ML18044A786
| ML18044A786 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 04/22/1980 |
| From: | Huston R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Ziemann D Office of Nuclear Reactor Regulation |
| References | |
| TASK-10, TASK-RR NUDOCS 8004250425 | |
| Download: ML18044A786 (5) | |
Text
consumers Power company
- Area Code 517 788-0550 April 22,.1980 Director, Nuclear Reacto1:' Regulation Att Mr Dennis L Ziemann, Chief Operating Reactors Branch No 2 US Nuclear Regulatory Commission Washington, DC 20555 DOCKET 50-255 -
LICENSE DPR PALISADES PLANT - ACTm!ATIC INITIATION OF AUXILIARY FEEDW.c\\TER SYSTE~! UPDA!'E NRC letter dated November 30, 1979 specified requirements applicable to the Auxiliary Feedwater System at Palisades.
Consumers Power Company responded to this letter on December 11, 1979.
During NRC review of our response, additional questions arose which were addressed in a meeting between NRG and Consumers Power Company on March 31, 1980.
The additional recommendations and Consumers Power Company responses discussed during that meeting are. docu!'nented be.low.
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 AF\\l flow.
Monthly inspec-tions should be performed to verify that these valves are locked and in the*
open position.
These inspections should be proposed for incorporation into the surveillance requirements of the plant Technical Specifications.
See Recommendation GL-2 for the longer term resolution of this concern.
Resnonse to GS-2 Valves in the AFW pump suction piping as weil as all other valves that could interrupt AFW flow 1.;ill be locked opened.
Monthly inspections will be conducted during power operation to verify that these valves remain locked open.
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2 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 start-up 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 generators.
The flow test should be conducted with AFW system valves in their normal alignment.
Response to GS-6 As stated in the response to GS-2 above, valves on the AFW pump suction or those in series that could interrupt all AFW flow will be locked open.
Any special test or maintenance activity that requires any valve position change must have a clearance initiated.
Upon completion of the action that required the clearance to be issued, the operator reinstates the valves t*o their normal position.
In the case of the AFWS, the valves that are required to be in a locked open position will be.
It is also standard practice that when a piece of safety-related equipment is taken out of service for some reason, this piece of equipment will be tested prior to being declared operable.
- Again, monthly inspections will be conducted during power operation to verify that these valves remain locked open.
The Palisades Plant utilizes a steam-driven main feed pump.
Therefore, for normal start-ups and shutdowns, the auxiliary feedwater pumps (AFWP) are used until temperatures are sufficiently high to supply steam to the main feed pump.
Use of the AFWP in this fashion is incorporated in the operating procedures..
Therefore, through the use of the clearance system, use of the auxiliary feed pumps for start-up and shutdown, and conducting monthly inspections on the locked open valves, proper verification of the AFWS flow path is ensured.
X6.3.1(5) Recommendation The licensee should verify that the air accumulator will hold the air-operated valves in the turbine-driven pump steam supply line open for at least two hours following loss of all a-c power.
J Response to X6.3.1(5)
As stated in our December 10, 1979 submittal, the air-operated valves in the turbine-driven pump steam supply have the capability of being "hand-jacked" opened in the event that all a-c power/air supply is lost.
The emergency
3 procedure "Plant Cooldown With Total Loss of A-C Power" instructs the operator in this operation.
X6.3.1(6) Recommendation The motor-driven pump and the pneumatic-operated valve (G) through which AFW flow to steam generator A is controlled receive motive and control power from Division I emergency buses.
Pneumatic valve (F), which supplies steam from steam generator A to the turbine-driven AFW pump, receives control power from a Division II emergency bus.
Similarly, AFW flow control valve (H) and steam supply valve (E) associated with steam generator B receive power from Divisions II and I emergency buses, respectively.
Upon loss of air or power, the AFW flow control valves (G) and (H) fail open and the turbine-driven pump steam admission valves (E) and (F) fail closed.
It is recognized that the AFW flow control valves are designed to. fail open upon loss of air or power so that AFW flow to the steam generators should be assured.
However, it cannot be concluded that all failures will result in opening these valves.
Degradation of Division I buses could potentially result in loss of the entire AFW system.
The licensee should analyze the consequences of Division I voltage degradation as well as other failures (eg, restric~ed airflow) to assure that there is no Division I failure mode that can result in loss of the entire AFW system.
Until this analysis is completed or the AFW system is modified to preclude such an occurrence, emergency procedures should be prepared to retain AFW system capability.
