ML20078D535
| ML20078D535 | |
| Person / Time | |
|---|---|
| Site: | McGuire, Mcguire  |
| Issue date: | 10/27/1994 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20078D531 | List: |
| References | |
| NUDOCS 9411040260 | |
| Download: ML20078D535 (6) | |
Text
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UNITED STATES j,
j NUCLEAR REGULATORY COMMISSION WASHINGTON, D C. 20555 4001
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SAFETY EVALVATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT N0.150 TO FACILITY OPERATING LICENSE NPF-9 AND AMENDMENT N0.132 TO FACILITY OPERATING LICENSE NPF-17 DUKE POWER COMPANY MCGUIRE NVCLEAR STATION. UNITS 1 AND 2 DOCKET NOS. 50-369 AND 50-370 1.0 JFTRODUCTION By letter dated November 21, 1991, Duke Power Company (the licensee) submitted a request for changes to the McGuire Nuclear Station, Units 1 and 2, Technical Specifications (TS).
The requested changes would revise the TS for the power-operated relief valves (PORVs) and block valves, and low-temperature overpressure protection (LTOP) systems as a result of NRC recommendations pertaining to Generic Letter 90-06. The purpose of this safety evaluation is to address the licensee's response changing the TS for the P0RVs and LTOP systems.
2.0 EVALUATION The proposed TS changes were submitted in accordance with the guidance provided by the NRC in its resolution of Generic Issue 70, "PORV and Block Valve Reliability" and Generic Issue 94, " Additional Low-Temperature Overpressure Protection for Light-Water Reactors." The specific changes are discussed individually in the following sections.
Regarding Generic Issue 94, licensees were requested to verify whether certain administrative restrictions concerning the restart of inactive reactor coolant pumps and concerning the operability of high pressure safety injection pumps have been implemented.
These restrictions were imposed as a result of Unresolved Safety Issue (USI) A-26, " Reactor Vessel Pressure Transient Protection (0verpressure Protection)." The licensee stated that these administrative restrict. ions have been previously implemented at McGuire.
Limiting Condition for Operations (LCO) 3.4.4
- Action statement a. becomes applicable only in the case of PORV inoperability due to excessive leakage. While GL 90-06 only refers to seat leakage, the new action statement a. simply refers to leakage in general, so that both seat leakage and packing leakage would constitute PORV inoperability under this action statement.
The phrase dealing with the removal of power from the block valve (s) is changed to require power to be maintained to the block valve (s).
This ensures that the valve (s) remain operable and capable of being opened to allow the PORV(s) to be used to 9411040260 941027 DR ADOCK 05000369 PDR
. control primary system pressure.
In addition, the action statement has been modified to terminate the forced shutdown requirement in hot shutdown rather than cold shutdown, since the LCO only applies to Modes 1, 2, and 3.
- Action statements b.,
c., and d. govern the cases of PORV inoperability due to causes other than excessive leakage for the cases of one, two, or three inoperable PORVs, respectively. Action statement b. allows continued plant operation with one inoperable PORV, provided its block valve is closed and power is removed from the block valve. The licensee's basis for this position is that following a steam generator tube rupture with loss of offsite power, only one PORV is required to depressurize the Reactor Coolant System. All three of McGuire's PORVs have nitrogen backup capability to cope with a loss of instrument air to the valves. Therefore, even with one PORV inoperable for an extended period of time, redundant capability exists to depressurize the Reactor Coolant System following an SGTR event.
- Action statements e.,
f., and g. govern block valve inoperability for the cases of one, two, or three inoperable block valves, respectively.
These action statements establish remedial measures consistent with the function of the block valves. The prime importance for the capability to close the block valve is to isolate a stuck-open PORV.
If the block valve (s) cannot be restored to operable status within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, the remedial action is to place the associated PORV switch (es) in the "close" position to preclude its automatic opening for an overpressure event and to avoid the potential for a stuck-open PORV at a time that the block valve is inoperable.
(The guidance contained in the generic letter states to place the PORV in manual control; however, McGuire's PORV control switches are labeled "open",
"close", and " auto", so the proposed change is consistent with the McGuire design.)
