ML20087J329
| ML20087J329 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 04/28/1995 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20087J326 | List: |
| References | |
| NUDOCS 9505080215 | |
| Download: ML20087J329 (6) | |
Text
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k UMTED STATES i
NUCLEAR REGULATORY COMMISSION wAswiworow. o.c. anses4eos j
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. SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION l
RELATED TO AMENDMENT NO.197 TO FACILITY OPERATING LICENSE NO. DPR-77 AND' AMENDMENT NO. 1AR TO FACILITY OPERATING LICENSE NO. DPR-79 TENNESSEE VALLEY AUTHORITY i
SE000VAH NUCLEAR PLANT. UNITS 1 AND 2 i
i DOCKET NOS. 50-327 AND 50-328
1.0 INTRODUCTION
i By application dated March 19, 1993; which was superseded by letter dated May 16,.1994; which was superseded by letter dated February 10, 1995; and i
amplified by information supplied by letter dated February 17, 1995; the Tennessee Valley Authority (TVA or the licensee) proposed amendments to the Technical Specifications (TS) for Sequoyah Nuclear Plant (SQN) Units 1 and 2.
The requested changes would clarify the Limiting Condition for Operation (LCO) i requirements applicable to the dual function of the containment vacuum relief.
(VR) isolation lines by indicating the actions that would be required should -
one or more of the VR lines be incapable of performing its containment i
isolation. function or incapable of performing its VR function.
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The proposed changes would revise TS 3/4.6.3, " Containment Isolation Valves,"
and TS 3/4.6.6, " Vacuum Relief Valves" action statements to separate the containment isolation requirements from the vacuum relief requirements. A change to Table 3.6-2 would add the containment vacuum relief valves. The j
proposed change to TS 3/4.6.6 would clarify that the specification is applicable to the primary containment vacuum relief lines (rather than valves) and a note as a reminder to refer to LCO 3.6.3 if the valves cannot perform i
their containment isolation function. Other proposed changes affect Bases 3/4.6.3, Bases 3/4.6.6, and index pages to reflect these changes.
2.0 EVALUATION i
The VR system consists of three identical flow paths,. each comprised of a
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self-actuating VR valve in series with a pneumatically operated isolation i
valve, associated piping, instrumentation, and controls.-
Each self-actuatina VR valve is a 24-inch, spring-loaded, swing-disc check valve that is normally closed and will start to open if containment internal pressure is 0.1 psi below atmospheric pressure.
The purpose of the valves is to protect the primary containment vessel from excessive external forces in t
excess of its design pressure of negative (-) 0.5 psig. This excessive j
pressure could result from excessive cooling in the containment as a result of l
l ENCLOSURE 3 l
1 9505000215 950429 i
PDR ADOCK 05000327 P
PDR I
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. inadvertent actuation of the containment spray system, inadvertent operation of the containment air return fan, or both events occurring simultaneously.
Two of the three VR lines are required to mitigate the limiting external differential pressure event (inadvertent spray actuation).
The check valves are also designed as containment isolation valves to provide a containment boundary against leakage of airborne fission products from the containment atmosphere under normal and accident conditions. They are tested for seat leakage in accordance with 10 CFR Part 50, Appendix J (Type C test) to ensure that they are capable of providing a qualified containment boundary. Open and closed position indication is provided in the main control room (MCR).
In contrast, each VR isolation valve is an air-operated butterfly valve that is normally open, and fails open on loss of control air pressure. Air is supplied to the three isolation valves from two separate trains of control air (designated Train A and Train B) through two separate solenoid valves.
The solenoid valves are designed to automatically close the isolation valves if pressure inside the containment increases to 1.5 psig in response to an isolation signal developed from either of two independent sets of three pressure sensors. Open and closed position indication is provided in the MCR and an alarm will sound if the isolation valve is not in the fully open position.
The vacuum relief system is designed to mitigate the following abnormal operational occurrences:
inadvertent containment spray actuation, inadvertent containment air return fan operation, and simultaneous occurrence of inadvertent spray and air return fan operation. Two of the three lines are required to met the design requirements.
