ML20045B375
| ML20045B375 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 06/10/1993 |
| From: | Feigenbaum T NORTH ATLANTIC ENERGY SERVICE CORP. (NAESCO) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| IEB-93-002, IEB-93-2, NYN-93084, TAC-M86514, NUDOCS 9306170254 | |
| Download: ML20045B375 (4) | |
Text
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P.O. Box 300 Seabrook, N H 03874 Telephone (603)474-9521 Facsimile - (603)474-2987 Energy Service Corporation Ted C. Feigenbaum Senior Vice President and Chief Nuclear Officer NYN-93084 June 10,1993 United States Nuclear Regulatory Commission Washington, D.C. 20555 Attention:
Document Control Desk
References:
(a)
Facility Operating License No. NPF-86, Docket No. 50-443 (b)
NRC Bulletin No. 93-02, dated May 11,1993, " Debris Plugging of Emergency Core Cooling Suction Strainers"
Subject:
Response to NRC Bulletin No. 93-02, (TAC No. M86514)
Gentlemen:
r NRC Bulletin 93-02 requested licensees to identify fibrous air filters or other temporary sources' of fibrous material, installed or stored in the Containment, but not designed to withstand a loss of coolant accident (LOCA). Upon identification of such material,' licensees were requested to take immediate compensatory measures followed by prompt action to remove the material from the Containment.
North Atlantic Energy Service Corporation (North Atlantic) reviewed the design'of' equipment permanently installed in the Containment and determined that fibrous air filters were installed in the Containment structure recirculating filter unit and the six Containment structure fan coil units. These units are described in the Updated Final Safety. Analysis Report (UFSAR), Section 9.4.5.2. No other fibrous material was identified as installed or stored in the Containment.
The Containment structure recirculating filter unit (recirculating filter unit) is '
installed on the outer periphery of the Containment.perating floor (elevation 25'-0"). The unit is accessible during power operation, in addition to high-efficiency particulate (HEPA).
and charcoal filters, the recirculating filter unit contains three pre-filters, each of nominal size 24" X 24" X 12."
Each ' pre-filter is constructed of fiberglass media woven around aluminum separators and set in a fire resistant particle board frame. The pre-filters are mounted within steel-framed walls of the recirculating filter unit, behind an inlet s'creen.
The six Containment structure fan coil units (cooling units) are located on the O'-0" elevation of the Containment, outside the secondary shield. The units are accessible during power operation. Each cooling unit was provided with a total of forty.(40) air filters.
Twenty (20) filters were located on each of two inlet faces of the plenum. Each cooling unit contained two filter sizes. Twenty (20) filters were of nominal size 20" X 20" X 1"; and the remaining twenty (20) were of nominal size 20" X 25" X 1". The six cooling units contained a total of 240 inlet air filters. Each air inlet filter element was constructed of pleated fiberglass. set in a non.flamable chipboard frame.
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a member of the Northeast Utilities system 9306270254 930610 PDR ADOCK 05000443 15 m-
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- .I United States Nuclear Regulatory Commission June 10,1993 l
Attention:
Document Control Desk Page two i
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1 On May 20,1993, Seabrook Station experienced an unplanned reactor trip. Prior to restart following this reactor trip, North Atlantic performed a preliminary engineering assessment of the above air filters relative to the concerns of the bulletin. It was judged that the pre-filters installed in the recirculating filter unit could be reasonably expected to withstand the effects of a LOCA. This judgement was based on consideration of the unit's j
design and location and the degree of filter encapsulation provided by the structure of the i
unit.
The pre-filters shall remain installed in the recirculating filter unit, pending verification of the initial assessment. The inlet air filters installed in the' cooling units were j
directly exposed to the Containment atmosphere. The only encapsulation of the cooling units' filter media was that provided by the chipboard frame of each filter element. Because of this configuration, it was not possible to judge, based on a preliminary engineering l
assessment, that these filters could be reasonably expected to withstand the effects of a
_j LOCA. Therefore, prior to commencement of reactor restart on May 21, 1993, the inlet j
filters were removed from the cooling units. The cooling units will be operated without inlet
-L filters pending further evaluation.
