ML20044G776
| ML20044G776 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 05/24/1993 |
| From: | CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | |
| Shared Package | |
| ML20044G593 | List: |
| References | |
| NUDOCS 9306040253 | |
| Download: ML20044G776 (5) | |
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CONSUMERS POWER COMPANY DOCKET 50-155
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l REQUEST FOR CHANGE TO THE TECHNICAL SPECIFICATIONS l
LICENSE DPR-6 For the reasons hereinafter set forth, it is requested that the Technical' l
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l-Specifications contained in the Facility Operating License DPR-6, Docketi 50-155, issued to Consumers Power Company on May 1, 1964, for the Big Rock Point Plant be changed as described in Section I below:
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CHANGES l__
N0JTE: Revised Technical Specification pag'es are attached.
l Proposed changes are shown by a vertical line or slash in the l
l right-hand margin.
A.
Section'6.1.2.
Sensor and Trio device: add the following description.below "LossD j
of auxiliary power supply":
j (CB-REllA and.CB-REllB undervoltage Release Device) l t
l The proposed change identifies the sensor and' trip device utilizing.the actual equipment identification of "CB-REllA and CB-RE11B" and the. term "undervoltage release device" to more i
accurately describe the equipment involved.
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B.
Section 6.1.2 l
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Scram Settino and Tolerance: delete "52 plus or minus 20. volts".
j Insert: greater than or equal to 32 Vac Limiting Setpoint.
The proposed change requests that the scram setting and tolerance utilize the current Technical Specification limiting 'value 'of
" greater than or equal to 32 Vac". and identify this value as the
" limiting setpoint".
This limiting value on undervoltage -(52 minus 20 = 32) has-been 'in-
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place since issuance of the ~ July 5,1962, Technical Specification.
No basis was provided for the selection and establishment of.this
. limiting value by General Electric Company (GE) in the design of.
the RPS.-The value of 52 plus or minus 20 was selected by'GE for both the Big Rock and Humboldt Bay Plant in 1962.
C.
Section 6.'1.2' i
Special Features: add (2) after " isolation valves" i
i This addition will direct the reader to an applicable note at the '
bottom of an appropriate page of the Technical. Specification.
1 9306040253 930524 PDR, ADOCK 05000155 P
PDR i
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2 I.
CHANGES (Continued) l l
D.
Section 6.1.2 At the bottom of the page, add a footnote for (2) added in C.
above:
(2) Loss of Reactor Protection System (RPS) Bus voltage from both motor-generator sets causes enclosure isolation via the fail-safe I
operation of the RPS per loss of power and not by virtue of the l
undervoltage release device associated with CB-REll.
l Addition of this note is needed to clarify that the tripping of l
CB-REll via the undervoltage release device results in only a j
single channel scram. A full RPS scram on both channels is required to initiate enclosure isolation.
II.
DISCUSSION l
1.
CB-REll GENERAL DESCRIPTION Circuit Breakers CB-REllA and CB-RE118 are located in the Reactor Protection System (RPS) Channels 1 and 2. These breakers provide 15 ampere thermal magnetic overload and short circuit protection.
In addition, each breaker contains an undervoltage release device which serves three functions:
(1) To rapidly deenergize the scram solenoid buses in the event of a manual scram (although a trip signal is also initiated in the RPS logic from the manual scram pushbutton).
(2) To rapidly deenergize the scram solenoid buses when the reactor mode switch is placed in the " shutdown" position; (3) To deenergize the scram solenoid buses if low voltage is sensed on the RPS bus.
The first two functions, 1 and 2 above, occur on removal of voltage through the undervoltage release device coil. The third function occurs when the coil voltage is_ reduced to a predetermined design value.
2.
CURRENT CB-REll UNDERV0LTAGE RELEASE DEVICE TRIP RANGE This circuit breaker and undervoltage release device 'is of original plant design and the trip range was based upon 30 - 60%
of nominal 120 Vac on the undervoltage release device coil. This resulted in a trip voltage of 36 - 72 Vac of a design scram setting and tolerance of 54 plus or minus 18 Volts. Thus, based upon design, the device would automatically trip CB-REll when line voltage drops below the 36 to 72 volt level.
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II.
-DISCUSSION (Continued)
It should be noted that the lower limiting setpoint.in the..
i Technical Specification remained at 32 Vac independent of the c' il o
design lower level-of 36 Vac.
3.
REPLACEMENT CB-REll UNDERVOLTAGE RELEASE DEVICE TRIP RANGE J
1 The original. type "TE" General Electric breakers are no longer ~
available. General Electric recommended.. replacement _.using type "TED". The'_undervoltage release device. for_ the replacement' breaker 1
trip range Lis based-on 35 - 70% of nominal 120 Vac on the:
-undervoltage release devicei coil. This results in.a trip voltage of 42 " 84 Vat or a design. scram. setting and tolerance of'63.plus) or minus 21 Vac.
