ML072841069
| ML072841069 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 12/05/1990 |
| From: | Devine J GPU Nuclear Corp |
| To: | Document Control Desk, NRC/SECY |
| SECY RAS | |
| References | |
| 50-219-LR, 5000-90-1995, AmerGen-Intervenor-21, C320-90-302, RAS 14331 | |
| Download: ML072841069 (10) | |
Text
Citizens Exhibits 21
~RA5
£ WdI-o WARZI
-mmm L--
% ^IM*NO 4'
GFFW by: Apfcn~cesýýý NRC Staff Other MU~tR~EJEM WmNMWW "M~ PIR muild Cne Upper Pond Road Parsippany, Now Jersey 07054 01.3 16-7000 TELEX 1416-482 Writer's Direct Dial Number Nuclear December 5, 1990 5000-90-1995 C320-90-302 DOCKETED USNRC October 1, 2007 (10:45am)
OFFICE OF SECRETARY RULEMAKINGS AND ADJUDICATIONS STAFF U.s.iuclsa~r itegu3.atory commission Attention: Document Contro2 Doak Waahintoa, tIC 20SSS Gentlemen:
subject:
oyster Creek Nuclear Docket No. 50-219 License No. DPR-16 Oyster Craak Drywall Generating StatLon (OCNGS)
Containment October 16, 1990 - Requested
References:
(2) NRC Letter dated clatificationg.
(2)
OPUN Letter dated November 26, 1990 - Drywell Inepection/Sampling Plan.
This letter, together with the Reference (2) submittal1 Completes the response to the Reference (1) request for claxifications on the drywell corrosion issue.
The attachments to this letter addreis Reference (1),
Items iL to iv, which correspond to Reference (2j., Items (2) to (4).
Attachment I to this letter provides the information requested by the NRC for item (2).
This attachment consists of GE/Teledyne Report TR-7377-1 "Justification for Use of Section III Subsection NE Guidance in Evaluating the Oyster Creek Drywell-.
This report provides the technical 3ustification for using ASME Section III NE guidance for the evaluation of membrane stress intensities which ere between 1.0Sm* and l.lSmo.
Attachment It to this letter provides the information requested by the NRC for Item (3).
This attachment consists of GE Reports Index No, 9-1 and 9-2, "An ASME Section VilI Evaluation of the Oyster Creek Drywell Stress and stability Analysis.-
This two part report covers the structural analysis of the oyster creek drywell through the 14P, outage with the current $and-In-place configuration and the bandbed portion of the drywell conservatively assumed corroded to 0.7000.
This report confirms the adequacy of the Oyster Creek drywell shell utilix-ng ASMS Section III guidance to demonstrate ASME Section VIIn Code compliance.
GPU Nuclear Corporatlon is a ubsiidiey of General Public Utiites Corporaton I~.,OCLR00029270 I emp14e- < y-o.?
" Oystor Creek Drywell Containment Page 2 Attachment IZI to this letter provides the information requested by the NRC for Item (4).
This attachment consists of a detailed summary of the actions GPUN has undertaken to identify and prevent water intrusion into the drywoll gap and addresses the effects of leakage on structures and equipment other than thee:
drywell.
In addition' to providing the requested Reference (1) clarification documentation, GPWI is proceeding with the analysis, engineering, and planning to support removal of sand from the drywell sandbed region.
Since our meeting with you on September 19, 1990, corrosion testing studies have reinforced our conviction that this will be a key step in arresting corrosion in' that regiono.
The technical evaluation supporting sand removal is well underway and thO structural calculations are expected to be completed in December.
Aseuming satisfactory results, we plan to submit this structural analysis to you by December 31, 1990.
If you have any questions on this submittal or the overall drywell corrosion.
program, ploase contact Mr. Michael Laggart, Manager, Corporlate Nuclear
- LiCensing at (201) 316-7968.
Ver J. C. DeVine, Jr.
Vice President, Technical Functions JCD/RZ/plp Attachments ct: Administrators Region I, NRC Resident Inspector Mr. Alex Dromerick, Jr.
C3ZO30Z 0CLR00029271
ATTACHMENT IT GFUIN LDtaLl.ed summa~ry 2Addzesaing Water inr~tusion anzd Leakage Effecta Related to the Oyseter Creek Drywall MOW3~
OCLR00029273
W=IRE INTRUSIrON The following dascribes GPON past actions to investigate, identify, and correct leak paths into the drywall gap, as well as our planned -future actions to prevent and surveil potential leakage.
