ML20206R537
| ML20206R537 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 06/30/1986 |
| From: | Cooney M PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8607070176 | |
| Download: ML20206R537 (12) | |
Text
PHILADELPHIA ELECTRIC COMPANY 2301 MARKET STREET P.O. BOX 8699 PHILADELPHIA, PA.19101 (21s)s4t so2o "f Cg,"l' June 30, 1986 faut t..N,RODUC, TON
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Docket Nos. 50-277 50-278 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation i
U.S.
Nuclear Regulatory Commission Washington, D.C.
20555
SUBJECT:
Peach Bottom Atomic Power Station Units 2 & 3 Compliance with 10 CFR 50.62
References:
1)
Letter from S.
L. Daltroff, PECo l
to H. R. Denton, NRC dated October 17, 1985 2) 10 CFR 50.62, " Requirements for reduction of risk from anticipated transients without scram (ATWS) events for light-water-cooled nuclear power plants,"
Dear Mr. Denton:
This letter provides information to demonstrate the adequacy of design modifications to be implemented at Peach Bottom 1
Atomic Power Station Units 2 and 3 to satisfy tne requirements of paragraphs (c)(3) and (c)(4) of 10 CFR 50.62.
The submittal of this information is required by paragraph (c)(6) of 10 CFR 50.62.
The reference 1 letter provided a proposed schedule for neeting the requirements of 10 CFR 50.62 and stated that detailed descriptions of our proposed modifications would be submitted by June 30, 1986.
The modifications are described in Attachments 1 and 2 to this letter.
The proposed modifications will fully satisfy the requirements of 10 CFR 50.62(c)(3) and 10 CFR 50.62(c)(4) without exception, including the guidance provided in the June 26, 1984, Federal Register.
The modifications involve installation of an alternate rod injection (ARI) system pursuant to paragraph (c)(3),
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Mr. Harold R. D:nton June 30,-1986 Page 2 and enrichment of the sodium pentaborate solution of the existing standby liquid control system pursuant to paragraph (c)(4).
A reactor recirculation pump trip, which satisfies the requirements of paragraph (c)(5), was installed on both units prior to commercial operation, but is being modified to ensure that recirculation pump trip and ARI system actuation occur simultaneously (see Attachment 3).
These modifications are scheduled to be implemented during the next refueling outages of each unit.
Since the time of the reference 1 letter, the beginning of the next refueling outages have been rescheduled from November 1986 and March 1987 to February 1987 and September 1987 for Units 2 and 3 respectively.
This schedule satisfies the requirements of 10 CFR 50.62 paragraph (d).
If you have any questions or comments regarding these modifications, please contact us as soon as possible so that your comments can be addressed prior to installation.
Ver,y truly yours, Attachments cc; T.
P. Johnson, Resident Site Inspector 9
l l
f Attachm:nt 1 Page 1 of 4 Docket Nos. 50-277 50-278 RESTATEMENT OF REQUIREMENT 10 CFR 50.62(c)(3) Each boiling water reactor must have an alternate rod injection (ARI) system that is diverse (from the reactor trip system) from sensor output to the final actuation device.
The ARI system must have redundant scram air header exhaust valves.
The ARI must be designed to perform its function in a reliable manner and be independent (from the existing reactor trip system) from sensor output to the final actuation device.
DESIGN DESCRIPTION The ARI System to be installed at Peach Bottom Atomic Power Station (PBAPS) Units 2 and 3 is shown in Figure 1.
A one-out-of-two twice, energize to trip logic is used to allow periodic testing at power and to minimize the possibility of spurious trips.
This design ensures that a single failure of a sensor, logic component, or single actuation cannot cause a reactor trip.
Redundant pressure and level sensors are provided in each logic so that a single sensor failure will not prevent a trip.
Bypasses are used to allow periodic testing of an instrument channel.
These bypasses are alarmed in the control room and no other bypasses are provided.
The
'A' train logic energizes the
'A' solenoid valves and the
'B' train logic energizes the
'B' solenoid valves.
If both
'A' and
'B' train solenoid valves are energized, air in the scram air header is vented and the air supply to the scram air header is blocked off causing a scram to occur.
The logic for train
'A' is shown in Figure 2.
The logic symbols are defined in Figure 3.
