ML20195H083

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Safety Evaluation Supporting Amends 237 & 226 to Licenses DPR-77 & DPR-79,respectively
ML20195H083
Person / Time
Site: Sequoyah  Tennessee Valley Authority icon.png
Issue date: 11/17/1998
From:
NRC (Affiliation Not Assigned)
To:
Shared Package
ML20195H081 List:
References
NUDOCS 9811230251
Download: ML20195H083 (6)


Text

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UNITED STATES s

NUCLEAR REGULATORY COMMISSION

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 236 TO FACILITY OPERATING LICENSE NO. DPR-77 AND AMENDMENT NO. 7A TO FACILITY OPERATING LICENSE NO. DPR-79 TENNESSEE VAli FY AUTHORITY SEQUOYAH NUCLEAR PLANT. UNITS 1 AND 2 DOCKET NOS. 50-327 AND 50-328 1

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1.0 INTRODUCTION

The Tennessee Valley Authority (TVA) requested amendments to Operating Licenses DPR-77 and DPR-79 for Sequoyah Nuclear Plant (SON), Units 1 and 2, respectively, in a letter to the U.S. Nuclear Regulatory Commission (NRC) dated February 13,1998. The amendments

  • would revise the SON Technical Specification (TS) requirements for main steam isolation i

valves (MSIVs). The amendments would incorporate new MSIV requirements that are consistent with the Standard TS (NUREG-1431), including testing requirements for the MSIVs i

that ensure the valves close on as automatic actuation signal. The need for these changes was identified during the Generic Letter (GL) 96-01 reviews conducted by TVA.

2.0 BACKGROUND

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TVA proposed a change to the current requirements for the MSIVs that will provide consistency j

with NUREG-1431. The following items were proposed, including TVA's reason for each change:

1.

Revision of the Limiting Condition for Operation (LCO) statement to require "four" MSIVs to be operable instead of "each" MSIV. Revision of the LCO statement from "each" to "four" provides consistency with NUREG-1431 and other specifications and clarifies the LCO scope.

2.

Removal of the option to close the MSIV for the Mode 1 action. In Mode 1, the closure of an MSIV is not practical because of the adverse effect on unit operation. Therefore, the action provision to close the valve has been eliminated. This change provides consistency with NUREG-1431.

3.

Revision of the action for Mode 1 to only require shutdown to Mode 2. When an MSIV cannot be returned to operable status in Mode 1, a shutdown below Mode 2 is not necessary. Actions for Mode 2 provide other options for continued operation without requiring a shutdown to lower modes. This change provides consistency with NUREG-1431.

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Revision of the Modesi 2 and 3 actions to allow one or more MSIVs to be inoperable.

The provision to allow one or more MSIVs to be inoperable in Modes 2 and 3 provide i

flexibility for continued operation when appropriate actions are taken to maintain safety functions. Immediate shutdown in accordance with TS 3.0.3 is not reasonable with more than one MSIV inoperable and the appropriate actions satisfied. This change provides consistency with NUREG-1431.

5.

Revision of the "a" item of the Modes 2 and 3 actions to provide the option to retum the MSIV to operable status and addition of the time interval required for this item. In addition to the option to close the MSIV in Modes 2 and 3, this change provides for the l

retum of the valve to operable status. Placing the valve in an operable condition without l

depending on action requirements is more desirable than isolating the path or initiating a shutdown to lower modes. A time interval has been added to ensure the establishment of the safety function within a reasonable time regardless of the method used. This f

change provides consistency with NUREG-1431, 6.

Addition of a new item to the actions for Modes 2 and 3 that will require the verification that the inoperable MSIV is closed once eve,ry 7 days. The addition of the 7-day i

verification provides confidence that the MSIV is closed and that the safety function is l

maintained. This provision supports the potential to be in this condition for a prolonged period of time. This change provides consistency with NUREG-1431.

7, Addition of a new item to the actions for Modes 2 and 3 that allows separate entry into the actions for each MSIV. The provision for separate entry into the Modes 2 and 3 actions for each MSlV clarifies the acceptability for multiple valves to be inoperable provided appropriate actions are taken. It also clarifies the application of the action times such that each MSIV is treated individually for meeting the requirements of this action. This change provides consistency with NUREG-1431.

8.

Addition of a new surveillance to verify closure of each MSIV on an actual or simulated automatic actuation signal once every 18 months. The addition of the actuation test is provided to ensure the entire main steam isolation function is properly tested. SON reviews for GL 96-01 identified the lack of a TS requirement to test the end device for this function. This addition resolves this concern by requiring a test that verifies the MSIVs will close when an actuation signal from the solid state protection system is generated. This change provides consistency with NUREG-1431.

