ML20214P507

Discusses 861027-30 Survey of Control Room Ventilation Sys. Review of Listed Observations & Confirmation That Util Analyses & Regulatory Commitments Re Control Room Ventilation Sys Are Still Valid Requested within 45 Days

ML20214P507
Person / Time
Site:	Fort Calhoun
Issue date:	05/28/1987
From:	Paulson W Office of Nuclear Reactor Regulation
To:	Andrews R OMAHA PUBLIC POWER DISTRICT
Shared Package
ML20214P511	List: ML20214P507 ML20214P560
References
REF-GTECI-083, REF-GTECI-NI, TASK-3.D.3.4, TASK-TM NUDOCS 8706030419
Download: ML20214P507 (6)

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[@ Clog %o UNITED STATES 8' 7o NUCLEAR REGULATORY COMMISSION g i WASHWGTON. D. C. 20666

\*****/ May 28,1987 Docket No. 50-285 Mr. R.L. Andrews Division Manager - Nuclear Production Omaha Public Power District 1623 Harney Street Omaha, Nebraska 68102

SUBJECT:

SURVEY OF FORT CALHOUN STATION CONTROL ROOM VENTILATION During the period of October 27-30, 1986 a survey was conducted at the Fort Calhoun Nuclear Power Plant. The survey was performed by John Driscoll and Roger Evans, Argonne National Laboratory (ANL), and Jack Hayes, NRC. The purpose of the survey was to evaluate: (1) the operation of the control room ventilation system and its ability to maintain the Fort Calhoun control room habitable and (2) the adequacy of the plant's technical specifications and procedures to demonstrate system operability and system capability consistent with the assumptions made in the plant's TMI Action Item III.D.3.4, " Control Room Habitability" analysis and the NRC staff's associated safety evaluation.

The survey team gathered flow rate data in various portions of the control room ventilation 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 specifica-tions and procedures, and the TMI Action Item III.D.3.4 analysis. The observa-tions were discussed with Omaha Public Power District personnel during the exit meeting; however, detailed results of the flow analysis were not available at that time.

The survey team's observations are listed below:

General Observations (1) Data gathered by the survey team showed that portions of the control room envelope were at a negative pressure when the ventilation systems were operating in the emergency mode of operation associated with a radiological challenge. This is contrary to plant technical specifications and the design basis for the facility which require it to be positive.

(2) There appears to be a significant amount of leakage from the air handling units such that under certain operating conditions a considerable amount i of unfiltered inleakage into the air handling unit may occur. Since you assumed no unfiltered inleakage into the envelope in your revised l III.D.3.4 analysis of September 23, 1985, the inleakage associated with j these units appears contrary to your assumption.

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May 28,1987 (3) There is a considerable amount of inleakage into the control room envelope when the control room ventilation system is operating in its emergency modes of operation. In the case of a radiological challenge, inleakage measured by the survey team includes 740-1100 cfm of flow through the outside air normal makeup damper; 500 cfm of inleakage into the air handling unit VF-468, and 2000-3800 cfm in the return duct work from the control room. For the toxic gas challenge, inleakage includes 600-1500 cfm through the normal and emergency outside air intakes, 4700 cfm into the air handling units when VF-46B is operating, 3900 cfm into the return ductwork from the control room when VF-46B is operating, and 2100 cfm in the control room supply ductworks when VF-46A is operating.

Because of these large inleakage rates and the fact that portions of the control room are at a negative pressure during the radiological mode of opera-tion, you should perform a reanalysis to determine whether the conclusions previously presented in your TMI Action Plan Item III.D.3.4 analysis are still valid.

Observations involving plant operation include:

(1) The members of the plant staff responsible for the ventilation system need to be familiar with the licensing basis for the plant so that they understand the impact of changes to design conditions involving the control room ventilation equipment and its envelope.

(2) The control room envelope should be at a positive pressure of 1/8 inch W.G. with respect to all adjacent areas under the emergency mode of operation for a radiological incident. Areas where improvements can be made include the sealing of doors, dampers, integrity, and the controlling of leaks in the air handling units.

(3) Additional attention should be given to maintaining the air handling units.

(4) Significant flow occurs between the idle control room air handling unit and the operating units. There seems to be recirculation through dampers which do not isolate.

(5) Control room temperature is the most evenly distributed of any control room the survey team has seen to date.

Observations involving system design include:

(1) The control room ventilation system is susceptible to single failure (e.g., normal intake damper 860C, emergency intake damper 860A, the toilet exhaust damper, and the control room exhaust damper RCV-846).

(2) The control room envelope pressure should be measured relative to all adjacent areas not just to atmosphere.

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. o May 28, W (3) The location of the control room ventilation system equipment may make it susceptible to a high energy line break and to steam intrusion into the control room.

