ML20238B192

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Requests That Util Review Encl Anl Observations from Control Room Ventilation Survey Conducted on 851003-04 & Provide Confirmation within 45 Days That Analyses & Regulatory Commitments Re Control Room Ventilation Sys Still Valid
ML20238B192
Person / Time
Site: Cooper Entergy icon.png
Issue date: 08/26/1987
From: Long W
Office of Nuclear Reactor Regulation
To: Trevors G
NEBRASKA PUBLIC POWER DISTRICT
References
TAC-60957, NUDOCS 8709010108
Download: ML20238B192 (9)


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NUCLEAR REGULATORY COMMISSION WASHINGTON, D, C. 20555 t / August 26, 1987 Dacket No. 50-298 Hr. George A. Trevors, Division Manager - Nuclear Support Nebraska Public-Dower District Post Office Box 499 Columbus, Nebraska 68601

Dear Mr. Trevors:

l

SUBJECT:

CONTROL ROOM VENTILATION SURVEY (TAC NO. 60957) l l Re: Cooper Nuclear Station During the period October 3-4, 1985, a survey was conducted by the staff and its contractor, the Argonne National Laboratory (ANL), at the Cooper Nuclear i Station 1 The purpose of the survey was to evaluate: (1) the operation of the l control room ventilation system and its ability to maintain the control room l habitatMe, and (2) the adequacy of the facility's technical specifications and procedures to dwonstrate system operability and performance. consistent with  !

l the cetrol room habitability analysis forwarded to the staff by your letter 1 dated December 30, 1980. (Similar surveys have been conducted at other facilities.)

l The survey team gathered flow rate data in the various portions of the control room v?ntilation system with the system operating in its normal mode of operation. . In addition, data was also gathered with the ventilation system operating in its emergency radiological and toxic gas operating modes. The survey team's observations covered system operation and design, plant technical specifications and procadures, and TMI Action Item III.D.3.4 analysis. The observations were discussed with the Nebraska Public Power District personnel during tho exit meeting; however, detailed results of the flow analysis were not availaole at that time.

Observations and information are presented in the attachment which is the ANL j report covering the Cooper Nuclear Station survey. The ANL report does not j constitute the NRC staff's position regarding these items.  !

1 We request that you review the ANL observations and provide confirmation within 45 days that your analyses and regulatory commitments regarding the Cooper control room ventilation system are still valid. Otherwise indicate those changes you propose and the schedule for their implementation.

The reporting and recordkeeping requirements contained in this letter affect i

B709010100 870826 l PDR ADOCK 05000298 .

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fewer than ten respondents; therefore, OMB clearance is not required under P.L.96-511.

i Sincerely, l3 i William 0. Long, Project Manager Project Directorate - IV-Division of Reactor Projects - III, IV, V and Special Projects

Attachment:

As stated cc w/ attachment:

See next page DISTRIBUTION W6cket File NRC PDR Local PDR PD4 Reading F. Schroeder J. Calvo 1 P. Noonan W. Long OGC-Bethesda E. Jordan J. Partlow ACRS (10)

J. Kudrick A. Chu i J. Craig i DCS-042 J. Hayes J. Jaudon PD4 Plant File PD4/L4 A PD4/PM v' SPSB PD4/D /#0 PNoond WLong:sr fJCraig JCalvo 8/)S/8 8/0 /87 8Q$87 8/n/87

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' Mr. George A. Trevors -

Nebraska Public Power District' Cooper Nuclear. Station I cc:

Mr. - G. D. Watson,. General: Counsel Nebraska Public Power District P. 0.' Box 499 Columbus, Nebraska 68601 j Cooper Nuclear' Station ATTN: Mr. Guy R. Horn, Division.

Manager of. Nuclear Operations P. O. Box 98 Erownville, Nebraska 68321 Cirector .

l j

hebraska Department of Environmental l

Control P. O. Box 94877 1 State House Station Lincoln, Nebraska 68509 3 i

Mr. William Siebert, Commissioner Nemaha County Board of Commissioners Nemaha County Courthouse Auburn, Nebraska 68305 Resident Inspector U.S. Nuclear Regulatory Commission P. O. Box 218 Brownville, Nebraska 68321 l Regional Administrator, Region IV ,

U.S. Nuclear Regulatory Commission 1~

611 Ryan Plaza Drive, Suite 1000 Arlington, Texas 76011 Mr. Harold Borchart, Director Division of Radiological Health Department of Health 301 Centennial Mall, South P. O. Box 95007 Lincoln, Nebraska 68509 .

