B13946, Provides Addl Info Requested During 910819 Telcon Re Second 10-yr Inservice Insp Testing Program.Info Clarifies Relief Requests Submitted in

Provides Addl Info Requested During 910819 Telcon Re Second 10-yr Inservice Insp Testing Program.Info Clarifies Relief Requests Submitted in

ML20085F766
Person / Time
Site:	Millstone
Issue date:	10/17/1991
From:	Sears C NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
B13946, NUDOCS 9110230038
Download: ML20085F766 (12)

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NORTHEAST UTILITIES o.nem om.o soia.n sireci. seruz.. conneci cui - l t [ , "lS l

October 17, 1991 Docket No. 50-336 H13946 Re: IST Program 10CFR50.55a(g)

U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington. DC 20555 Gentlemen:

Millstone Nuclear Power Station, Unit No. 2 Response to Request for Additional Information Second 10-Year in-Service LqsAqqtion Testi_na Proaram The purpose of this letter is to provide the additional:information requested of Northeast Nuclear Energy Company (NNECO) du n.g a telephone conference with the NRC Staff on August 19, 1991, regarding the second 10-year in service inspection - testing- (IST) progrant for Millstone Unit No. 2. During this conference. call, the NRC requested UNECO to submit clarifications g certain relief requests previously . submitted by letter dated June 18, 1991.

su The changes submittals~ which dated have October 30,been ,1988,gquent 1987,made g and Augustthe 'IST which to formed program, NNEC0's the basis of.the St&ff's letter dated -July ~ 19, 1990, g" are identified-in Attach-ment 1. The information included as Attachment 1 supersedes the information (1) G. S. Vissing - letter to E. J. Mroczka, " Request for- Additional Information Regarding Relief Concerning Second Ten-Year Inservice . Testing Program (TAC No. 79688)," dated June 18, 1991.

(2) E. J. Mroczka letter to U.S. Nuclear Regulatory Commission, " Millstone l Nuclear. Power Station, Unit No. 2, Inservice Inspection Testing Program,"  !

dated October 30, 1987.

(3); E. J. Mroczka letter to U.S. Nuclear Regulatory Commission, " Millstone i Nuclear Power Station, Unit No. 2, Inservice Inspection Testing Program 1 (TAC No 59265)," dated August ?6, 1988.

(4) :J. F. Stolz letter to E. J. Mroczka, "Second Ten-Year Inservice Testing Program and the Granting of Relief from lesting Requirements Determined to be Impractical for Millstone, Unit 2 (TAC No. 75977)," dated July 19, , ,

1990.

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1 U.S. Nuclear Regulatory Commission B13946/Page 2 October 17, 1991 4 previoutly provided by Footnotes 1, 2, and 3 for the identified relief requests, We trust the submittal of this information will provide the NRC Staff with the .

information necessary to complete the review of NNECO's regt.est for relief from certain ASME Code testing requirements.

As always, should you have any further questions relating to this issue, please contact my Staff.

Very truly yours, ,

NORTHEAST NUCLEAR ENERGY COMPANY FOR: E. J. Mroczka Senior Vice President BY: C Llth L. F. Sears Vice PresVent cc: T. T. Martin, Region I Administrator G. S. Vissing, NRC Project' Manager, Millstone Unit No. 2 W. J. Raymond, Senior Resident inspector, Millstone Unit- Nos.1, 2, and 3 P. J. Habighorst, Resident inspector, Millstone Unit No. 2

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Docket No.__50-135

!!1.3145.

t Attachment 1 Millstone Nuclear Power Station, Unit No. 2 Response to Request for Additional leformation Second 10-Year In-Service Inspection Testing Program RR-IWP-1, RR-lWV-3, RR-lWV-5, RR-IWV-8, RR-IWV-9, RR-lWV-13, and RR-lWV-34 l

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RelicLikuucsda. RR-lWP-1 Cnmponents Affccied All safety-related pumps Code Reference Article IWP-4510 Article IWP-3210, Table IWP 3100-2 (Vibration)

Code _Te1LRequirement Measure during each in-service test, displacement vibration amplitude (mils) flass for Relief Experience has shown that measurement of oserall vibration amplitude in mils does not provide the desired early warning of pump degradation. Vibration amplitude is adequate for measuring unbalance, misalignment, and other low frequency failure modes, it does not give early warning of bearing degradation since the magnitude of higher frequency vibrations created by such degradation is 10 to 1.000 times lower than the normal pump movements. Expenence at Northeast Utilities has shown that monitoring pump vibration velocity (in/see) provides earlier warning of pump degradation. Collection and resiew of vibration " signatures" (plots of vibration velocity vs. frequency) over a range from slightly below running frequency to several times running frequency provides optimal early warning of pump degradation.

