ML19257A856
| ML19257A856 | |
| Person / Time | |
|---|---|
| Site: | Trojan File:Portland General Electric icon.png |
| Issue date: | 12/31/1979 |
| From: | Goodwin C PORTLAND GENERAL ELECTRIC CO. |
| To: | Eisenhut D Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0578, RTR-NUREG-578 NUDOCS 8001090240 | |
| Download: ML19257A856 (11) | |
Text
.;
m y
Pcrtland General Electric Cctrpany
-C
- at x:-.c n a-
- + =,: 1: ~
December 31, 1979 Trojan Nuclear Plant Docket 50-344 License NPF-1 Mr. Darrell B. Eisenhut Acting Director Division of Operating Reactors Office of Nuilear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C.
20555
Dear Mr. Eisenhut:
In accordance with your request of October 3,1979 and our partial response of November 26, 1979, we are providing the attached addi-tional information concerning the Trojan Nuclear Plant Auxiliary Feedwater (AFW) System. We are also including those responses pro-vided in our letter of November 26, 1979 so as to provide a single document with all responses included. New information is denoted by side bars.
The information requested in Enclosure 2 of your letter of October 3, 1979 will be provided as soon as it is available.
Sincerely, o
C. Goodwin, Jr.
Assistant Vice President Therral Plant Oper tion and Maintenance CG/SML/4 sala 16 Attachments c:
Mr. Lynn Frank, Director State of Oregon Department of Energy b9\\
1707 017 t
80010902-@
0
ATTACHMENT 1 Responses to October 3,1979 NRC Questions Concerning the Trojan Auxiliary Feedwater System X.15.3.1 NRC Short-Term Recommendations For This Plant:
1.
Recommendation GS-2 The Licensee should lock open single valves or multiple valves in series in the AFW system pump suction piping and lock open other single valves or multiple valves in series that could interrupt all AFW flow. Monthly inspection should be performed to verify that these valves are locked in the open position. These inspections should be proposed for incorpocation into the surveillance require-ments of the Plant Technical Specifications (see Recommendation GL-2 for the longer-term resolution of this concern).
PGE Response The Trojan Plant Operating Test (POT) which meets the Technical Specification surveillance requirement for monthly checking of auxiliary feedwater flow path valves will be revised as necessary to check all locked valves. These valves include MD050, FWO87-094, FW103-ll4, and FW119-120. This POT and the Administrative Order on lockad valves will be revised by January 1,1980. A review of the Trc, a Technical Specifications was conducted and no revisions were felt to be necessary. An additional means of verifying the availability of the flow path will be by aanual valve position indication presently being installed.
2.
Recommendation GS-4 Emergency procedures for transferring to alternate sources of AFW supplies should be available to the Plant operators. These procedures should include criteria to inform the operators when and in what order the transfer to alternate water soerces should take place. The following cases should be covered by the procedures:
- The case in which the primary water supply is not initially available. The procedures for this case should include any operator actions required to pro-tect the AFW system pumps against self-damage before water flow is initiated; and
- The case in which the primary water supply is being depleted. The procedure for this case should provide for transfer to the alternate water sources prior to draining of the primary water supply.
1707 018
TGE Response The case where auxiliary feedwater primary water supply, the conden-sate storage tank (CST), is not available is already adequately covered in existing Plant procedures. The proctJure for shif ting auxiliary feedwater suction to the zervice water supply is con-tained in Trojan Emergency Instruction EI-5, Emergency Backup Core Heat Removal.
