ML20197G487

Forwards Sser Re TMI Action Item II.E.1.1, Auxiliary Feedwater Sys. Recommends Licensee Submit Limiting Condition for turbine-driven Auxiliary Feedwater Pump. Response Requested within 30 Days of Ltr Receipt

ML20197G487
Person / Time
Site:	Maine Yankee
Issue date:	06/04/1984
From:	John Miller Office of Nuclear Reactor Regulation
To:	Randazza J Maine Yankee
References
TASK-2.E.1.1, TASK-TM NUDOCS 8406150268
Download: ML20197G487 (18)

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Docket No. 50-309 Distribution:

LAXicket File EJordan LPDR JNGrace PDR WJones Mr. J. B. Randazza ORB #3 Reading DBrinkman Executive Vice President DEisenhut RDiggs Maine Yankee Atomic Power Company 0 ELD KHeitner 83 Edison 0.-ive LHarmon PKreutzer Augusta, Maine 04336 Gray Files 4 ACRS 10 HDenton TBarnhart 4

SUBJECT:

SAFETY EVALUATION REPORT UPDATE - TMI ACTION PLAN ITEM II.E.1.1 AUXILIARY FEEDWATER SYSTEM We have continued our review of your auxiliary feedwater system under the TMI Action Plan, Item II.E.1.1. This review includes the meeting we held with you on June 28, 1983 and our evaluation of your submittal dated September 22, 1983. This review updates the status report we provided to you by letter dated March 24, 1983, which reflected your earlier submittals.

We conclude that you have now provided acceptable commitments for all but four items. The responses to two of these four items are acceptable pending receipt of an additional submittal by you; they are:

1. Short Term Recomendation 1 - Technical Specification regarding AFWS operability testing;

2. Long Term Recomendation 4 (part b) - Evaluation of postulated steam and feedwater line breaks.

Regarding the second two items, your responses are unacceptable. They are:

3. Additional Short Term Recomendation 1 - Redundant level instrumentation and low level alarms for the AFW primary water source;

4. Long Term Recomendation GL Automatic initiation of the turbine-driven pump.

We have enclosed a supplement to cur SE (Enclosure 1) which closes out the open items which we have found to be acceptable. -The supplement also

. provides the bases for our conclusions regarding the four remaining items.

In addition, the Maine Yankee Technical Specifications contain Limiting Conditions for Operation Specifications (LCOs) only for the two motor-driven AFW system pumps, k)[kbo ON P

The turbine-driven pump is not included in the Technical Specifications and, as a result, may be continually inoperable without any requirement to be returned to an operable status. We require that you propose an LC0 for this pump. This LC0 should follow the format of the Standard Technical Specifications and should not allow the turbine-driven pump to be inoperable for in excess of seven days. Enclosure 2 provides the basis for this position.

It is the Comission's goal to complete our review of these items related to the TMI Action Plan by September 30, 1984. Therefore, we request that you provide the requested items within 30 days of your receipt of this letter.

Any(questions at 301) 492-7364. should be addressed to the NRC Project Manager, Kenneth C. He The infomation requested in this letter affects fewer than ten respondents; therefore OMB clearance is not required under P. L.96-511.

Sincerely, original signed by G Q")L$b

{ James R. Miller, Chief Operating Reactors Branch No. 4 Division of Licensing

Enclosures:

As stated cc w/ enclosures:

See next page ORBA3 ORB #3:DL r #3:DL 658

'PXf,dtzer KHeitner;ef 1 JMiller (sli/F 09/,f,0/84 60F/ l /84 'Of/f/84 g gg 4,4 O DN

Maine Yankee Atomic Power Company ,

cc: '

Charles E. Monty, President -

Mr. P. L. Anderson Maine Yankee Atomic Power Company Pro.iect Manager Edison Drive Yankee Atomic Electric Company Augusta, Maine 04336 , 1671 Worcester Road Framingham, Massachusetts 01701 Mr. Charles B. Brinkman U.S. Environmental Protection Agency Manager - Washington Nuclear Operations Combustion Engineering, Inc. Region I Office 7910 Woodmont Avenue ATTN: Reg. Radiation Pepresentative Bethesda, Maryland 20014 JFK Federal Buildi.ng Boston, Massachusetts 02203 John A. Ritsher, Esquire Ropes A Gray Mr. John H. Garrity, Senior Director 225 Franklin Street Nuclear Engineering and Licensing Boston, Massachusetts 02110 Maine Yankee Atomic Power Company 83 Edison Drive State Planning Officer Augusta, Maine 04336 Executive Department 189 State Street Augusta, Maine 04330 Mr. E. C. Wood, Plant Manager Maine Yankee Atomic Power Company P. O. Box 3270 Wiscasset, Maine 04578 Regional Administ'rator. -

