ML20043D525

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Summary of 900511 Meeting W/Util in Rockville,Md Re Facility Steam Generator Tube Integrity.Attendance List Encl
ML20043D525
Person / Time
Site: Millstone 
Issue date: 05/29/1990
From: Vissing G
Office of Nuclear Reactor Regulation
To:
Office of Nuclear Reactor Regulation
References
NUDOCS 9006080174
Download: ML20043D525 (36)
v • d • e


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g NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C 20555

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May 29, 1990 Docket No. 50-336 LICENSEE: Northeast Utilities FACILITY; Millstone, Unit No. 2

SUBJECT:

SUMMARY

OF MEETING WITH REPRESENTATIVES OF NORTHEAST UTILITIES CONCERNING THE STEAM GENERATOR TUBE INTEGRITY OF MILLSTONE, UNIT 2.- MAY 11, 1990 INTRODUCTION On May 11, 1990, representatives of the NRC and Northeast Utilities (the licensee) met in the NRC office in Rockville, Maryland to discuss the licensee's plans for a steam generator tube inspection at Millstone 2 during the current shutdown. The attendance list is provided in Enclosure 1.

A copy of the slides presented at the meeting is provided in Enclosure 2.

DISCUSSION The licensee had originally been scheduled to discuss the basis for operation to the end of the current cycle (September 1990) without a steam generator tube inspection. However, due to an increasing trend of primary to secondary lea cage from May 8 to 10, the licensee decided to go to cold shutdown and 4

l perform a steam generator tube inspection. The plant was at hot shutdown due to a manuel shutdown to repair a. automatic feedwater valve. The unit had L'

been operating with 20 to 30. gal / day indicated primary to secondary leakage and by May 10 leakage had increased to 80 to 90 gal / day which was at about 3/4-of =

  • he TS limit.

The licensee indicated that the Corporate mission statement charges them to provide a safe, dependable and economical sound energy-source. The company fosters an environment to consider differing opinions from their technical staff. Staff opinions are given consideration by the corporate management in making final corporate decisions. Sometimes the decisions may be different o

l-than some staff opinions. With respect to their belief that continued operation through this cycle without a shutdown for steam generator repair, given that no increase leakage existed, the licensee had considered the opinions of the technical staff.

l The licensee plans to do a 100% inspection of the affective area with a rotating pancake coil inspection and an UT inspection of tubes with detected cracks. They predict less than 40 defective tubes with cracks. They will not be inspecting for pits. They expect 150 to 200 man rems for the inspection and direct costs of $10,000,000. They plan on a 35 day outage for the inspection.

I A report on' inspection results will be presented following the inspection.

They will be using a nitrogen overpressure to detect the leak. One concern i that they will not find the leak.

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. May 29, 1990 The licensee has made the decision to replace the steam generators in 199?,

i during shutdown following the next cycle. The new steam generators will be delivered in April 1991 and the licensee might be able to install them before 1992. The steam generator replacement cost will be approximately $186,000,000 and.will take less than 6 months to complete, j

i The licensee reviewed their approach to support their operation if they would not have had an increase in primary to secondary leakage. The licensee had two models to predict crack growth and in their probabilistic determinations it did not make much difference in the end result which model was used. With a steem i

generator tube rupture they estimated '7 man rems of exposure. They were not concerned for a circumferential crack developing into a full tube break from fatigue. The licensee indicated that they needed an extreme steam line break or feedwater line break to result in a large enough delta p to have a tube J

rupture.

The A Steam Generator has a 180 tube margin before reaching the plugging limit.

t Approximately 20% of the A Steam Generator tubes are plugged. The future operation of M111 stone'2 is dependent on what is found during this inspection.

Whether to have a meeting and/or a submittal following the inspection will be i

determined after reviewing the inspection results. The staff agreed that in as much as the plant is shutdown for a steam generator inspection, the sub-mittal of-June 1,1990, that was a commitment of the licensee's May 10, 1990 letter, is not necessary.

i

/s/

Guy S. Vissing, Senior Project Manhger 3

Project Directorate I-4 Division of Reactor Projects - 1/II L

l Office of Nuclear Reactor Projects

Enclosures:

l As stated cc w/

Enclosures:

See next page i

DISTRIBUTION _

@ Docketfile > '

E. Jordan (MNBB 3302)

NRC & Local PDRs M. Caruso (13E4)

F. Miraglia C. Cheng (9H15)

J. Partlow E. liurphy (9H15)

PDI-4 Rdg.