Response to X6.3.1(6)
Consumers Power Company will include appropriate steps in the operating or emergency procedures to address the coincident failure of an auxiliary feedwater pump steam supply valve (CV-0522 A or B) from either steam g~nerator and an auxiliary feedwater valve (CV-0736 A or B) of the other steam generator.
In the longer term, an investigation as to whether or not a different valve power supply arrangement would reduce the likelihood of such a failure will be conducted.
Modifications will be proposed as necessary.
X6.3.1(7) Recommendation Each steam generator has two pneumatic-operated atmospheric steam dump valves connected in parallel.
These four valves have the same controller which presumably receives power from only one source and, therefore, is vulnerable to a single failure even~. Concern was expressed to the licensee as to whether the steam supply to the turbine AFW pump is adversely affected by the potential simultaneous opening of all atmospheric dump valves due to a single failure at the controller or its:power source.
The licensee has indicated that the pressure drop across the valves is sufficiently large to assure adequate steam supply to the turbine-driven pump from the steam generators.
We require that the licensee provide analyses to confirm this assertion.
Response to X6.3.1(7)
All four atmospheric steam dump valves are controlled by the same controller and receive power from the same power source.
However, loss of power to the controller will result in the valves failing closed rather than open; ie, the valves fail in the safe position on loss of controller ou~put signal.
4 Turbine trip coincident with either a failure in the controller or in the process sensing circuits could cause all the valves to open.
However, by switching the controller to manual (this can be performed in the control room, and operating and emergency procedures explicitly instruct the operator to verify the proper action of the steam dump system following any reactor/turbine trip), the operator can effectively control this situation.
A failure of a single valve in the open position cannot be corrected in the control room; however, the operator has easy and quick access outside the control room to the manual air valves which control the dump valves.
Simply closing the appropriate manual air valve will cause the dump valve to close (ie, the dump valves fail closed on loss of air).
In the interim, we will modify the appropriate operating and emergency procedures, as necessary, to provide the required operator guidance for handling a failure in the steam valve controller or steam dump valve.
In the long term, Consumers Power Company will investigate whether or not a different valve power supply arrangement would reduce the likelihood of such a failure, and propose modifications, as necessary, as a result of our feasibility study.
X6.3.2(1) Recommendation The licensee should provide redundant level indications 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 alternate water supply and prevent a low pump suction pressure condition from occurring.
The low level alarm set point should allow at least 20 minutes for operator action, assuming that the largest capacity AFW pump is operating.
Response to X6.3.2(1)
In a telephone conversation with NRC (Richard Silver) on April 1, 1980, Consumers Power Company (Steven Frost) was informed that the.short-term requirements of X6.3.2(1) have been eliminated.
However, the January 1, 1981 requirement to* install a safety grade redundant water level indication still holds true for the condensate storage tank.
Consumers Power Company is investigating the availability of equipment to comply with this requirement.
X6.3.2(2) Recommendation The licensee should perform a 72-hour endurance test on all AFW system pumps,
. if such a test or continuous period of operation has not been accomplished to
5 date.
Following the 72-hour pump run, the pumps should be shut down and cooled down and then restarted and run for one hour.
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.
Response to X6.3.2(2)
The test as stated above has been updated by NRC letter dated February 11, 1980, Auxiliary Feedwater Pump (AFWP) Endurance Test.
This test will be conducted for the Palisades Plant's AFWPs as plant conditions allow (eg, when enough steam can be generated by the*system to run the TDAFP in an acceptable manner).
The results will be 'submitted to the NRC upon completion of the analysis.
Basis for AF'W System Flow Requirements We find it difficult to understand the need for providing such a basis, particularly as it will require a significant effort to collect the requested information.
Past operating experience at the Palisades Plant indicates that an auxiliary feedwater flow of 300 gpm is sufficient to recover from a complete loss of main feedwater while operating at full power late in core life.
As 300 gpm is less than two-thirds of the deliverable flow from only one auxiliary feed pump at a steam generate~ pressure of 1000 psia (and less than one-half of runout flow), it is apparent that the auxiliary feed pumps are more than adequate.
However, we have asked our reactor vendor, CE, to provide us with a proposed schedule for addressing your concerns.
As soon as the schedule becomes available, we will provide it to you.
Huston Senior Licensing Engineer CC JGKeppler, USNRC NRC Resident Inspector, Palisades oc04B0-02 lla-43