ML19351G483
| ML19351G483 | |
| Person / Time | |
|---|---|
| Site: | Fort Calhoun  |
| Issue date: | 02/02/1981 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19351G482 | List: |
| References | |
| NUDOCS 8102240006 | |
| Download: ML19351G483 (14) | |
Text
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O SAFETY EVALUATION REPORT FORT CALHOUN IMPLEMENTATIONS OF RECOMMENDATIONS FOR AUXILIARY FEEDWATER SYSTEPS I.
Introduction and Background The Three Mile Island Unit 2 (TMI-2) accident and subsecuent investigations and studies highlighted the importance of the Auxiliary Feecwater System (AFWS) in the mitigation of transients and accioents. As part of our assessment of the TMI-2 accident and related implications for operating plants, we evaluated the~ APA systems for all operating plants having nuclear steam supply systems
'.NSSS) designec cy Westinghouse (NUREG-0611) or Combustion Engineering (NUREG-0625). Our evaluations of these system designs are contained in the NUREGs along with our recomendations for each plan and the concerns which led to each recomendation. The objectives of the evaluation were to:
(1) identify neces-sary changes in AFW system design or related procedures at the operating facili-ties in order to assure the continued safe operation of these plants, and
- (2) to identify other system characteristics of the AF4 systems which, on a long term basis, may require system modifications. To accomplish these objec-tives, we:
(1) Reviewed plant specific AFW system designs in light of current regulatory requirements (SRP) and, (2) Assessed the relative reliability of the various AF4 systems under various loss of feedwater transients (one of which was the initiating event of TMI-2) and other postulated failure conditions by determining the potential for AFJ system failure due to comon causes, single point vulnerabilities, and human error.
8102 2 4 0 00G>
. We conclude that the implementation of the following recommendations identi-fled during this review will considerably improve the reliability of the AFW systems for each operating plant.
The folicwing plant specific recommendations did not apply to this plant:
G3-1, GS-3, GS-5, GS-8, GL-3 and GL-4 The basis for :nese recommendations can be found in Appendix III of NUREG-0635 and the system.descriptien which determined the basis for not applying these
.recc=mendations can be found in Section X of NUREG-0635.
II.
Imolementat1on of Our Reccmmendations A.
Short Term Recommendations 1.
Recommendation 35 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 interr'upt all AFW flew. Monthly inspections should be performed to verify that these valves are locked and in the open position. These inspections should be proposed for incorcoration into the surveillance requirements of tne plant Technical Specifications. See Recommendation GL-2 for the long term resolution of this concern.
In a letter dated January 9,1981, the licensee stated that the appro-priate valves have been locked in the recuired position to insure a The ifcensee further stated that flew path to the steam generators.
an additional surveillance test has been preoared and implemented to check the position of critical valves in the auxiliary. feedwater system on a monthly basis. An auxiliary feedwater system normal line up e
. checklist has been completed to verify proper valve position. The licensee will perform these checks on a monthly basis during power operation until the above referenced surveillance test is implemented.
A proposed change to Technical Specification section 3.9 requiring the monthly surveillance test was provided.
We conclude that the licensee's response adequately meets this recem-mendation and is, therefore, acceptable. Approval of the proposed Technical Specification Section 3.9 was granted by License Amendment 49 on July 25, 1980.
2.
Recce.endation GS 4_ - Emergency crocedures for transferring to alter-nate sources of AFW supply should be available to the plant operaters.
These crocedures should include criteria to inform the operator when, and in what order, the transfer to alternate water sources should take place. 'The following cases should be covered by the procedures:
(1) ine case in wnich the primary water supply is not initially avail-abl e. The procedures for this case should include any operator actions required to protect the AFW system pumps against self-damage before water flow is initiated; and, (2) The case in wnich the primary water supply is being depleted. The procedure for this case should provide for transfer to the alter-nate water sources prior to draining of the primary water supply.
In a letter dated January 14, 1980, the licensee stated that the appro-priate operating instructions and emergency procedures have been changed
4 as necessary to incorporate the emergency sources of water for the emergency feedwater tank including criteria for when they will be used. The necessary training for operator action has been completed.
We conclude tnat the licensee's resoonse is acceotable. The Office of Inscection and Enforcement has verified that the procedures are in place.
3.
Recommendation GS The licensee should confirm flow path availability cf an AFW system flow train that has been out of service to perform periodic testing or maintenance as follows:
(1) Procedures snould be implemented to require an operator to deter-mine that :ne AFW system valves are properly aligned anc a secccc operator to indecendently verify that the valves are properly-aligned.
(2) The licensee should crocose 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 generators.
The flow test should be conducted with AFW system valves in their normal alignment.
In a letter dated January 14, 1980, the licensee stated that the current procedure for _ tagging equipment out of service requires confir-mation that a system is returned to service follcwing maintenance. All e
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. valves are returned to their normal position. The current maintenance order system provides for verifying system operability at the completion of the maintenance task. This insures that the system is ope-able at that time. The licensee further stated that a second independent verification of valve position will be previced in tne monthly test Performance of the proposed in the response to recommendation GS-2.
surveillance test following maintena.nce on the auxiliary feedwater system will be required. A proposed technical specification which requires a ' low test to verify the normal flow path after a cold snut-down was proviced.