While the auxiliary feedwater pumps are capable of taking suction from the primary supply, the CST, until the water level is just above the pump suction nozzle, they are not currently protected against the loss of suction except by operator action. A proposed modification will provide each auxiliary feedwater pump with: an automatic trip to protect it against the low suction pressure con-dition, a manual override for the automatic trip, alarms for each pump to annunciate the auto trip and the override condition, and l
redundant CST low-low level alarms. When operating at rated flow, the auxiliary feedwater pumps begin to lose suction pressure with approximately 195,000 gal remaining in the CST. With flow reduced, each auxiliary feedwater pump is capable of pumping the CST to the nozzle level without losing suction. Manual override, operated from the control room, will allow continued operation af ter reducing flow should the auxiliary feedwater pumps trip with water remaining in the CST. An additional low-low CST level alarm set just above the auxiliary feedwater pump suction nozzle will signal the tank level below which auxiliary feedwater pump opera-tion must stop.
If continued auxiliary feedwater pump operation is required, suction will be manually shif ted to the Lervice Water System. This modification will be reflected in the appropriate Operating Instructions when completed. It is anticipated the com-pletion of this modification will be prior to startup of Cycle 3.
3.
Recommendation GS-5 The as-built plant should be capable of providir the required AFW flow for at least 2 hr from one AFW pump train independent of any alternating current power source.
If manual AFW system initiation or flow control is required following a complete loss of alternat-ing current power, emergency procedures should be established for manually initiating and controlling the system under these condi-tions. Since the water for cooling of the lube oil for the turbine-driven pump bearing may be dependent on alternating current power, design or procedsral changes shall be made to eliminate this depen-dency as soon as practicable. Until this is done, the emergency procedures should provide for an individual to be stationed at the turbine-driven pump in the event of a loss of all alternating cur-rent power to monitor pump bearing and/or lube oil temperatures, and, if necessary, this operator would operate the turbine-driven pump in an on-off mode until alternative current power is restored.
Adequate lighting powered by direct current power sources and 1707 019
_2-
communications at local stations should also be provided if manual initiation and control of the AFW system is needed (see Recommen-dation GL-3 for the longer-term resolution of this concern).
PGE Response Currently, the Plant is not capable of providing AFW flow independent of AC power sources. This is due to dependence of the bearing and jacket cooling water supply on AC power sources. Emergency proce-dures are being implemented to:
a.
Make every effort to restore AC power within 20 min (30 min water inventory availabic in steam generators).
b.
Provide a material " kit" for use by operators which provides the hardware necessary to hook up temporary coolina water to the steam-driven AFW pump bearing lube oil heat exchanger.
c.
Provide a procedure that instructs the operator to hook up the temporary cooling system if the AC power is not restored within 20 min, manually valve in steam to the AFW pump turbine and align the CST and AFW pump to feed the steam generators.
Included in this procedure will be a statement directing the operator to take portable lighting and a portable communication device with him to the AFW pump operation station.
If these measures are required, an individual will be stationed at the turbine-driven pump to monitor pump bearing and/or lube oil temperatures.
4.
Recommendation GS-6 The Licensee should confirm flow path availability of an AFW system flow train that has been out of service to perform periodic testing or maintenance as follows:
- Procedures should be implemented to require an operator to determine that the AFW system valves are properly aligned and a second operator to independently verify that the valves are properly aligned.
- The Licensee should propose Technical Specifications to assure that prior to Plant startup, following an extended cold shutdown, a flow test would be performed to verify the normal flow path from the primary AFW system water source to the steam genertors. Flow tests should be conducted with AFW system valves in their normal alignment.
1707 020
PGE Response Plant procedures for clearing tagged-out equipment that has been removed from service for maintenance require that the equipment, such as valves in this case, be returned to service per the appli-cable Operating Instruction. The person red.ving the tag must raport to the Control Operator that the equipment has been returned to service. If a tag must be cleared without returning an item to service at that time, the clearance is left in the clearance log in the control room. This log is one of the items that will be included in our shif t turnover procedure / checklist by January 1, 1980 in accordance with the Three Mile Island short-term Lessons Learneo action item requirements. We have committed to the iden-tification system connected to all main flow path valves such that a condition where any single valve is out of position will be annunciated in the control room. The combined affect of all these increased controls is such that a two-operator check is not con-sidered necessary.