The VR system is not required to actively mitigate a loss-of-coolant accident or any other accident scenario that might result in the release of radioactivity inside the containment. As an extension of the primary containment boundary, the VR system provides a barrier against leakage of airborne fission products from the containment atmosphere under normal and i
accident conditions. To accomplish this, the isolation valves shut automatically to isolate the containment should internal pressure reach 1.5 psig. They will also shut if control power is lost.
As explained in LER 50-327/92015, the licensee discovered that the configuration of air supplies and solenoid valves for the isolation valves would result in loss of the guaranteed automatic closure capability if Train A control air pressure is lost, causing the isolation valves to remain in their fail-open position. This would render them inoperable as the result of a single failure, since they would then be incapable of shutting in response to an isolation signal. Under this condition, the normally-shut self-actuating check valves would seat more tightly with increasing containment pressure and i
would provide the containment barrier.
Therefore, containment integrity is not lost.
This fail-open design of the isolation valve was previously evaluated and the staff found it acceptable in NUREG 1232, Volume 2, " Safety Evaluation Report on Tennessee Valley Authority: Sequoyah Nuclear Performance Plan," as an i
exception to General Criterion 56 of Appendix A to 10 CFR Part 50.
This NUREG
J recognized that the fail-open position provides the greatest safety for the plant since it protects against containment collapse in the event of inadvertent actuation of containment sprays.
It did, however, indicate that since the two solenoids were located in redundant air supplies, a single failure would not render the valves inoperable. Once this single-failure inconsistency was discovered for loss of Train A air as it applies to the high containment pressure protection function, the licensee initiated temporary
- instructions to remove fuses from the Train A solenoid valve circuit if Train A control air becomes unavailable, as indicated in the LER. This would establish a flow path for Train B control air to operate the butterfly isolation valves should it become necessary.
For the long-term solution, the licensee proposed this amendment to clarify and strengthen the actions to be taken should one or more of the VR lines become inoperable.
Due to the configuration of the solenoid valves, the same problem does not occur for loss of Train B air.
Upon loss of Train A air the present TS 3.6.3.b Action Statement would require that the affected vacuum relief lines be isolated within four hours or a shutdown started.
Isolation of the line would involve closing the affected air-operated butterfly isolation valve (s) and removing electrical power in order to fulfill the isolation requirement.
Since this would conflict with TS 3/4.6.6 that requires the vacuum relief lines be open for operability of the vacuum relief system, the licensee has proposed amending the TS to clarify the requirements.
The change to TS 3.6.3 would add an action statement to allow one or more of the containment vacuum relief isolation valves listed in Sections D.1 through D.3 of Table 3.6-2 to be inoperable for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or be in at least hot standby within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in cold shutdown within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.
When the isolation valve is inoperable, the vacuum relief line isolation function and containment integrity function is being sernd by the self-actuating swing check valve that has been leak rate tested in accordance with 10 CFR 50 Appendix J.
The valve is normally shut and would shut more tightly if containment pressure increased, with an alarm if it left its shut seat.
Therefore, the staff finds the proposed change acceptable.
The applicability of the present TS 3.6.3 action statement would be changed to indicate that the present requirements apply to Sections A, B, C and D.4 through D.7 of Table 3.6-2.
These are the containment isolation valves, including-the three vacuum relief valves.
This change would, therefore, I
result in the present containment isolation valves' requirements becoming applicable to the vacuum relief valves and is acceptable.
A proposed change to Table 3.6-2, Section D, would add the three vacuum relief valves to the list of containment isolation valves.
In addition, a note would be added, referenced to the vacuum relief valves, to indicate that the relief valves perform a containment isolation function and that the maximum isolation time is not applicable to them since they are normally closed, self-actuating valves. The staff finds the proposed change acceptable.
, Another proposed change to Table 3.6-2 would remove double asterisks from Valves FCV-67-89, FCV-67-90, FCV-67-105, FCV-67-106, and FCV-70-141, and the referenced note that states that the valve is required after completion of the associated modification. Since the modification was completed in 1988-89 during the Cycle 3 refueling outage, the staff finds the change acceptable.