H. Conrad (9H1B)

J. Stolz J. Richardson (8H3)

S. Norris A. Thadani (8E2)

G.'Vissing ACRS (10)

OGC J. Caldwell (17G21)

S N:LAPDI-4)

PM-4 PD:

s ng:rc JStol S/d9/90 f//f/90

[/g/90 DOCUMENT HAME: MS MILLSTONE 2 5/11

Mr. Edward J. Mroczka Millstone Nuclear Power Station Northeast Nuclear Energy Company Unit No. 2 cc:

Gerald Garfield, Esquire R. M. Kacich, Manager Day, Berry and Howard Generation Facilities Licensing Counselors at Law Northeast Utilities Service Company City Place Post Office Box 270 Hartford, Connecticut 06103-3499 Hartford, Connecticut 06141-0270 W. D. Romberg, Vice President D. O. Nordquist Nuclear Operations Director of Quality Services Northeast Utilities Service Company Northeast Utilities Service Company Post Office Box 270 Post Office Box 270 Hartford, Connecticut 06141-0270 Hartford, Connecticut 06141-0270 Kevin McCar. thy, Director Regional Administrator Radiation Control Unit Region I Department of Environmental Protection U. S. Nuclear Regulatory Commission State Office Building 475 Allendale Road Hartford, Connecticut 06106 King of Prussu, Pennsylvania 19406

, Bradford S. Chase, Under Secretary First Selectmen Energy Division Town of Waterford Office of Policy and Management Hall of Records 80 Washington Street 200 Boston Post Road Hartford, Connecticut 06106 Waterford, Connecticut 06385 S. E. Scace, Nuclear Station Director W. J. Raymond, Resident Inspector Millstone Nuclear Power Station Millstone Nuclear Power Station Northeast Nuclear Energy Company c/o U. S. Nuclear Regulatory Commission Post Office Box 128 Post Office Box 811 Waterford, Connecticut 06385 Niantic, Connecticut 06357 J. S. Keenan, Nuclear Unit Director Charles Brinkman, Manager Millstone Unit No. 2 Washington Nuclear Operations Northeast Nuclear Energy Company '

C-E Power Systems Post Office Box 128 Combustion Engineering, Inc.

Waterford. Connecticut 06385 12300 Twinbrook Pkwy Suite 330' Rockville, Maryland 20852

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ENCLOSURE 1 ATTEllDANCE LIST FOR MEETIllG WITH NORTHEAST = UTILITIES CONCERNIllG r

STEAM GENERATOR TUBE INTEGRITY-AT MILLSTONE 2 - MAY 11, 1990 NAME ORGANIZATION Guy S. Vissing, Project Manager NRR/PDI-4 Fred Sears, VP-Nuc & Env. Eng.

Northeast Utilities--

' Steve Scace,-Director - Millstone Station Northeast Utilities Matthew Kupinski, Manager - Piping Systems Engr.

Northeast Utilities David Peiffer, Millstone 2 Chemistry Northeast Utilities

'Rik Wells, Manager - NMC Northeast Utilities i

Paul Parulls, Senior Eng. - Millstone U-2 Northeast Utilities Mark Caruso. Section Chief, Reactor Syst. Br.

NRC/NRR C. Y. Cheng, Branch Chief NRR/DET/EMCB Emmett Murphy, Materials Branch NRR/DET/EMCB.

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H. F._Conrad, Materials Branch NRR/DET/EMCB

'J. F. Stolz, Project Director - PDI-4 ilRR/DRP J. E. Richardson, Director - Division of Eng. Tech.

NRR/DET A. Thadani, Director - Div. of Systems Technology.

NRR/DET Ji

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i MILLSTONE UNIT 2

STEAM JET AIR EJECTOR RADIATION MONITOR SPIKING MAY 1990 i

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MILLSTONE UNIT 2 I

STEAM JET AIR EJECTOR RAD MONITOR SPIKING.

