ML19254D396
| ML19254D396 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 10/11/1979 |
| From: | Ziemann D Office of Nuclear Reactor Regulation |
| To: | Peoples D COMMONWEALTH EDISON CO. |
| References | |
| NUDOCS 7910250435 | |
| Download: ML19254D396 (9) | |
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UNITED STATES y Ti s-q h
NUCLEAR REGULATORY COMMISSION W ASHINGTON, D. C. 20555 j
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October 11, 1979
- ocket tio. 50-10 Mr. D. Louis Peoples Director of Nuclear Licensing Cc=onwealth Edison Company Post Office Box 767 Chicago, Illinois 60690
Dear Mr. Peoples:
We are continuing our review of the reactor protection system and high pressure coolant injection system design and find that additional information is required to enable us to complete our review. The enclosed request for additional infor-mation is based on concerns raised by T. Dunning during his visit to Dresden 1 on arch 19 - 23, 1979.
Please provide a schedule for your response within 20 days of receipt of this letter. Your prompt reoly to the enclosure would allow a reasonable schedule for completion of our evaluation and your implementation prior to your scheduled return to operation.
If ycu have questions concerning the enclosure, please contact Stanley J. Nowicki.
Sincerely, 0
t W~
46 A Dennis L. Ziemann, hief Operating Reactors Branch #2 Division of Operating Reactors
Enclosure:
Request for Additional Information and Staff Positions 1208 310~
m o e.s o 4 3 5 g
Mr. D. Louis Peoples October 11, 1979 W/ enclosure:
CC Isham, Lincoln & Beale Counselors at Law One First National Plaza, 42nd Floor Chicago, Illinois 60603 Mr. B. B. Stephenson Plant Superintendent Dresden Nuclear Power Station Rural Route #1 Morris, Illinois 60450 U. S. Nuclear Regulatory Commission ATTN: Jimmy L. Barker P. O. Box 706 Morris, Illinois 60450 Susan N. Sekuler Assistant Attorney General Environmental Control Division 188 W. Randolph Street Suite 2315 Chicago, Illinois 60601 Morris Public Library 604 Liberty Street Morris, Illinois 60451 1208 31!
DRESDEN UNIT 1 REQUEST FOR ADDITIONAL INFORMATION AND STAFF POSITIONS 1.
It appears that several aspects of the design and implementat'on of the reactor protection system modificadons may not satisfy the requirements of the Order for Modification of License dated June 23, 1976, nor the commitments contained in your letter of January 12, 1976. Therefore, for each of the concerns presented below, describe how the implemented design satisfies items 2, 3, 4 and-5 of the June Order and items 1, 2 and 3 af the third paragraph of your January 12, 1976 letter:
(1) Field wiring for Al and B1 should be via separate field cables.
Al and B1 circuits should not exist in the same multiconductor cable.
Cables for Al and B1 circuits may be routed in the same condui t.
(2) Terminal strips for the termination of Al and B1 circuit conductors should be physically separated at all locations, (panels, control boards, and junction boxes). The cable outer covers should not be removed exposing individual insulated circuit conductors until the Al and B1 cables are physically separated.
(3) Field cables for input circuits should not include conductors for other circuits such as alarms or scram pilot solenoids.
(4) Color coded wiring should be used for Al and B1 circuits within control boards and panels and the wiring should be physically separated including separation from alarm or other circuits.
(5) Power source wiring should be physically separated from all individual fused circuit wiring within panels, control boards, and field runs.
Circuit breakers should be provided to isolate the power source supply to Al and A2 circuits (81 and B2 circuits).
(6) Relays which initiate channel trip should have alarm annunciation.
(7) The above requirements for separation for Al and B1 circuits apply to A2 and B2 circuits.
(8) The above requirements also apply to redundant input circuits which initiate ECCS.
(9) The primary steam valve position switches which have inputs to the RPS should be modified to meet the single failure criterion.
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. (10) Process sensing lines may be shared for Al and B1 sensors but should not be shared with A2 and B2 sensors.
(11) Field cables for output logic circuits should not include conductors for other circuits, including input logic circuits.
(12) Two manual scram push buttons should be provided with Al and Bl trips wired to one and A2 and 82 trip wired to the other.
Each circuit should be individually and exclusively field run in conduit.
(13) Two key locked switches should be provided, one for Al and B1 circuit
( A2 and 82), to replace the mode switch CS-451 contact which maintains a trip condition in the shutdown mode.
Key removal should be possible only in the shutdown position.
Each circuit should be individually and exclusively field run in conduit.
(May be combined with 12 above on an individal Ic.gic basis).
(14) The penetration trip switch, CS-2S4 should be used with contacts to actuate the channel logic valve isolation circuit relays (CR-2K24A and B typical) between the circuit fuse (2F23A typical) and the relay coil circuit.
