ML20081H624
| ML20081H624 | |
| Person / Time | |
|---|---|
| Site: | Clinton  |
| Issue date: | 03/21/1995 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20081H613 | List: |
| References | |
| NUDOCS 9503240330 | |
| Download: ML20081H624 (6) | |
Text
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NUCLEAR REGULATORY COMMISSION t
WASHINGTON, D.C. 20566 4 001 4..*4 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 99 TO FACILITY OPERATING LICENSE NO. NPF-62 ILLIN0IS POWER COMPANY. ET AL.
CLINTON POWER STATION. UNIT NO. 1 DOCKET NO. 50-461
1.0 INTRODUCTION
The Clinton Power Station implemented the improved Technical Specifications (ITS) on January 1, 1995.
These were adapted from NUREG-1434, " Standard Technical Specifications, General Electric Plants, BWR/6," and included significant changes in both format and content.
The ITS permitted limited relaxation to some of the Technical Specification (TS) requirements, more restrictions to other TS requirements and relocation of other requirements to i
licensee controlled documents.
Some of the more restrictive requirements resulting from the ITS are found in the shutdown requirements of TS 3.8, " Electrical Power Systems." This portion of the ITS is less prescriptive than the former TSs in that it does not address individual components or systems. However, new TS 3.8 is more restrictive in that it requires more components to be operable while in the shutdown modes.
Limited Condition for Operation (LCO) 3.8.10, " Distribution Systems-Shutdown," states:
The necessary portions of the Division 1, 2, and 3 AC, Division 1, 2, 3, and 4 DC, and Division 1, 2, 3, and 4 uninterruptible AC bus electrical power distribution subsystems shall be OPERABLE to support equipment required to be OPERABLE.
Some of the equipment required to be operable is determined from TS 3.5.2, "ECCS-Shutdown," which requires that two ECCS injection / spray subsystems shall be operable during MODES 4 and 5.
One of the ECCS systems that could be required to be operable during these modes is the high pressure core spray (HPCS) system. At the Clinton Power Station, the HPCS system is powered from the Division 3 diesel generator. The HPCS system is supported by the Division 3 and 4 DC electrical power distribution subsystems.
Technical Specifications 3.8.2, "AC Sources-Shutdown;" 3.8.5, "DC Sources-Shutdown;" and 3.8.8, " Inverters-Shutdown," have similar wording that links operability of Division 3 AC or Division 3 and 4 DC systems to those systems required to be operable by LCO 3.8.10.
Specifically, TS 3.8.2 requires operability of a separate offsite circuit or the Division 3 diesel generator when the Division 3 onsite Class IE electrical power distribution subsystem is required to be operable; TS 3.8.5 requires operability of the Division 3 and 4
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DC electrical power subsystems when the Division 3 and 4 onsite Class IE DC l
electrical power distribution subsystems are required to be operable; and TS 3.8.8 requires operability of the Division 3 and 4 inverters when the Division-l 3 and 4 onsite Class IE uninterruptible AC bus electrical power distribution subsystems are required to.be operable. Operability of the inverters requires operability of the associated batteries and battery chargers.
The former TSs only required the above systems to be operable when the HPCS system was required to be operable. However, the ITS introduced additional j
restrictions because the Division 3 and 4 DC systems have loads beyond the HPCS system. Since some of these non-HPCS Division 3 and 4 loads must remain operable during MODES 4 and 5, TS 3.8.10 requires that the components i
identified in TSs 3.8.2, 3.8.5 and 3.8.8 remain operable. These new restrictions reduce the licensee's operational flexibility and will have a significant impact on the fifth refueling outage which began on March 12, 1995.
Accordingly, by letter dated February 14, 1995, the licensee proposed changes i
to the Technical Specifications that would revise the operability requirements for the Division 3 diesel generator and the Division 3 and 4 batteries, battery chargers, and inverters to apply only when the high pressure core j
spray system is required to be operable.
j 2.0 EVALUATION TS 3.8.10. " Inverters-Shutdown" l
TS 3.8.8 requires operability of the Division 3 and 4 inverters when the i
Division 3 and 4 onsite Class IE uninterruptible AC bus electrical power distribution subsystems are required to be operable. The Clinton Power-l Station has a solid state logic protection system and has four divisions of 120 VAC uninterruptible power.