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ANL REPORT

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Copper Nuclear Station Page 1

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PLANT VISIT

SUMMARY

REPORT 1 Plant: Cooper Nuclear Station

2. Utility: Nebraska Public Pcver District
3. Location: Brownsville Nebraska 4 NRC Region: IV
5. Visit Date: October 2-3. 1985
6. Participants from Argonne National Laboratory: M. D. Carnes J. W. Driscoll l 7. Scope:

The plant visit was cade to gather information on control room habitability - Generic Issue 83. Specifically tr.e Plant Technical Specifications were reviewed and compared to the safety analysis )

l (including III.D.3.h. sutmittal and the NRC staff safety evalua- i tion) and plant procedures to determine what operational practices

! are being employed. Information relating to loss of cooling in the control room envelope was reviewed to determine the impact of such an event on continued plant operations duc to loss of plant instru- .

I mentation. Air flow and temperature measurements were taken in various places throuEhout the CR HVAC system and envelope.

6. Findings:

8.1 General l The Control Room (CR) HVAC system was found to be as described in the USAR and the material provided by the utility (NPPD),

except as follows:

8.1.1 The USAR and III.D.3.4 submittal says that the emerEency bypass is designed for 225 cfm at 2 in.

static pressure. This conflicts with surveillance procedure 6.317.5 which says the system is designed for 341 cfm. In fact, we measured flow in excess of 600 cfm. Test reports by an independent orEaniza-tion showed flow rates of 341 cfm and 600 cfm mea-sured on the same day. The problem is that the emergency supply ran will not see 2 in. of static pressure unless all other fans in the system are shut down. With the normal supply and exhaust fans running, the differential pressure is a function of the condition of the isolation dampers.

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(4 8.1.2 There is no backdraft damper in the toilet and kitchen exhaust as shown on plant drawings.

8.1 3 The USAR and III.D.3.4 submittal do not properly describe the events that occur when the emergency filtration is placed in service. . Emergency supply lineup says that damper AD1021D will open. It should say AD1021-D2 will open and AD1021-D1 will ',

close.

8.1.4 There seemed to be confusion on the part of most licensee employees about the source of cooling water for the HVAC chillers. Some said the cooling tower on the roof was used in summer. Most seemed con-fused abut the source of power for the HVAC systems.,

Af ter lengthy inquiry, we found that turbine equip- .

- ment cooling (TEC) is the primary source of cooling, s but it does not have emergency power. The backup cooling source is Plant Service Water (PSW) which does have emergency power supply. The feeling was that PSW did not have adequate capacity for the HVAC chillers because of a 2-in, cross connect between TEC and PSW which have 3-in. Iines.

( 6.1.5 The III.D.3.4 submittal indicates that dose rates were conservatively calculated based on control roon volume, but the calculations were made using the total volume of 65,300 cu ft instead of the free air space volume of 33,060 cu ft.

6.2 Technteal Specifications The plant is operated and surveillance is performed in accor-dance with the existing Technical Specifications. However, the following changes are recommended to better monitor the performance of the control room HVAC system.

8.2.1 Limit 3.12.A.2.a which requires in place cold DOP

  • testing does not specify a limit for bypass leakaEe or a testing frequency. Bases 3.12.A indicates there is a limit of less than one percent bypass leakage.

8.2.2 Limit 3.12.A.2.c. requires the fans to be tested and shown to operate within 210% of d6ften flow. The design flow rate and fans tested should be stated.

There was a discrepancy in design flow rate of the

  • emergency supply ran as described in the USAR.}.D.3.4 submittal and the procedure used to test

( the fan. The ran actually operates at a higher flow rate than design. This reduces the resident time in the charcoal bed which reduces the lodine removal

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( efficiency. Design. flow and operating flow should be verified by the licensee. 8.2 3 Limit 4.12.A.2.a. requires in place cold DOP and 1' halogenated hydrocarbon tests be conducted once per year for standby service and after every 720 hours of operation. This is more frequent than recom-mended by Regulatory Guide _.1.52. j 8.2.4 The 112.D.3.4. analysis states that the control room is pressurized during operation of the emergency supply fan. There should be a Technical Specifica-tion for pressurization tests. The AP gauge the operators used as an indicator of 1 control room AP was, in fact, measuring the control building which is not the control room envelope. The fact that it Indicated a negative pressure in an isolation mode did not seem to concern operators. 8.2.5 There is no list of equipment required for the system to be operable. The supply fans, recirculat-i ing fan, dampers, and radiation monitor should be listed. Apparently the emergency filtration system (, is the only part of the system required to be c;crs-ble. 8.2.6 Limit 4.12. A.2.d. requires operation of the system for at least 10 hours every month. The basis for j i this limit is to remove moisture in the charcoal  !! adsorber. Since there is no heater in the filter train, a lesser run time to verify operability should be considered. (See Regulatory Guide 1.52 section 4.d.) 8.2.7  ! There is no limit as to the naximum temperature in the control room envelope. An assessment should. be made of the instrument ratings and a limit estab-lished where instrumentation will not be adversely 1 a f fteted.  ; l 8.2.8 The action statement in Limit 3 12. A.3. allowing the system to be inoperable for seven days generally applies to a system that has redundant components throughout the system. This limit should be rev,ewed to determine its adequacy for a nonredun-dant system and for exposure rates expected from a design base accident. I 8.2.9 Consideration should be given to providing a redundant radiation monitor.

