ML20138F800

Forwards Control Room Emergency HVAC Sys Repts & Test Results,Per 850404 Meeting & Re NUREG-0737, Item III.D.3.4, Control Room Habitability. Results Indicate Control Room Habitable

ML20138F800
Person / Time
Site:	Three Mile Island
Issue date:	10/18/1985
From:	Hukill H GENERAL PUBLIC UTILITIES CORP.
To:	Stolz J Office of Nuclear Reactor Regulation
Shared Package
ML20138F805	List: ML20138F800 ML20138F831 ML20138F868 ML20138F938
References
RTR-NUREG-0737, RTR-NUREG-737, TASK-3.D.3.4, TASK-TM 5211-85-2172, NUDOCS 8510250354
Download: ML20138F800 (3)

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I GPU Nuclear Corporation g gf Post Office Box 480 Route 441 South Middletown, Pennsylvania 17057-0191 717 944 7621 TELEX 84 2386 Writer's Direct Dial Number October 18, 1985 5211-85-2172 Office of Nuclear Reactor Regulation Attn: J. F. Stolz, Chief Operating Reactors Branch No. 4 U.S. Nuclear Reglatory Commission Washington, D.C. 20555

Dear Mr. Stolz:

Three Mile Island Nuclear Station Unit 1 (TMI-1)

Operating License No. DPR-50 Docket No. 50-289 Control Room Habitability (III.D.3.4, NUREG-0737)

Control Room Emergency Ventilation System Test Results In response to the NRC letter of June 3,1985, GPUN has completed the Control Room HVAC System Tests (Emergency and Failure Modes) with positive results.

The purpose of this letter is to provide the analytical and test results and respond to the NRC questions raised during our April 4,1985 meeting. The attached Test Report and the PLG-0433 report respond to the NRC concerns and contain the information which demonstrates the acceptability of the Control Room HVAC System to provide a safe environment for the Control Room Operators (CR0s).

Permanent door seals were installed on the doors of the Control Building Envelope prior to testing per GPUN commitment (ref. 2). The improved leak-tightness resulted in achieving a positive pressure of 0.1" w.g. or greater in the Control Room (CR) during normal, emergency and various failure mode testing as discussed in references 3 & 4.

As a result of testing, GPUN has decided to change the Control Building HVAC System operating procedure so that damper AH-D-41 A or B is not a single fail ure. This will provide assurance that the positive pressure of 0.1" w.g.

is maintained in the Control Room, elevation 355'-0" of the Control Building, as defined in TDR-728,Section I.l.

Some air registers were blanked off during these tests. An engineering evaluation concluded that this modification does not have an adverse impact on the Control Building HVAC System operation. There is enough spare capacity in the HYE system operation to compensate for the reduction in return flow.

Hence the relocation of the return air register, as committed in reference 2, is not necessary. However, the air registers, which were blanked off during the test, will be permanently isolated.

The PLG report (Attachment 1) provides the details of the analytical model used to determine the radiation dose to the CR0s during radioactive releases as discussed with NRC (during a meeting on April 4,1985). In general, the model is based on:

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5211-85-2172 October 18, 1985

a. Criteria provided in the Murphy-Campe report

b. CR0s stay in the CR for first 24 hrs af ter an incident (24 hr.

shift).

c. Per NRC concurrence and direction during a meeting on April 4,1985 and a subsequent telephone call on April 16, 1985; only beta skin and gamma whole body dose is addressed. The Iodine source term for thyroid dose is being re-evaluated by HRC.

d. The dose analysis includes the contribution from inleakages through the exhaust damper (AH-D-37) as well as that from other in-plant sources such as the patio area.

A parametric study of total intake flow (including various sources) versus beta skin dose and gamma whole body dose was conducted and the results are tabulated in the report.

The report shows that the beta skin dose will never exceed 30 rem for the LOCA as long as the inleakage through the exhaust damper (AH-D-37) is less than 53%

of total inflow or that from the auxiliary building and fuel handling building is less than 95% of the total inflow. The leakage rates which cause gamma whole body dose to exceed 5 rem are larger than those discussed above for the beta skin dose for all flow rates.

The Technical Data Report (TDR), Attachment 2 discusses the objective and the results of testing. The objective was to maintain a positive pressure of 0.1" w.g. in the Control Room during emergency mode of operation as well as during single failure of the components identified in the FMEA study (ref. 4) and to determine that exhaust damper AH-D-37 is not an entry point for toxic gases during normal operation of the system.

The HVAC test was repeated for each failure mode, i.e. failure of dampers AH-D-28, 37 and 41 with an added provision of modulating air intake damper AH-D-39, which contributed to increased Control Room pressure. The TDR also describes the methodology of determining inleakages through the exhaust damper, in-plant leakages such as the patio area as well as possible inleakages through sealed doors and penetrations.

The TDR concludes that the Control Building HVAC System is capable of maintaining a positive pressure of 0.1" w.g. or greater in the Control Room during emergency and all failure mode testing, except simulated failure of dampers AH-D-41 A or damper AH-D-28. As noted previously, to avoid any concern for failure of damper AH-D-41 A or B, GPUN will revise the operating procedures to start the standby train for all Er?rgency Mode actuation. To assure a positive pressure of 0.1" w.g. in tha Control Room during a single failure of damper AH-D-28, damper AH-D-39 must be opened to a predetermined position.

GPUN will revise the operating procedures to open damper AH-D-39 to a predetermined position for all emergency modo actuation.

The TDR concludes that the beta skin dose and gamma whole body dose is always less than 30 rem and 5 rem respectively, for all damper failure modes, as shown by the test results.

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, w 5211-85-2172 October 18, 1985 It also concludes th1t the Control Building HVAC exhaust is not an entry point for toxic gases during normal operation of the system.

Attachment 3 is the test procedure used to perform the HVAC test. The test procedure describes in detail how the test was performed and whicn parameters were measured.

In conclusion, the test results and the radiological analysis show that the TMI-l Control Room will be habitable for the operators during radiological releases. All necessary modifications to the system have been completed except updating the procedure which is currently in progress, installation of the chlorine detection system and permanent isolation of air registers, which will be completed by the end of the cycle 6 refueling outage.

With respect to adequacy of the smoke detection system (ref 5), the Control Building Ventilation System as well as the Control Room proper are provided with smoke detection devices which alert the operator to potential smoke intrusion. These detection systems have been reviewed and approved by the NRC Staff (ref. 6) and provide adequate protection to assure continued habitability of the Control Room.

Sincerely, u

Director, TMI-l HDH/MI/spb nk:2378f/0387A Attachments cc: 0. Thompson R. Conte

References:

1. Letter from NRC, (#5211-85-3154) dated June 3,1985

2. GPUN Letter #5211-85-2043 dated February 28, 1985

3. GPUN Letter #5211-85-2085 dated May 20, 1985

4. GPUN Letter # 5211-84-2289 dated November 30, 1984

5. NRC Letter dated December 28, 1983

6. Fire Protection SER Suppl. No. 4, dated Sept 19, 1980

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