BEFORE APRIL 28, 1990 THE SPIKING IS A RESULT OF ACTIVITY IN THE RADIATION MONITOR AND IS NOT AN ELECTRONIC NOISE PROBLEM THE LEAK IS NOT A DIRECT LEAK FROM THE PRIMARY TO SECONDARY SIDE OF THE STEAM GENERATORS. THERE IS A MECHANISM WITHIN THE LEAKAGE PATH WHICH IS CAUSING A DELAY PERIOD IN THE SPIKING EVENT THE CAUSE OF THE SPIKING DOES NOT APPEAR TO BE THE DIRECT RESULT OF AN ACCUMULATION OF ACTIVITY IN THE SECONDARY PLANT WHICH IS THEN RELEASED TO THE l

CONDENSER BASED UPON THE RESPONSE OF THE SPIKING, THE READING OF THE RADIATION MONITOR IS NOT INDICATIVE OF AN INSERVICE CRACKED OR PITTED TUBE SPIKE EVENT QE APRIL 11. 1990

- THERE WAS NO DELAY MECHANISM PRESENT DURING THE EVENT THROUGHOUT THE DAY ON SATURDAY AND SUNDAY THIS EVENT APPEARS TO-BE A DIRECT PRIMARY TO SECONDARY LEAK THE. EVENT MAY BE THE COMBINATION OF A DIRECT LEAK CAUSED BY PLANT PERTURBATIONS AND AN INDIRECT LEAK CHARACTERISTIC OF PREVIOUS EVENTS THIS EVENT VERIFIED THE EFFECTIVENESS OF THE N16 RAD MONITOR IN TRACKING A DIRECT PRIMARY TO SECONDARY LEAK i

THERE WAS NO LARGE ACTIVITY SPIKE ASSOCIATED WITH TNIS EVENT, ie; ACTIVITY REMAINED UNDER 2000 CPM P

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c MILLSTONE UNIT 2 STEAM JET AIR EJECTOR SPIKING THE SPIKING IS A RESULT OF' ACTIVITY IN THE RADIATION MONITOR AND IS NOT AN ELECTRONIC NOISE PROBLEM o Grooming performed with known sample for 24 hr period.

Monitor straight line tracked sample with no evidence of spiking.

o Grab-samples were taken when spiking occurred. Sample activity consistent with rad monitor spike activity.

o Temporary Rad Monitor installed st chemistry gas sample point upstream of SJAE'RM. Both monitors track activity changes.

o Tritium samples showed elevated activity during a long spiking event.

THE LEAK IS NOT A DIRECT LEAK FROM THE PRIMARY TO SECONDARY. THERE IS SOME MECHANISM WITHIN THE LEAKAGE PATH CAUSING A DELAY IN THE SPIKING EVENT.

o Installed N16 monitors checked during spiking events show no increased activity. N16 is extremely sensitive to short lived activity which would be generated from a direct primary to secondary leak.

o Decay ratios'of isotopes of Xenon, Argon and Krypton from primary and secondary samples indicate a delay time from 10 to 30 minutes.

THE CAUSE OF THE SPIKING DOES NOT APPEAR TO BE THE DIRECT RESULT OF AN ACCUMULATION OF ACTIVITY IN THE SECONDARY PLANT WHICH IS THEN RELEASED TO THE CONDENSER o A test was performed utilizing the injection of helium in the neck of the condenser. The' helium detector was placed near the SJAE= rad monitor sample tap. Immediate response was noted with no activity or accumulation hold up detected as long as 30-40 minutes later.

o Future-tests being planned to further substantiate this fact.

BASED UPON THE RESPONSE OF THE SPIKING, THE READING OF THE RADIATION MONITOR IS NOT INDICATIVE OF AN INSERVICE CRACKED OR PITTED TUBE o The evidence of activity decay time' indicates a situation.t pical of a leak into an out-of-service or repaired tube, o The most probable configurations are: 1) cracked mechanical plug; 2) leaking welded pluo; 3 tube ovality with an installed mechanical plug;)and 4) installed mechanical sleeve

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4 MILLSTONE UNIT 2 STEAM JET AIR EJECTOR SPIKING TOUR TYPES OF SPIKING EVENTS

1) SMALL, SHORT DURATION SPIKES o Activity increases a few hundred counts above baseline o Event lasts a few seconds to a few minutes o Normally not associated with a Blowdown isolation o Most numerous of the spiking events Average Frequency: 1 to 10 per day o Longest activity decay delay ratiost 30 minutes o No N16 response
2) LARGER, SHORT DURATION SPIKES i

o Activity increases of thousands of counts above baseline o Event lasts a few seconds to a few minutes o Usually associated with Blowdown isolation o Average Frequency from a few per day to a few'per week o Activity del 3y ratio reduced 10-20 minutes o No N16 response

3) HIGH ACTIVITY, LONG DURATION o Activity increases Wickly by a few thousand counts in a short period of time (similar to 2), then reduces to some lower level and tapers off to original baseline over time o Event may last for days before settling back to a lower baseline o BloWJour isclGtion occurs o only 3 of these events have been recorded.