3.0 EVALUATION The MSIVs are 32-inch globe valves that utilize air to open and spring to close. The MSIVs are provided to protect the plant during breaks in the steam line upstream and downstream of the valves and steam generator (S/G) tube rupture events. The closure of the MSIVs ensures that no more than one S/G will blowdown for the steam-line break events. This closure will minimize the positive reactivity effects of the reactor coolant system cooldown resulting from the blowdown and limit the pressure rise in containment for ruptures inside the containment structure. For S/G tube rupture events, the MSIVs serve to limit the total amount of primary

3 coolant leakage by isolating the damaged S/G after pressure is reduced below shell side design pressure. The isolation of the steam line for this event does not require a fast operating MSIV.

The MSIVs are capable of closina v.ithin the required actuation times assumed in the accident analysis.

l The TVA request stated that these changes to the SON TSs provide consistency with NUREG-1431 requirements. These changes will not alter the design or operating characteristics of the main steam isolation function. Some of the changes will enhance the requirements that ensure the MSIVs are operable by adding requirements for verifications that

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l the valves are closed every 7 days when inoperable and a new surveillance that provides end-device testing to verify the actuation capability. Changes to the allowed action times for inoperable MSIVs in Modes 2 and 3 could result in longer periods of time when the valves are not fully functional. The remaining changes do not reduce the effectiveness of the MSIV operability requirements, but do provide reasonable provisions consistent with the design of the MSIVs. Specific justifications for the impact of each of the changes described above is as follows:

1.

The LCO statement change to four MSIVs does not change the intent or application of TS requirements. There is no adverse impact to, nuclear safety as a result of this change.

1 2.

The removal of the option to close the MSIV in Mode 1 does not reduce safety. The current action for an inoperable MSIV in Mode 1 provides for continued operation provided the valve is restored to operable status or closed. Closure of an MSIV in Mode 1 could initiate severe S/G level problems that may result in a reactor trip. This result is more likely at higher power levels, but could also result at low power levels and l

unnecessarily challenge safety systems. The proposed requirement to reduce power to l

Mode 2 or lower, where the MSIVs can be safely closed, will provide adequate actions to l

establish the safety function of the valves in a reasonable length of time. There is no adverse impact to nuclear safety as a result of this change.

3.

The current SQN requirement for an inoperable MSIV in Mode 1, that cannot be restored to operable status within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, is a shutdown to Mode 3 in 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and Mode 4 in the following 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />. This action is not reasonable when indefinite operation in Modes 2 and 3 is allowed by this specification. The proposed requirement to shutdown to Mode 2 will provide the appropriate actions to continue shutdown to lower modes or establish conditions that ensure the safety function of the MSIVs. Therefore, the current requirement is overly restrictive and requires the shutdown of the unit to an operating condition that may not be necessary. There is no adverse impact to nuclear safety as a result of this change.

4.

The allowance to have one or more MSIVs inoperable in Modes 2 and 3 is acceptable based on the proposed actions to allow continued operation in these modes. These actions ensure that the safety function of the MSIVs are established or require a i

shutdown to Mode 4 where the MSIV safety function is not assumed in the accident l

analysis. If an MSIV continues to remain inoperable in Modes 2 and 3, the required j

actions will close and periodically verify that the valve is closed, in the closed position,

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the MSIV satisfies the safety function to isolate steam flow. If these actions are maintained for more than one MSIV, there will be no reduction in safety. There is no adverse impact to nuclear safety as a result of this change.

5.

The current SON requirements for inoperable MSIVs in Modes 2 and 3 only provide actions to maintain the valves closed. This was based on the expectation that inoperable MSIVs would be closed when these modes were entered and did not specifically address valves becoming inoperable in these modes. The proposed change to the Mode 1 action statement provides a more appropriate action that would require entry into Mode 2 with the inoperable valves open. Therefore, this change will provide the option to continue efforts to return the valve to operable status or to close the valve.

