ML15218A146
| ML15218A146 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 01/19/1996 |
| From: | Milano P NRC (Affiliation Not Assigned) |
| To: | Hampton J DUKE POWER CO. |
| References | |
| TAC-M93942, NUDOCS 9601230391 | |
| Download: ML15218A146 (5) | |
Text
January 19, 1996 Mr. J. W. Hampton Vice President, Oconee Site Duke Power Company P.O. Box 1439 Seneca, SC 29679
SUBJECT:
REQUEST FOR ADDITIONAL INFORMATION RELATING TO TENDON SURVEILLANCE REPORT, OCONEE NUCLEAR STATION, UNIT 3 (TAC NO. M93942)
Dear Mr. Hampton:
On October 11, 1995, you submitted report entitled, "Unit 3 Reactor Building Post-tensioning System Sixth Surveillance." During our review of this report, the NRC staff has determined that additional information is needed. The specific details of the staff's request for this additional information is provided in the enclosure to this letter. Your response to this request for additional information is requested by February 23, 1996.
This requirement affects nine or fewer respondents and, therefore, it is not subject to the Office of Management and Budget review under P.L.96-511.
If you have questions regarding this matter, contact me at (301) 415-1495.
Sincerely, Original signed by:
Patrick D. Milano, Sr. Project Manager Project Directorate 11-2 Division of Reactor Projects-I/Il Office of Nuclear Reactor Regulation Docket No. 50-287
Enclosure:
As stated cc w/encl:
See next page Distribution:
Docket File CPTan PUBLIC OGC PD 2-2 Reading ACRS SVarga RCrlenjak, RH JZwolinski EMerschoff, RII LWiens LBerry PMilano DOCUMENT NAME: G:\\OCONEE\\0C93942.RAI To receive a copy of this document, indicate in the box C=Copy w/o attachment/enclosure E=Copy with attachment/enclosure N No copy OFFICE LA:PD2-2
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WASHINGTON, D.C. 20555-0001 o
January 19, 1996 Mr. J. W. Hampton Vice President, Oconee Site Duke Power Company P.O. Box 1439 Seneca, SC 29679
SUBJECT:
REQUEST FOR ADDITIONAL INFORMATION RELATING TO TENDON SURVEILLANCE REPORT, OCONEE NUCLEAR STATION, UNIT 3 (TAC NO. M93942)
Dear Mr. Hampton:
On October 11, 1995, you submitted report entitled, "Unit 3 Reactor Building Post-tensioning System Sixth Surveillance." During our review of this report, the NRC staff has determined that additional information is needed. The specific details of the staff's request for this additional information is provided in the enclosure to this letter. Your response to this request for additional information is requested by February 23, 1996.
This requirement affects nine or fewer respondents and, therefore, it is not subject to the Office of Management and Budget review under P.L.96-511.
If you have questions regarding this matter, contact me at (301) 415-1495.
Sincerely, Patrick D. Milann, Sr. Prcn4+
Manager Project Directorate 11-2 Division of Reactor Projects-I/II Office of Nuclear Reactor Regulation Docket No. 50-287
Enclosure:
As stated cc w/encl: See next page
Mr. J. W. Hampton Duke Power Company Oconee Nuclear Station cc:
Mr. Paul R. Newton Mr. Ed Burchfield Duke Power Company, PB05E Compliance 422 South Church Street Duke Power Company Charlotte, North Carolina 28242-0001 Oconee Nuclear Site P. 0. Box-1439 J. Michael McGarry, III, Esquire Seneca, South Carolina 29619 Winston and Strawn 1400 L Street, NW.