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Replacing CB_-REll breakers having a higher undervoltage release i
device design trip voltage of. 42u-84 Vac lversus the original design trip voltage of.36 - 72 Vac is-judicious because:
- A-higher; trip voltage results in an increase Lin. sensitivity toward undervoltage conditions which'is considered to be in the conservative direction for. reactor safety;-and l
This. higher trip voltage will not: lead to an increase in spurious undervoltage tripping of, the RPS system because.the-replacement breaker design trip; voltages are still well below l
the operating voltage settings of_ RPS bt.s components and the undervoltage protecti_on devices associated with the.MG sets and-Station Power System.
i 4.
UNDERVOLTAGE PROTECTION FEATURES i
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Two undervoltage protection devices-exist within the RPS power
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supplies to guard against undervoltage conditions.
A. Undervoltage protection is provided by an under-voltage relay in the 480 Vac cont _rol circuitry of the motor generator _(MG) sets that:
- functions as a loss-of-voltage sensor to annunciate that a loss of_ power to the MG sets has occurred; and
- trips the MG sets' output' after a.10 second time delay.
'The MG set undervoltage relay will' not: protect against degraded conditions on the-480 Vac'MG set supply. buses' This l
protection is provided by the Station Power. System-(SPS) relaying' schemes,.that trip the supply breaker to the 2400-Vac bus breakers. The trip occurs.after-as sustained: degraded voltage' level of about 89% rated voltage (about' 107: Vac on-i the 120 Vac potential transformers).- ThisLdegraded level must be experienced on all three phases of the 2400 Vac bus that
-feed the 480 Vac system in order for the trip to' occur.
. I' II.
DISCUSSION (Continued)
B.
The other device associated with the RPS bus supply is the undervoltage release device associated with CB-REll described in the previous sections of this request.
In general, it is doubtful that the RPS bus 120 Vac supply through the contacts and undervoltage release device of thef CB-REll breakers. will experience undervoltage conditions that would deenergize the breaker. The MG set outputs are essentially constant down to 70% of rated 480 Vac input with full load on the generator; and the capability of the 2400 Volt bus undervoltage relaying at about 89% rated' voltage -
lends support to this generalization.
III.
ANALYSIS OF N0'SIGNIFICANT HAZARDS CONSIDERATION Consumers Power Company finds, in compliance with 10 CFR 50.92(c), that activities associated with this change request involve no significant hazards. The following evaluation supports that finding.
1.
Will the proposed change involve a significant increase in the probability or consequences of an accident previously evaluated?
l The Final Hazards Summary Report (FHSR) Accident and Transient analyses do not take credit for CB-REll operation during any of the previously evaluated accidents. Therefore, the proposed change will have no significant effect on the probability or consequences of accidents that have been previously evaluated at the facility.
2.
Will the proposed change (s) create the possibility of a new or different kind of accident from any accident previously evaluated?
The replacement breakers contain an additional test mechanism designed with linkages to mechanically simulate over-current trips. This device provides a means of exercising the breaker.
In-the event that the mechanism were to fail the breaker in the open or closed position, the overall common mode failures, as previously evaluated, remain the same.
3.
Will the proposed change involve a significant' reduction in the margin of safety?
l There is no basis provided in the Technical' Specifications.for the l
-setting and tolerance of the CB-RElls. The Current Licensing Basis L
and Facility Design Basis Documents have been researched, and do not define a basis for the 52 plus or minus 20 setting and tolerance. The setting appears to be based on the undervoltage-release device coil and-mechanism designed with a lower limiting setpoint established at " greater than or equal to 32 Vac".
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5 IV.
CONCLUSION The Big-Rock Point Plant Review Committee (PRC) has reviewed this Technical Specification Change Request and has determined this-change '
does not involve:an unreviewed. safety question.and, therefore, involves no significant hazards consideration. This change has been reviewed by the Nuclear ~ Performance Assessment Department. A copy of-this Technical Specification Change Request has been submitted-to the State of-l Michigan official designated to receive such Amendments to the-I Operating License.
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CONSUMERS POWER COMPANY To the best of my knowledge,-information and~ belief, the contents of this submittal are truthful and cm te.-
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'obe~rt J g<flevak, Vice President of j
Gas Supply & Transmission l
l Sworn and subscribed to before me this 25th day of May 1993.
h a t/k h h ut a re Beverif Avery, Notafy Public Jackson County, Michigan My commission expires BEVERLY A AVERY
_j NOTARY PUBLIC STATE OF MICHICAN q
JACKSON COUNTY MY COMMISSION EXP. DEC. 3,1996 a
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