The addition of a 4-hour time limit to establish operability or close the MSIV is provided because the valve may be open when entering this condition or become inoperable in these modes. This time ensures the establishment of the safety function in a reasonable length of time considering the low probability of an accident occurring during this time period that would require closure of the MSIVs. This time limit, coupled with the Mode 1 action times, could allow an MSIV to remain inoperable for up to 14 hours1.62037e-4 days <br />0.00389 hours <br />2.314815e-5 weeks <br />5.327e-6 months <br /> prior to being closed, This time interval 13 within the potential 16-hour period that could result with the current requirements where an inoperable MSIV in Mode 1 could remain open while making the transition to Mode 4. The proposed change could result in a 26-hour period of time that an inoperable MSIV can be open from Mode 1 to Mode 4. This increase in time is acceptable based on the additional provisions to close or return the MSIV to operable status and the value of limiting shutdown activities when safety functions can be established in higher operating modes.

The NRC staff has reviewed TVA's justification for these changes and finds that they will result in greater assurance that MSIVs perform their design function of isolating steam line breaks.

The staff notes also that the proposed changes are consistent with, but more conservative than, NUREG-1431, the Revised Standard TSs for Westinghouse-designed plants. For example, NUREG-1431 requires an inoperable MSIV to be restored within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> whereas the proposed change to the SQN TSs requires restoration within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. The NRC staff, therefore, finds the subject TS changes proposed by TVA to be acceptable.

4.0 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.

5.0 ENVIRONMENTAL CONSIDERATION

The amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes surveillance requirements. The NRC staff has determined that the amendment involves 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 exposure. The Commission has previously issued a proposed finding

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that the amendment involves no significant hazards consideration, and there has been no public comment on such finding (63 FR 38204, dated July 15,1998). Accordingly, the amendments meet the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 5122(b), no environmentalimpact statement or environmental assessment need be prepared in connection with the issuance of the l

amendments.

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6.0 CONCLUSION

The Commission has concluded, based on the considerations discussed above, that: (1) there is reasonable assurance that the health and safety of the public will not be endangered by l

operation in the proposed manner, (2) such activities will be conoucted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.

Principal Contributor Ronald W. Heman Datei Noveter 17, 1998

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tbveter 17, 1998 Mr. J. A. Scalic]

Chief Nuclear Officer and Executive Vice President Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801

SUBJECT:

ISSUANCE OF TECHNICAL SPECIFICATION AMENDMENTS FOR THE SEQUOYAH NUCLEAR PLANT, UNITS 1 AND 2 (TAC NOS. MA1319 AND MA1323)(TS 97-07) 2

Dear Mr. Scalice:

The Commission has issued the enclosed Amendment No. 236 to Facility Operating License No. DPR-77 and Amendment No. 226 to Facility Operating License No. DPR-79 for the Sequoyah Nuclear Plant (SON), Units 1 and 2, respectively. These amendments are in response to your application dated February 13,1998. The amendments revise the SQN Technical Specification (TS) requirements for main steam isolation valves (MSIVs). The amendments incorporate new MSIV requirements that are consistent with the Standard TS (NUREG-1431), including testing requirements for the MSIVs that ensure the valves close on an automatic actuation signal. The need for these changes was identified during the Generic Letter (GL) 96-01 reviews conducted by the Tennessee Valley Authority (TVA).

The amendment request indicates that TVA condu$ted a very comprehensive' review in response to GL 96-01. The justification in the request was very thorough and well-written.

A copy of the Safety Evaluation is also enclosed. Notice of issuance will be included in the Commission's biweekly Federal Reaister notice. Please direct any questions you or your staff should have to me at 301-415-2010.

Sincerely, Original signed by:

Ronald W. Hernan, Senior Project Manager Project Directorate 11-3 Division of Reactor Projects - 1/II Office of Nuclear Reactor Regulation Docket Nos. 50-327 and 50-328 Distribution (w/enclosurek Docket Files W. Beckner

Enclosures:

1. Amendment No.236 to PUBLIC G. Hill (4)

License No. DPR-77 SON r/f T. Harris (TLH3 w/ SE)

2. Amendment No.226 to L. Plisco, Ril J. Zwolinski(A)

License No. DPR-79 ACRS OGC

3. Safety Evaluation R. Hernan B. Clayton F.Hebdon R. Wessman cc w/ enclosures: See next page Document Name: G:\\SQN\\1319.AMD To receive a copy of this document, indicate in the box:

"C" a Copy without attachment / enclosure "E" = Copy with attachment / enclosure

  1. 3ta a No copy OFFICE PDil-3/PM,

E PDll-3/LA lE-EME.J/,B,C)

OGC,y1 PDil-3/D C.

NAME RHernan M BClayton /AERWebKiiifn F~

FHebdon d.

DATE 10/N /98 10/ 2 )( /98 to Si /98

///.5 /98 n / n /98 OFFICIAL RECORD COPY