U.S. Nuclear Regulatory Commission Region I 631 Park Avenue King of Prussia, Pennsylvania 19406 First Selectman of Wiscasset Municipal Building U.S. Route 1 Hiscasset, Maine 04578 Mr. Cornelius F. Holden ,

Resident Inspector c/o U.S. Nuclear Regulatory Commission P. O. Box E Wiscasset, Maine 04578 1

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\%*...- j# SUPPLEMENTAL SAFETY EVALUATION AUXILIARY FEEDWATER SYSTEM EVALUATION,

TASK ACTION PLAN, ITEM II.E.1.1 MAINE YANKEE ATOMIC POWER COMPANY l MAINE YANKEE ATOMIC POWER STATION l DOCKET NO. 50-309 l

1. Shcrt: Tem'Recomendation 1 "The licensee should propose a revision to !

the Technical Specifications to require periodic AFWS operability testing on a monthly frequency rather than quarterly in ca.fifomance with current I

Standard echnical Specifications."

l In a su5mittal dated September 22, 1983, the licensee comitted to sub-mit a propcsed change to the Technical Specif'ications to require monthly auxtliary feedwater system operability testing in lieu of the present testing on a quarterly 5 asis. Thelicensee;froposestoperformthese pump tests at minimum recirculation flow with separate cycle testing r

of key valves. We conclude that.this comitment is acceptable provided that the licensee staggers the tests so that a single emr cannot

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. make more than 'one train or pump inoperative. Pending receipt of a clarification on this one point we consider this item resolved.

2. Sh::rt Tem Recomendation 2 "The licensee did not submit sufficient

! i information for us to conclude that all ' failures will result in opening the pneumatic-operated AP.4 flow control valves and steam admissien valves f- '

to the turbine-driven AFW. pump.

)[e[concludethatthelicenseeshould esta511sh stiitable emergency procedures for operation cf the pneumatic-

, c g operated valves in the event that valves were to fail closed due to an unanticipated failure mode of the comon AC bus."

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l In a submittal dated August 21, 1981, the licensee specified that the l

Maine Yankee emergency procedures include direction for manual control of feedwater control valves, if necessary. In a meeting on June 28, 1983, the licensee stated that the amergency procedures for loss of all AC power i include manual control of the valves in the line carrying steam to the  ;

turbine of the AFW steam-driven pump. On loss of AC the valves would nomally fail in the open position (see Long Tem Recomendation GL-3 for detailed discussion); manual control serves as a precautionary measure in  !

t the event an unusual failure should occur. We find this to be acceptable.  !

3. Additional Short Tem Recommendation 1 "The licensee should provide redundant level indications and low level alams in the control room for t!ie AFW system primary water supply, the demineralized water storage tank (.DWST), to allow the operator to anticipate the need to make up water or transfer to an alternate water

• prevent a low pump l suction pressure condition from oc' ine low level setpoint sheuld allow at least 20 minutes ;rator action, assuming that the largest capacity AFW pump is operating."

In a su5mittal dated August 21, 1981, the licensee reported that the following instrumentation was available for the DWST:

1. A low level alam (at the control board) when the volume of water l in the tank is reduced to 100,000 gallons (six-hour supply of water),

2. A low-low level alam (at the control board) at 10,000 gallons (30-minute supply),

3. Level indication at the control board, and

4. Local level indicating gauge at the tank.

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- In addition to the instrcmentation, the auxiliary operator records the level of water in the DWST twice each shift.

The plant Technical Specifications require that at least 100,000 gallons ,

of primary grade feedwater be available to allow the reactor to be l maintained in a power operating condition (Condition 7. Specification 3.8D) but do not specify where these 100,000 gallons are stored. The licensee corrected this condition by providing a Technical Specification (Proposed Change No. 97) which includes a requirement that a volume of feedwater in excess of 100,000 gallons be held in the demineralized water storage tank in order to be able to maintain the reactor in a power  ;

operating condition. We. find this change to the Technical Specifications (Paragraph 3.8.E.2) acceptable. However, we find that the licensee

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is not in ' compliance. with the recommendation which specifies that redundant level alarms and indications be provided in the control room i so that the control room operator has at least twenty minutes to shift

,the AFW system to an alternate water supply. The Maine Yankee licensee

'should provide the redundant alarms and indications as recommended below.

