ML032040036
| ML032040036 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 08/08/2003 |
| From: | Travers W NRC/EDO |
| To: | Owings J - No Known Affiliation |
| Jabbour K, NRR/DLPM, 415-1496 | |
| Shared Package | |
| ML032040026 | List: |
| References | |
| G20030355, LTR-03-0402 | |
| Download: ML032040036 (5) | |
Text
August 8, 2003 Dr. Jon M. Owings, MD, FACS 111 Jenni Leigh Dr.
Huntsville, AL 35806
Dear Dr. Owings:
I am responding to your May 29, 2003, letter to Senator Richard Shelby which was recently forwarded to the U.S. Nuclear Regulatory Commission (NRC). In your letter, you discussed concerns related to the main steam safety/relief valves (S/RVs) at the Browns Ferry Nuclear Plant. Your concerns are related to steam corrosion causing deterioration and sticking of the reactors main steam pressure relief valves, leakage of steam, and overpressurization if sticking valves do not release. Also, you expressed concerns about the increased operating cost, lost revenue associated with steam leakage through the valve, and unscheduled shutdowns for repairs.
Although your letter did not specifically mention the S/RV pilot disks, we are aware that corrosion of pilot disks, an internal component in the S/RV, has resulted in setpoint drift.
Therefore, it is our understanding that you are concerned about the current S/RV pilot disks and the need to replace them with a new design. Our evaluation of your concerns is discussed below.
Regarding the tendency of the S/RV pilot disks to stick during valve opening and, thus, cause the S/RVs to open at higher pressures than designed, the licensee performs routine setpoint testing of the S/RVs in accordance with the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) to ensure that the necessary setpoint criteria are met.
The operational history has shown that the installed pilot disks may develop corrosion bonding, which can raise the opening setpoints of the S/RVs above values allowed by plant technical specifications. At Browns Ferry Units 2 and 3, the facility mentioned in your letter, the licensee installed pressure switches that ensure the S/RVs will open at the correct setpoints. The pressure switches provide a signal to the S/RV pneumatic actuators which in turn provide a large motive force to open the pilot disks, thereby, opening the S/RVs even if there is corrosion bonding. The installed pilot disks, the amount of setpoint increase experienced, and the installed pressure switches are described in more detail in Licensee Event Report 50-296/2000-006-00 (enclosed). Even without the pressure actuation switch system, the setpoint drift experienced would not have caused any safety limits to be exceeded or resulted in a serious overpressurization event. There are multiple S/RVs installed at Browns Ferry Units 2 and 3 such that adequate overpressure protection is provided, even if several S/RVs have significant setpoint drift. In addition, the control room operator can manually open the S/RVs to depressurize the reactor if necessary.
Regarding the tendency for the S/RVs to leak steam into the suppression pool, the licensee also performs leakage testing on the S/RVs in accordance with the ASME Code to ensure that leakage is within applicable, allowable regulatory limits. However, the operational history has shown that S/RV pilot disks may develop seat leakage occasionally during a plant operational cycle. In accordance with the plant administrative guidelines, the licensee will take specific actions, including shutdown, if the leakage exceeds specified limits. Such leakage is directed to
Dr. J. M. Owings the suppression pool where it is condensed, resulting in no challenge to plant safety systems.
In the unlikely event that seat leakage results in inadvertently opening the S/RV, the full S/RV discharge is also directed to the suppression pool where it is condensed. The consequences of such an event are bounded by the licensees safety analysis, which demonstrates that no safety limits are exceeded. Your letter specifically refers to a recently leaking S/RV. Among other items, this S/RV was replaced by the licensee during a brief planned Unit 3 outage in June 2003. Your letter also refers to the increased operating cost and lost revenue associated with steam leakage through the valve seats, and unscheduled shutdowns for repairs. While of concern to the licensee, these are not public health and safety issues regulated by the NRC.
Regarding the need to replace the installed S/RV pilot disks with a new design, the NRC staff has determined that the currently installed S/RVs meet NRCs regulations and that the issue of setpoint drift in the S/RVs due to corrosion bonding to the valve seats has been acceptably resolved at Browns Ferry Units 2 and 3. Any modifications to or replacement of the valves to improve their reliability are made at the licensees discretion. However, any licensee who elects to modify these valves must ensure that the valves continue to meet all regulatory requirements.
Based on the above, we find that the current S/RVs at Browns Ferry are adequate to protect the public health and safety and, therefore, we do not plan any further action on your concerns.
Thank you for bringing these issues to the attention of the NRC, and we hope you find this information responsive to your concerns.
Sincerely,
/RA/
William D. Travers Executive Director for Operations Docket Nos. 50-260 and 50-296
Enclosure:
As stated cc w/encl: See next page
Dr. J. M. Owings the suppression pool where it is condensed, resulting in no challenge to plant safety systems.