One change to TS 3/4.6.6 would change the applicability of the specification from vacuum relief " valves" to vacuum relief " lines." The SQN design assumes single failure of.one line such that two of the three vacuum relief lines are required to mitigate the limiting event.
Failure of a line can result from failure of any component in the line, not just the valve. Therefore, the change clarifies the applicability of the requirement and is more conservative.
It also conforms with the Westinghouse Standard TS (STS). The staff finds the change acceptable.
Another proposed change to TS 3/4.6.6 would remove the words "with an actuation setpoint of less than or equal to 0.1 PSID" from the LCO. Testing of the vacuum relief valve setpoint is performed in accordance with the In-Service Test Program, which is required by Surveillance Requirement 4.6.6.1 by referencing Specification 4.0.5.
This change also conforms to the STS and is acceptable.
Another proposed change to TS 3/4.6.6 would modify the allowed outage time (A0T) for an inoperable vacuum relief line(s) from 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> tt. 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. This change is based on the Westinghouse STS A0T for vacuum relief valves and is consistent with the A0T change for the containment vacuum relief isolation valves.
The staff finds it acceptable.
Another proposed change to TS 3/4.6.6 would add a footnote as a reminder to refer to LC0 3.6.3 if one or more containment vacuum relief isolation or containment vacuum relief valves are incapable of performing a containment isolation function. This will ensure that appropriate actions are taken if valves in a vacuum relief line cannot perform their isolation function. The staff finds this change acceptable.
Other proposed changes affect Bases 3/4.6.6 section and TS index pages to reflect the proposed changes indicated above. These. changes are acceptable.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Tennessee State official was notified of the proposed issuance of the amendments.
The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
The amendments change a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20.
The NRC staff has determined that the amendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation
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, exposure. The Commission has previously issued a proposed finding that the amendments involve no significant hazards consideration, and there has been no public comment on such finding (58 FR 28060, 59 FR 32237, and 60 FR 16202).
Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendments.
5.0 CONCLUSION
The Commission has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the-health and safety of the i
public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendments will not be inimical to the coramon defense and security or to the health and safety of the public.
Principal Contributor: David E. LaBarge Dated: April 28, 1995 i
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4 Mr. 01'iver D. Kingsley, 'Jr.
SEQUOYAN NUCLEAR PLANT t
Tennessee Valley Authority cc:
Mr. 0. J. Zeringue, Sr. Vice President TVA Representative
- Nuclear 0perations Tennessee Valley Authority Tennessee. Valley Authority 11921 Rockville Pike 3B Lookout Place Suite 402 1101 Market Street Rockville, MD 20852 Chattanooga, TN 37402-2801 Regional Administrator Dr. Mark 0. Medford, Vice President U.S. Nuclear Regulatory Commission 3
Engineering & Technical Services Region II Tennessee Valley Authority 101 Marietta Street, NW., Suite 29001 l
3B Lookout Place Atlanta, GA 30323 1101 Market Street Chattanooga, TN 37402-2801 Mr. William E. Holland Senior Resident Inspector l
Mr. D. E. Nunn, Vice President Sequoyah Nuclear Plant New Plant Comnletion U.S. Nuclear Regulatory Commission Tennessee Valiey Authority 2600 Igou Ferry Road
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3B Lookout Place Soddy Daisy, TN 37379 1101 Market Street Chattanooga, TN 37402-2801 Mr. Michael H. Mobley, Director
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Division of Radiological Health i
Site Vice President 3rd Floor, L and C Annex Sequoyah Nuclear Plant 401 Church Street i
Tennessee Valley Authority Nashville, TN 37243-1532 P.O. Box 2000 Soddy Daisy, TN 37379 County Judge Hamilton County Courthouse i
General Counsel Chattanooga, TN 37402 i
Tennessee Valley Authority ET 11H 400 West Summit Hill Drive Knoxville, TN 37902 i
Mr. P. P. Carier, Manager Corporate Licensing Tennessee Valley Authority 4G Blue Ridge 1101 Market Street Chattanooga, TN -37402-2801 Mr. Ralph H. Shell Site Licensing Manager Sequoyah Nuclear Plant
. Tennessee Valley Authority P.O. Box 2000 Soddy Daisy, TN 37379 i
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