Absolute maximum limits are set for each pump. l-ligber maximum limits are appropriate for the Service Water Pumps since the measurements taken at the upper motor bearing housing are significantly affected by the height of the monitoring point above the actual pump, the lack of stiffness in the pump structure, and the fact that the pump natural resonance frequency is within 10 percent of the running frequency.. Millstone Unit 2 has shown that the pump vibration levels are extremely sensitive to small amounts of unbalance or pump shaft bearing looseness.

Inspections have shown minimal pump or motor degradation after extended operation at vibration levels near the proposed maximum allowable levels. Because of these factors a " service factor" of 2 has been assigned to the vibration limits for these pumps and the maximum allowable vibration adjusted accordingly. The absolute maximum limits specified in the Alternate Testing have been discussed with the pump manufacturer (llayward-Tyler) and the motor manufacturer (General Electric). Both have agreed that since the vibration increase is primarily caused by the pump natural resortnee frequency being so close to the running frequency the proposed limits for these pumps are acceptable.

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4 d ReheLReguest No. RR-lWP-1(Continued)

Aliennte_ Testing For centrifugal pumps, at least two measurements will be taken in a plane perpendicular to the rotating shaft in two orthogonal directions and one measurement taken in the axial direction.

Vibration will be monitored during each in-service test using equipment which collects vibration velocity signatures For recipretating pumps, similar measurements will be taken on a bearing housing of the crankshaft.

On vertical line shaft pumps, measurements ... De taken on the upper motor bearing housing in three orthogunal directions including one axial direction Vibration will be monitored during each in-service test using equipment which collects vibration velocity signatures over a range from less than on-half running speed to at least eight times running speed.

Overall vibration velocity (in/see Peak) will be compared to the following acceptance criteria.

1. Acceptable Range - less than 2.5 times Reference Velocity

2. Alert Range - 2.5 to 5 times Reference Velocity or greater than l 0.3?5 inches per second (Peak)

3. Required Action ibnge - Greater than 5 times Reference Velocity or greatet than 0,70 inches per second (Peak). E Reference Velocity t: hall be the usetage overall velocity determined durice -service test at reference conditions when the pump is kn . . a be operating acceptably.

In addition to the above quantitative analysis of o'cerall vibration lesels, for all pumps vibrvion signatures will be reviewed at least quarterly to identify potential bearing de,radation or other developing faults. When potential faults are identified, action, as required fo a pump in the Alert Range of vibration will be initiated.

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Editf_1kguest No. RR-lWP-1(Continued)

Alternate Testi - 'ontinued)

The Service Water Pump maximum values shall be:

Alert Range - 2.5 to 5 times Reference Velocity or greater than g 0.65 inches per second.

Required Action Range - Greater than 5 times Reference l Velocity or greater than 1.0 inches per second. l

,!dition, when Service Water Pump vibration levels are in the Alert Range, pump shaft displacement measurements will be madc whenever pump vibration measurements are requ; red.

These measurements taken directly on the pump shaft rather than the the relatively stiff pump casing or bearing housing are most indicatise of actual pump conditions. Pump shaf t displacement will be limited to 30 mi!s. If pump shalt displacement exceeds 30 mils the pump will je declared in the Required Action range and appropriate corrective actions taken.

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1 Edid_Reuur1LN0h RR-lWV-3 Xahr Containment Spray lleader Check Valves 2-CS-5 A, 2-CS-511 Qttegury A and C Gdit 2 Eundien inside containment check vahes in the Containment Spray header.

i Su ve as nside comainment isolation valve on a line u hich is open to containment atmosphere and penetrates the containment boundary.

Codc_Rdstente Article IWV-3521 and 3522 g Test Requitentent Exercise full stroke every three mumbs.

Untitter_Jittid Valve operation cannot be verified during reactor operations since the valves are inaccessible during plant operation. Water cannot be used for this test since massive containment wetting would occur if fuh or partial flow was passed through this valve. Thus the valve cannot be tested with fluid flow under any plant conditions.

AllcInale_Iriting Disassemble, exan: ne and full stroke one valve each refueling outage. A partial 'troke test (with air) will be performed prior to returning the valve to service following disassembly for examination.

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l RelisLRegucilh RR-1WV-5 Yalic 2-CS-15 A, 2-CS-150 Gregory C Dan 2 Eunction Prevent backflow from the Safety injection System suction header to the Conta:'nment Sump.