Contacts of the velve isolation circuit relays should be wired to trip the scram logic relays in place of the, trip swi tch. Separate contacts of relays 2K2 and 2K8 should be provided to actuate the valve isolation circuit relays.
(15) Isolation should be provided between the reactor mode switch, CS-4S1 and the output logic by the use of relays to effect a bypass of protective action trip contacts. Note 1 (16) Isolation should be provided between the scram dump tank level bypass switch, CS-2S6, and the output logic by the use of relays.
Note l (17) Isolation should be provided between the coincidence mode switch Cs-352, and the output logic by the use of relays. Note 1 (18) Two logic reset switches should be provided; one for Al and B1 circuit (A2 and B2), to replace reset switch CS-257.
Each circuit should be individually and exclusively field run in conduit.
(May be combined with 12 above on an indivieil logic basis).
(19) The vent duct trip relays (2K23A typical) should be actuated by contacts of the output logic trip relays.
(20) The logic output relays used to interrupt power to the individual scram solenoids should be replaced with relays with heavy duty contac ts. HFA relays should not be used for this purpose.
(21) Separate field cables should be used for each train of pilot solenoids.
Note 1: Status indication should be provided from bypass relay contacts.
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. (22) Train All and Bil circuits should be field run in a separate conduit from. Train A12 and 812 circuits exclusive of all other circuits.
(23) Panel AP-5 wiring for each train circuit should be color coded and mutually physically separated.
(24) Wiring at fuse panel BZ3 for all train circuits should be physically separated from any other circuits.
2.
It appears that the implementation of the nuclear instrumentation may not satisfy the requirements of the Order for Modification of License L ted-June 23, 1976, nor the comitments contained in your letter of January 12, 1976.
Note that the nuclear instrument channels operate on the basis of one out of three twice with the car ability to bypass an inoperable channel. The six channels have beer divideo into the basic four channel input configuration used for one out of two twice logic.
The cnannels assigned to the Al and B1 group have not been physically separated; therefore channels powered from independent power sources are intemixed.
The design does not meet the single failure criterion when one channel is bypassed. Furthemore, two channels of incore nuclear flux initiate a trip based on a one out of two logic. The incore nuclear trips are backed up. by the excure nuclear trips.
The arrangement of the logic for the incore nuclear trip results in a reactor trip on the loss of either of the RPS M-G set power supplies. While this is undesireable from a plant avail-ability view point, it further limits testing-to periods of plant shutdown.
No separation is provided for the two incore flux analog channels.
Di gi tal inputs to the input trip logic relays are separated to the extent possible forthis design configuration. Therefore, for each of the concerns presented below, describe how the implemented design satisfies items 2, 3, 4, 5 and 12 of the June order and items 1, 2 and 3 of the third paragraph and item 8.
of the fourth paragraph of your January 12, 1976 letter.
(1) The nuclear channel analog circuits should be assigned to an A1, A2, A3, B1, B2, B3 and all channels mutually separated including circuits to console indicators and range switches.
(2) The trip contact digital signals and input logic auxiliary relays for the six nuclear channels should carry the same channel designation noted above and be mutually separated and color coded as indicated for input logic circuits noted in Question 1 above.
(3)
The wiring for the channel bypass switch CS-2S2 should meet the requirements noted in 2 above.
(4) The incore nuclear channels s tould be modified to permit testing during operation.
Test features should meet single failure requirements and separation requirements to the extent possible for this design configuration, consistent with the requirements noted in Question 1 above.
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It appears that several aspects of the design and implementation of the backup scram solenoid circuits do not satisfy the requirements of the Order for Modification of License dated June 23, 1976, nor the comitments contained in your letter of January 12, 1976, please note that the scram backup solenoids circuit logic operates on the basis of one out of two with power required to energize the pilot solenoid to actuate a trip.
The Train A and B circuit are routed in separate conduit using multiconductor cables which include trip input logic circuits.
The backup trip circuits follow the same area routing path as the individual solenoid trip circuit. The following changes should be made to separate the backup scram trip from the individual solenoid scram trip and to increase the system re.li abili ty.
Therefore, for each of the concerns presented below, describe now the implemented design satisfies items 4 and 10 of the June order, and items 2 and 3 of the third paragraph and ite: 3 6 of the fourth paragraph of your January 12, 1976 letter.
(1) Redundant lE de powersourtes should be used for the backup scram trip power sources.
(2) The field cable routing path and cablo penetrations should be widely separated from the individual solenoid trip circuits, e.g., new HPCI routing path to containment.
(3) The two out of four logic networks for automatic actuation should actuate an auxiliary relar, contacts of which should initiate the trip solenoid. The relay should be located remote from the automatic trip logic panel, AP-5.
(4) One maintained position backup manual trip switch should be provided to each backuo trip circuit. An auxiliary relay should be provided for is.olation as provided for the automatic trip input.
