ML20090G639
| ML20090G639 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 09/23/1983 |
| From: | Selan J LAWRENCE LIVERMORE NATIONAL LABORATORY |
| To: | NRC |
| Shared Package | |
| ML20090G641 | List: |
| References | |
| CON-FIN-A-0250, CON-FIN-A-250 UCID-19720, NUDOCS 8310200445 | |
| Download: ML20090G639 (10) | |
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Urin-197 2o TECHNICAL EVALUATION REPORT ON Tile MONITORING OF ELECTRIC POWER TO THE REACTOR PROTECTION SYSTEM FOR THE PEACH BOTTOM ATOMIC POWER STATION UNITS 2 AND 3 (Docket Nos. 50-277, 50-278)
James C.
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This is an informal report intended primarily for internal or limited external distribution.
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":3+ e The opinions and conclusions stated art those of the author and may or may not be those
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'Q This work was supported by the United States Nuclear Regulatory Commission under hfYb3A e,d8;t g;. f' a Memorandum of Understanding with the United States Department of Energy.
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AESTRACT This report documents the technical evaluation of the monitoring of electric power to the reactor protection system (RPS) at the Peach Bottom Atomic Pouer Station, Units 2 and 3.
The evaluation is to determine if the proposed design modification will protect the RPS from abnormal voltage and frequency conditions which could be supplied from the power supplies and will meet certain requirements set forth by the Nuclear Regulatory Commiccion.
The proposed design modifications and Technical Specification changes will provide the required protection for the RPS components from sustained abnormal power.
FOREWORD This report is supplied as part.cf the Selected Operating Reactor Issues Program II being conducted-for the U. S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation, Division of Licensing, by Lawrence Livermore National Laboratory.
The U. S. Nuclear Regulatory Commission funded the work under the authorir.ation entitled " Selected Operating Reactor Issues Program II," B&R B&R 20 19 10 11 1, FIN No. A0250.
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TABLE OF CONTE!;TS Pane 1.
INTRODUCTION.
1 2.
DESIGN DESCRIPTION 2
3.
EVALUATION 3
4.
CONCLUSION 5
REFEREl:CES 6
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TECHNICAL EVALUATION REPORT ON TIIE MONITORING OF ELECTRIC POWER TO TIIE REACTOR PROTECTION SYSTEM AT TIIE PEACH BOTTOM ATOMIC POWER STATION UNITS 2 AND 3 (Docket No. 50-277, 50-278)
James C. Selan Lawrence Livermore National Laboratory, Nevada 1.
INTRODUCTION During the operating license review for Hatch 2, the Nuclear Regulatory Commission (NRC) staff raised a concern about the capability of the Class lE reactor protection system (RPS) to operate after nuffering sustained, abnormal voltage or frequency conditions from a non-Class 1E power supply. Abnormal voltage or frequency conditions could be produced as a result of one of the following causes:
combinations of undetected, random siagle failures of the power supply components, or multiple failures of the power supply components caused by external phenomena such ac a seismic event.
The concern for the RPS power supply integrity is generic to all General Electric (GE) boiling water reactors (BWR) MARK 3's, MARK 4's, and MARK 5's and all BWR MARK 6's that have not elected to use the solid state RPS design.
The staff therefore pursued a generic resolution. Accordingly, CE proposed a revised design, in conceptual form, for resolution of this concern [Ref. 1].
The proposed modification consists of the addition of two Class 1E " protective packages" in series between each P.PS motor generator (M-G) set and it's respective RPS bus, and the addition of two similar
' packages in series in the alternate power source circuit to the RPS buses.
Each protective package would include a breaker and associated overvoltage, undervoltage and underfrequency relaying.
Each protective package would meet the testability requirements for Class 1E equipment.
With the protective packages installed, any abnormal output type failure (undetectable random or seismically caused) in either of the two RPS M-G sets (or the alternate supply) would result in a trip of either one or both of the two Class lE protective packages.
This tripping would interrupt the power,to the effected RPS channel; thus producing a scram signal on that channel, while retaining full scram capability by means of the other channel.
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Thus, fully redundant Class lE protection is provided, bringing the overall l
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.RPS_ design into full conformance with General Design Criteria (GDC)-2 [Ref. 2],
and CDC-21 [Ref. 3] (including IEEE-279 [Ref. 4] and the standard review plan
[Ref. 5]).
The NRC staff reviewed the proposed GE design and concluded that the modification was acceptable [Ref. 6], and should be implemented in confor-mance with the applicable criteria for Class 1E systems.
The NRC requires that the components of the RPS not be exposed to unacceptable electric power of any sustained abnormal quality that could damage the RPS.