During a Plant startup following any cold shutdown, auxiliary feed-water is always required for feeding steam generators prior to power operation. It presently would not be possible to start up the Plant without feeding all four steam generators with at least one safety grade AFW pump. This, in combination with the items in the above paragraph, and the current Technical Specification requirements to bring the pump testing surveillance up-to-date prior to entering a hot standby condition (Mode 3) is considered sufficient.
Once the nonsafety grade electric-driven AFW pump is installed, the AFW pump Periodic Operating Test will be changed to include a step to verify the ability of each safety grade AFW pump to feed all four steam generators following an extended Plant outage. No Technical Specification change is needed since Technical Specification 3.7.1.2 requires that a flow path be maintained in Modes 1, 2 and 3 and the above test will verify this flow path.
5.
Recommendation GS-7 The Licensee should verify that the automatic start AFW signals and associated circuitry are safety grade.
If this cannot be verified, the AFW system automatic initiation system should be modified in the short-term to meet the functional requirements listed below. For the longer term, the automatic initiation signals and circuits should be upgraded to meet safety grade requirements as indicated in Recommen-dation GL-5.
- The design should provide for the automatic initiation of the Auxilicry Feedwater System flow.
- The automatic initiation signals in circuits should be designed so that a single failure will not result in the loss of Auxiliary Feedwater System function.
1707 021
- Testability of the initiation signals and circuits shall be a feature of the design.
- The initiation signals and circuits should be powered from the emergency busses.
- Manual capability to initiate the Auxiliary Feedwater Sys-tem from the control room should be retained and should be Laplemented so that a single failure in the manual circuits will not result in the loss of system function.
- The alternating current motor-driven pumps and valves in the Auxiliary Feedwater System should be included in the automatic actuation (simultaneous and/or sequential) of the loads to the emergency buses.
- The autoratic initiation signals and circuits shall be designed so that the failure will not result in the loss of manual capability to initiate the AFW system from the control room.
PGE Response The auxiliary feedwater pump auto start signals and associated circuits are safety grade, Seismic Category I and Class lE with the exception of the loss of both main feedwater pump circuits which are not safety grade. The above concerns have been previously discussed in our response to NUREG-0578 recommendations, Section 2.1.7.a, submitted October 17, 1979.
X.15.3.2 Additional Short-Term Recommendations 1.
Recommendation - The Licensee should provide redundant level indi-cation and low level alarms in the control room for the AFW system primary water supply to allow the operator to anticipate the need to make up water or transfer to an alternating water supply and prevent a low pump suction pressure condition from occurring. The low level alarm setpoints should allow at least 20 min for operator action assuming that the largest capacity AFW pump is operating.
PCE Response Redundant CST level indication to LI 5201 with a low-low level alarm set at approximately 9 percent tank level (40,500 gal) will be provided by the startup of Cycle 3.
These low-low level alarm setpoints allow more than 30 min of single AFW pump operation prior to required operator action to realign pump suction.
1707 022 2.
Recommendation - The Licensee should perform a 72-hr endurance test on all AFW system pumps if such a test or continuous period of operation has not been accomplished to date. Following the 72-hr pump run, the pumps should be shut down and cooled down and then restarted and run for 1 hr.
Test acceptance criteria should include demonstrating that the pumps remain within design limits with respect to bearing / bearing oil temperatures and vibration, and that pump room ambient conditions (temperature, humidity) do not exceed environmental qualification limits for safety-related equipment in the room.
PCE Response This type of test (at reduced load) is strongly discouraged by the pump / driver vendor. However, if the NRC is adamant that this test be performed, it will be done prior to startup of Cycle 3.
We have previously demonstrated the reliability of the automatic starting of these pumps during 1976 by performing a test requiring a series of automatic pump starts.
3.
Recommendation - The Licensee should implement the following require-ments as specified by Item 2.1.7.b on Page A-32 of NUREG-0578:
' Safety grade indication of auxiliary feedwater flow to each steam generator shall be provided in the control room.
