ML20214M154

Forwards Rept of 851107-08 Survey of Util Control Room Re Control Room Habitability.Survey Part of Industry Sampling of Several Plants & in Near Future Will Be Included in Formal Rept to Be Used in Considering Regulatory Activities

ML20214M154
Person / Time
Site:	Vermont Yankee File:NorthStar Vermont Yankee icon.png
Issue date:	05/20/1987
From:	Rooney V Office of Nuclear Reactor Regulation
To:	Capstick R VERMONT YANKEE NUCLEAR POWER CORP.
References
NUDOCS 8706010197
Download: ML20214M154 (14)

Text

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Docket No.: 50-271

^'w Mr. R. W. Capstick

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Licensing Engineer

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Vennont Yankee Nuclear Power Corporation 1617 W( tester Road i

Framingham, Massachusetts 01701

Subject:

Control Room Habitability Survey During November 7 and 8,1985, representatives from the NRC staff and our contractor, Argonne National Laboratory, surveyed the Vermont Yankee con-trol room with respect to control room habitability. The survey was part of an industry sampling of several plants, and in the near future will be included in a formal report which will be used in considering further regulatory activities.

For your information we have enclosed a report of our survey. No action is required of you at this time.

Sincerely Vernoh Rooney, Project Manager Project Directorate T-3 Division of Reactor Projects I/II

Enclosure:

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r, Docket No.: 50-271 Mr. R. W. Capstick Licensing Engineer Vermont Yankee Nuclear Power Corporation 1617 Worcester Road Framingham, Massachusetts 01701

Subject:

Control Room Habitability Survey During November 7 and 8,1985, representatives from the NRC staff and our contractor, Argonne National Laboratory, surveyed the Vemont Yankee con-trol room with respect to control room habitability. The survey was part of an industry sampling of several plants, and in the near future will be included in a fomal report which will be used in considering further regulatory activities.

For your information we have enclosed a report of our survey. No action is required of you at this time.

Sincerely Vernoh Rooney, Project Manager Project Directorate I-3 Division of Reactor Projects I/II

Enclosure:

As stated cc: See next page DISTRIBUTION:

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Mr. R. W. Capstick Vermont Yankee Nuclear Power Corporation Yemrmont Yankee Nuclear Power Station cc:

Mr. W. G. Weigand W. P. Murphy, Vice President President & Chief Executive Officer and Manager of Operations Vermont Yankee Nuclear Power Corp.

Vermont Yankee Nuclear Power Corp.

R.D. 5, Box 169 R.D. 5, Box 169 Ferry Road Ferry Road Brattleboro, Vermont 05301 Brattleboro, Vermont 05301 Mr. Donald Hunter, Vice President Mr. Gerald Tarrant, Commissioner Vermont Yankee Nuclear Power Corp.

Vermont Department of Public Service 1671 Worcester Road 120 State Street Framingham, Massachusetts 01701 Montpelier, Vermont 05602 New England Coalition on Nuclear Public Service Board Pollution State of Vermont Hill and Dale Farm 120 State Street R.D. 2, Box 223 Montpelier, Vermont 05602 Putney, Vermont 05346 Mr. Walter Zaluzny Vermont Yankee Decommissioning Chairman, Board of Selectman Alliance Post Office Box 116 Box 53 Vernon, Vermont 05354 Montpelier. Vermont 05602-0053 J. P. Pelletier, Plant Manager Resident Inspector Vermont Yankee Nuclear Power Corp.

U.S. Nuclear Regulatory Commission Post Office Box 157 Post Office Box 176 Vernon, Vermont 05354 Vernon, Vermont 05354 Raymond N. McCandless Vermont Public Interest Research Vermont Division of Occupational Group, Inc.

and Radiological Health 43 State Street Administration Building Montpelier, Vermont 05602 10 Baldwin Street Montpelier, Vermont 05602 Acting Regional Administrator Region I Office Honorable John J. Easton U.S. Nuclear Regulatory Commission Attorney General 631 Park Avenue State of Vermont King of Prussia, Pennsylvania 19406 109 State Street Montpelier, Vermont 05602 Mr. R. W. Capstick Vermont Yankee Nuclear John A. Ritscher, Esquire Power Corporation Ropes & Gray 1671 Worcester Road 225 Franklin Street Framingham, Massachusetts 01701 Boston, Massachusetts 02110 t