The Apr 7th event was the greatest magnitude and duration o Activity delay ratio as fast as 10 minutes o No N16 response

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MILLSTONE UNIT 2 STEAM JET AIR EJECTOR SPIKING 1

4) LONG DURATION, DIRECT PRIMARY TO SECONDARY o Indications of direct primary to secondary leakage o Activity ratios show no delay mechanism o N16 indicates and tracts direct leakage from S/G #1 o SJAE activity remained less than 2000 cpm throughout the event o Baseline activity at a higher plateau than before the event (600 cpm vs 200 cpm) 9 v

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1.0000 01/1S/90 15:58 700 13.6660 01/16/90 00:00 kM S.P.= 600 01/18/90 02:23 1,000 2.4340 01/18/90 19:16 1,000 0.7028 01/18/90 20:40 1,000 0.0590 01/19/90 00:00 RM S.P.= 800 01/19/90 19:14 2,000 0.9403 01/20/90 03:28 1,000 0.3431 01/22/90 01:30 970 1.9181 01/23/90 08:45 1,000 1.3021 2.4450 01/25/90 02:31 1,172 1.7403 01/2S/90 21:12 1.300 0.7785 01/26/90 00:54 600 0.1542 01/26/90 02:00 1,500 0.0458 01/24/90 09116 000 2.3021 01/28/90 17:00 2,000 0.3229 01/29/90 00:14 1,000 0.3042 01/30/90 15:05 900 1.6160 01/31/90 00:17 1,000 0.3833 01/31/90 06:16 1,000 0.2493 0.7497 02/01/90 03:19 1,000 0.4771 1.SS69 02/01/90 21:10 1,000 0.7438 02/04/90 08:30 7,000 2.4722 02/05/90 01:07 980 0.4924 02/05/90 02:25 1,300 0.0542 02/06/90 09 22 880 1.4=?4

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\\._/14/90 09:23 1,130 0.0139 02/14/90 10:30 1,200 0.0465 0.0603 02/15/90 00:00 RM S.P.= 2000 02/17/90 07:40 3,000 2.8819 0.6760 02/19/90 07:05 2,400 1.9757 02/20/90 08:40 2,500 1.0660 02/20/90 09t26 S,000 0.0.13 02/20/90 17655 3.100 p.J547 02/22/90 14:27 2.300 1.8556 02/26/90 10:35 2,490 3.8389 02/28/90 00:00 RM SP = 4000 1

02/28/90 03 05 2,000 1.6875 1

03/01/90 09:05 4,363 1.2500 03/02/90 06:00 4,800 0.8715 1.5813 03/05/90 00:56 9.200 2.7899 0.7800 03/05/90 19:10 6,200 0.7697 03/07/90 08129 7.000

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MILLSTONE UNIT 2 STEAM JET AIR EJECTOR RAD MONITOR SPIKING SINCE APRIL 10, 1990 l

l DATE TIME ACTIVITY (CPM)

CAUSED BLOWDOWN ISOL I

4/18 1030 500 YES 4/18 2143 3500 YES 4/20 2137 2000 YES 4/23 1114 1100 YES 4/23 1602 2700 YE3 4/26 2000 3200 YES 4/28 0320 1600 **

YES 1

START OF EVENTS ASSOCIATED WITH APPARENT DIRECT PRIMARY TO SECONDARY LEAKAGE TIME S/G 1 N16 S/G 2 N16 SJAE 0320 12.8 GPD 0.35 GPD 21.6 GPD 0550 16.0 GPD 0.30 GPD 26.0 GPD

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Unit 2 Steam Generator Update The Unit 2 Steam Generators continue to be a focus of the steam generator blowdown system and the Unit 1 attention and interest both in the media and within our stack (our release paths to the environment), the Station. This messenger provides an update and steam line N16 monitors as well as sampling systems.

further discussion of the steam generator status.

These other indicators,are showing normal indications for operating conditions.

In a Messenger published last week, the periodic l

spiking of the Unit 2 steam jet air ejector (SJAE)

To help put the current situation in perspective, note l

radiation monitor was discussed.

That spiking is that radia' ion is detectable at truly microscopic levels.

centinuing at a frequency of once or twice a day, in The Radiological Assessment Branch of NUSCO l

addition, a radiation monitor on the main steam line has calculated the dose that would be received by someone

)

i begun to spike also. At this time, we do not believe the who stayed at the site boundary 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> a day for one two ere related. This is based on two considerations:

year with a daily spike of 10,000 counts per minute.