The design of each train logic is identical.
A trip of any one reactor vessel high pressure or reactor vessel low level channel will trip the associated train.
The circuit will remain sealed in for a minimum of 30 seconds.
A subsequent trip of the other train will cause a scram.
The j
circuits can be reset 30 seconds or more after initiation if all initiation signals have cleared.
The operator may manually initiate the ARI system by turning both train
'A' and train
'B' control switches to the TRIP position.
I Page 2 of 4.
Docket Nos. 50-277 50-278 I
The ARI scram, once initiated, will go to completion and cannot be interrupted by operator action until all trip signals are cleared and 30 seconds have elapsed.
A subsequent return to operation cannot be made until the operator manually resets the ARI logic.
The operator will have an alarm to indicate if either ARI train A'
or train
'B' is tripped.
This will alert the operator to a half scram condition.
A second alarm is provided to indicate that an ARI initiated scram has occurred.
Indicating lights for the train
'A' solenoid valves and indicating lights for the train
'B' solenoid valves will be provided.
The indicating lights will be energized by position switches mounted on the solenoid valves.
All train
'A' or train
'B' valves in the tripped position will de-energize a green indicating light.
All train
'A' or train
'B' valves in the normal position will de-energize a red indicating light.
This design will allow detection of a ' stuck' valve (both lights on) or lack of j
continuity in the indicating light circuits (both lights out).
The i
train
' A' and train
'B' indicating lights will be located above the train
'A' remote manual switch and train
'B' remote manual switch, 4
respectively.
Comparison with " Guidance Regarding System and Equipment Specifications," published in the June 26, 1984, Federal Register 4
1)
Safety Related IEEE-279 - The ARI implementation assures that the existing protection system continues to meet all applicable safety related criteria.
i 2)
' Redundancy - The Rule requires redundant scram air header j
exhaust valves, which are provided.
3)
Diversity from Existing Reactor Trip System - Equipment diversity to the extent reasonable and practicable to minimize the potential for common cause failures will be provided, as required, from the sensors to and including the components to vent the scram air header.
The ARI sensors and logic will be diverse from the Reactor Protection System as required.
The sensors and logic may be of the same design and the circuit components may be of the same manufacturer as the existing protection system,
- l as, permitted.
Existing protection system instrument sensing lines have been used.
Sensors and instrument sensing lines will be selected such that adverse interactions with existing control systems are avoided.
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Attcchmsnt 1 Page 3 of 4 Docket Nos. 50-277 50-278 4)
Electrical Independence from Existing Reactor Trip System The equipment furnished for ARI will be electrically 3
independent from the existing Reactor Protection System from sensor output to the final actuation device.
Relay i
coil to relay contact isolation or relay contact isolation i
will be used as Class lE isolators to interface the ARI system with safety related systems.
5)
Physical Separation from Existing Reactor Trip System The ARI system will be physically separated from the Reactor Protection System.
The installation will be such that separation criteria applied to the existing protection system are not violated.
6)
Environmental Qualification The ARI equipment will be qualified for anticipated 2
operational occurrences as required.
7)
Seismic Qualification Seismic qualification is not required by the Rule and will 1
not be applied to ARI equipment.
8)
Quality Assurance for Test, Maintenance, and Surveillance Quality Assurance for design, procurement, installation, and testing associated with the non-safety related portions of this modification will conform to NRC Generic Letter 85-06.
Interfaces with safety-related equipment will be governed by the PBAPS QA plan.
9)
Safety-Related (lE) Power Supply The 125 VDC power sources used for the ARI are independent from the Reactor Protection System and will not be affected by loss of offsite power.
l 10)
Testability at Power The ARI system will be testable during reactor power operations from the sensors and up to and including the scram air header solenoid valves.
Testing of a single train at a time will not trip the plant unless a valid trip signal occurs on the other train.
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Attachmsnt 1 Page 4 of 4 Docket Nos. 50-277 50-278 11)
Inadvertent Actuation The design will be such that the frequency of inadvertent actuation and challenges to other safety systems is minimized.
The requirement to energize two sets of valves on the scram air header from two coincident logic channels minimizes the probability of inadvertent actuation.