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In a submittal dated September 22, 1983, the licensee stated that the annunciator system at Maine Yankee is not Class lE; therefore, any level alarms will not be safety grade. The staff is aware that annunciator systems are not necessarily Built to Class lE standards. For this recommendation it would be acceptable to provide a second, redundant alarm Which uses a power sourca different from the alarm already in place and of the same quality as the existing alarm. The redundant level indication, however, should be Class 1E, utilizing a lE power source separate from the level indication already in place. Both of the redundant alarms should annunciate in the control room; both level indications should also be provided in the control room. The licensee should commit to supply the redundant alarm and indication.

4. Short Term Recmmtendation GS-5 "The as-built plant should be capable of providing the required AFW flow for at least two hours from one AFW pump train independent of an ac power source. If. manual AFW system initiation flow control is required following a complete loss of ac power, emergency l

procedures should be established for manually initiating and controlling the system under these conditions. Since the water for cooling the lube oil for the turbine-driven pump bearings may be dependent on ac power, design or procedural changes shall be made to eliminate this dependency as soon as practicable. Until this is done, the emergency procedures

! should provide for an indiv'idual to be stationed at the turbine-driven l

pump in the event of the loss of all ac power to monitor pump bearing i

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and/or lube oil temperatures. If necessary, this operator would operate  :

the turbine-driven pump ir, an on-off mode until ac power is restored.

Adequate lighting powered by direct current (de) power sources and ,

communications at local stations should also be provided if manual initiation and control of $he AFW system is needed (see Recommendation GL-3 for the" longer-term resolution of this concern)."

. See response to Item GL-3 below.

" Licensees with plants in which all

5. Lono Term' Recommendation'GL-2 (primary and alternate) water supplias to the AFW system pass through YalYes in a single flow path should install redundant parallel flow '

paths (piping and valves). Licensee with plants in which the primary AFW system water supply passes through valves in a single flow path, but the alternative AFW system water supplies connect to the AFW system pump suction piping downstream of the above valve (s) should f

install redundant valves parallel to the above valve (s) or provide automatic opening of the valve (s) from the alternate water supply The licensee should propose Technical upon low pump suction pressure.

Specifications to incorporate appropriate periodic inspections to verify the valve positions."

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The primary water supply for the Maine Yankee AFW system (from the demineralizedwaterstoragetank-DW5T)passesthroughavalvein a single flow path with the alternative water supply '(from the primary water storage tank - PWST) connecting to the AFW pump suction piping downstYeamofthesinglevalve. In a submittal dated September 22, 1983, the licensee proposes to remove the internals from the valve in order to avoid possible valve failure which wuld b' lock the flow of water from the DWST to the AFW pumps. The licensee comitted to remove the valve internals during the next refueling outage. We find this acceptable.

6. Long Tem Recomendation 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 ac power source for at least two hours. Conversion of de power is acceptable."

In a submittal dated August 21, 1981, the licensee reported that water for cooling both the turbine bearings and the lube oil for the turbine-driven AFW pump is provided by a tap off the pump discharge. There are three soler.oid-controlled, air-operated valves in the steam  !

admission line to the turbine intercept valve; presently, two are designed to fail open en loss of air or power while one, the contain-ment isolation valve, is designed to close on loss of air or ac.

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Power for the isolation valve may be provided by the station battery ,

through inverters on loss of ac or the valve may be operated manually.

i In addition, the air-operated turbine governor has an independent air receiver which will permit the governor to maintain control for four ,

hours. .

Thus, the turbine-driven pump may be operated for two hours following a loss of all ac, as specified in the recongendation. This complies  ;

with all parts of the recommendation except the automatic initiation requirement. The licensee, in a submittal dated September 22, 1983, ,

notes that the steam-driven AFW pump is initiated manually instead

-- of being initiated automatically followi'ng station blackout. (loss of all AC). The licensee is also modifying the' containment isolation , l

- valve on the steam admission line to the steam-driven AFW pump so that the valve will receive its control air from the excess flow control valve accumulator, a reliable source of control air; thus, the valve will remain open in the event of a station blackout. The licensee also [

f states that the steam-driven AFW pump is not required to mitigate any design basis accident at Maine Yankee and that it is required following a station blackout which is, the licensee notes, a nondesign basis event.

t The licensee states further, that the operator has "...more than sufficient time..." (i.e., 30 minutes) to start the steam-driven AFW pump in the event of a station blackout. Note that the 30-minute time interval includes loss of water from the steam generators due to normal blowdown.