The issuss discussed below occurred from 198$ to date.
Actions taken to address the impact of leakage on, other structures and equipment are also described.
- 3..
mUELTIO CAVITY Cr~id-f ui The stainless steel liner was inspected both by visual and dye penetrant methods.
A significant number of cracks were found as well.
as; some through-wall
- damage, most probably caused by mechanical impact..
As a result., an analysis was performed for determining the failure mechanism (i.e., IGSCC, fatigue, etc.) and it was d6termined that the cracking was mechanically induced and not XCSCC inducedo.
The most probable cause was thermal fatigue, (A sample, was removed, from the liner and metallurgically examined.)
To prevent leakage through these cracks during refueling, we install an adhesive type stainless steel tape to bridge any large. cracks observed, and subsequently, apply a strippable coating.
Both the tape and the coating, have been qualified by GPUN and vendor for us* in the environment-that they normally see.
This method-of repair is-temporary (refueling only) and both the tape and coating are removed prior to the end of the outage.
No leakage concerns exist at any other times since the cavity is dry.
b)
Bellows The bellows allow for expansioni between the drywli and the refueling cavity and are made of stainless steel.
They were repeatedly tested using helium (external) and air (internal) without any indication of leakage.
Any. leaks from the refueling bellows would wind up. in the Po al3 concrete trough, which has. a leakage detection/cOllection system.
No M. b 1I*n*
S leakage has been observed for the last two refuelings.
c)
Eiping prains gf
'Y There are two drain lines from the cavity that all6w for water removal from the cavity and trough.
They have been preosure tested with no evidence of leakage.
d)
Metal Trouah The metal trough is located between the drywell and the reactor
- building, It was tested visually and with helium without any positive leaks identified, JDA/Misc/WATERINT/I 0C-LROD029274
WATER InTUS ION Page 2 A gasket at the drain line from the trough was replaced.
- However, no clear leakage path was identified from thIs source.
This portion of the cavity is coated during refueling with atrippable coating.
e)
Con=rete Mr-ough The concrete trough is located under the metal trough and is designed to collect any leakage from the bellow area and direct, it to a drain.
This area was inspected by removing the drain plate attachment, to the metal, trough and visually inspected,, using remote Video.
An area.
where concrete was found to be chipped was repaired and the drainage.*
capability restored.
no further problems axe known to exiet.;
f)
Stoe IStainleseSteel Linerg, These are the steps that receive the shield plugs sno plugs from the fuel pool to the cavity and cavity to equipment pool gatas, Thes.
steps were examined visually and by PT with no indications.. of-.
cracking.
These steps will also be periodically.coated during.
refueling, s) kiimmer The skimmer system is designed-to maintain water. clarity in the cavity.
It. consists of ducts and piping connected to the liner With most, of the ducting and piping encased in concrete.,
A pressure test was performed. in the skinmer system and as a result,. aome skimmners are removed from adrvica by plugging them prior to 'each refueling.
In conclusion,, we believe that all potential water leakage pathwdyý from the refueling cavity into the drywell gap. havs been thoroughiy checked and the continuation of. our current tape/Btrippable coating method during future refueling outaged. is adequate for prevention of isakage" from this source.
- 2.
EQUIPHIST POLq The liner was inspected both visually and dye penetrant tested, with any PT indications vacuum box checked.
No through wall leakage was found.
Additionally, the equipment pool has a leak detection system under the welds in the plate which is routed to drains.
Any leak$
into the colleotion system would not reach the drywell.
While the leak detection system indicated leakage, no liner leaks were found.
JDA/Mias/WATE1INT/2 OCLR00029275
- WATER INTRUSION Page 3 Preventively, the equipment pool will be taped using the SS tape and then coated with a strippablo coating prior to the refueling outage, further reducing the probability of leakage.
b). Drain The drain was checked for leaks via pressure test and found to be leak free.
c)
Sungggot Pad Concern. with the pad to liner welds arose.
AS a result, the pad wag removed-and the liner, weld area checked prior to replacing the pad.
No leakage was identified.
In conclusion, no leaks have been found reiated to' the equipment pooi.
Preventively, the equipment pool will be protectively coated similar to the refueling cavity.
Drains from the leak detection system axe monitored on *a periodip basis to detect any changeý.
The fuel. pool has a leak detection system similar to the equipment pool..
The leak detection i for all welded joints in the stainless steel liner.
Minor' leakage' (drippingc) has been noted over the years at infrequent intervalS, even though the pool is continuously, flooded..
Leakage or.
condensation has been postulated as the source.