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I VISIT TO VERMONT YANKEE i

System Description and Operation On November 7 and 8,1985, representatives from Region I, NRR and Argonne National Laboratory surveyed the Vermont Yankee control room. The control room is designed.to take 3700 cfm of outside air and 8800 cfm of recirculated control room air, pass it through a prefilter, c. hiller, and heater prior to discharging a portion of it back into the control room. Of this air flow of 12,500 cfm of air, 3400 cfm is sent to the cable vault. The III.D.3.4 submittal had indicated the 3400 cfm first went to the computer room and then to the cable vault. However, the ventilation system has been modified such that only 200 cfm of control roon intake air is supplied to the computer room.

l The computer room is cooled by a separate cooling unit which provides no additio'nal ventilation air. The remaining flow (3200 cfm) is sent to the cable vault. A total of 300 cfm is exhausted by control room toilet and the control room kitchen fans.

During a toxic gas incident, the supply / recirculation fans for the control room continue to operate but the intake, which has a circular damper shaped like a satellite dish, is isolated. The exhaust fans from the toilet and kitchen are automatically shut off. The control room is pressurized to 1/8" W. G. through the use of bottled air with a halon type discharge. A total d

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3 of 106 ft of air is discharged into the control room at a pressure of 440 psi in a period of 20 seconds. Another four bottles of air gradually discharge j

their contents, also at 440 psi to bring the control room to a positive pressure of 1/8" W. G in a period of 4 minutes. Operators are expected to have donned their bio-packs within this period of time.

The only mechanism for isolating the control room is with a toxic gas signal.

Placing the system in recirculation does not shut off the toilet and kitchen exhaust fans. This was demonstrated when the control room operator placed the system in recirculation.

Plant personnel did not seem to be aware that the radiological analysis of III.D.3.4 had assured the control room isolated so that that the only source 4

of activity was an inleakage of 20 cfm which the licensee indicated was verified by a SF test. Plant personnel presumed that the exhaust fans could 6

continue to operate during such an incident.

A check of operating procedures also confirmed this. The operation of such fans made the control room extremely negative in terms of pressure.

This was evidenced when the fans were turned off after recirculation was ended. The blades of the kitchen and toilet exhaust fans quickly reversed their direction.

1 The control room appeared to be neutral when operating in the nomal makeup.

mode. Measurements of flow were not taken at the exhaust dampers and at the I

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. discharge to the computer room and to the cable vault.

It is possible that the significant negative pressure seen by the control room during recirculation may occur as a result of pulling air from these two general areas.

The intake damper seemed to seal very tightly. The cognizant engineer at Vermont Yankee indicated that this damper had replaced a louvered damper.

Leakage seemed minimal during recirculation.

Control Room Temperature Control room temperatures seemed to be constant throughout the control room envelope. When the system was placed in recirculation the control room

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temperature increased from 71*F to 74*F in about 20 minutes. One shift supervisor indicated that this was not unusual and that temperatures had reached 90'F in the control room. Another indicated that they often placeo the system in recirculation during the winter to provide some additional heat to the control room. One individual indicated that the chillers are continuously maintained but do not begin operation until reaching 74*F.

The controi room equipment qualification temperature has not been determined.

There are no technical specifications addressing temperature limitations in the control room.

System Integrity and III.D.3.4 Analysis The radiological dose evaluation consisted of 2 sources. One was MSIV leakage and the other was the filtration of various leakage by the equivalent of a I

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standby gas treatment system (SGTS) and subsequent release from the stack.

Their respective contribution to the thyroid dose was 18.8 and 8 rem. Vermont Yankee did not add these two values together because they maintained that the control room operator could only receive one or the other due to meteorological conditions. This is most probably true.

It was difficult to assess the SF experiment in the control room. Since a 6

portion of the total 20 cfm inleakage was attributed to ingress and egress of the control room, the acceptance criteria should have been somewhat less than 20 cfm. The data reported to Vennont Yankee seemed to indicate that during a 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> period of the test, there was a decrease in SF concentration while a 6

concentration. This could not similar 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> period showed an increase in SF6

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be explained by the cognizant engineer.

The control room at Yermont Yankee and its ductwork appeared to be very tight. A considerable amount of time had been spent to ensure this.

Vermont Yankee utilizes Beckman instrumentation to monitor for toxic gases.

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They originally experienced some problems with radio frequency interference causing the CL detectors to spike. Water sometimes masked the reference cell 2

for the CO m nitor but a periodic N2 purge has corrected this problem. The 2

methanol detector experienced a problem with its dry cell power supply. A recent technical specification submittal addressing toxic gases has been rejected by the NRC.

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D The control room intake does not have a radiation monitor nor does it have an area radiation monitor.

