ML20211Q031
| ML20211Q031 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 09/10/1999 |
| From: | Peterson S NRC (Affiliation Not Assigned) |
| To: | Scalice J TENNESSEE VALLEY AUTHORITY |
| References | |
| TAC-MA4999, NUDOCS 9909140174 | |
| Download: ML20211Q031 (6) | |
Text
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y-4 UNITE ") STATES j
j NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 2055H001 September 10, 1999 t-
' Mr. J. A. Scalice Chief Nuclear Officer and Executive Vice President
' Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, Tennessee 37402-2801
SUBJECT:
REQUEST FOR INFORMATION REGARDING SEQUOYAH NUCLEAR PLANT, UNITS 1 AND 2 (TAC NO. MA4999)
Dear Mr. Scalice:
On August 11,1999, members of the U. S. Nuclear Regulatory Commission (NRC) staff met with representatives of the Ice Condenser Mini Group (ICMG) in a public meeting at the NRC Headquarters Building in Rockville, Maryland. The ICMG includes representation from Duke Energy Corporation, Tennessee Valley Authority (TVA), American Electric Power and Westinghouse Electric Corporation and was established for the purpose of facilitating ice condenser containment technical information exchange as a Westinghouse Mini Group. The primary purpose of the meeting was for the ICMG to update the NRC staff on efforts to revise Technical Specifications (TS) surveillance testing requirements that are intended to assure that ice condensers are properly maintained and continue to meet their design-basis function.
During the meeting, the staff asked several questions regarding findings at the Sequoyah i
Nuclear Plant related to inspections of ice condenser operations conducted by NRC Region ll personnel during the March-April 1998 and September-October 1998 timeframes. The questions dealt predominantly with the TS requirements for weighing the ice condenser ice
. baskets to ensure that at least the minimum amount of ice needed to mitigate a design-basis accident is present in the condenser. A member of the Sequoyah engineering management staff was present at the meeting and provided reasonable answers to the staff's questions.
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Specifically, we discussed Unresolved item (URI) No. 50-327,328/98-04-02 from NRC Inspection Report No. 50-327,50-328/98-04. This URI questions whether an acceptable
" representative sample," as described in the surveillance TS for Sequoyah, for determining ice basket weight can be obtained given the large number of ice baskets that are unweighable due to being frozen in place at both Sequoyah units.
To assist NRC Region ll in dispositioning the URI cited above, the NRC staff hereby requests written documentation from TVA to provide technical assistance to Region 11 regarding TS compliance and ice condenser maintenance practices at Sequoyah. Our questions are contained in the enclosure to this letter. None of the information requested goes beyond that
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provided verbally by TVA during the August 11 meeting with the ICMG. Therefore, we reached I
agreement, during a telephone conversation with Mr. P. Salas of your staff on September 2, 1999, that TVA's response to this reqwst can be reasonably provided by October 1,1999,
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Mr. J. A. Scalice September 10, 1999 Please direct any question you have regarding this request to Mr. Ronald W. Hernan, the NRC Project Manager assigned to the Sequoyah Plant. He can be reached at (301) 415-2010.
Sincerely, Original signed by:
Sheri R. Peterson, Chief, Section 2 Project Directorate 11 i
Division of Licensing Project Management Office of Nuclear Reactor Regulation i
Docket Nos. 50-327 and 50-328
Enclosure:
Request for Information cc w/ enclosure: See next page DISTRIBUTION:
Docket File 7 OGC SBlack ACRS PUBLIC GHubbard SO N R/F JHannon HBerkow PFredrickson, Rll SPeterson CLI BClayton RHernan
- DOCUMENT NAME: G:\\PDil-2\\SQN\\RAIA4999.wpd To receive a copy of this document, indicate in the box: "C" = Copy without attachment / enclosure "E" = Copy with attachment / enclosure "N" = No copy i
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DATE 9/ S /99 1 9/ A /99 7 /g /89
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t Mr. J. A. Scalice.
t Please direct any question you have regarding this request to Mr. Ronald W. Hernan, the NRC Project Manager assigned to the Sequoyah Plant. He can be reached at (301) 415-2010.
Sincerely, i
Gb R h Sheri R. Peterson, Chief, Section 2 Project Directorate ll Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket Nos. 50-327 and 50-328
Enclosure:
Request for Information cc w/ enclosure: See next page l
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4 REQUEST FOR INFORMATION REGARDING ICE CONDENSER ISSUES i
SEQUOYAH NUCLEAR PLANT. UNITS 1 AND 2 DOCKET NOS. 50-327 AND 50-328 t
Sequoyah Technical Specification (TS) 4.6.5.1.d.1 requires, at least once per 18 months, weighing a representative sample of at least 144 baskets and verifying that each basket contains at least 1,071 lbs of ice. The requirement states:
The representative sample shallinclude 6 baskets from each of the 24 ice condenser bays and shall be constituted of one basket each from Radial Rows 1,2,4,6,8 and 9 (or from the same row of an adjacent bay if a basket from a designated row cannot be obtained for weighing) within each bay.
The surveillance requirement includes an expanded sample size requirement in the event that any of the baskets weighed contains less than 1,071 pounds of ice. The surveillance requirement also contains the following statement (emphasis added):
The minimum total ice condenser weight at a 95% level of confidence shall be calculated using all ice basket weights determined during this weighing program and shall not be less than 2,082,024 pounds.