Ms. Karen E. Long Washington, DC 20005 Assistant Attorney General North Carolina Department of Mr. Robert B. Borsum Justice B&W Nuclear Technologies P. 0. Box 629 Suite 525 Raleigh, North Carolina 27602 1700 Rockville Pike Rockville, Maryland 20852-1631 Mr. G. A. Copp Licensing -
ECO50 Manager, LIS Duke Power Company NUS Corporation 526 South Church Street 2650 McCormick Drive, 3rd Floor Charlotte, North Carolina 28242-0001 Clearwater, Florida 34619-1035 Dayne H. Brown, Director Senior Resident Inspector Division of Radiation Protection U. S. Nuclear Regulatory Commission North Carolina Department of Route 2, Box 610 Environment, Health and Seneca, South Carolina 29678 Natural Resources P. 0. Box 21681 Regional Administrator, Region II Raleigh, North Carolina 27611-7687 U. S. Nuclear Regulatory Commission 101 Marietta Street, NW. Suite 2900 Atlanta, Georgia 30323 Max Batavia, Chief Bureau of Radiological Health South Carolina Department of Health and Environmental Control 2600 Bull Street Columbia, South Carolina 29201 County Supervisor of Oconee County Walhalla, South Carolina 29621
REQUEST FOR ADDITIONAL INFORMATION OCONEE NUCLEAR STATION, UNIT 3 TENDON SURVEILLANCE REPORT
- 1.
In the Summary section of report, "Unit 3 Reactor Building Post tensioning System Sixth Surveillance," it was stated that the mean lift off force for each surveillance tendon group (hoop, vertical and dome) exceeded required values. In Table 3 the report appears to indicate that, for tendons which were detensioned and retensioned, the "as-left" forces are larger than "as-found" forces. However, Section 3.5 states that "(f)ollowing wire removal the relaxed tendons were retensioned, as closely as possible to the same stress level indicated by the lift-off force data obtained during this surveillance." If the "as-left" forces are larger than the "as-found" forces, the tendon prestress losses are either reduced or eliminated and the lift-off forces in the associated subsequent tendon surveillances will probably not be below the required values. While there is no mention of the required value for each group of tendons, the force-time plots in the report indicate that 7.00 kips per wire is the required values for all tendons. Each tendon in each group has undergone 2 detensionings and retensionings and 4 lift-offs during the 6 surveillances performed to date.
Based on its observations, the NRC staff requests that:
- a. A re-analysis of the lift-off data from all the surveillances be performed that modifies, if applicable, each lift-off force by the difference between "as-found" and "as-left" values obtained from preceding surveillances.
- b. All lift-off force data be plotted on a graph similar to that shown in Figure 2 of Regulatory Guide (RG) 1.35.1 and including the minimum required value (MRV) identified for each group of tendons.
The values to be plotted are the individual data obtained without averaging or taking mean values. On the basis of the plotted data, a regression analysis should be performed for each group of tendons to establish the trend of the prestress force.
- c. Indicate how the MRV is determined for each group of tendons.
- d. Provide all the data used in the above regression analysis.
- 2.
The analysis of the data indicated above may remedy some of the deficiencies resulting from using pre-selected tendons for surveillance.
Although the Technical Specifications requirement for using the pre selected tendons was approved by the NRC, the staff has found that, by using randomly selected tendons for each surveillance, the lift-off forces obtained are more representative of the actual tendon force. In view of this fact, the NRC staff encourages licensees to use the randomly selected tendons for surveillance as proposed in RG 1.35, Revision 3. Indicate whether you plan to adopt such an approach for the next scheduled tendon surveillance at Oconee.
Enclosure
-2
- 3.
In Table 2 of the report, the shim thicknesses at both ends of a tendon are listed. Discuss the significance of this information. Were the tendon elongations recorded during the retensioning along with the force measurements? If so, provide them. Elongations can be used to check the corresponding force measurement, especially if the retensioning is accomplished in two or more steps.
- 4.
In Table 1 of the report, grease in the amounts of 18 and 15 gallons was shown to have been added for tendons 23V14 and 45V16, respectively. The NRC staff does not completely agree with the explanation given for these excessive amounts. Therefore, provide the rational as to why it occurs only in vertical tendons. The voids in the grease give rise to two concerns: (1) the tendon may be subjected to corrosion and (2) the voids may result from the leakage of the grease into the concrete which may affect the concrete strength.