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We have considered the information provided by the licensee. However, it is the staff's position that for station blackout, the only source of cooling to the plant will be that turbine-driven AFW pump. We do ,

not believe that the station operators should be depended upon to

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perform .this important function. Therefore we require that the licensee

' i provide automatic initiation of the steam-drivan pump in the event of a station blackout. ,

7. Long Term Recommendation 4 (part b) "In tha event of a steam o'r

.feedwater line break (main or auxiliary), isolation of.the auxiliary feedwater flow path to the affected steam generator is accomplished manually. The licensee should evlauate these postulated pipe breaks and (1) determine any.AFW system design changes or procedures necessary 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 safe shutdown condition by use of other systems which would be available following such postulated events."

In a submittal dated April 28, 1981, the licensee reported that the ,

1 AFW system would be modified (and verified that modification had been  ;

accomplished during the cycle 6 outage) as follows: l l

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(1) Provision of automatic starting of the two motor-driven AFW pumps upon low water level signal from any one of the three steam generators.

(2) Modification of the auxiliary feedwater control valves so that each ,

closes individually upon a low steam generator pressure signal. In the event of a steam line break this will isolate the steam generator in the train which contains the ruptured piping, (3) Provision of a five-minute delay in initiation of the two motor-driven l AFW pumps (or tripping of the two motor-driven pumps for five minutes if already running) upon receipt of the steam generator low pressure signal, tn order to prevent an overpower transient in the event of a steamline Break. ,

Note that this design requires operator intervention to direct AFW flow to the undamaged steam generators, if the control valve in the damaged steam generator were to fail and remain open after receipt of the EFCV signal, in order to prevent stemm generator "dryout" Because most of the water from the AFW system would then be diverted to the damaged steam generator.

In a further submittal dated September 22, 1983 the licensee stated their plans to install additional AFW valves, in series with the existing flow control valves and to remove the 5-minute delay (or

pump trip and delay in the event of operating AFW pumps) in starting the motor-driven AFW pumps. In this way the auxiliary feedwater will be isolated from the affected steam generator and no operator intervention will be required to assure continued water flow to the unaffected steam generators in the event of a feedwater or steam-line break. However, the licensee has not provided us with sufficient design details to assure us that the design is single-fai'ure proof.

Therefore, pending receipt and satisfactory review of a .further submittal by the licensee, we find that the licensee has complied with the portion of the recastendation relating to a main feedwater or steamline Break.

e With regard to failure of the common AFW system discharge manifold, the' licensee noted that each AFW pump discharge can be directed to the feedwater pump discharge lines upstream of the first point heaters. This involves closing one AFW pump discharge valve, opening another valve at the discharge of each AFW pump (leading to the normal feedwater lines) and opening one valve in the common manifold to the nornal feedwater lines. Thus, three valves will need to be operated (one closed, two opened) to switch the first AFW pump flow to the alternate flow path (each of the otht : two pumps only requires closing one discharge valve and opening another if either pump is needed). The licensee should show that the AFU pumps can be diverted by the plant operators in sufficient time to prevent steam generator

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dryout in the event of an AFW manifold break when either (or both) motor driven pump is fieing used in its normal operating mode (not foraccidentmitigation). Pending receipt of a satisfactory submittal regarding operator diversion time, we find the portion of the recomendation relattrg to an AFW line break complete.

8. Basis for AFW System Flow Reouirement "In Enclosure 2 to our letter of Octo5er 18,1979, we requested the licensee '.o provide certain information regarding the design basis for AFW flow require-ments. The licensee stated in a letter dated November 20, 1979, that the required infomation would -be :,ubmitted at a later date."

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In a submittal dated August 21, 1981, the licensee noted that the design basis events for the Maide Yankee AFW system were those shown in Ta51e 1, 5elow. The bounding event for the design of the AFW systs is the loss-of-rsain-feedwater (LMFW). The licensee reported that loss of a,11 AC and feedwater line break were not part of the spectrum of design Basis events for Maine Yankee.

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Table 1

1) Loss of Main Feedwater (LMFW)

2) LMFW w/ loss of offsite AC Power

3) Turbine Trip with and without bypass

, 4) Main Steam Isolation valve closure

5) Main Steam Line Break

6) Small break LOCA l In the eventJ LMFW event occurred, the licensee stated that the steam generators would dry out in 13 minutes with offsite power available and in 30 minutes with offsite power unavailable assuming the AFW system did not j start. Further, the licensee noted that, in the event of a loss of all AC,  ;

the operator would have 30 minutes in which to start the turbine driven AFW pump before steam generator dryout occurred.