"The auxiliary feedwater flow instrument channels shall be powered from the emergency busses consistent with satisfy-ing the emergency power diversity requirements for the Auxiliary Feedwater System set forrh in Auxiliary Systems Branch Technical Position 10-1 of the Standard Review Plan, Section 10.4.9."
PGE Response Auxiliary feedwater flow indication is already provided in the control room. The existing indication is being upgraded, as indi-cated in our response to NUREG-0578 recommendations, Section 2.1.7.b, submitted October 17, 1979, such that it is powered from an emergency power supply.
4.
Recommendation - Licensees with plants which require local manual realignment of valves to conduct periodic tests on one AFW system train and which have only one remaining AFW train available for operatica should propose Technical Specifications to provide that a dedicated individual who is in communication with the control room be stationed at the manual valves. Upon instruction from the control room, this operator would realign the valves in the AFW system train from the test mode to its operational alignment.
1707 023.
PGE Response This item is not applicable to Trojan since manual realignment of local valves is not required when conducting periodic operating tests.
X.10.3.3 NRC Long-Term Recommendations 1.
Recommendation GL-2 Licensees with plants in which all (primary and alternate) water supplies the AFW system pass through valves in a single flow path should install redundant parallel flow paths (piping and valves).
Licensees with plants in which the primary AFW system water supply passes through valves in a single flow path, but the alternate AFW system water supplies connect to the AFW system pump suction piping downstream of the above valve (s), should install redundant valves parallel to the above valves or provide automatic opening of the valves from the alternate water supply upon low pump suction pressure.
The Licensee should propose Technical Specifications to inenrporate appropriate periodic inspections to verify the valve positions.
PGE Response The Auxiliary Feedwater System design at Trojan employs a common suction line from the primary water source (CST) to the safety-grade AFW pumps. The single valve (MD050) in this suction line is locked open, is subject to monthly surveillance and is provided with position indicator au described in the response to Recommen-dation GS-2.
In addition, a separate flow path exists from the CST to the electric motor-driven AFW pump currently being installed.
Taken in combination with the low AFW pump suction trips and alarms (see response to Recommendation GS-4) and the redundant CST level indications and alarms, no additional modifications are considered necessary to increase the reliability of this aspect of the AFW System.
As discussed in response to Recommendation GS-6, current Periodic Operator Tests and Technical Specifications exist to ensure flow path valve position.
2.
Recommendation GL-3 At least one AFW system pump and its associated flow path and essential instrumentation should automatically initiate AFW system flow and be capable of being operated independently of any alter-nating current power source for at least 2 hr.
Conversion of direct current power to alternating current is acceptable.
)]Q]
Q}k
~7 -
PGE Response Automatic initiation and operation of one AFW pump, flow path and essential instrumentation will be provided independent of any a-c power source for at least 2 hr.
The turbine-driven AFW pump and its associated systems will be modified such that all 480 V a-c operated equipment will be independent of any 480 V a-c power source or fail in the proper position to allow the AFW pump to operate.
3.
Recommendation CL-4 Licensee having plants with unprotected normal AW system water supplies should evaluate the design of their AFW systems to deter-mine if automatic protection of the pump is necessary following a seismic event or a tornado. The time available before pump damage, the alarms and indications available for the control room operator, and the time necessary for assessing the problem and taking action should be considered in determining whether operator action can be relied on to prevent pump damage. Consideration should be given to providing pump protection by means such as automatic switch over of the pump suction to the alternate safety grade source of water, automatic pump trips on low suction pressure, or upgrading the normal source of water to meet Seismic Category I and tornado protection requirements.
PGE Response As previously discussed, we are planning to provide a low pump suction pressure trip on the auxiliary feedwater pumps. This modification will be complete prior to startup of Cycle 3.
4.
Recommendation GL-5 The Licensee should upgrade the AFW system automatic initiation signals and circuits to meet safety grade requirements.