Since the proposed Technical Specifications (TS) do not require the plant to be shut down for the case of one inoperable PORV or one inoperable block valve, action statement e. includes the additional requirement to remove power from the associated PORV solenoid valve. This provides additional assurance that the PORV with the inoperable block valve will not be inadvertently opened at a later date, because if the block valve is not capable of being closed, an unisolable leak path would be created if the PORV were to fail open. The requirement to remove power from the PORV solenoid valves is not necessary for action statements f. and
- g. since these action statements possess time limitations for restoring the block valves to operability. The time allowed to restore the block valve (s) to operable status is based upon the remedial action time limits for inoperable P0RVs per action statements b.,
c., and d. since the PORVs are not capable of mitigating an overpressure event when the PORV switches are in the "close" position. The same basis proposed for allowing continued plant operation with one inoperable PORV in action statement b.
also applies to action statement e.
Finally, action statements e.,
f.,
and g. include a provision in parentheses which precludes entering action statements b.,
c., and d. respectively, for inoperable PORVs once the PORV switch (es) have been placed in the "close" position. This is necessary
j i because placing the PORV switch (es) in the "close" position renders the PORV(s) inoperable and the resulting requirements for inoperable PORV(s) in action statements b.,
c., and d. (i.e., close the block valve (s) and remove power) are inappropriate since the block valve (s) are already inoperable under action. statements e.,
f., and g.
These changes are acceptable.
Old action statement c. becomes new action statement h.
Surveillance Requirement 4.4.4.1 The generic letter recommends that PORVs be stroked during Mode 3 or Mode 4 in order to accurately simulate environmental effects on the valves. The basis for this recommendation is that testing during Mode 5 may not be a representative test for assessing PORV performance under normal plant operating conditions.
Surveillance Requirement 4.4.4.1.b has therefore been modified to require that the PORVs be cycled during Modes 3 or 4.
It clarifies that the PORVs should only be cycled during that part of Mode 4.
which is not in the LTOP regime and further specifies that the block valve must be closed prior to stroking the PORV to preclude the possibility of a loss of coolant should the PORV fail open with the block valve open..(The block valve would be closed just prior to stroking the PORV.so that environmental conditions on the PORV are maintained.)
Surveillance Requirement 4.4.4.2
- This surveillance requirement exempts the block valve from having to be demonstrated operable when it is closed to isolate an inoperable PORV.
The exemption is maintained for the case when a block valve is closed with power maintained to isolate a PORV which is inoperable due to excessive leakage. This is to prevent having to open the block valve and discharging large quantities of effluent to the pressurizer relief tank in the case of a severely-leaking PORV.
If the block valve is closed with power removed to isolate an otherwise inoperable PORV (the proposed TS allows McGuire to operate with one PORV/ block valve inoperable for an extended period of time), the block valve would not need to be demonstrated operable because redundant accident mitigation capability would be provided by the two i
remaining PORVs/ block valves.
Surveillance Requirement 4.4.4.3
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- Surveillance Requirement 4.4.4.3 has been added which requires demonstrating the PORY emergency power supply operable.
It requires the valve motive power to be transferred from its normal instrument air supply to its emergency nitrogen supply, the air supply to be isolated and vented, and the PORV to be operated through a completed cycle of full travel.
The generic letter also recommends that the surveillance requirements require operating solenoid air control valves and check valves on air accumulators in PORV control systems through a complete cycle of full travel.
Surveillance Requirement 4.4.4.3 requires the PORVs to be stroked while
. aligned to the emergency nitrogen supply, with the normal air supply vented; this cycles the necessary valves.
It is therefore not necessary to expand the surveillance requirements any further in this regard. Also, the guidance contained in the generic letter indicates that motive and control power for the PORVs and block valves should be manually transferred from the normal to the emergency power bus. At McGuire, transferring control power does not apply because the PORVs and block valves are normally powered from an essential bus. Transferring motive power does not apply to the block valves; they are not pneumatic.
