ML20128A718
| ML20128A718 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 05/20/1985 |
| From: | Hukill H GENERAL PUBLIC UTILITIES CORP. |
| To: | Stolz J Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737, TASK-3.D.3.4, TASK-TM 5211-85-2085, NUDOCS 8505240307 | |
| Download: ML20128A718 (5) | |
Text
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o GPU Nuclear Corporation Nuclear-
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Middletown, Pennsylvania 17057-0191 717 944 7621 TELEX 84 2388 Writer's Direct Dial Number:
May 20, 1985 5211-85-2085 Office of Nuclear Reactor Regulation Attn:
J. F. Stolz, Chief Operating Reactor Branch No. 4 Division of Licensing U.S. Nuclear Regulatory Commission Washington, DC 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)
Plan of Action As a result of recent discussions with the NRC staff, GPU Nuclear Corporation (GPUN) is continuing to evaluate the control room HVAC System to insure that optimum protection-is provided for the control room operators. As this evaluation continues, we felt it necessary to keep you informed of our activities and plan of action.
Since our letters of November 30,-1984 and February 28, 1985 the NRC Staff has asked that we review various aspects of the Failure Mode and Effects Analysis. The purpose of this review is to establish an increased level of confidence of satisfying NUREG-0737.
Three specific areas will be analyzed.
In a phone conversation with NRC staff on April 16, 1985, we were informed that doses due to Beta radiation should be considered as limiting vice those due to iodine releases. Secondly, the NRC staff has requested that additional conservatism associated with operator stay time be factored into the dose analysis per the Murphy-Campe Report. As a result, parametric studies are being performed to better define the margin of safety the Control Room HVAC system provides in both the emergency and single failure modes with respect to the above requirements. Although the control room HVAC System maintains a positive pressure during single failure events, as demonstrated by tests, the third review is being performed to determine what steps can be taken to improve the positive pressure margin.
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GPU Nuclear Corporation is a subsidiary of the General Public Utilities Corporation
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5211-85-2085.. May 20, 1985 The results of'these studies will. be verified by a test of the Control Room
'HVAC System.
The.. test will be performed within 90 days of issuance of this
. letter. This duration will allow completion of the planned upgrade to the Control. Room HVAC ducting. However, in the event that the test cannot'be
. performed due..to plant restart activities, the test will be performed no
-later than 6 months after plant start-up.
The attachments summarize the activities in these areas. We will keep you
. informed as this work progresses.
Sincerely, f
1 Director, TMI-1 MI: dis:1790f-Attachments-7 cc:
R. Cbnte J. 'Ihoma
~
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xy. n "m . Attachment'- 1
- InthefGPUNshbmittals'ofNovember30,1984 and February 28,'1985 GPUN provided the acceptance criteria and proposed modifications to achieve
' sufficient. control room habitability conditions.- These criteria and the ~
- proposed modifications met the requirements of NUREG 0737. Although it has been demonstrated by tests that the TMI-1 Control' Room remains at a positive
- 2 pressure even with a single' failure,-during recent conversations with NRC
? Staff,=GPUN was: asked to provide _ built-in conservatism and additional positive-pressure margin; Following are.the revised. criteria and the plan
- of: action _to' satisfy these requests:
Clarified Habitability Requirements 1.: The, dose assessment'should include inleakage;of unfiltered air from sources-(both outside of the plant and inside)_ sIf the positive ~ pressure of the Control: Room is less than 0.1" water-gauge, then-sufficient inleakage'should be assumed to achieve up to 0.1" pressure in the Control. Room during HVAC emergency mode. operation with or without single. failures.. "2. The'30-day. beta dose will not exceed-30 Rem (SRP 6.4). Wnole body _ gamma (dose.should not exceed 5 Rem _(GDC --19, 10 CFR 50 Appendix A). These doses will be based upon-the shift.. occupancy requirements of the Murphy-Campe Report., 3.. The thyroid _ dose will be addressed at a later time, since the NRC is-developing a-Branch Technical Position on Iodine releases. LGPUN's Plan'of Action cTo address-the above re_quirements for the emergency mode.of operation _ and Lthe single. failure of components identified in the FMEA the following actions.are_ underway: 1. Dose Assessment Analysis Analysis'is underway to detemine the integrated dose to the Control s ' Room-operator utilizing Murphy-Campe assumptions for-the shift occupancy ~ Lfactor. This analysis will determine. unfiltered inleakage flow.lfmits and filtered flow limits which when integrated will provide parametric . values contributing to 30~ day dose limit. Preliminary results of.the dose assessment.show that increased outside ai_r. intake through damper AH-D-39 is desirable because -it reduces beta !and: gamma dose. The results of these' analyses will provide the -information required for-the test discussed in the following section. m
y g:.ej YU$: s 2.~ Basistfor Test? I It'was demonstrated'in.the-January 1985 test that a positive pressure
- higher than 0.1" W.G. was attained in the Control Room due to increased outside air intake during~ the single failure ' test of damper AH-D-37._ It' is, therefore, expected that under single failure conditions operator
' action will admit increased air intake through -damper AH-D-39. This [ action will provide additional capability _ to maintain higher positive pressure margin (close to 0.1" WG) in the control room during emergency -operation with 'or without the single failure of any ' damper and satisfy the 30-day. dose limit. Should a-single failure of any damper result in infringing on the 30 day dose limit, then manual corrective action will -be taken into account. If this manual action is required, the 30 day
- dose assessment will include unfiltered flow for. the initial interval up' to the time when manual corrective action is assumed to be taken consistent with. requirements of. ANSI /ANS-58.8-1984. Corrective action
.may include.the closure of adjacent dampers. - The testing _ outlined in. Attachment II will verify the conditions that exist (e.g. flowrates, direction, and-control: room pressure) during emergency operation with.'or e without single ~ failure of a component.
- 3. _ Toxic Gas Assessment p~ >
The' Control Building Ventilation System-(CBVS) is' designed to have a-minimum of 20% outside. air intake during the normal operation mode. The- -system will be in this operation mode -during the initial phases of' any -toxic gas' releases. Due to the positions of the dampers during normal opefation mode the probability of backflow through damper AH-D-37 is - small. To confirm this the testing outlined in Attachment II will include-a test to detennine' the direction of air flow through AH-D-37 with the HVAC System in the normal operation mode with.and without the Control Building hallway fans on to simulate the worst cases. 1 . I 2 L e
e=- ..-w; e TEST GUTLINE 'GPUN plans to perform confirming tests to verify that-the habitability of the Control Room is not jeopardized,for the radiological and toxic gas releases.. The purpose of these tests is to determine the capability of the HVAC' system to maintain.a' positive pressure in the Control Room up to 0.1" W.G. even with single failures of dampers. This will be accomplished by - opening the' Intake Air Damper AH-D-39. During Emergency Mode of Operation -Tests the 'following-information will. be recorded as a minimum: Flow rate through AH-D-39 damper-Flow rate and direction through the failed damper
- -Pressure in Control Room FR-271 and FI-834 flow indications Back flow through damper AH-D-37 The Control Room pressure versus. inflow will be measured by varying the position of damper AH-D-39.
The purpose of the toxic gas normal operation mode test is to demonstrate ' that the1 system design requirement of a minimum of 20% outside air intake in s.
- conjunction with the normal position of-the system dampers insures a idischarge flow through damper AH-D-37. To simulate the worst case configuration,Lthe AH-D-37 damper will be adjusted to this setting and the direction of flow through AH-D-37 will be recorded with the Control Building -
Lhallway fans AH-E-93A'and AH-E-94A both "on" or "off." t l l l l. =. - -, _}}