Conclusion Based upon the survey, Vermont Yankee should have technical specifications on the control room which:

(1) Demonstrate that the control room isolates on a toxic gas incident and a radiological incident.

(2) Demonstrate that control room envelope is maintained so that in

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leakage is no greater than 20 cfm.

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(3) Limit equipment temperatures.

Similar to other facilities surveyed, there seems to be a breakdown in the transfer of information from those doing the safety evaluation to those implementing the safety evaluations assumptions through operations and procedures.

Radiation monitors should be added to the control room intake and to the control room area.

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Vermont Yanke t Nuclear Station Page i PLANT VISIT

SUMMARY

REPORT 1.

Plant:

Vermont Yankee Nuclear Station 2.

Utility:

Vermont-1 Yankee Nuclear Power Corp.

3.

Location:

Vernon. Vermont 4

NRC Region:

I S.

Visit Date:

November 7-8, 1985 6.

Participants from Argonne National Laboratory:

J. W. Driscoll R. J. McConnell 7.

Scope:

The plant visit was made to gather information on control room j

habitability - Generic Issue 83.

Specifically the safety analycis (including III.D.3.4. submittal and the Nac starr safety evalua-(.

tion) and plant procedures were reviewed to determine what cpora-tional practices are being employed.

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

8.

Findings:

8.1 Procedures I

8.1.1 Ceneral In preparation for the review. several maintenance and operating procedures were reviewed. The proce-dures were remarkably clear as to the purpose and method to be employed and in general the best we have reviewed to date.

8.1.2 Findings (1) The procedures did not require an automatic or manual isolation of the normal air intake after a high radiation alara.

(2) Alars response and calibration procedures t

indicated different trip setpoints for the initiation of the automatic isolation of the toxic gas isolation system on a high Cle signal. The design analysis indicated a third value based on time required to put the system I

in the isolated mode of operation.

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Vermont Yankee Nuclear Station Page 2 (3) The safety analysis performed by Yankee Atomics involvin6 the radiation dose to the control room operator was based on the control room being isolated. The intent of the safety analysis was not included in plant proce-dures.

It is recommended that a member of the safety analysis group be included or the Proce-dures Review Committee for the review of proce-dures related to safeguards system.

8.2 Technical Specifications 8.2.1 Ceneral There is no existing Technical Specification for the Control Room HVAC System at Vermont Yankee..The review team was informed that a Technical Specifica-tion is being prepared to cover the Toxic Gas Isola-tion System and the Emergency Breathing Air System.

8.2.2 Findings

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The following items should be considered for inclu-sion as Technical Specification items:

(1)

The basis for the control room operator dose uses standard evaluation methods and assumptions are in general agreement with other plants reviewed.

The key item among the assumptions is that the unfil-tered infiltration rate is 20 CFM for the duration of the accident.

Since the safety analysis assumed a 20 CFM infiltestion rate, the Technical Spacificit!<.:

snould require the same automatic isolation on a high ractation as is provided by a high toxic gas signal. This would require the addition of a radiation detector (s) at the outside air inlet and control circuitry to place the con-trol room HVAC system in the recirculation mode. See discussion in Section 8.4. Outside Air Infiltration.

(2)

The equipment, e.g., bottled air, toxic gas monitors, radiation monitors, needed during a toxic gas release or radiation accident should be evaluated and this equipment should be specified in the Technical Specifications.

(3) A limit for maximum temperature in the control room envelope should be included in the Tech-i nical Specifications. An assessment of the f

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instrument rating should be made and a limit established where instrumentation will not be adversely affected.

(4)

A test should be run periodically to verify the leaktightness of the control room envelope.

This could be accomplished by pressurizing the control room emergency breathing air bottles and observing that control room envelope pressure was maintained at 1/8-in. WG for four minutes (design criteria of emergency air breathing system based on a 20 CFM inleakage).

or by using a small fan to pressurize the control room through the toilet and kitchen exhaust fan penetration on an alternating bases.

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(5)

Response time limits should be established for the time from sensing a toxic gas to the actual closure of inclation valves.

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The minimum pressure required on the emergency breathing air banks snould be included in the Technical Specifications.

8.3 HVAC Flow and CRE Temperature Measurements 83.1 Ceneral The control room HVAC system is a very tight system and there are very few places provided to obtain air flow measurements.

During normal operation.

3700 CFM of unfiltered cutside air is mixed with the control room return air (about SS00 CFtt).

The intake structure for the control room HVAC system is shared with another system.