In the unlikely event that seat leakage results in inadvertently opening the S/RV, the full S/RV discharge is also directed to the suppression pool where it is condensed. The consequences of such an event are bounded by the licensees safety analysis, which demonstrates that no safety limits are exceeded. Your letter specifically refers to a recently leaking S/RV. Among other items, this S/RV was replaced by the licensee during a brief planned Unit 3 outage in June 2003. Your letter also refers to the increased operating cost and lost revenue associated with steam leakage through the valve seats, and unscheduled shutdowns for repairs. While of concern to the licensee, these are not public health and safety issues regulated by the NRC.
Regarding the need to replace the installed S/RV pilot disks with a new design, the NRC staff has determined that the currently installed S/RVs meet NRCs regulations and that the issue of setpoint drift in the S/RVs due to corrosion bonding to the valve seats has been acceptably resolved at Browns Ferry Units 2 and 3. Any modifications to or replacement of the valves to improve their reliability are made at the licensees discretion. However, any licensee who elects to modify these valves must ensure that the valves continue to meet all regulatory requirements.
Based on the above, we find that the current S/RVs at Browns Ferry are adequate to protect the public health and safety and, therefore, we do not plan any further action on your concerns.
Thank you for bringing these issues to the attention of the NRC, and we hope you find this information responsive to your concerns.
Sincerely,
/RA/
William D. Travers Executive Director for Operations Docket Nos. 50-260 and 50-296
Enclosure:
As stated cc w/encl: See next page Distribution: See attached list Incoming: ML031820593 Response: ML032040036 Package: ML032040026
Enclosure:
ML003736685 *See previous concurrence OFFICE PDII-2/PM PDII-2/LA Tech Editor* EMEB/BC*
NAME KJabbour BClayton PKleene EImbro (KManoly for)
DATE / /03 / /03 07/14/03 07/22/03 OFFICE SRXB/BC* Region II/DRP/BC* PDII-2/SC PDII-2/D*
NAME JWermiel SCahill AHowe EHackett DATE 07/18/03 07/21/02 / /03 07/18/03 OFFICE DLPM/D* ADPT* NRR/D* EDO NAME LMarsh (HBerkow for) BSheron (HBerkow for) SCollins (HBerkow for) WTravers DATE 07/23/2003 07/25/03 07/25/03 08/08/03 OFFICIAL RECORD COPY
Tennessee Valley Authority BROWNS FERRY NUCLEAR PLANT cc:
Mr. J. A. Scalice Mr. Mark J. Burzynski, Manager Chief Nuclear Officer and Nuclear Licensing Executive Vice President Tennessee Valley Authority Tennessee Valley Authority 4X Blue Ridge 6A Lookout Place 1101 Market Street 1101 Market Street Chattanooga, TN 37402-2801 Chattanooga, Tennessee 37402-2801 Mr. Timothy E. Abney, Manager Mr. Karl W. Singer, Senior Vice President Licensing and Industry Affairs Nuclear Operations Browns Ferry Nuclear Plant Tennessee Valley Authority Tennessee Valley Authority 6A Lookout Place P.O. Box 2000 1101 Market Street Decatur, AL 35609 Chattanooga, TN 37402-2801 Senior Resident Inspector Mr. James E. Maddox, Vice President U.S. Nuclear Regulatory Commission Engineering & Technical Services Browns Ferry Nuclear Plant Tennessee Valley Authority P.O. Box 149 6A Lookout Place Athens, AL 35611 1101 Market Street Chattanooga, TN 37402-2801 State Health Officer Alabama Dept. of Public Health Mr. Ashok S. Bhatnagar, Site Vice President RSA Tower - Administration Browns Ferry Nuclear Plant Suite 1552 Tennessee Valley Authority P.O. Box 303017 P.O. Box 2000 Montgomery, AL 36130-3017 Decatur, AL 35609 Chairman General Counsel Limestone County Commission Tennessee Valley Authority 310 West Washington Street ET 11A Athens, AL 35611 400 West Summit Hill Drive Knoxville, TN 37902 Mr. Robert J. Adney, General Manager Nuclear Assurance Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801 Mr. Robert G. Jones, Plant Manager Browns Ferry Nuclear Plant Tennessee Valley Authority P.O. Box 2000 Decatur, AL 35609
DISTRIBUTION FOR GREEN TICKET CONCERNING BROWN FERRY Dated: August 8, 2003 PUBLIC PDII-2 R/F B. Clayton (hard copy)
K. Jabbour (hard copy)
W. Travers C. Paperiello W. Kane P. Norry W. Dean S. Collins R. Borchardt B. Sheron L. Marsh E. Hackett A. Howe E. Imbro J. Wermiel S. Burns/K.Cyr L. Reyes RII S. Cahill, RII B. Smith, EDO K. Johnson L. Cox T. Gorham/S. Taylor (G20030355)