Additionally, in 1985 while, r_
po.ol,
.a leak was found.
Ad a result,_vacuum testing.
was perfozrmed to find the leak and underwater divers were used to confirm the leak location and. to repaix the leak.
NO further problems were-encountered.
. Ongoing monitoring of the leak dotectiod, ensures early leakage. detection.
- 4.
PIPXHG PNETRATjON5 Piping that is buried in concrete and whose leakage. could become a leak path to the dryweli gap was investigated.
The piping penetrating the drywell was not investigated since it was either tested as parti of 10 CFR 60 Appendix 47 or any significant leakage would be detected as part of operability/system operation, other piping such as the drains from the cavity and equipment pool are disoveed above.
In conclusion, no leakage is expected from the buried piping or piping penetrating the drywell.
JDA/Misc/WATERINT/3 0CLR00029276
YWATER INTRUSION
- Page 4
- 5.
WALXDOWNS POR VISUAL LnARAGE walkdowns are periodically conducted to identify any leakage in. the Reactor Building wall, under the two poolB, and on the drywell wall.
While minor staining can be seen, samples of water were obtained (isand bed, drywell wall, etc.) and analyzed without being conclusive as being reactox refueling water.
- 6.
SAND BED DRAINS In. the sand bed region of the drywell, there are five sand bed drains egiaally spaced around the drywell.
Some of these drain. were known; to drip/leak.
When ca thodio protection was installed,. water was observed coming out of the CP holes.
As a result, every effort to remove any 'water entrapped in the sand bed wan initiated.
The five drains were cleared using a "roto-rooter" approach and approximately 500 gallons of water were removed'.
Presently, the drains are not leaking and preventive maintenance to clear the drains periodically hag boen initiated.
A routine walkdown.
to identify changes in leakage is in place.
In conclusion, while the sand Wa4 retaining water due-to blockage of the drains, after clearing the drains, the sand bed area apfears to be free of water.
AS a result of the above described approach to identify and correct potential water source leak paths and our ongoing pr0gram for surveillance for water intrusions, as discussed in the presentations made to the. NRC. on september 19, 1990. and the NRC site visit and inspection on.
October 29-31, 1990, we believe we have a thorough program for managing leakage that could affect drywell integrity.
In addition to the efforts described above, actions have also been taken to address the potential impact of leakage on other structures, and equipment.
These actions are described below.
Cracks have been identified in the concrete walls and floor of the spent fuel pool and equipment pool.
These cracks are routinely inspected and, mOnitored for changes in size and condition.
Numerous analyses have been performed which conclude that the identified cracking does not degrade the ability of the building to perform its intended function.
Xnepect*ions of these cracks indicate no evidence of leakage around or 17*
under the spent fuel pool.
EvIdence of leakage has been observed in both A
the floor and wall of the equipment pool and In the reactor cavity wall Sabove ele vation 95'-0'.
Based on visual inspections, thin leakage has not affected any equipment.
The water stains observed on the underside of the equipment pool contain no evidence which would indicate teihforcing bar corrosion.
In addition, visual inspections indicate no general concrete degradation associated with these cracks.
JDA/Hisc/WATERiNT/4 0CLR00029277 -
WATER INTRUSION Page 5 Stains on the equipment pool and reactor cavity wal3_g above elevation 953--o do indicate slight corrosion of the reinforcing oar., To determine the potential effect of this corrosion, a compositional analysis of a repreoentative concrete core 29imple iwas performe*d in Ocitober, 1988.
This analysis indicates that the diameter of a typical reinfmrcing bar could be expected to be reduced by 0.002 inch/year.
The wal3a in qestion are, reinforced with I8 and #II reinforcing bar.
Therefora, if the corrosion continues, the dianeter of the reinforcing bar would bm reduced by 8% and sk respectively over a 40-year period.
Since the corrosion in 100aii ed, thin reduction has no impact on cOncrete integrity.
JDA/Minc/WATIRINT/5 0CLR00029278
TOP -OF REACTOR VESSEL 4
STEPS i ýl
.BELLOWS.
II INSULATION.
0C-)
0 0
0 CD I",
CD DFLY WELL VESSEL 33!.0t`.
-1ý..
.. 0.....
.. ý----..
i DRYWELL TO CAVITY SEAL I
DRYWELL METAL TROUGH BELLOWS BOTTOM PLATE 2" DRAINS CONCRETE TROUGH m
INSULATION MATERIAL 0
C~)
r-
- 0 0
o0
...................1-...............
.......