PGE Response The auxiliary feedwater pump auto start signals and circuits with the exception of the main feedwater trip signals meet safety grnde l
requirements. This concern has been previously addressed in our response to NUREG-0578 recommendations, Sect ion 2.1.7.a, submitted October 17, 1979, and in our response to Recommendation GS-7 above.
5.
Recommendation A motor-driven pump is currently being installed or planned to be installed by the Licensee. Present plans are for a nonsafety grade ~
1707 025
motor-driven pump system. Based on past experience of the prob-lems associated with the speed control (overspeed trips) of both the diesel-and turbine-driven pumps and other Licensee Event Reports on the Trojan AFW system, the Licensee should further review the proposed installation to determine if the motor-driven pump should be safety grsde and automatically actuated by the AFW automatic start logic.
PGE Response We are evaluating the feasibility of supplying power to the new motor-driven pump through an emergency diesel generator powered bus.
In addition, a procedure will be provided such that if:
a.
Water is nct available from the CST to the safety-grade AFW pumps: or b.
Both safety grade AFW pumps fail to operate, then the motor-driven AFW pump will be manually switched to an emergency diesel powered bus and started if normal AC power has been lost (these operations can be conducted in the control room).
As presently designed, this pump may be manually started and used for Plant shutdown in lieu of safety-grade pump operation.
We believe that this procedural change will substantially enhance the reliability of the AFW System for normal loss of main feedwater transients since the operator action required for manual actuation of the motor-driven pump closely parallels the operator action that would be required to verify that this pump had auto started.
Providing emergency diesel power, if possible, will enhance the reliability of the AFW System for less probable loss of offsite power transient events. Accordingly, we have concluded that upgrading the electric motor-driven AFW pump to safety grade or automatically actuating this pump by the AFW auto start logic is not justified.
6.
Recommendation A pipe break in certain locations of the turbine-driven auxil-iary feedwater pump discharge piping may affect both AFW trains since a portion of this piping passes through the diesel-driven pump room. The motor-driven pump to be installed should be located such that a break in the AFW system (not associated with the motor-driven pump train) could not affect the motor-driven pump.
- Also, the Licensee should:
a.
Install the motor pump with appropriate valves in the pump discharge line connections to meet the high energy line break criteria in SRP 10.4.9 and Branch Technical Position 10-1; namely, the AFW system should maintain the capability to supply the required 1707 026
AFW flow to the steam generators assuming a pipe break anywhere in the AFW pump discharge lines, plus a single active failure; or b.
Describe how the plant can be brought to a safe shutdown condition by use of other available systems following such a postelated event.
PCE Response Based on the Trojan Nuclear Plant Analyses of Pipe System Breaks Outside Containment, PGE-1004, rupture of that portion of the turbine-driven auxiliary feedwater pump discharge piping passing through the diesel-driven pump room is not considered a credible event due to:
1.
The quality control associated with the fabrication and installation of this safety-grade piping; 2.
The periodic inspection required for the Auxiliary Feedwater System; 3.
The low usage factor associated with the operation of the system; 4.
The low operating temperature of the system; and 5.
The strict administrative controls associated with system operation.
Regarding Item 5 above, it should be noted that the present design of the Auxiliary Feedwater System, upon which the aforementioned report is based, is such that the system pumps, in addition to their opera-tion during surveillance testing, are expected to operate during Plant startup and shutdown. Addition of the non-safety grade motor-driven pump is intended to minimize the need to operate the safety-grade pumps during Plant startup or shutdown, thereby minimizing the already low ussge factor associated with these pumps.
It should also be noted that the piping in question is a straight run of pipe and does not include any terminal ends or branch connections, nor does it contain any points of high combined stress. Consequently, it appears unreasonable to expect a break at any point in this piping run, based on the break criteria provided in Section 1.2 of PGE-1004.
1707 027 SML/4sa4All