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4 4
Page 1 of 1 Docket Nos. 50-277 50-278 RESTATEMENT OF REQUIREMENT 10 CFR 50.62(c)(4) Each boiling water reactor must have a standby liquid control system (SLCS) with a minimum flow capacity and boron content equivalent in control capacity to 86 gallons per minute of 13 weight percent sodium pentaborate solution.
The SLCS and its injection location must be designed to perform its function in a reliable manner.
The SLCS initiation must be automatic and must be designed to perform its function in a reliable manner for plants granted a construction permit after July 26, 1984, and for plants granted a construction permit prior to July 26, 1984, that have already been designed and built to include this feature.
DESIGN DESCRIPTION The SLCS solution will be enriched.
Utilizing the equivalency relationship defined in NEDC-30912 " Assessment of ATWS Compliance Alternatives," dated July 1985, the new sodium pentaborate solution properties at a minimum will be:
Enrichment
61.92% atom B-10 Concentraticn
8.32% weight This solution will be used in the existing manually initiated system.with a flow rate of 43 gpm.
The above values will be the minimum Technical Specification allowable values and will meet the requirements of the Rule.
Because construction permits were issued for PBAPS Units 2 and 3 prior to July 26, 1984, and the plants were not designed and built with the automatic feature, the SLCS will remain a manual system.
Comparison with " Guidance Regarding System and Equipment Specifications," published in June 26, 1984, Federal Register The SLCS at PBAPS is a manually initiated system.
The guidance requirements listed in the Guidance are applicable to an automatically initiated SLCS; therefore, a comparison with the guidance requirements is not applicable.
However, Quality j
Assurance for design, procurement, installation and testing will conform to the NRC Generic Letter 85-06.
Attachmsnt 3 Page 1 of 2 Docket Nos. 50-277 50-278 RESTATEMENT OF REQUIREMENT 10 CFR 50.62(c)(5) Each boiling water reactor must have equipment to trip the reactor coolant recirculating pumps automatically under conditions indicative of an ATWS.
This equipment must be designed to perform its function in a reliable manner.
DESIGN DESCRIPTION The Recirculation Pump Trip (RPT) system was installed prior to commercial operation, but will be modified to ensure that RPT and ARI System actuation occur simultaneously.
Simultaneous l
trip will be achieved by using the same sensors to initiate ARI and RPT.
(See Figure 2.)
Spurious RPT will also be minimized by revising the logic to a one-out-of-two twice energize to-trip logic.
This design ensures that a single failure of a sensor or 4
i logic component cannot cause a recirculation pump trip.
Redundant i
pressure and level sensors are provided in each logic so that a single sensor failure will not prevent a trip.
Bypasses are used to allow periodic testing of an instrument channel.
These bypasses are alarmed in the control room and no other bypasses are provided.
The logic for train A is shown in Figure 2.
The logic symbols are defined in Figure 3.
The design of each train logic is identical.
Any of two reactor vessel low level or two reactor vessel high pressure signals will trip train A.
If a coincident trip occurs on train B, the recirculation pump circuit breaker trip mechanism will be activated to trip the recirculation pumps.
When all trip initiation signals have been cleared, the recirculation pumps may be restarted in the normal manner.
Comparison with " Guidance Regarding System and Equipment Specifications," published in June 26, 1984, Federal Register i
m
Page 2 of 2 Docket Nos. 50-277 50-278 The responses listed for ARI, items 1,2,4,5,6,7,8 and 9, in Attachment 1 apply to RPT.
The remaining items are listed below:
3)
Diversity from Existing Reactor Trip System Equipment diversity to the extent reasonable and practicable to minimize the potential for common cause failures will be included as required from the sensors to, and including the recirculation pump circuit breaker.
The RPT sensors and logic will not be shared with the Reactor Protection System.
The sensors and logic may be of the same design and the circuit components may be of the same manufacturer as the existing protection system, as permitted.
Existing protection system instrument sensing lines have been used.
Sensors and instrument sensing lines will be selected such that adverse interactions with existing control systems are avoided.
10)
Testability at Power The RPT system will be testable from the sensors up to and including the relays that energize the RPT circuit breaker trip mechanism.
The circuit breaker trip mechanism is testable only during shutdown.
11)
Inadvertent Actuation Inadvertent actuations are minimized by a system design which requires two relays to be energized from two coincident logic channels before RPT can occur.
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