This involves providing means to detect any overvoltage, undervoltage, or underfrequency condition that is outside the design limits of the RPS equipment and to disconnect the RPS from such abnormal electric power before damage to the RPS can occur.
The equipment which performs these functions must satisfy the single failure criterion and be seismically
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qualified. The NRC issued a generic letter [Ref. 7] to all operating BWR's requesting the licensees to submit design modification details and Technical Specifications for post implementation review.
By letters dated November 26, 1980 [Ref. 8], March 9, 1981 [Ref. 9],
October 30,1981 [Ref.10), December 23, 1981 (Ref. 11], May 21, 1982 [Ref. 12],
November 8, 1982 [Ref. 13), March 30, 1983 [Ref. 14), June 2, 1983 [Ref. 15),
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and a telephone conference on September 12, 1983 [Ref. 16], Philadelphia Electric Comoany, the licensee, submitted design modification details and Technical t
i Specifications changes regarding the monitoring'of electrical power to the RPS at the Peach Bottom Atomic Power Station, Units 2 and 3.
The purpose of this report is to evaluate the licensee's submittal with respect to the NRC criteria and present the reviewer's conclusion on the adequacy of the design modifications to protect the RPS from abnormal voltage and frequency conditions.
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2.
DESIGN DESCRIPTION 1
The licensee has proposed to install two Class lE detection and isolating packages (similar to the approved CE conceptual design) to monitor the electric power in each-of the three sources of power (two M-G sets and an i
alternate source per each unit) to the RPS. Each package is identical'and consists of a circuit breaker, undervoltage relay (ITE 27), overvoltage relay (ITE 59), underfrequency relay (SFF 31), and a time-delay relay (ETR).
The time-delay relay is used only in conjunction with the underfrequency relay.
The control power for the time delay relay is 125 Vdc. When abnormal electric power is detected by either package, the respective circuit breaker will trip and disconnect the RPS from the abnormal power source.
The monitoring packages associated with the MG sets will detect overvoltage. and undervoltage conditions and provide an instantaneous trip '
when the voltage setpoints are exceeded, while providing a time-delayed trip upon detection of an underfrequency condition when the frequency setpoint is exceeded.
The monitoring packages associated with the alter-nate sources provide an instantaneous trip when the overvoltage, under-voltage and underfrequency setpoints are exceeded. -
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EVALUATION The NRC stated several requirements that the licensee must meet in their design modification to monitor the power to the RPS. A statement of these requirements followed by an evaluation of the licensee's submittals are as follows:
(1)
Each monitoring package will detect overvoltage,.under-voltage, and underfrequency conditions with the following setpoints.
- Nominal voltage 120 volts, 60 Hz nominal Condition Setpoint Time Delay Overvoltage 131 + 2 volts Instantaneously for MG sets and alternate sources Undervoltage 113 j; 2 volts Instantaneously for MG sets and alternate sources Underfrequency 57 + 0.2 Hz 6 j,- 1 seconds for MG sets s
Instantaneously for alternate sources
- Voltage measurements indicated a 6.5 to 7.5 volt drop in voltage 4
from the MG set output to the scram solenoid valve fuse panels.
The MG set output will be adjusted to maintain 115 + 2 volts at the hydraulic control units [Refs. 14 and 16].
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GE. certified RPS component (relays and contactors) operating capability is + 10% of 115 volts and - 5% of 60 Hz on its terminal, resulting in a voltage range of 126.5 to 103.5 volts and a frequency range of 60 to 57 Hz [Ref.17).
For the above proposed setpoints and measured voltage drops, a minimum RPS component terminal ~ voltage of 103.5 volts and a maximum terminal voltage of 127 volts could occur at which time the protective relaying will-trip instantaneously.
The 6-second time delay associated with the 57 Hz.underfrequency setpoint is greater than the time delay recommended or accepted by CE.
Tests results on MG set coast-down showed that the. _
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s lowest frequency of 54.4 Hz was reached in a maximum of 11 seconds [Ref. {3].
Based on this, the licensee performed tice/underfrequency tests on an HFA relay, scram contactor, and a scraa solenoid valv.e to determine the effects on component coil temperature rise a's'a result of stistained underfrequency.
These tests were'c9ndu'eted by graduall ' decreasing the frequency to 53 Hz during(ll-second and 15-second intervals. A total of 20 testa per Soaponent (10 for the ll-second interval and 10 for the 15-sefcond interval) was made.
For the proposedIsn'derfrequency setpoint, theErinimumterminal frequency of 56.8 Br for a maximum of.7 seconds would result before prorective re12y tripping occurs.