l 1 1 Copper Nuclear Station l Page 4 8.3 HVAC Flow and CRE Temocrature Measurements 8.3.1 Although the emergency air flitration units were not in operation, field measurements indicated that air j was flowing through these units at 45-50 percent of the flow which passed through the unit during opera-tion in the emergency supply mode. 8.3.2 Air temperatures behind the control room instrument 1 i panels were slightly above control room ambient generally about +3*F and in no case more than 7*F  ! above normal ambient. 833 The cable room was negative with respect to the computer room and control building. There was significant air movement into the cable room from these areas as indicated by smoke tests with the  ; system in the emergency supply mode of operation. I This allows unfiltered air to be supplied to the control room via the" cable room. l t 8.3.4 It was reported that during halon system testing in ) the computer room, halon leaked into the cab 1'e '

room.

' '( B 3.5 Air flow velocities through the charecal adsorber were about 2005 of design when the system was oper- ' ating in the emergency mode. 8.4 Outside Air Infiltration - I A review of the III.D.3.u. submittal is very confusing as to what the design inleakage is. One could assume design inleak-age of 10-450 crm from the submittal. We were unable to measure the infiltration rate but the following observations were made. 8.4.1 Access to the control room was through a single door which communicated with the control building (not part of the control room envelope). This access places you in a hallway (part of the control room envelope) outside the control room. The hellway is in the same ventilation zone as the control room. A locked door provided access to the control room from the hallway. 8.4.2 The control room hallway had access to the computer room. 8.4.3 The doors from the control building to the control room hallway and from the control room hallway to the computer room were provided with seals to mini-mine air leakage across the control room envelope l

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J boundary. These were the only doors that were provided with seals to minimize air leakage across the control room envelope boundary. _ { 8.h.4 Access to the cable room was through a locked door ' in the computer room, down a stairway, and through another door. There is also an emergency exit door j from the cable room to the control building.

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8.h.5 The control room, control room hallway, and cable room are in the control room envelope. These areas are in the control building. Most of the control 3 l building including the computer room is outside the  ! control room envelope. $ 8.4.6 There was an alarmed emergency exit from the cable l l 0 room to the control building. 8.h.7 Smoke tests showed pressure in the control room ' \ hallway was positive with respect to the control I tullding and to the. computer room. The CR-HVAC l system was in the emergency supply mode of operation when the tests were made. , E.h.8 Air flow velocities through the main supply 1:cle-tion valve when isolated was about 20% of the air flow measured in normal operation. This was about five times the air flow through the emergency supply 1 filtration unit. 6.4.9 Air velocity measurements on the intake stack and exhaust stack during emergency supply mode of opera-tions showed that four times more air was being exhausted from the control room envelope than was being supplied. This was apparently because of exhaust damper leakage and the inleakage of air across the control room envelope boundary into the cable room. This inleakage allows unfiltered air to enter the control room envelope. 8.5 LER Evaluation Since there is no Technical Specification limit on operability of equipment or high temperature LER's have not been written concerning loss of cooling to the control room envelope. Discussion with plant personnel did reveal that there has been several times that cooling has been lost to the control room HVAC system. One such event was identified by searching for maintenance work requests that was issued on associated com- _ ponents. All cooling water was secured to the refrigeration l

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>( unit for a period of about 26 hours. The plant was in the refueling mode of operation. There were no log entries concerning the event '(certain logs were' not found for the dates involved) other' than the issuance of the work request and powering down'of the plant computer. Subsequent discussions with plant personnel revealed that control panel covers were removed and portable fans were positioned to cool Instrumentation. The maximum temperature reached was 97'T but it was uncertain exactly where the tem-perature was read. There was .no apparent loss of instruments- - tion. i f f i t i

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