The totalice weight must be calculated at a 95 percent confidence level. NRC Inspection Report 50-327, 328/98-13 discusses the results of NRC inspection of ice beskci weighing activities at Sequoyah Unit 1 during the period September 14 through October 16,1998. The report states in part:
Based on the review of all the data described above, field inspections described in Section M1.1, sublimation rates being experienced, and discussions with licensee personnel, the inspectors considered that with reasonable assurance the ice bed contained sufficient ice weight to meet design basis requirements. However, the inspectors were cancerned with the licensee's ability to demonstrate meeting the TS basis for verifying fufficient ice weight. Although the TS allows alternate samples, the inspectors questioned whether the intent of the TS was being met regarding " representative" samples to support the statistical 95 percent confidence calculation. Only by review of additional weight data were the inspectors able to gain a reasonable assurance of sufficient ice..
Observations and detailed data reviews provided assurance that sufficient ice remained in the ice condenser to meet the design basis. However, the high number (850-900) of frozen baskets challenged the ability of the licensee to obtain a statistically valid " representative" sample required by the TS. NRC review of the issue was identified as a continuation of an existing URI.
ENCLOSURE
o 4 f A TVA engineering assessment completed on December 18,1998, concludes that "the validj.ty of this method (the one used by TVA during the 1998 outage and currently used for ice basket weighing)is maintained irresoective of the number of alternate samole locations since the location of the alternates is always distributed in a cattern which represents a full cross-section of the ice bed."
In light of the large number of ice baskets that are frozen in place at Sequoyah, the NRC staff needs the following information in order to arrive at a conclusion on (a) whether or not the TS ice basket weighing requirements were met, and (2) whether TVA took reasonable measures to ensure that the total ice condenser ice mass was at least 2,082,024 pounds as required by TS:
- 1. What is TVA's interpretation or understanding of the relationship between " calculating the total ice condenser ice weight at a 95% level of confidence" and the fact that the TS require one ice basket in each of six specified rows in each ice condenser bay to be weighed (144 of 1,944 baskets total)?
- 2. Are the rows specified in TS 4.6.5.1.d.1 for weighing ice baskets based upon a 95%
confidence level in calculating the total ice basket weight or upon engineering judgment?
Please explain the answer.
- 3. What is the practical upper limit to the number of alternate baskets selected for weighing (e.g., due to being frozen) as allowed by the TS7 What is the relationship between this limit and having 95% confidence in calculating the total ice weight of the ice condenser?
- 4. How many " alternate" baskets were selected for weighing during the last surveillance inspection for each Sequoyah unit?
- 5. How many totalice baskets were actually weighed (vs. The 144 required) of 1,944 total installed as part of ice basket surveillance / servicing during the last refueling outage at each of the Sequoyah units?
6: Were any frozen baskets freed and weighed at either unit during that unit's last refueling outage? If so, did these baskets meet the minimum required weight? If so, were these caskets compared to other baskets that could not be weighed to form an engineering judgment basis for determining if the unweighable basket would have met the TS requirements had they been weighable?
- 7. What methods have been employed at Sequoyah in the past, other than weighing per the TS, to confirm that the ice condensers would meet their design basis of limiting containment pressure during a design-basis accident?
- 8. What are TVA's plans, if any, to incorporate methods other than weighing into the Sequoyah TS to assure continued design-basis operation of the Sequoyah ice condensers?
4 Mr. J. A. Scalice SEQUOYAH NUCLEAR PLANT Tennessee Valley Authority cc:
Mr. Karl W. Singer, Senior Vice President Mr. Pedro Salas, Manager Nuclear Operations Licensing and Industry Affairs Tennessee Valley Authority Sequoyah Nuclear Plant 6A Lookout Place Tennessee Valley Authority 1101 Market Street P.O. Box 2000 Chattanooga, TN 37402-2801 Soddy Daisy, TN 37379 Mr. Jack A. Bailey Mr. D. L. Koehl, Plant Manager Vice President Sequoyah Nuclear Plant Engineering & Technical Services Tennessee Valley Authority Tennessee Valley Authority P.O. Box 2000 j
6A Lookout Place Soddy Daisy, TN 37379 1101 Market Street I
Chattanooga, TN 37402-2801 Mr. Melvin C. Shannon Senior Resident Inspector Mr. Masoud Bajestani Sequoyah Nuclear Plant Site Vice President U.S. Nuclear Regulatory Commission
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Sequoyah Nuclear Plant 2600 Igou Ferry Road Tennessee Valley Authority Soddy Daisy, TN 37379 P.O. Box 2000 Soddy Daisy, TN 37379 Mr. Michael H. Mobley, Director TN Dept. of Environment & Conservation General Counsel Division of Radiological Health
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Tennessee Valley Authority 3rd Floor, L and C Annex ET 10H 401 Church Street 400 West Summit Hill Drive Nashville, TN 37243-1532 Knoxville, TN 37902 County Executive Mr. N. C. Kazanas, General Manager Hamilton County Courthouse Nuclear Assurance Chattanooga, TN 37402-2801 Tennessee Valley Authority SM Lookout Place 1101 Market Street Chahooga, TN 37402-2801 l
1 Mr. Mark J. Burzynski, Manager Nuclear Licensing Tennessee Valley Authority 4X Blue Ridge 1101 Market Street i
Chattanooga, TN 37402-2801 I