

Please find attached a revision to the June 10, 1993 response to NRC Bulletin 93-02, Debris Plugging of Emergency Core Cooling Suction Strainers for McGuire Nuclear Station.

This revision documents actions taken on the Containment Purge Ventilation System after discussions with members of your staff.

The changes are identified by lines in the right margin.

If you have any questions concerning this response, please call Robert Sharpe at (704) 875-4447.

I declare under penalties of perjury that the statements set forth herein are true and correct to the best of my knowledge.

Very truly yours, WA't z

T. C. McMeekin 010009 p\\

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I U.S. Nuclear Regulatory Commission I

September 20,1993 Page 2 I

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Mr.

S.

D.

Ebneter Administrator, Region II U.S. Nuclear Regulatory Commission 1001 Marietta St.,

NW, Suite 2900 Atlanta, GA 30323 Mr. Victor Nerses U.S.

Nuclear Regulatory Commission Office of Nuclear Regulatory Management i

One White Flint North, Mail Stop 9H3 Washington, DC 20555 Mr. George Maxwell Senior Resident Inspector McGuire Nuclear Station i

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i ATTACHMENT DUKE POWER COMPANY McGUIRE NUCLEAR STATION RESPONSE TO NRC BULLETIN 93-02 NRC REQUESTED ACTIONS Identify fibrous air filters or other temporary sources of fibrous material, not designed to withstand a LOCA, which are installed or stored in your primary containment.

Take any immediate compensatory measures which may be required to assure the functional capability of the ECCS.

Take prompt action to remove any such material.

Duke Power Company Response Duke Power Company performed a review of all containment ventilation systems to determine the amount and location of any fibrous filter media either permanently or temporarily stored inside containment.

The potential to block the sump screens with insulation or paint flakes has been previously analyzed and is not included in this evaluation.

There is no fibrous filter media stored temporarily inside the containment at the McGuire Nuclear Station.

The ECCS sump screens are inspected each outage for any damage or debris using a maintenance procedure, PT/1,2/A/4700/56, Containment Building Civil Structures Inspection.

Any material taken into containment during an outage is removed prior to unit startup.

Additionally, prior to entering Mode 4,

procedure PT/1,2/A/4600/03F, Containment Cleanliness Inspection, is performed to verify that there is no material l

left inside containment which would have the potential to block the ECCS sump.

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There are six ventilation systems inside the primary containment.

Of these six systems, three, the Containment air Return and Hydrogen Skimmer System (VX), the Lower Containment Ventilation System (VL) and the Control Rod Drive Mechanism Cooling System (VR) do not contain any fibrous filter media.

The other three systems will be discussed individually below.

Upper Containment Ventilation System l

The Upper Containment Ventilation System (VU) consists of four main water cooled air handling units and four axial vane type air return fans.

The main air handling units are located in upper containment and use pre-filters for course

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l (2) air cleaning.

These eight filters are either a cotton / synthetic fiber blend or fiberglass and are 20 inches by 25 inches by 2 inches in size.

The filters are mounted in " slide in" frames with no other fastening mechanism.

These filter units are above the flood level for a LOCA and there are no LOCA line breaks postulated for this ares.

There also does not appear to be any plausible mechanism for the filter media used on the VU main air handling units to i

migrate to the Lower Containment recirculation sump.

Therefore, Duke Power Company does not plan to remove these filters.

Incore Instrumentation Room Ventilation System The Incore Instrument Room Ventilation System (VT) uses two air handling units, each of which use four low efficiency pre-filters which are 16 inches by 25 inches by 2 inches in size.

These filters are also mounted in " slide in" frames with no other fastening mechanism used.

The units are above the flood level for a LOCA and there are no LOCA line breaks postulated for this area.

There does not appear to be any plausible mechanism for the filter media used on the VT units to migrate to the Lower Containment recirculation sump.

Therefore, Duke Power Company does not plan to remove these filters.

Containment Purge Ventilation System The Containment Purge Ventilation System (VP) Auxiliary Carbon Filter uses two non-safety filters to clean up the air in lower containment prior to and during outages.

Each filter is located inside the crane wall and consists of a prefilter, high efficiency filter, HEPA filter and carbon bed.

Each of the two VP filters has eight prefilters, 24 inches by 24 inches by 2 inches in size, eight high efficiency filters, 24 inches by 24 inches by 6 inches in size and 8 HEPA filters, 24 inches by 24 inches by 12 inches in size.

The prefilters are fibrous filters which are wired in place per a maintenance procedure.

The high efficiency l

and HEPA filters are metal cased filters which contain a fibrous filter media.

After discussions with the NRC staff and a review of piping drawings, Duke initially assumed that there was the l

potential of various line breaks associated with a LOCA in the area of

- /P prefilters that could impinge on the prefilters.

conservatively, the prefilters, high efficiency and HEPA filters were removed on Unit 2 as a condition for restart after the End of Cycle 8 outage pending field investigations to determine the actual location of the piping.

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Engineering personnel performed field inspections on both units to determine if there was an impingement concern with the VP filters.

The results of this investigation showed there were no direct impingement concerns with the 1A and 2A VP filters units.

There is a postulated LOCA break which could impact the IB and 2B VP filter units.

This postulated break is above and in the middle of the filter unit housing, t

which is rugged metal construction.

There is no direct jet impingement to the replaceable filters (prefilter, high efficiency, HEPA).

The 1B and 2B filter housing units would sustain damage from the postulated jet impingement but the replaceable filters are not in the direct impingement path and will not be affected by the LOCA.

Prior to the startup from the steam generator outage on Unit 1,

the fibrous prefilters will be replaced with metal prefilters, which do not contain any fibrous material, and the high efficiency and.HEPA filters will not be removed.

It is planned to install the metal prefilters and replace the high efficiency and HEPA filters on Unit 2 during the next shutdown of sufficient length.

Based on the evaluation of the temporary and permanent use of fibrous filter material, the only compensatory measures taken were those discussed above for the VP system.

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