The Division 1, 2, 3 and 4 uninterruptible AC buses are supplied from the inverters which, in turn, are supplied by the battery chargers and batteries. The proposed changes would permit the batteries, battery chargers and inverters to be taken out-of-service if the HPCS system is not required to be operable. With these components out-of-service, the 120 VAC buses would no longer have an uninterruptible power supply and would be powered from the alternate AC source.
The Division 3 and 4 inverters supply a number of non-HPCS loads that must be operable during MODES 4 and 5.
These non-HPCS loads are powered from the 120 VAC buses and would normally be powered by an uninterruptible power supply.
These loads, which require operability by the Technical Specifications, i
consist of:
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Several Reactor Protection System (RPS) functions per LC0 3.3.1.1, "RPS Instrumentation," (including Intermediate Range Monitor Neutron Flux, i
Scram Discharge Volume Water Level, Reactor Mode Switch - Shutdown l
Position, and manual scram functions) i
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Instrumentation;"
-Actuation instrumentation for the HPCS System and Division 3 DG per LCO 3.3.5.1, "ECCS Instrumentation," including the Low Reactor Water Level (Level 2) Function;"
Isolation actuation instrumentation for primary containment, the Reactor Water Cleanup System, and the RHR System shutdown cooling suction line per LCO 3.3.6.1, " Primary Containment and Drywell Isolation Instrumentation," including the Low Reactor Water Level (Level 1, Level 2 and Level 3) and manual isolation functions; Isolation actuation instrumentation for secondary containment isolation dampers and the Standby Gas Treatment System (SGTS) per LCO 3.3.6.2,
" Secondary Containment Isolation Instrumentation," including the Low Reactor Water Level (Level 2) and manual isolation functions; Loss of power instrumentation for the Division 3 DG per LC0 3.3.8.1,
" Loss of Power Instrumentation;" and Control power for the HPCS System when required by LC0 3.5.2, "ECCS-Shutdown."
As a result of the proposed changes, the above loads may not be powered by an uninterruptible power supply when HPCS is not required to be operable.
Therefore, the licensee has examined the consequences of losing these loads during MODES 4 or 5.
The licensee's analysis determined that with the exception of the SRMs, support of the HPCS system, and actuation of the Division 3 diesel generator, the above components fail in a safe condition upon loss of power. That is, upon deenergization of the associated uninterruptible AC bus, the safety function will automatically be performed by generating a scram, control rod block, isolation, actuation, or inhibit signal, as applicable.
The staff discussed the consequences of losing power to the above components with the licensee.
In particular, the staff focused on the RHR shutdown cooling lines and questioned whether a loss of power and its subsequent restoration would result in an inadvertent isolation of the shutdown cooling lines. The licensee confirmed that a power-on initialization circuit would block any isolation signals for three seconds thus blocking out any spurious isolation signals that may accompany a resumption of power. The staff therefore concurred with the licensee's analysis that, with the exception of the SRMs, the components would fail in the safe position.
The propo:;ed change will permit the SRMs to be powered from a non-uninterruptible power supply. Neither TS 3.3.1.2, " Source Range Monitor (SRM)
Instrumentation," nor the definition of operability requires that the SRMs be powered from an uninterruptible power supply. As discussed in the Bases, the SRMs have no safety function and are not assumed to function during any design basis accident or transient. Only two of the four SRMs are required to be
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' operable during MODES 4 and 5 and their only purpose is to monitor neutron flux.
If the SRMs become inoperable, TSs require that core alterations be suspended (except to insert control rods) and that actions be immediately taken to insert all insertable control rods into core cells containing fuel.
Since the reactor is designed to remain subcritical with the most reactive control rod fully withdrawn, shutdown requirements provide reasonable assurance that the core will remain subcritical if the SRMs become inoperable.