The tests indicated for a 1.10 *F ambieltt ' temperature (maximum te.uperature of 105 *F expected in the operating environment) and. decreasing frequency to 53 Hz during an ll*-second and 15-second interval, less than a 0.2 *F rise in coil temperature resulted., Since high coil temperature is the most significant contributing factor affecting component operation, these tests demonstrated that the resulting small rise in the coil temperature did not degrade component
, performance (nor effect the pickup and dropout capability of the components. T'-
s Based on the above maximum measured voltage drops and the recults of the, tire /underfrequency tests, the proposed trip setpoints and time delaysfw!11 provide RPS compcnent protection from sustained abnormal poyer.
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(2)
" Disconnecting the RPS from the abnormal power source shall be automatic."
The monitoring module will automatically disconnect the RPS buses from the abnormal power supply after the set time delay should the parameters setpoints be exceeded.
(3)
"The power monitoring system shall meet the requirements of IEEE 279-1971, GDC-2 and GDC-21."
The monitoring packages meet the Class'1E^ requirements of IEEE 279, the single failure criteria of'GDC-21, and the seismic qualifications of GDC-2.
,a (4)
" Technical Specification, shall.i.nclude limiting conditions for operatioti, surveillance requirements,.and trip setpoints."
lucaccordance with the'Scandard Technical Soecifications, the licensee submitted [Refs. 11, '14,15, and 16] Technical Specifi-cation changes which included liraiting conditions for operation when the number of operable monitoring. systems is less than required and surveillance requirements which included a functional test, channel, calibration, and verification of the ' trip setpoints.
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CONCLUSION Based on the information submitted by Philadelphia Electric Company for the Peach Bottom Atomic Power Station, Units 2 and 3, it is concluded that:
(1) The proposed setpoints of the relays in the two protective packages to be installed in series, in each of uhe power sources to the RPS buses, will automatically protect the RPS components from sustained abnormal overvoltage, under-voltage, and underfrequency conditions outside the design limits of the RPS components.
(2) The protective packages meet the requirements of Class lE equipment (IEEE 279), single failure criteria (GDC-21), and seismic qualification (GDC-2).
(3) The proposed time delay before circuit breaker tripping will not result in damage to components of the RPS or prevent the RPS from performing its safety functions.
(4) The following minimum and maximum limita to the trip cet-points, limiting conditions for operation (LCO), and sur-veillance requirements, as proposed by the licensee in accordance with the Standard Technical Specifications, will protect the RPS cocponents from sustained abnormal power:
(a) Overvoltage j[ 133 volts Instantaneously Undervoltage
> 111 volts Instantaneously Underfrequency > 56.8 Hz Time delay j[ 7 seconds for MG sets Instantaneously for alternate sources (b) With one RPS electric pcwer monitoring channel for an inservice RPS MG set or alternate power supply inoperable, restore the inoperable channel to operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or remove the associated RPS MG set or alternate power supply from service.
(c) With both RPS electric power monitoring channels for an inservice RPS MG set or alternate power supply inoperable, restore at least one to operable status within 30 minutes or remove the associated RPS MG set or alternate power supply from service..
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(d) A functional' test.at least oace 'per 6; months and a channel calibratio' anc.e -pari operating cycle 'to determine the opera-n bility-otl the prptecitive instrumentation including simulated
^5' sutomatid.ucti.ation, tripping logic,. output circuit breaker tripping',' and. veri ficati.on of. the se'thoints.
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According,1y j I recommend the NRC', approve, the piroposed design modifi-cation ard Technical Specificati9n chant,es for monitoring the electric power 6
to the reactor /, protection' system.
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./. f REFERENCES
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f;f e2.. Genev31 Design Criteria-1 (CDC-2), " Design Bases for Protection
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3.
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Centratir[htapions."
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Repcets fop Nuc?. ear Power Plants.". I,.
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6.' NRC hevrsuderu f rom Faustlosr-rtd J. Stolz, T. Ippslito, 'and G. Lainas, i
dated Fe'b$uarpl3,1979. /f
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NRC, letter"tolOperatin3 EUR,'s.,di)e,d September'24, 1930.
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C.,'?hiladelphiaElicerihCb.'l[tkIr('S.[il.Daltr'of.Q. TONIC (R.W.Reid),
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dated" November' 26',;1.980.
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LO.,' Phil4delphia Flectric Co. lei:ter (S..br Daltroff) to'NRC (J. F. Stolz),
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Philhdelphia Electric Co. let.te date?,Dec.eEber[23,1981.
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Philadelphia Electric Co. letter (S. L. Daltroff) to NRC (J. F. Stolz),
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13.
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Philadelphia Electric Co. letter (S. L. Daltroff) to NRC (J. F. Stolz),
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16.
Telephone conference; W. Birely (PECo), G. Gears (NRC), and J. Gelan (LLNL),
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17.
CE letter No. G-EE-8-86 (R. F. Thibault) to the Northeast Utilities Service Company (A. Roby).
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