ML053270506

Hairline Crack in IPEC Unit 2 Spent Fuel Pool South Wall, Revision 4

ML053270506
Person / Time
Site:	Indian Point
Issue date:	09/15/2005
From:	- No Known Affiliation
To:	Office of Nuclear Reactor Regulation
References
FOIA/PA-2005-0369
Download: ML053270506 (8)

Text

Hairline Crack in IPEC Unit 2 Spent Fuel Pool South Wall Revision 4, 9/15/05 ItormnatnIn s wcoadwasdeleWd inabidance Wvth te Freedom of hbnTMV Adexempbn AFQX 4

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Background

I IPEC is in the process of implementing dry cask storage capability for Unit 2.

This requires that the Fuel Storage Building (FSB) loading bay floor be removed and replaced with a significantly more substantial structure. The original floor has been removed, and excavation of soil and rock in the loading bay is in progress. During removal of loose soil and rocks in the north area of the loading bay (along the SFP south wall), approximately horizontal cracks were exposed at an elevation of approximately 65 feet, and an approximately vertical crack above.

The cracks are very narrow (less than 1/64-inch wide). One of the cracks, on the west side of the south SFP wall, has moisture in and near it.

\ 'a SFP wall structure N R.;W I,

In the area of the crackL

. The cracks have been visually V~

inspected by an IPEC civil/structural engineer, and the IPEC Supervisor of Civil/Mechanical Engineering. The condition is typical of cracking due to shrinkage during post-construction concrete curing. The moisture in and around.

one of the cracks is very slight, essentially a film which is not dripping or beading.

The moisture has been analyzed and found to contain trace amounts of Cesium 134 and 137, Cobalt-60, and Boron. The Boron concentration is about 6 to 15 times less than the concentration in the SFP, and the ratio of Cesium-134 to 137 indicate the activity is about 6 to 10 years old. The crack has calcium stains emanating from it, as is expected when moisture leaches through concrete, and no visual evidence of steel corrosion products (rust). Due to the thickness of the SFP wall, amount of steel reinforcement, and lack of evidence that the small amounts of moisture and boron have caused corrosion of the reinforcing rods, there is reasonable assurance that-the SFP wall is structurally sound and capable of performing it's intended function.

• Potntialsources of moisture The moisture in and around the crack could be from one or a combination of several sources.

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1. A leak, either active or in the past, through the SFP stainless steel liner, jjand leach through the wall into the crack.

a. The Unit 2 SFP does not have a leak detection system'. Usually ex F such a system consists of a drain pathL 2

J(Unit 3 has such a leak detection system). The Unit 2C.

3 An active leak, depending on it's age and volume, could be determined when it develops by a change in frequency of pool water make-up and/or a change in pool boron concentration. A discussion with Unit 2 licensed operators indicated the frequency of make-up has not changed, other than that expected due to seasonal changes in pool water evaporation rate, and as a separate attachment to this paper, a trend graph of boron concentration in Unit 2 SFP is attached indicating no unexpected/unexplained loss of boron. However, due to the lack of a leak detection system, and the large volume of pool water normally lost due to evaporation, a small liner leak could go undetected.

b. Based on isotopic ratios and radionuclide type, the existence of radionuclides such as Cesium and Tritium in the moisture could provide an indicator of whether there is an active leak, or whether the moisture source could have been from a since-repaired liner leak. Soil and moisture samples are being collected and will be sent to a laboratory. for analysis which can detect the presence of Tritium.

2. Contamination of the soil in the FSB loading bay, above and adjacent to the moist crack, and subsequent entry of contaminated liquid into the crack due to hydraulic pressure from the loading bay side.

Historical information

1. Inthe northeast area of the SFP stainless steel liner at about the 89 foot level, a small hole occurred during a 1990 pool re-racking project. The damage was discovered in 1992 when boron powder was found on the SFP east exterior wall. During subsequent radiological recovery and repair of the hole, .outside soil adjacent to the SFP east wall was found to contain Antimony-1 24 and 125, and Cesium-137. Approximately 100 55-gallon barrels of soil, down to a depth of eight feet below grade (72 foot level) required remediation. The leakage through the hole in the pool liner was estimated to have been 20-30 gallons per day, which was unnoticed due to the much large volume of normal evaporative loss from the pool.

2. The original loading bay floor had a drain system (see attached elevation sketch), above.and adjacent to the area of the moist crack, which was piped through the wall separating the FSB loading bay and SFP heat exchanger room to a sump in the heat exchanger room. When the floor was removed in 2004 for the dry cask storage modifications, the drain pipe was found to be cracked, and the wall penetration through which the drain 3

pipe was installed was found to be unsealed. Discussions with personnel who were working at Unit 2 at the time indicated that in years past, the level in the sump rose above the drain pipe penetration. This, along with the cracked pipe, resulted in contamination of the soil beneath the floor.