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The cooling unit inlet filters were removed from the Containment and stored in accordance with applicable administrative controls. The absence of inlet filters constituted a temporary modification to the cooling units. A 10 CFR 50.59 evaluation was performed which considered the advantages and potential disadvantages of operating the cooling units without inlet air filters. The 10 CFR 50.59 evaluation concluded that operating the cooling units without inlet air filters would not involve an unreviewed safety question.
i Station administrative controls specify requirements for housekeeping and temporary storage of equipment and materials in seismic areas. In general, procedures require that equipment and material not in use should be removed from seismic areas. In accordance with this general requirement, fibrous air filters are not stored in the Containment.
i However, procedures do not explicitly prohibit storage of fibrous air filters and other fibrous material in the Containment.
i Station operating procedure.OX1406.12 (18 Month Containment and Containment f
Spray Recirculation Sump Surveillance) requires visual inspection of the Containment for loose debris and Containment sump blockage. The requirements of this procedure are summarized as follows. Prior to establishing Containment integrity, accessible areas of the Containment shall be visually inspected to verify that no loose debris is present which could l
f be_ transported to the Containment sump and restrict flow to the Residual Heat Removal (RH) pumps' suction during the recirculation phase of a LOCA. Rags, trash, clothing and bubbling or chipped paint are specifically identified as unacceptable, loose debris which, if found, shall be removed from the Containment. With Containment integrity established,
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areas affected by each Containment entry shall be visually inspected for loose debris. The Containment sumps shall be visually inspected on a periodic basis to verify that suction inlets -
l are not restricted by debris and that sump components show no evidence of structural j
distress or abnormal corrosion.
On May 20,1993, an inspection of accessible areas of the Containment was conducted.
The inspection verified that no loose debris was present and that no air filters or other i
fibrous material was stored in the Containment. The inspection also verified that the Containment sump inlet gratings and screens were not blocked by any visible material.
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United. States Nuclear Regulatory Commission June 10,1993 Attention:
Document Control Desk Page three l
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North Atlantic plans to take the following, additional actions in response to NRC Bulletin 7
93-02:
a)
As stated above, a preliminary engineering assessment concluded that pre--
filters installed in the recirculating ritter unit can be reasonably expected to withstand the effects of a LOC,s.
This conclusion will be verified and documented by September 3,19'3.
Inlet air filters shall not be re nstalled in the cooling units until they can be i
i b) reasonably expected to withstind the effects of a LOCA.
c)
Station Operating Procedure OX1406.12 will be revised by September 3,1993 I
to specifically define loose air filter media in the Containment as unacceptable loose debris.
i' d)
Station administrative controls will be reviewed and revised, if necessary, by September 3,1993 to ensure that fibrous air filters and other fibrous material, not designed to withstand a LOCA, are not permitted to be installed or stored in the Containment during Operational Modes 1 through 4.
The above information describes the actions North Atlantic has taken and planned in response to NRC Bulletin 93-02 at Seabrook Station. Should you have any questions on this matter, please contact Mr. James M. Peschel, Regulatory Compliance Manager at (603) 474-9521 extension 3772.
i Very truly yours, i
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Ted C. Feigenb m
i TCF:GK/ tad i
STATE OF NEW HAMPSHIRE t
Rockingham, ss.
June 10,1993 Then personally appeared before me, the above-named Ted C. Feigenbaum, being duly sworn, did state that he is Senior Vice President and Chief Nuclear Officer of the North Atlantic Energy Service Corporation that he is duly authorized to execute and file the foregoing information in the name and on the behalf of North Atlantic Energy Service Corporation and.
that the statements therein are true to the best of his knowledge and belief.
rwdle b Mhnsyu Beverly E. Silloway, Notary Pub ic My Commission Expires: February 28,1995 l
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United. States Nuclear Regulatory Commission June _10,' 1993 -
J Attention:
Document Control Desk-Page four cc:
Mr. Thomas T. Martin Regional Administrator U. S. Nuclear Regulatory Commission Region 1 475 Allendale Road King of Prussia, PA 19406 Mr. Albert W. De Agazio, Sr. Project Manager Project Directorate I-4 Division of Reactor Projects U.S. Nuclear Regulatory Commission Washington, DC 20555
- Mr. Noel Dudley NRC Senior Resident inspector P.O. Box 1149 Seabrook,' NH 03874 e
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