The licensee reports that a single AFW pump is capable of removing the total x

combined heat resultiing from reactor coolant pump operation and decay heat seven minutes after the i.MFW event begins. In addition, the minimum inventory of 100,000 gallons of water available (discussed above in Additional Short Tem Recomendation 1) to the AFW system in the DWST is sufficient to remove the I combined heat load (generated by reactor coolant pumps and decay heat) for at t least four hours -- eight hours if the reactor coolant pumps do not operate. ,

r We find the licensee's design basis flow requirements for the AFW system l acceptable because the licensee has shown that the design flow rat.. is capable of mitigating those transients and accidents for which use of the AFW system ,

is necessary to assure a safe plant shutdown. ,

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Enclosure 2 Basis for Position The Technical Specifications for the Maine Yankee Atomic Power Plant presently The require only that two AFW pumps Be available during normal operation.

technical specifications consider only the motor-driven pumps, thus allowing the tur5ine-driven pump to be out of service for an indefinite period of time. This is unacceptable since the turbine-driven pump is the main soorce of plant protection in the event of. loss of all AC power, In several plants, loss of all AC power h'as been found to be a significant contributor to the risk of core melt. Thus, the Standard Technical Specifications (STS) for Com5ustion Engineering Pressurized Water Reactors (NUREG-0612, Revision 2} require that three AFW pumps (two driven by electric power, one by steam) Se operable when the nuclear power plant is in the operational mode (Mode 1),in the startup mode (Mode 2), or in the hot standby mode (Mode 3).

In the event one AFW pump becomes inop~erable, the Technical Specifications allow 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> (three days) for repair before requiring that the plant shut down; the plant must be in hot standby within six hours and in hot shutdown in the ,next.six hours.

In the event of inoperability of two AFW pumps, the STS require that the plant be in hot standby within six hours and in hot shutdown within six hours thereafter.

In a Peview of the Zion Station, detailed studies were made of the problem of pump inoperability with special concern in the area of loss of all AC and the effect of steam-driven. pump inoperability upon the risk of core melt.

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These studies which utilized AFW pump outage data for the Zion plant did not show significant improvement in risk of core melt when considering pump unavailability of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> in contrast to a seven day unavailability for operation for assumed infrequent outages when applied to the motor driven AFW pumps. However, they did indicate that a major accident sequence contributor to the total plant risk of core melt, namely loss of all ac power (in which case the motor-driven pumps anr unavailable and cannot be given credit for mitigation of this event) is affected by the availability of the turbine-driven AFW pump. Discussions with,the licensee indicated that.the turbine-driven pump was down for repair at fairly frequent intervals.

Consequently, we determined that turbihe-driven pump availability should be more closely followed and kept at the maximum possible level. Thus, we concluded that the licensee's technical specifications should be revised to allow a motor-driven pump to be inoperable for seven days prior to beginning hot shutdown. However, we recommended that the licensee propose modifications to the technical specification concerning the operability of the turbine-driven pump to indicate that every measure possible be taken (including continuous work on all shifts) to restore that pump to operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

Should all efforts to complete the repairs within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> fail, the turbine-driven pump may remain inoperable up to seven days before initiating hot shutdown. .

Independent evaluations of the effect on the risk of core melt resulting from various allowable outage times for two AFW pumps simultaneously have been performed which show only an insignificant effect on core melt if a  !

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second pump is allowed to Se inoperable for as much as eight hours before proceeding to hot stand 5y witMn six hoors thereafter and thence to hot shutdown within the next six hours. In our judgement, it is prudent to allow some time period to assess the caose of a loss of redundancy in the ARIS rather than immediately challenging the one operable purap by initiating a reactor shutdown.

Thus, in reviewing the Zion technical specifica,tions we recomended that an eight hour interim be allowed before requiring that the plant shut down with two AR1 pumps simultaneously inoperable.

In conclusion, we are willing to accept a modified version of the STS which allows the turbine-driven pump to be inoperable for a period of up to seven days. However, we believe such a specification should include a provision to assure that overall availability of the turbine-driven pump remains high. The AFW system pumps should be required to be operable in the hot shutdown condition (condition 5), the hot standby condition (condition 6), and the power operation condition (condition 7) in order to conform with the modes (1, 2 and 3) in which AFW pump operability is required in the STS, i