Contamination of this soil, primarily in the northwest area of the loading bay, was found and remediated during excavation in 2004 and 2005 for the dry cask storage project.

3. From 2003 through 2005, various activities associated with the dry cask storage project inthe area above and adjacent to the crack required the use of water as a dust-inhibiting and cooling measure, which was allowed to drain into the FSB loading bay soil. These activities included core-boring, saw cutting of the original loading bay floor, and excavation, Six core-bore samples, to a depth of greater than 20 feet, were taken in the FSB loading bay (four cores), and FSB access roadway (2 cores) in 2003 during the dry cask storage engineering study activities.

Industry operating experience In September 2002 the Salem nuclear plant found evidence of contaminated water leaking through a wall and onto the floor of the auxiliary building. This leak was found as a follow-up to unexpected shoe contaminations. There were other leaks through walls and penetrations that appeared to be originating from the Unit 1 SFP. It was determined that the tell-tale drains for the SFP were plugged with debris, so there was a build up of hydrostatic pressure between the liner and concrete wall. This caused the leakage to find alternative through-wall paths.

When these drains were cleaned, the leakage flowed to a collection system, essentially terminating the through wall leakage. The pool leakage was then identified via the drain system. This pool leakage occurred for an indeterminate time.

Salem conducted sampling and analysis of the environment surrounding Unit 1 FSB, in a phased approach, to identify potential release of the water outside the building confines; On February 6, 2003, Salem found tritium (H-3) contamination in close proximity to the Unit I FSB. By now the tell-tale drains were functioning, so the through wall leakage had stopped. Salem reviewed other spills that could have contributed to the tritium contamination.

Salem performed test core borings in various site locations and initially identified five areas with varying tritium contamination levels. 37 well locations were installed around the site to better characterize the extent of contamination, and 30 of the areas found some tritium contamination. There were no locations that found tritium in unrestricted-access areas 4

Action Plan The following actions (see next page) are being implemented to aid in determining the source of moisture, potential amount and extent of related soil contamination, conclusions, and remediation/repair plan and schedule.

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Updated as of 9113105

1. The IPEC Manager of Dry Cask StoragG. ix 6684 as overall responsibility for executing this plan, updating it, land keepingtanior management, NRC Unit 2 Shift Ma er informed daily. The IPEC Director of Special

/ Mayer, x55214who- has responsibility for Health Physics Department) will assist.

I (ManagerofMy Cask Storage) Issue Condition Report-and submit Operability Evaluation information to Shift Manager; develop and issue ODMI. CR-IP2-2005-03557 included Operability Evaluation). ODMI issued.

3. (Radiological Waste Department) Take radiological samples at'damp crack, and take dirt samples from where excavation

£J, 4. materialwas placed. Complete, see discussions below.

4. (Civil-structural Engineering) Determine rebar location in relation to cracks, using a rebar detection device. Completed 9 05. Rebarisl ,jto cracks.

5. (Radiological Waste DepartmentlCivil-structural Engineering) Hand-drill (small diameter bit) several inches into the SFP wall in the area of the moist crack and analyze drill-bit finds for contamination. Completed 9-7-05. Finds appeared to be damp in first several inches of depth, then appeared to be dry. Results:

Sample of Hole Drilled Co-60 Cs- Cs-137 Iron Boron In North FSB Wall uCRLigm 134uClIgm uCUgm ppm ppm Base line 11.74 ND - ND ND 96 159 First 2" (0-2") of crack 10.7 8.31 E-05 2.65E-05 1.65E-03 628 72 Second 2" (2-4") of crack 11.46 . 4.04E-05 1.39E-05 8.46E-04 640 56 Third 2" (4-6") of crack 11.75 1.02E-05 ND 1.27E-04 3285 28 Fourth 2" (6-8") of crack 11.79 ND ND 1.75E-05 60 226

6. (Radiological Waste Department) Place a plastic covering over the moist cracks to attempt to capture of a sufficient volume of liquid for radiochemistry analysis. Collected 12 mL sample 9112-13105. Contained low levels of Cs-137 and Co-60.

Contained approximately 1265 ppm Boron and approximately .02 micro-c/mL H-3. This indicates the moisture is from the-pool.

7. (Chemistry Department) Sample the soil beneath the area of the crack for H-3. Sample collected, sent off-site to laboratory for Tritium analysis. Results received 913105, indicating low level H-3 near (within a foot) of the wall, decreasing within 2-3 feet to nearly undetectable.