(5) The automatic trip and manual trip relay circuits should be fused individually and separate from the solenoid fused circuit.
4.
The new HPCI system and its related plant modifications should, as a minimum, satisfy the same criteria as the reactor trip system modifi-cations. Accordingly, justify the following aspects of your implementation of the ECCS modifications:
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~
(1) The control circuits for the redundant essential service auxiliary power. (ESAP) diesel generators are dependent upon the operation of switchgear circuit breakers which operate from a single de control power source. Therefore, separate Class 1E de power sources should be provided for the operation of switchgear, contacts of which interface with the control circuits of the redunde.c onsite ESAP power sourcc5.
(2)
The control circuits for the ESAP diesel generators operate from the same fused control circuits as used for HPCI operation.
Therefore,
separate fused control circuits should be provided for ESAP and HPCI operation.
(3) The HPCI and ESAP auxiliary 480 volt loads are fed from a 480 volt motor control center which is normally tied :o the ESAP 4160 volt bus via a transformer. Automatic transfer.ircuits are provided to transfer the power source to the HPCI 4160 volt bus on the loss of power to the normal supply, exceeding a 15 second time delay, to permit restoration of power by the ESAP diesel generator. This transfer is not based upon the availability of power on the MPCI bus. Ycu have indicated that design changes will be made to allow automatic transfer back to the normal power source. Therefore, all automatic transfer circuits for the supply source to Buses 115 and 116 should be deleted.
(4) The de control power source for recur. dant 480 volt switchgear buses and their intertie to nonessentici busa is a common source subject to a single failure. Therefore, redunds at Class 1E de power sources should be provided for redundant essential switchgear including ties to non-essential buses so that the system will meet the single failure criterion.
(5) A sing.le load shed circuit is provided and operated from the existing single dc power source. This circuit is being revised. The revised load shed circuit should incorporate independent load shed circuits for each of the redundant essential power buses. The load shed circuits should be operated from separated Class lE power sources.
(6) Redundant power centers SA and 6A and centers 5 and 6 have interties controlled by a single manually operated tie breaker.
This represents a single failure point for redundant essential buses.
Therefore, the intertie should be eliminated or an additional tie treaker orovided which is separated from the existing single tie t re aker.
5.
Provide the following additional information on your plant drawings:
(1)
(Ref. DWG 12E-1420A).
The diagram for control switch 1-6140-36A notes " Maintained con. tacts". What does this mean? Are switch positions OPEN, AUTO, CLOSE maintained positions or spring return to auto?.
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~ (2)
(Ref. DWG 12E-14208). Same questions as above for control switch 1-6140-35A.
(3)
(Ref. DWG 12E-1420C). Same questions as 1 above for control switch 1-6140-28.
(4)
(Ref. DWG 12E-1420D). Diesel fuel oil transfer control: What is the basis that automatic operation is blocked when control switch is in auto position after stop (Contact 5-ST not closed in auto after s top) ?
(5)
(Ref. DWG 12E-41200).
Diesel service water pump: What is the basis that automatic operation is bic-ked when control switch is in auto position after start (Contact 3-3T stated as closed in auto after stop)?
(6)
(Ref. DWG 12E-1420E). What does contact M/a seal in CR only for manual start and not for auto start (Contact 6-6T not closed in auto after stop)?
(7)
(Ref. DWG 12E-1420F). Why does the R5 contact only seal in Relay R5 for manual starting (Contact 6-6T not closed in auto after stop)?
(8) Please clarify the operation of the primary and secondary vent supply fans for the pump rooms.
The secondary fan cycles on and off based upon room temperature at 75'F regardless of the fact that the control switch is in the lock out position.
The primary fan can be manually started but the control relay will not seal in if the room temperature is below 95 F.
If the room temperature exceeds 95'F, the fan is not automatically started. What is the logic for these control circuits?
What is the safety significance for each of the HPCI building ventilation systems?
(9)
(Ref. DWG 12E-1420G). The electrical equipment r om supply fan, if manually started,. ins continuously.
If in auto after stop, it cycles to maintain a room temperature of 50*F.
Why doesn't manual start condition include interlock to shutdown fan if temperature falls below 50*F? How does operator recognize operating modes which are different when control switch is in auto position and control logic is dependent upon prior position of start or stop?
(10) Describa the means to makeup to the demineralized water storage tank, T-6101. Why does 50V l-7102 only open on LO-LO level and not have manual control?
(11) What is the significance of the failure of the water tank room tempera-ture switch TS 1-ll41-45A? Why are contacts with two different ser. tings used to control the exhaust fan (Ref. DWG '.2E-1422D)?
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- (12) (Ref. DWG 12E-1422E). What is the shunt trip circuit classified as non-essential? What is the impact of a failure of this circuit to operate? Dual contacts are used to actuate trip, why use contacts of same relay?
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