We conclude that the licensee's response adecuacely meets this recom-mendation and is, therefore, acceptable. Approval of the proposed Technical Specification was granted by Arendment 49 issued on July 25, 1980.
a.
Recommendation GS-7_ - The licensee should verify that the automatic start AFW system signals and associated circuitry are safety-grade.
If this cannot be verified, the AFW system automatic initiation system l
should be modified in the short-term to meet the functional require-l ments listed below. For the longer term, the automatic initiation signals and circuits should be upgraded to meet safety-grade require-ments a-indicated in Recommendation GL-5.
(1) The design should provide for the automatic initiation of the auxiliary feedwater system ' low.
.(2) The automatic initiation signals and circuits should be designed so that a single failure will not result in the loss of auxiliary feedwater system function.
(3) Testability of the initiation signals and circuits shall be a feature of the design.
(4) The initiation signals and circuits should be powered from the emergency buses.
(5) Manual capability to initiate the auxiliary feedwater system from the centrol room should be retained and should be implemented so that a single failure in the manual circuits will not result in the loss of system function.
(6) 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.
(7),The automatic initiation signals and circuits shall be designed so that their failure will not result in the loss of manual capabili y to initiate the AFW system from :ne control room.
The licensee in a letter dated December 13, 1979, and subsequently updated-by a letter dated April 18, 1980, described a means of providing control grade automation of the auxiliary feedwater system.
The modification.has been installed.
We conclude that the licensee's response to this recommendation is I
l acceptable for control grade AFW initiation. The Office of Inspection l
and Enforcement has verified that the system is installed and operable.
l t
. The long term counterpart of this recommendation, GL-5 (safety grade),
is still under staff review.
Recommendation - The Itcensee should prepare a procedure that assures 5.
that the operator manually connects the motor-driven pump tre.in to the bus powered by the emergency diesel generator following loss of offsite acuer.
In a letter dated December 13, 1979, the licensee stated that following loss of offsite power the electric driven pumo is prevented from loading onto the emergency bus until the diesel generator has restored power to.
Af ter the diesel is started and is croviding power to the bus, the bus.
the cump will then be loaded automatically by the sequential loading circuit.
We conclude that the automatic secuencing cf the pump onto the energized bus is acceptable and that the recommendec procedure is not required.
Reccmmendation - Since valves FW 744 and 7'5 in ene of the AFW pump 5.
discharge headers are normally open, a postulated break in this header would cause loss of the capability to provide AFW flow to both steam The licensee should re-evaluate the position of these generators.
valves considering such a postulated pipe break to revise the valve alignment to reduce the impact of such an event on the AFW capability (e.g., close valves FW 744 and FW 745).
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. The licensee responded in a letter dated January 14, 1950, that valves FW 744 and FW 745 are nor= ally maintained in the closed position to citigate the consequences of a pipe break between FW 744, FW 745 and FW 746.
We conclude that the itcensee's response is acceptable.
B.
Additional Short Term Recommendations 1.
Recommendation - The licensee should provide redundant level indication and low level alarms in the control room for the AFW system primary water sucoly, to allow the coerator to anticipate the need to make uo water or transfer to an alternate water supply and prevent a low pump su:: ion pressure condition from occurring. The low level alarm set-coint should allow at least 20 minutes for coerator action, assuming that the largest capacity AFW pump is coerating.
Tne licenses stated in a letter dated December 31, 1979, that, to meet tne requirements of this item, an additional level transmitter, level indicatot, and associated alann have been added to the AFW system.
The alarm se point is set to allow at least 20 minutes for operator action. The licensee stated that the above modified system provides a
- ontrol grade redundant level indication and low level alann to the AFW system primary water suoply.
O 4
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We find the Itcensee's response to this renmendation is acceptable.
Recomendation (This recomendation has been revised from the cricinal 2.
recomendation in NUREG-0635) - The itcensee should perform a 48-hour endurance test on all AFW system pumos, if such a test or continuous period of operaticn has not been accomplisned to cate. Following the 48-hour pump run, the pumps should be shut down and cooled dcwn and then restarted and run for one hour. Test acceptance criteria should include demonstrating that tne pumos remain within design limits with
-esoect to bearir.g/ bearing oil temperatures and. vibration and that pump
-com ancien: concitions (:emperature, humditiy) do not exceed environ-mental qualification limits for safety-rela:ec equipment in the room.
The Itcensee should provide a sumary of.he conditions and results of the tests. The sumary should include the following:
- 1) A brief descriotion of the test nethod (including flow schematic diagram) and how the test was instrumented (i.e., where and how bearing tempera-
_;ured). 2) A disbussion of how the test conditions (pumo flow, ead, speed and steam temperature) compare to design operating conditions.
- 3) Plots of bearing / bearing oil temperature vs. time for each bearing -
of each AFW pump / driver demonstrating that temperature design limits were not exceeded. 4) A plot of pumo room ambient tempera'ture and humidity vs. time demonstrating that the : ump room ambient conditions do not exceed environmental qualification limits for safety-related equipment in the room. 5) A statement confirming that the pump vibra-tion did not exceed allowable limits during tests.