8. (Chemistry Department) Scrape material from an unaffected area of the SFP wall and test for boron content. Used dry finds from drilling, low-level Boron detected (less than 400 ppm).

9. (Civillstructural Engineering) Determine the typical level of boron in clean concrete. Attempted, no information available.

10. (Civillstructural Engineering) Determine expected corrosion rates for steel reinforcing rods subjected to an. environment containing boron. See #11 and #19 below.

11. (Licensing Department) Gather historical written records on SFP stainless steel liner damage and SFP sump overflows.

Some Liner damage information recovered, including Calculation CGX-00006 (Structural Evaluation of Unit 2 Fuel Pool Wall) and Technical Report ME-3802 (Evaluation of Spent Fuel Pool Walls - IP2 NPP). These are considered 6

bounding for the current situation in terms of wall and rebar structural integrity. No information on sump overflows (other than tribal knowledge) has been recovered.

12.(Civil/structural Engineering) Arrange a ground-penetrating radar (GPR) inspection (or other methodology) of the crack to determrine Qfpossible) crack depth. GPR determined not feasible. Two 4-inch diameter corestE t wwere taken 9-8-05 in the area of the moist crack. One appeared to be dry on 9-8-05 and it is presumed this was affected by boring bit heating. 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> later on 9-9-05 it was damp. The rebar exhibits normal surface oxidation. Visual inspection on 9112105 to 9115105 appears to indicate moisture is lessening.

13. (Chemistry Department) Determine if a Unit 2 Spent Fuel Pool Integrity Evaluation from Tritium Measurement, was performed, similar to that performed for Unit 3. Not performed for Unit 2. TBD whether to perform this, as it requires a lengthy period of data collection.

14. (Radiological Waste and Chemistry Departments) Gather radiological results of test core borings accomplished for dry cask storage inside FSB loading bay (4)and in FSB loading bay access road in 2003. Completed. Low-level surface contamination was found consisting of Cs-134, Cs-137, Co-58 and Co-60.

15. (Manager of Dry Cask Storage) Bring in expert structural engineer from ABS Consulting with past experience in SFP leakage. Arrived 9112105, performing calculation of seepage rate discussed in #19 below.

16. Conduct Challenge Meeting with IPEC'management. Completed 9112105.

17. Contact JAF to obtain input based upon recent experience with leaking Spent Fuel Pool liner. Conference call conducted with JAF 9113105. Discussed conditions and status of IPEC issue, and draft ODMI. No additional recommended actions were suggested, however valuable information was learned - JAF had an active pool liner leak earlier this year, but the leakage has appeared to cease on it's own, potentially indicative of a pinhole forming then being closed by some debris, or by the leak path (crack in concrete) being closed in some manner.

18. Inspect other accessible exterior areas of SFP wall. Other accessible areas in addition to the south wall include the west wall in the pipe penetration space ("Pipe Pen"), the west wall in between the FSB, VC and PAB, and the east wall outside adjacent to the MOB (where the 1990-92 leak was discovered). The east wall has no evidence of a problem subsequent to the 1990-92 leak. The west wall in the Pipe Pen has some cracking and dry white streaking with no evidence of moisture. The white material will be sampled for radiochemistry by 9116105. The west wall in between the FSB, VC and PAB has some shrinkage cracking but no evidence of moisture.

19. (Manager of Dry Cask Storage) Issue final version of this paper with conclusions and recommendations for physical actions (as deemed necessary, such as repairs, test wells, etc.) and schedule. This will include a calculation of seepage rate of pool water through the wall, and characterizations of environmental impact and structural impact, as well as a schedule for implementation of recommended physical-actions. Target 9-23-05.

Summary as of 9113105 Due to the thickness of the SFP wall, amount of steel reinforcement, small volume of moisture and-boron impingement on the reinforcing rods, there is reasonable assurance that the SFP wall is structurally sound and capable of performing it's intended function. This is additionally supported by the bounding calculation and study referred to above.

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The data collected so far appears to indicate a pinhole in the SFP liner. Location and whether the leak path is active is undetermined. As indicate in #19 above, a final version of this paper with conclusions and recommendations for physical actions (as deemed necessary, such as inspections/repairs, test wells, etc.) is targeted to be completed next week. This will include a calculation of seepage rate of pool water through the wall, and characterizations of environmental impact and structural impact, as well as a schedule for implementation of recommended physical actions Attachments (See Rev.1 issue of this paper dated 9/9/05)

Elevation sketches (2)

Moist crack photograph Unit 2 SFP Boron graph.

Core bores photograph Draft ODMI 8