ML19317H486
| ML19317H486 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 06/04/1980 |
| From: | Hovey G Metropolitan Edison Co |
| To: | Jay Collins Office of Nuclear Reactor Regulation |
| References | |
| TLL-261, NUDOCS 8006110114 | |
| Download: ML19317H486 (3) | |
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Metropolitan Edison Company Magg Ng[.w-j /"
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Micatetown Pennsy!vame 17067 717 944-4041 Wnter's Direct Dial Numoer June 4, 1980 TLL 261 TMI Program Office Actn:
J. T. Collina, Deputy Program Director U. S. Nuclear Regulatory Commission c/o Three Mile Island Nuclear Station Middletown, Pa.
17057
Dear Sir:
Three Mile Island Nuclear Station, Unit II (TMI-2)
Operating License No. DPR-73 Docket No. 50-320 Plant Vent Stack Cap The purpose of this letter is to inform you that we intend to remove the cap on the plant ventilation stack and discontinue use of the supplemental ventilation system atop the Auxiliary Building on or about June 10, 1980. This letter discusses briefly the current ventilation system and discusses the work that is in progress and which has been completed in connection with uncapping the stack.
Shortly after the incident at TMI-II on March 28, 1979, several plant modifications were made.
One of these modifications included the addition of the supplementa ventilation system atop the Auxiliary Building. This system provided additional fans and filter banks for the processing of ventilation system effluent prior to its release to the atmosphere.
In addition to the additional filter banks and fans, a cap was installed on the top of the ventilation stack, the normal ventilation system effluent point, as a further precaution to ensure that the entire ventilation system flowrate passed through the supplemental filters.
At the time of installation of this supplementary system it was considered appropriate and prudent to add the additional filtering capability offered by this system.
Since that time, however, airborne radioactivity levels, both gaseous and particulate, have decreased to the point that continued operation of the supplemental ventilation system is no longer justified.
Furthermore, you are aware of the existence of potential bypass paths in the ventilation system that may preclude HEPA filter treatment of the effluent gas stream prior to atmospheric release if the supplemental ventilation system were taken out of service.
These potential bypass paths were identified incident to occasionsl indication " spikes" on AM-5, the inlet flow stream radiation mcnitor to the supplementary ventilation system filters.
With the present ventilation system configuration, pressure in the ventilation f j
davork is negative with respect to the Auxiliary Building and Fuel Handling / /
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IfD i.totropohtar: Ecson Comoany is a Momw of tne General Puche Utaties System 8006110(
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TMI - II BCC LIST Mrs. Pat Higgins Mr. George Kulynych Edison Electric Institute Babcock & Wilcox 1111 19th Street, NW P.O. Box 1260 Washington, D.C.
20036 Lynchburg, VA 24505 l
lir. E. L. Blake, Jr.
Mr. T. F. Hartley, Jr.
Shaw, Pite=an, Potts & Trowbridge Marsh & McLennan, Inc.
1800 "M" Street, NW 1221 Avenue of the Americas Washington, D.C.
20036 New York, NY 10020 Mr. R. Sanacore Mr. A. S. Dam American Nuclear Insurers Burns & Roe, Inc.
The Exchange - Suite 245 650 Winters Avenue 270 Farmington Avenue Parmus, NJ 07652 Far=ington, CT 06032 Dr. Steve Long, Director Ms. Margaret Reilly Power Plant Siting Program Chief Div. of Reactor R'eview Department of Natural Resources PA Dept. of Environmental Resources Tawes State Office, Building B-3 Fulton Bank Building 580 Taylor Avenue Harrisburg, PA 17120 Annapolis, MD 21401 U. S. Nuclear Regulatory Commission i
J. C. DeVine - TMI Trir. 110 c/o Document Management Branch R. W. Heward - TMI Trir. 180 Washington, D.C. 20555 W. N. Moreau - Met-Ed Reading J. T. Collins - NRC Trir. 1 G. Hovey - TMI - Trir. 105 E. G. Wallace - Parsippany Licensing P. Clark - GPUSC Parsippany W. F. Schmauss - TMI-II GRC Chairman-Parsip.
