ML20213G412
| ML20213G412 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 05/11/1987 |
| From: | Gallagher J PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | Varga S NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM), Office of Nuclear Reactor Regulation |
| References | |
| GL-87-05, GL-87-5, NUDOCS 8705180274 | |
| Download: ML20213G412 (9) | |
Text
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O PHILADELPHIA ELECTRIC COMPANY 2301 MARKET STREET P.O. BOX 8699 PHILADELPHIA, PA.19101 12151 8 41 5001 JOstpH W. G ALLAGHER 7."..".'/.'.".5"I.-.
May 11, 1987 Docket Nos. 50-277 50-278 Mr. Steven A. Vorga, Director Division of Reactor Projects I/II U.S. Nuclear Regulatory Commission ATTN:
Document Control Desk Washington, D.C.
20555
SUBJECT:
Peach Bottom Atomic Power Station Generic Letter 87-05 dated March 12, 1987 Degradation of Mark I Drywells
Dear Mr. Vorga:
On March 12, 1987, the NRC issued Generic Letter 87-05 titled " Request for Additional Information-Assessment of Licensee Measures to Mitigate and/or Identify Potential Degradation for Mark I Drywells".
The Generic Letter concerns the discovery of corrosion in the Mark I BWR Containment Drywell Shell at the Oyster Creek Nuclear Generating Station.
This letter provides information pertaining to Peach Bottom Atomic Power Station (PBAPS) Unit 2 and Unit 3, in accordance with the Generic Letter.
Each request is restated below, followed by the Philadelphia Electric Company's (PECo's) response.
1)
" Provide a discussion of your current program and any future plans for determining if the drain lines that were provided at your facility for removing any leakage that may result from refueling or from spillage of water into the gap between the drywell and the surrounding concrete or from the sand cushion itself are unplugged and functioning as designed."
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Mr. StGvan A. Vdrga May 11, 1987 Page 2
Response
Exhibits 1 and 2 are attached to supplement the following information.
The design of PBAPS Unit 2 and Unit 3 provides for the collection and removal of leakage from the two-inch air gap space between the exterior of the steel drywell containment _ vessel, and the surrounding reinforced concrete drywell shield wall, by air gap drain lines.
These drain lines are located adjacent to the drywell immediately above a compacted sand pocket at elevation 120'-1".
The drain lines and the sand pocket are separated by 18-gauge sheet metal.
Each PBAPS unit has four four-inch air gap drain lines which are routed from the air gap at elevation 120'-1" to elevation 93'-0" in the Torus Room.
The location of each of these drain lines are as shown on Exhibit 1.
A detail displaying the location of the drain lines relative to the same pocket is shown-on Exhibit 2.
On February 4, 1987, with PBAPS Unit 2 at full power, plant personnel determined that each of the four air gap drain lines were operable.
This determination was based on the observation of an air flow into the outlet of each of the vessel air gap lines.
The air flow was identified utilizing ventilation smoke tube kits.
This air flow test will also be performed on the air gap drains of Unit 3 when the unit returns to power.
The NRC will be advised if the observations made during these tests vary from the results obtained during the Unit 2 tests.
A new surveillance test, based on the aforementioned test, is in development for the performance of a functional test of the air gap drains once per operating cycle.
2)
" Provide a discussion of preventive maintenance and inspection activities that are currently performed or are planned to minimize the possibility of leakage from the refueling cavity past the various seals and gaskets that might be present."
~
~Mr. Stavan A. Vorga-May-ll, 1987 Page 3
-Response:-
.At.the present time, no preventive maintenance or inspection activities are performed on the drywell
~
bellows or the penetration weld around the seal drains.
A-study will be performed by PECo Engineering and.
Research Department to determine the feasibility of such an inspection.
The PBAPS design utilizes drains to remove any leakage.
A brief description of'the seal and drain mechanisms is provided below.
f The PBAPS design utilizes stainless steel drywell bellows to prevent water from entering the Reactor Building when the reactor cavity is flooded for refueling operations..The drywell bellows seal has a guard ring plate to protect.it from damage during refueling activities.
The PBAPS Unit 2 and Unit 3 design also provides an
-eight-inch. drain line to divert potential bellows leakage to a waste collector tank.
This eight-inch drain line is fed by four four-inch seal rupture drains located-as shown in the attached Exhibit 3.
A monitoring device is located in the eight-inch drain line for leak detection.
A flow of ten gallons per minute through the eight-inch drain line will result in an annunciator alarm on the refuel floor panel and also will result in an alarm in the main control room.
The r-alarm and flow switch are tested once per operating cycle.
Unlike the Oyster Creek design (displayed in Figure 1 of Generic Letter 87-05),.the PBAPS design
-utilizes a full penetration weld around the seal drains.
Exhibit 3 locates the full penetration weld, the drywell l
bellows, the guard ring, the seal rupture drains, and the monitoring device.
l 3)
" Confirm the information listed in Table 1 is correct 4
with regard to your facility".
r l
Response
The information for PBAPS as listed in Table 1 of Generic' Letter 87-05 is correct.
The attached Exhibit l-2,
" Sand Pocket Detail", and Exhibit 4,
" Sand Pocket Location Detail", provides the NRC with the sand pocket and air gap details missing from the table.
In addition, the material used to form the air gap is
Mr. Stsvan,A. V6rgn.
May 11, 1987 Page 4 expanded polyethylene with the trade name "Ethafoam".
Following the concrete pour, the "Ethafoam" was removed.
The air gap was then sealed with a strip of polyurethane elastic foam material.
If you have any questions or need additional information, please do not hesitate to contact us.
Very truly yours, fi Attachments cc:
Addressee W. T. Russell, Administrator, Region I, USNRC T.
P. Johnse. Resident Site Inspector
4
- COMMONWEALTH OF PENNSYLVANIA ss.
COUNTY OF PHILADELPHIA J. W. Gallagher, being first duly sworn, deposes and says:
That he is Vice President of Philadelphia Electric Company;
, that he has read the foregoing response to the NRC request for information on potential degradation of Mark I drywells as identified in Generic Letter 87-05 and knows the contents
- thereof; and that the statements and matters set forth therein are true and correct to the best of his knowledge, information and belief.
'hal bs.ffu&
u o
Vice President i
Subscribed and sworn to before me this/)Pday
. of//cc 1987 pub s /2 $ wk Notary:Public MELANIE R. CAMPANELtA Notary Public, Philadelphia Philadelphia Co.
My Commission Espires February 12,1990
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