Code Requirement Article IWV-3521 and 3522 l Test Requirement Exercise full stroke every three months.

l} asis for Relief These valves cannot be stroke tested using system fluids. To attempt to do to would require filling the containment to design post-accident water depth and drawing water from the containment with safety-related pumps. This would result in massive spread of radioactive contamination.

Alternate 'f esting Part stroke exercise valve every three months. Disassemble, examine, and full stroke exercise one valve each refuelin 4 outage.

A partial stroke test will be performed prior to returni . .- valve to service following disassembly for examination.

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11 licLRegunLN2 RRlWY-6 Y.ahr 2-SI-215, 2-SI-225, 2-SI-2.15, 2-SI-245 Cattgen C Cla13 1 Euntlion l'revent backflow into the Safety injection Tants. Allow Iapid discharge of the safety injection tank in the esent of a loss-of-coulant accident.

Cede _EtyuitcDient Article IWV 3521 and 3522 l leideyuittmeni lixercise full stroke every three months Basis _feLRthef Valves cannot be full stroke exercised during actor operations, cold shutdov,n or refueling since design flow :nnot be achieved during any norinal operation. Whes cannut t. mart stroke tested during reactor operation since failure of the ' ...e isolation valve to shut would icsult in loss of safet) .non tant level and conscquent plant shutdown. Further, if uie vahe failed to resent only single valve isolation would exist tietocen the reactor coolant sptem and the low pressure safety iri etion tank. The flow rates available through the small diameter test line would not sesult in significant operation of the valves during operation or cold shutdown.

Aliculats_Intjug Full strole exercise each valve if

.oring refcan acceptable non-intrusive monitoring techniques ueling outages be used. g ll l unable to full strole exercise disasientble, examine, anu full stroke test one valve each refueling outape. A partial stroke test will be performed prior to returning the valve to service following disassembly for examination.

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4 e IkliclJkuuciLNu. l(11-IWV-9 Yahr 2-SI-217, 2-51-22 7, 2-SI-237, 2-S1-217 Cillrgeix C Clithh i I!unctien l'revent backflow from iteactor Coolant System io safety injection header. Allow rapid discharge of the safety injection tank and injection of water to the scactor coolant system in the esent of a loss-of-coolant accident.

Cedt'kkirner Aiticle IWY-3521 and 3522 g It1Lik4ulisluent Excreise f o'l sitole eve y thsee months ljabilleL}kliti Vahes cannot be full sitole or past situle exercised during teactor opelations since titcle is no pf essute soulee able to o\creome f(cactor Coolant System Pressute which can fully open the valves.

Valves cannot be pari stroke tested during scactor operation since injection of cokl water wouhl lesult in an unacceptable thermal shock to the safety injection norile. Valves cannot be full stroke tested during cold shutdown and refueling since these is no source of water able to provide full design flow.

Alleinattlriling Full stroke exercise each valve during refueling outages il acceptable non-intrusisc monitoring techniques can be used. II l unable to f ull strole exercise then disassemble, examine, and f ull stroke test one valve cach lefueling outage. A partial stioke test will be performed prior to icturning the valve to se vice following disassembly for examination, 8

4 RelicLReyuchLNo. Ill(-lWV- 13

.\'uhe 2-l;W-5 A, 2-l:W-51)

Categely 1.1and C Cidu 2 hultliel) Prevent bacLilow in main feed line to No. i Steam (icnerator and No. 2 Steam Generator.

Code lieference Article IWV-3113 and 3115 g Icillicquirement lisercise full strole and measure strole time eseiy three months.

Test for fail-safe operation.

Dmidedidici Valve exercise during icactor operation would require stopping feed flew to the steam generator with consequent plant shutdown.

Valve has no part strole capability. Valve actuator is not connected to valve disk. Dist cannot be exercised during cold shutdown or refueling.

These sahes have no safety function in the open position.

While the valve will normally close during shutdown from power operation, and valve closure can be visually determined, there is no practical method to meet the Code requirement to " prove that the disk travels to the seat promptly on cessation or reversal of flow." Deliberate, abrupt cessation or reversal of flow in the 18-diameter feed line is not considered prudent. Such action could result in system damage or undesirable tiansients in steam generator level.

AltenlatcJnting lixercise vahe operator, measure stroke time and fail-safe test during cold shutdown 1)isassemble, examine, and test one valve each refueling outage. A partial stroke test will be performed piior to returning the valve to service following disassembly for examinatloc.

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