Hence, the McGuire specification, as currently modified, complies with the guidance contained in the generic letter and is therefore acceptable.
Limiting Condition for Operation 3.4.9.3
- In LC0 3.4.9.3, the applicability is modified to change the phrase "with the reactor vessel head on" to "when the head is on the reactor vessel."
It should be noted that in the guidance contained in the generic letter, it is suggested that the applicability of the LC0 be clarified to exclude Mode 6 when the Reactor Coolant System is adequately vented and that the depressurizing and venting of the Reactor Ccolant System should no longer be classified as an overpressure protection system.
The generic letter recommends that an additional action statement be added to specify verifying the vent pathway when the Reactor Coolant System is depressurized and vented.
This appears inappropriate, because once the Reactor Coolant System is vented, LC0 3.4.9.3 would no longer apply and the action statement requiring verification of the vent pathway would therefore not have to be entered.
For this reason, the licensee proposed that the present structure of the McGuire TS be maintained in that the depressurizing and venting of the Reactor Coolant System will continue to be classified as an overpressure protection system and the requirement to verify the vent pathway when the system is depressurized and vented will continue to be governed by Surveillance Requirement 4.4.9.3.2.
The staff agrees with the licensee's proposal.
- Action statement a. is modified to clarify that it is only applicable in Mode 4.
Also, the phrase "depressurize and vent" has been changed to
" complete depressurization and venting of" to avoid any possible questions as to when the required depressurization and venting action must be completed.
It also provides for consistency in wording throughout the LC0 and is therefore acceptable.
- A new action statement b. is added which prohibits entering a water-solid condition in the Reactor Coolant System when one PORV is inoperable while in Mode 5.
The licensee proposed an allowable outage time of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> for one PORV while in Mode 5.
When the Reactor Coolant System is not water-solid, 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> is viewed as a reasonable compromise between the 7-day allowable outage time for Mode 4 and the 24-hour allowable outage time for Mode 6 (see below).
Also, 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> provides sufficient time for completing crud burst activities. The licensee proposed a 24-hour time limit for
. 1 completing depressurization and venting activities for this action statement in order to allow for a more controlled depressurization that could be accomplished in 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />. The staff agrees with this proposal.
- A new action statement c. is added to reduce the allowable outage time for an inoperable PORV to 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> while in Mode 6.
- Old action statement b. becomes new action statement d. and the phrase "depressurize and vent" has been changed to " complete depressurization and venting of" for the reason as stated before.
- Old action statement c. becomes new action statement e.
- Old action statement d. becomes new action statement f.
These changes are acceptable.
Surveillance Requirement 4.4.9.3.1
- Surveillance Requirement 4.4.9.3.1.a. is simplified by removing requirements that exist because of general requirements applicable to all surveillance requirements as specified in Section 4.0 of the TS.
This is consistent with GL 90-06 and is acceptable.
Bases Section 3/4.4.4
- The Bases for the PORV and block valve TS have been expanded to identify the major functions of the PORVs and block vaives. These major functions are as follows:
1)
Manual control of Reactor Coolant System pressure following accidents; 2)
Maintaining reactor coolant pressure boundary integrity by controlling leakage; 3)
Manual control of block valves to isolate and unblock PORVs (for manual pressure control and for controlling PORV leakage);
4)
Automatic control of Reactor Coolant System pressure to prevent code safety valve challenges; and 5)
Manual control of block valves to isolate a stuck-open PORV.
The expanded Bases more clearly delineate these functions.
i
. 3.0 STAIE CONSULTATION j
In accordance with the Commission's regulations, the North Carolina State official was notified of the proposed issuance of the amendments. The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
The amendments change requirements with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and change surveillance requirements. The NRC staff has determined that the amendments involve no significant increase in the amounts, and no significant change in the types, of any effluent 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 that the amendments involve no significant hazards consideration, and there has been no public comment on such finding (58 FR 59748 dated November 10,1993). 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 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 common defense and security or to the health and safety of the public.
Principal Contributor:
V. Nerses Date: October 27, 1994 T
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