8 3.2 Findings (1)

Readings were taken at the intake structure with the control room and administration build-ing HVAC systems in normal operation and with the control room system in the rectroulation (Administration Building HVAC system mode.

remains in normal operation.) The difference of the two readings indicated that 3700 CFM fresh air makeup to the control room HVAC system is accurate.

(2)

Measurements using a smoke gun indicated that 4

the control room was at a neutral pressure with J

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Vermont Yankee Nuclear Station Pacc 4 respect to adjacent areas when the system was in the normal supply mode and that the control room is at a negative pressure with respect to adjacent areas when in the emergency isolation mode.

(3) Normal flow through the kitchen and toilet exhaust fan was measured to be about 150 CFM Flow measurements were not taken in the each.

Emergency Isolation mode.

(4)

When the system is in the Emergency mode, the Kitchen and Exhaust Fans continue to run and their respective isolation dampers remain open.

(5)

Temperature measurements throughout the control room envelope indicated an even temperature in all areas. The maximum variation was about 3*F.

(6)

When the 00ntr01 room was isciated in the

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emergency ~.0c9 the temperature of the cettrol s

g' room general arca rese about 5'F in 20-30 minutes.

(7)

Measurements were not taken with the system operating in the Toxic Gas Isolation mode.

(8)

Flow readings were not taken in the supply line of the cable valut and battery rooms due to inaccessibility to ducting.

Flow reading in this line in the Emergency Isolation Mode may have some bearing on the control room negative pressure durine syntet is0lation.

t 8.4 Outside Air Infiltration i

i 8.4.1 General The Vermont Yankee control room system is very tights we believe this is the tightest control room envelope that we have seen to date.

In 1982 an SF.

air dilution test was run to confirm the leaktight-ness of the control room envelope. The data that was obtained is somewhat inconclusive since the system was not placed in the emergency mode but in what is now called the toxic gas isolation mode, which closed the fresh air inlet isolation valve, the supply to the computer and cable vault isolation valve, and the kitchen and toilet fans were stopped e

l with their respective isolation valves closed.

The SFs test indicated in this condition the control l

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room has little or no inleakage. However, if the system is placed in the emergency mode using a switch in the control room the kitchen and toilet exhaust fans are not secured and their respective isolation dampers remain open. Furthermore, we are not convinced that the SF. test data is conclusive for the low inleakage found in the Vermont Yanvae control room.

It was also not evident that the control room temperature was considered as having any affect on the SF concentrations during the course of the test (see Item 8.5.2).

8.4.2 Findines Since the safety analysis assumed a 20 CFM infil-tration rate based upon the control room being isolated, the review team wanted to know what caused 3

isolation of the control room and how quickly the outside air makeup was stopped.

The following observations were made:

1 A review of plant drawings and the FSAR indicated that no automatic action occurred.

2.

A review of plant procedures did not indicate any operator action was required.

3.

On discussing items 1. and 2. above with the plant staff, the plant staff seemed to be under the impression that it was not necessary, under an accident condition, to secure the fresh air makeup because the radiation challenge was below the linits set forth in General Design Criterion 19.

The plant staff did, however, point out that fresh air makeup could easily be shut off by placing a control switch for the control room HVAC system, located in the control room, in the emergency position. The review team requested that this be done. The result of shutting off make up air was that the control room envelope went from a neutral pres-sure to a negative pressure with respect to the surrounding areas.

The negative pressure was apparently created due to the continued operation of the kitchen and toilet exhaust fans while in the emergency recirculation mode of opergtion.

It was apparent to the review team that under the negative pressure conditions, infiltration r;

would certainly exceed the 20 CFM assumption.

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Concern by the review team about how the control room operators would spat down the exhaust fans and dampers indicate that a con-venient method is not available within the control room.

The conclusion, on air infiltration, by the review team is:

Adequate procedures and or controls are not avail-able to ensure that the safety analysis assumption (20 CFM unfiltered inleakage) can be met.

B.5 LER Evaluation 8.5.1 ceneral Since there is no Technical Specification applicable to the control room HVAC system, LER's have not been written concerning loss of cooling to the control room envelope.

8.5.2 Findings

,fs When the systo:a was placed in the emergency recircu-lation mode. 1 noticeable increase in control room ambient temperature in a short period of time was observed by the review team (see Itse 8.3.2(6)3.

Discussion with the shift supervisor indicated that the temperature has risen to above 90*F with the system in the emergency mode for about two hours.

An evaluation should be made to determine that the cooling equipment operates to provide cooling in both normal and emergency modes of operation.

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