(4) The location of the diesel generator exhaust is at the same elevation as the control room intake. A concern is the drawing of CO into the control room envelope through the control room emergency intake.2 (5) The licensee should verify whether the capacity of the HEPA filter utilized in the control room emergency ventilation system is 1000 cfm or 1200 cfm. Flow appears to be outside the technical specification limit of design 110%. The design value should be noted in the technical specification.

(6) The toilet exhaust damper seals the tightest of any the staff has seen to date.

(7) The modification to one of the auxiliary building fans to allow it to operate at a variable speed should be considered for two fans so that redundancy is provided. With such a change, credit could be taken for the ECCS charcoal adsorber units in the LOCA dose analysis and the control i room operator dose analysis.

(8) The adequacy of system cooling capability is questionable because both air handling units must be operated during the summer to maintain the control room comfortable.

Observations on technical specifications included:

(1) The present technical specifications do not track with the licensee's I

assumptions utilized in their analyses and accepted by the NRC staff in their SER. Technical specifications should reflect licensing basis assumptions. Proposed changes were discussed with the OPPD staff and include acceptance criteria of the laboratory test of charcoal and the acceptance criteria to which positive pressure is to be maintained in the control room envelope.

(2) The equipment qualification temperature should be measured in cabinets and not on the control room wall or in the operator station area.

I (3) Other comments were provided to the OPPD staff and included acceptance criteria for in place tests of HEPA filters and charcoal adsorbers, control room equipment and instrumentation qualification temperature.

May 28,1987 Observations on procedures include:

(1) Procedures need to address operation of both air handling units simultaneously as is done in the summer.

(2) Clarification should be provided to the procedure which addresses opera-tion with the control room at a high temperature so that it includes instructions which restore control room integrity in the event of a toxic gas challenge.

(3) The proposed loss of ventilation test should incorporate a temperature criteria such that the tests is halted when either steady state '

temperature is reached and the control room temperature remains constant or the temperature rise is such that the instrumentation and the equipment in the control room are threatened.

Other observations and information are presented in the Enclosure which is the ANLreportcoveringtheFortCalhounSurvey. The ANL report does not consti-tute the NRC staff s position regarding these items.

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

The reporting and/or recordkeeping requirements contained in this letter affect fewer than ten respondents; therefore, OMB clearance is not required under P.L.96-511.

Sincerely,

/A/

Walter A. Paulson, Project Manager Project Directorate - IV Division of Reactor Projects - III, IV, V and Special Projects

Enclosure:

As stated cc w/ enclosure:

See next page DISTRIBUTION Docket File NRC PDR Local PDR PD4 Reading 3 WMt44 F. Schroeder JACalvo P. Noonan WPaulson JCraig OGC-Bethesda EJordan JPartlow ACRS (10)

Fort Calhoun Plant File

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(2) Clarification must be provided to the procedure which addresses operation with the control room at a high temperature so that it includes instructions which restore control room integrity in the event of a toxic gas challenge.

(3) The proposed loss of ventilation test should incorporate a temperature c'riteria such that the tests is halted when either steady state temperature is reached and the control room temperature remains constant or the temperature rise is such that the instrumentation and the equipment in the control room are threatened.

Other comments and/or findings are presented in the Enclosure which is the ANL report covering the Fort Calhoun Survey.

We request that you respond to each of the items discussed above within 45 days of the receipt of this letter. j

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The reporting and/or recordkeeping requirements contained in this letter affect fewer than ten respondents; therefore, OMB clearance is not required under P.L.96-511. /

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Since/ely,

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/ Walter A. Paulson, Project Manager ProjectDirectorate-IV Division of Reactor Projects - III,

Enclosure:

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/ IV, V and Special Projects As stated /

cc w/ enclosure: /

See next page /

DISTRIBUTION /

Docket File .NRC PDR Local PDR / PD4 Reading en "rM'ieM / F. Schroeder J. Calvo P. Noonan W. Paulson '

OGC-Bethesda E. Jordan J. Partlow ACRS (10) /_ PD4 Plant File ybP ognan

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May 28,1987 Mr. R. L.~ Andrews Fort Calhoun Station Omaha Public Power District Unit No. 1 cc:

Harry H. Voigt, Esq.

LeBoeuf, Lamb, Leiby & MacRae 1333 New Hampshire Avenue, NW Washington, D.C. 20036 Mr. Jack Jensen, Chairman Washington County Board of Su Blair,pervisors Nebraska 68008 Mr. Phillip Harrell, Resident Inspector U.S. Nuclear Regulatory Commission P. O. Box 309 Fort Calhoun, Nebraska 68023 Mr. Charles B.' Brinkman, Manager Washington Nuclear Operations C-E Power Systems 7910 Woodmont Avenue Bethesda, Maryland 20814 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission Office of Executive Director for Operations 611 Ryan Plaza Drive, Suite 1000 Arlington, Texas 76011 Harold Borchert, Director Division of Radiological Health Department of Health 301 Centennial Mall, South P.O. Box 95007 Lincoln, Nebraska 68509