ML20249B596
| ML20249B596 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 06/05/1998 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20249B594 | List: |
| References | |
| NUDOCS 9806230355 | |
| Download: ML20249B596 (4) | |
Text
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UNITED STATES g
j NUCLEAR REGULATORY COMMISSION 2
WASHINGTON, D.C. 2000H001 o%...../
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 127 TO FACILITY OPERATING LICENSE NO. DPR-80 AND AMENDMENT NO. 125 TO FACILITY OPERATING LICENSE NO. DPR-82 PACIFIC GAS AND ELECTRIC COMPANY DIABLO CANYON NUCLEAR POWER PLANT. UNITS 1 AND 2 DOCKET NOS. 50-275 AND 50-323
1.0 INTRODUCTION
By ap)lication dated February 27, 1997. as supplemented by letter dated Decem)er 4, 1997. Pacific Gas and Electric Company (licensee) requested changes to the Technical Specifications (Apaendix A to Facility Operating License Nos. DPR-80 and DPR-82) for the Dia)lo Canyon Nuclear Power Plant.
Units 1 and 2.
The proposed changes revise the combined Technical Specifications (TS) for the Diablo Canyon Power Plant (DCPP) Unit Nos.1 and 2 to revise TS 3/4.8.1.1 "A.C. Sources - Operating," to clarify that emergency diesel generator (EDG) testing is initiated from standby conditions rather than " ambient' conditions. The associated TS Bases were revised to discuss the temperature range that satisfies EDG standby conditions.
This amendment also revises TS 3/4.3.2 " Instrumentation - Engineering Safety Features Actuation System Instrumentation." This revision clarifies that when one or both of the first level load shed relays, or one or both of the second level undervoltage relays are inoperable, the associated EDG for that bus shall be declared inoperable.
The December 4, 1997, supplemental letter provided additional clarifying information and did not clange the initial no significant hazards consideration determination published in the Federal Reaister on April 9.1997 (62 FR 17240).
2.0 EVALUATION l
2.1 EDG Standbv Conditions l
Each unit at Diablo Canyon has three independent automatic starting EDGs to power essential loads if normal power sources are not available.
The EDGs are normally maintained in a standby condition by means of two warming systems when not in operation. The lubricating oil is warmed and continually circulated by means of a recirculating oil system. The jacket water is kept warm with thermostatically controlled immersion heaters.
During outages or maintenance periods, the EDG temperature may be outside the range provided by the warming systems, but still within acce) table temperature ranges established by vendor recommendations and 3G&E test results.
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- Surveillance Requirement 4.8.1.1.2a.2 requires that the EDGs be started from
-ambient conditions. This implies that the EDGs must be started at room temperature. The jacket water and lube oil warming systems are normally in operation or, if not. the EDG temperatures are within an acceptable range. A more accurate term to describe the conditions in which it is acceptable to start the EDGs is " standby condition."
NUREG-1432. Revision 1. " Standard Technical Specification - Westinghouse Plants." states that for the purpose of EDG testing, the EDGs are to be started from standby conditions; that is, with the engine coolant and lube oil continuously circulated and temperature maintained consistent with manufacturer recommendations.
The replacement of the term " ambient" with " standby" clarifies the TS, and more accurately describes the condition in which the EDGs are maintained, and would be required to start under in an accident condition. The change to the TS Bases 3/4.8.1 defines standby temperatures for EDG surveillance testing as recuiring the lubricating oil and jacket water temperatures to be between 90*F anc 175*F based on vendor recommendations and PG&E test results.
.The staff reviewed the change and finds that the word " standby" to be more descriptive of the actual conditions of the diesel: therefore, this change is acceptable.
2.2 4kV Undervoltaae Relays There are two levels of undervoltage detection and automatic transfer provided for the 4kV (4160V) vital buses to transfer vital loads to the EDGs in the event of an undervoltage condition.
The first level of undervoltage protection detects the loss of bus voltage
(<69 percent bus voltage) and has sufficient time delay to allow transfer of the vital busses to the startup transformer. Two first level undervoltage load shed relays (FLURs) one instantaneous and one time delayed, are used to prevent spurious transfers.
EDGs are automatically started on sustained bus undervoltage (approximately 0.7 seconds at 0 volts).
If the transfer to the startup transformer is unsuccessful. the FLURs will shed the vital bus motor loads. After the EDG breaker closes. the vital bus loads are started by individual load sequencing timing relays.
In 1977. each 4 kV vital bus was provided with a second level undervoltage relay (SLUR) protection to detect voltages under 3785V.
This setting is based on requirements that there be a minimum of 90 percent voltage at the 120V vital loads.
Once the second level undervoltage is detected by the relays, timing relays provide two sequential time delays to EDG starting and' loading.
The EDGs are started after a delay of approximately 10 seconds and after an additional 10 seconds, all 4160V motors are shed in preparation for EDG loading.
EDG breaker closing is delayed approximately 2 seconds to allow motor breakers to trip and bus voltage to decay. After the EDG breaker closes, the vital loads are started by individual load sequencing timing relays.
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. The current TS 3.3.2. Table 3.3-3 Functional Unit 7. " Loss of Power (4.16kV Emergency Bus Undervoltage)." Section 7.a.2 "First Level - Initiation of Load Shed." and Section 7.b.1 "Second Level - Undervoltage Relays" lists the total number of channels as 2/ bus and the minimum number of channels operable as i
2/ bus. The action associated with this (Action 16) states:
"With the number of OPERABLE channels one less than the Total Number of Channels, declare the affected Emergency Diesel Generator (s) inoperable-and comply with ACTION statements of Specification 3.8.1.1: however, one channel may be bypassed for up to 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> for surveillance testing per Specification 4.3.2.1."
The action statements for TS 3.8.1.1 require verification of operability of the offsite power sources within one hour and once per eight hours thereafter, and verification of operability of the remaining EDGs.
- There is no stated action for a condition where both load shed FLURs or SLURS are inoperable.
This could imply that the plant would be in a TS 3.0.3 action statement.which contains a one hour limiting condition for operation.
However having both FLURs or SLURS inoperable affects only one vital 4 kV bus and its associated equipment. Technical Specification 3.0.3 is intended to place the plant in a safe configuration when no other action statements are applicable.
Technical Specification 3.0.3 would result in placing the plant in a transient condition due to an unnecessary shutdown, which increases the risk of an accident.
The FLURs and SLURS contacts are connected in series for two-out-of-two logic, and both FLURs and SLURS are required to actuate to cause a bus transfer to the EDG. This assures that a single failure of a FLUR or SLUR does not cause an unnecessary transfer of the vital bus to the EDGs.
Since both FLUR or SLUR relays are required to be operable to cause an undervoltage actuation, entry into Action Statement 15 recognizes that the undervoltage function will not operate. The inoperability of the second relay does not result in a change of conditions and therefore. Action Statement 15 should be applied rather than entry-into TS 3.0.3.
The staff reviewed the change and finds that the revision to be consistent with the Improved TS. This is an improvement from the existing TS. and.
therefore, the proposed TS change is acceptable.
3.0 STATE CONSULTATION
In accordance with the Commission's regulations, the California State official was notified of the proposed issuance of the amendments.
The State official had no. comments.
4.0 ENVIRONMENTAL CONSIDERATION
These amendments' change a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CF2 Part 20 and change surveillance requirements. The NRC staff has i
',' 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 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 (62 FR 17240). Accordingly, the amendments meet the eligibility criteria for 1 categorical exclusion set forth in 10 CFR 51.22(c)(9).
Pursuant to 10 CFR j
.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: S. Bloom Date:
June 5, 1998 i
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