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. In a letter dated January 14. 1980, the licensee stated that both pumos were tested for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> and that for both pumps all operating parameters remained within design limits. The licensee further stated that the pump test data is available at the station.
We consider this response acceptable. The Office of Inspection and Enforcement has verified that the pump test data successfully demon-strated that the test objectives were met.
3.
Recen endation - The licensee should implement the following require-ments as specified oy Item 2.1.7.b on page I-32 of NUREG-0578:
" Safety-grade indication of auxiliary feedwater flow to each stera generater !^all re
- 0"'ced ia :"e con--61 -com.
Tne auxiliary feedwater flew instrument channels shall be powered
,from the emergency buses consistent wi n satisfying the emer-gency power diversity requirements for the Auxiliary feedwater system set forth in Auxiliary Systems Branch Technical Position 10-1 of the Standard Review Plan, Se: tion 10.4.9."
In a letter dated December 31, 1979, the licensee stated that control grade flow transmitters have been provided for the AFWS.. Modification for upgrading the flow indication to safety grade category will be completed prior to heatup following the station's 1981 refueling outage.
We consider that the licensee's. response is acceptable for the short However, the long tem recomendatien, i.e. providing safety-tem.
grade flow indication, is still under staff review.
11-4.
Recommendatien_ - Licensees with plants which require local manual realignment of valves to conduct periodic test on one AFW system train, and there is only one remaining AFW-train available for opera-tion should propose Technical Specifications to provide that a dedicated individual wno is in communication with the centrol rocm be stationed at the manual valves. Upon instruction from the control room, this cperator would reali5n the valves in the AFW systen train from the test mode to their operational alignrent.
- n a letter dated January 12, 1950. tne licensee stated that local manual realignment of valves is r.ot required to perform the present periodic testing recuirements of the auxiliary feedwater system;
- nerefore, no Technical Specification changes are proposed.
We have evaluated the licensee's response and we conclude that the response is acceptable.
C.
Lene Term Recemrendatiens.
1.
Recommendation GL-i - Licensees with plants having a manual starting AFW system should install a system to automatically initiate the AFW system flow. This system and associated automatic initiation signals should be designed and installed to meet safety-grade require-Manual AFW system start and control capability should be ments.
retained with manual start serving as backup tc automatic AFW system initiation.
O e
9
In letters dated December 13, 1979, and April 8,1980, the licensee stated that installation of the safety grade system requires a plant shutdown which they propose to postpone until the 1981 refueling outage, scheduled to comt.ence in. September 1981.
The staff will evaluate the licensee's response to this recommen-dation and provide their SER input at a later date.
2.
Recommendation GL > icensees witn plants in wnich all (primary and alternate) water supplies to the AFW systems pass through valves in a single flow path-should install redundant parallel flow paths (piping anc vaives).
The licensee stated in a letter dated January 9,1981, that redundant parallel flow paths (pioing and valves) from all water supplies to the A?4 pumas suction will be provided for Fcrt Calhoun Station dering the 1981 refueling outage.
We conclude that the licensee's response is acceptable. pending verification by the Office of Inspection and Enforcement that the additional value has been ins:c111ed.
F I
I
. 3.
Recommendation GL The licensee should upgrace the AFW systen auto-matic initiation signals and circuits to meet safety-grade require-ments.
In a letter dated January 14, 1980, the licensee stated that the response to this recommendation was provided in their letter of Decam-ber 13,1979.
The staff is evaluating the licensee's response to the safety grade requirements of this recommendation and provide an SER input at a later date.
4.
Recommendation - The licensee should evaluate the following concerns:
The discharge lines of both AFW pumps combine into a single a.
header through which all AFW water must flow. A pipe break in this sir.gle flow path could result in the loss of the entire AFN system function.
b.
The Fort Calhoun AFW system design does not meet the high energy break criteria in SRP 10.4.9 and Branch Technical Position 10-1; namely, that the AFW system should maintain the capability to supply the recuired AFW flow to the steam generator (s) assuming a pipe break anywhere in-the AFW pump discharge lines concurrent with a single active failure.
The licensee should evaluate the postulated of pe breaks stated above.
and (1) determine any AFW system design changes or procedures neces-sary to detect and isolate the break and direct the required feedwater flow to the steam generator (s) before they boil dry. or (2) describe how the plant can be brought to a safe shutdown condition by use of other systems which would be available following such postulated events.
14-In a letter dated January 9,1981, the licensee subnitted an AFWS design modi.ffcation which provides a redundant AFW pump discharge line to the steam generators.
We have evaluated the design modification and conclude that it meets both parts of the requirement of this recommendation.
5.
Basts for Auxilfary Feedwater System low Recufrement - In our letter dated October 22, 1979, we requested the Itcensee to respond to Enclosure 2, regarding the Auxiliary Feedwater System flow design casis.
In a letter dated January 14, 1980, the licensee stated that the information requested in Enclosure 2 would be submitted when available. We will evaluate the licensee's response when it is submitted and provide a supplement to this SER input.
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