R. Fenti - QA - TMI Trir. 22 D. H. Reppert - TMI GORB Secretary - Parsip.
J. J. Barton - TMI Trir. 102 C. E. Hartman - IMI-I PORC Chairman - TMI-I L. W. Harding - TMI Licensing M. A. Shatto - TMI-I PORC Secretary - TMI-I
.R. M. Klingaman - Met-Ed Reading G. A. Kunder
'DfI-I PORC Chairman - Trl. 104 N. Kazanas - Parsippany - QA D. C. Carl - IMI-II PORC Secretary - Trl. 104 J. F. Wilson - TMI Trir. 14 B. A. Hockley - Discovery Room Crawford J. G. Herbein - TMI Trir. 118 J. Theising - Bechtel,'IMI - Admin Bldg B. Dallard - TMI Trir. 16 R. L. Rider - Bechtel - TMI Trir. 173 G. P. Miller - IMI-I D. Smith - Reading - Production Supervision R. C. Arnold - TMI Trir. 201 P. S. Walsh - GPU Parsippany D. G. Mitchell - Met-Ed Reading C. A. Negin - TMI - Trir. 24 S. D. Chaplin - TMI Licensing B. Elam - TMI Trir. 104 L. L. Lawyer - TMI Trir. 118 J. Chwastyk - TMI-II Ops.
G. J. Troffer - TMI - Trir. 198 File:
02.0016.0001.0001.02 44
.. i.' s J. T. Collins TLL 261 atmosphercs, including the ductwork and penthouse located on the exhaust fan discharge sides. Therefore, in the current mode of operation, any openings (leakage paths) in that ductwork downstream of the exhaust filters has the potential to allow particulate contamination to enter cne system and bvpuss the in-plant filters.
In the current mode, any bypass leakage would be trapped in the supplementary filters.
.\\fter uncapping the vent stack, however, with the supplementary ventilation system out of service, the ventilation duct pressure on the exhaust fan discharge will become positive with respect to sources of airborne centamination and will no longer represent a leakage path with the potential for bypassing the ventilation system filters. However, the ventilation ductwork from the outlet of the filters to the inlet of the exhaust fans could remain as a source of potential bypass leakage flow since it will continue to be negative with respect to Auxiliary Building and Fuel Handling Building atmosphere.
In order to minimize the possibility of the existence of leakage flow path; between the filters and the fans, work is currently underway to inspect the ductwork, to identify potential leakage paths, and to rspair ther..
This work will be completed prior to removing the plant vent stack cap.
The Service Building ventilation system incorporates a potentially contaminated exhaust system that is serviced by a HEPA filter bank (AH-F-28) prior to input to the plant vent stack. One area exhausted by this system is the hot instrument shop. This shop is physically located over an area that communicated directly with the Auxiliary Building 280 ft. elevation.
Floor penetrations in the shop for piping represent potential flow paths for the Anv414=ry Building air to pass to the Service Building.
Even though this potential consnunication of the atmospheres exists, the HEPA filters will remove any particulate airborne radioactivity prior to atmospheric release.
In addition to the ductwork inspection program addressed previously, additional precautions have been enken prior to the removal from service of the supplemental ventilation system and the removal of the cap from the stack.
These additional precautions have included the re-balancing of the ventilation system to ensure proper operation and correct ventilation system flow rr.te.
The Auxiliary Building and Fuel Handling Building exhaust filters have been successfully re-tested with DOP to the requirements of the TMI-II Technical Specifications.
Testing was completed on May 10, 1980.
filter bank was successfully tested with DOP.In addition, the Service Building HEPA Testing on this filter bank was completed on May 28, 1980.
Should you desire to discuss this matter further, please contact either Mr.
E. D. Fuller or Mr. L. J. Lehman, Jr. of my staff.
Sincerely,
/s/ G. K. Hovey G. K. Hovey Director, TMI-II GKH:LJL: hah cc:
B. J. Snyder n