The Division 3 and 4 inverters will remain operable when the HPCS system is required to be operable. Therefore, the proposed changes will not impact the capability of the HPCS to perform its intended function.
TS 3.8.5. "DC Sources-Shutdown" TS 3.8.5 requires operability of the Division 3 and 4 DC electrical power subsystems when the Division 3 and 4 onsite Class IE DC electrical power distribution subsystems are required to be operable. The Division 3 and 4 batteries and battery chargers supply power to the inverters and the DC buses.
The impact of the loss of power to the affected inverters is described above.
The DC sources supply control power to the HPCS system and the Division 3 diesel generator. The proposed changes do not alter the requirement that both Division 3 and 4 batteries and battery chargers remain operable when the HPCS system is required to be operable by TS 3.8.10.
TS 3.8.2. "AC. Sources-Shutdown" TS 3.8.2 requires operability of a separate offsite circuit or the Division 3 diesel generator when the Division 3 onsite Class IE electrical power r
distribution subsystem is required to be operable.
The Division 3 AC distribution system supplies power to both the HPCS system and a number of systems that support HPCS operation. These support systems include the Division 3 shutdown cooling water pump and Division 3 switchgear room cooling.
When HPCS is not required to be operable by TS 3.8.10, these support systems are not required to be operable. Therefore, the proposed changes do not alter the requirement that a separate offsite circuit or the Division 3 diesel generator will be operable when the HPCS system is required to be operable by l'
The staff has reviewed the proposed changes and notes that (1) all electrical systems supporting HPCS operation will remain operable when the HPCS system is required to be operable by TS 3.8.10 and (2) the resulting changes will permit a number of non-HPCS Division 3 and 4 loads to be supplied by a non-uninterruptible power supply. The licensee's analysis determined that all the non-HPCS loads would fail in the fail-safe mode with the exception of the SRMs. As previously stated, the SRMs do not perform any safety function and Technical Specifications severely restrict refueling operations if the SRMS fail.
The proposed changes will permit the licensee to take both the Division 3 and 4 batteries out of service concurrently when the HPCS is not required to be operable. TS 3.8.5 also permits either the Division 1 or 2 battery to be
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. taken out-of-service. This could result in three of the four battery divisions being out-of-service concurrently during MODES 4 and 5.
In response to staff questions on the outage schedule, the licensee stated that it is not their intent to have three divisions of batteries inoperable concurrently.
During each refueling outage, the licensee performs battery discharge tests on each of the battery divisions. The licensee's practice is to have separate divisional outages between Division 1, Division 2 and the combined Divisions 3 and 4.
Specifically, upon completion of the battery discharge test for Division 3, the licensee would begin recharging the Division 3 battery coincident with initiating the Division 4 battery discharge test. While both Division 3 and 4 batteries would be inoperable at the same time, they would both be operable prior to beginning a Division 1 or 2 battery test. The licensee also stated that man-power resources would restrict them from performing tests on three separate battery divisions.
The staff was satisfied with this understanding.
The staff concludes that the licensee has adequately addressed the potential safety issues involved in the proposed changes.
The licensee's request does not involve any changes to Division 1 or 2 Class IE electrical power systems, nor does it involve any changes related to plant operation in Modes 1, 2 and 3.
The proposed changes are limited to the operability requirements of Division 3 and 4 Class IE electrical power systems during operating Modes 4 and 5.
While the proposed changes represent a relaxation over the ITS, the staff concludes that the revised Technical Specifications will continue to provide adequate controls over plant operation in these modes.
Therefore, the staff finds the licensee's proposed changes acceptable.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Illinois State official was notified of the proposed issuance of the amendment. The State official had no comments.
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4.0 ENVIRONMENTAL CONSIDERATION
This 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.
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 i
exposure.
The Commission has previously issued a proposed finding that the amendment involves no significant hazards consideration and there has been no public comment on such finding (60 FR 9412). Accordingly, the amendment meets 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 amendment.
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r 5.0 CONCLUSJD!!
The staff has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the public l
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 amendment will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor: Douglas V. Pickett Date:
March 21, 1995 i
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