(The average SJAE spike is now 4000 cpm. The

1) If the two spikes were measuring the same highest recorded levol of 9200 cpm has occurred only radioactive matter, the Main Steam Line twice in three months).

That dose would be 4 monitor would spike first, then the SJAE millionths of 1 milliRomi The dose that one recolves by monitor would spike. This is because the flying round trip coast to coast one time is about 4 main steam line monitors are upstream of milliRom.

the SJAE monitor, in f act, the main steam line spikes occurred both before and after The staff at Millstone Unit 2 and supporting corporate the SJAE spike. This indicates that the resources are not being complacent about safe spkes are unrelated. We continue to monitor operation of the unit. We are vigorously pursuing for correlation between the various courses of action that will help us to understand the parameters that we are monitoring, situation without ambiguity.

This includes the j

acquisition of an adcitional portable monitor to detect J

2) The design and purpose of the main steam low energy gamma. This will be used to monitor line monitors is for measuring high levels of selected steam trape and drains to the condenser. This radiation that would be present if,a investigation will help to confirm our understanding of significant tube leak or rupture had the situation,
occurred, if actual radiation levels were present at the levels indicated on the steam While it may sound as though the conservative course line monitor spikes, the SJAE monitor would to take would be to preemptively shut down the unit, receive a significantly higher signal and that is not the best course of action. Beside our strong several other indications would also be conviction that Unit 2 is safe to operate, the small size o

present. The current behavior of the main and intermittent nature of whatever leak may be steam line and SJAE monitors just don't add present makes it unlikely that we would find it. The up to a common cause, search activities would add to the exposure of our staff and increase radioactive waste. As long as our We continue to believe the leak path is as described in' assessment continues to indicate we can operate last wuk's Messenger. The main steam line monitor Millstone 2 safely, it is not prudent to shutdown and spikes appear to be an intermittent malfunction of the incur these personnel and environmental impacts.

monitor. This is being investigated, if the situation changes, we will address conditions 11 is important to remember that there are other proactively to ensure that the safe operation of the monitors and means of measuring the condlion of the unit is maintained,

[

i Unit 2 steam generators. These include monitors on l March 29 1990 Millstone Messenger Page 1 l

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MILLSTONE UNIT 2 STEAM GENERATOR LEAK DETECTION: METHODS STEAM JET AIR EJECTOR RADIATION-MONITOR STEAM GENERATOR BLOWDOWN RADIATION MONITOR STEAM GENERATOR BLOWDOWN' GRAB SAMPLES N16 RADIATION MONITORS PLANT' PROCESS COMPUTER (DAILY LEAK 2AT!; CALCULATION)

TEMPORARY SJAE RADIATION MONITOR MAIN STEAM RADIATION MONITORS TRITIUM-CALCULATION SJAE GRAB SAMPLES

s]

MILLSTONE UNIT 2 STEAM JET AIR EJECTOR RAD MONITOR SPIKING l

CONCLUSIONS i

THE SPIKING IS REPRESENTATIVE OF ACTUAL OCCURRENCE AND NOT NOISE OR INSTRUMENT PROBLEMS THE SPIKING EVENTS ARE OCCURRING IN A RANDOM FASHION, ALTHOUGH PLANT PERTURBATIONS APPEAR TO DRIVE SOME EVENTS SPIKING DOES NOT APPEAR TO BE THE DIRECT RESULT OF ACCUMULATION OF ACTIVITY IN THE SECONDARY PLANT

~ THERE ARE FOUR DISTINCT TYPES OF SPIKES 1) LOW ACTIVITY, SHORT DURATION; 2) HIGHER ACTIVITY, SHORT DURATION;

3) HIGHER ACTIVITY WITH A MID RANGE PLATEAU, LONG DURATION; 4) LONG DURATION, DIRECT PRIMARY / SECONDARY l

THE DELAY MECHANISM HAS SOME RELATIONSHIP WITH SPIKING ANY ONE OR MORE LEAKING PLUGS CAN YIELD A LEAK RATE EQUAL TO OR IN EXCESS OF THE PRESENT LEAK RATE PRIMARY TO SECONDARY-LEAKAGE WITH A DELAY MECRANISM CAN OCCUR THRU CRACKED PLUGS, SLEEVES, OVALIZED TUBES AND WELDED PLUGS THERE ARE NUMEROUS METHODS AVAILABLE AT MP2 TO DETECT AND MONITOR STEAM GENERATOR PRIMARY TO SECONDARY LEAKAGE l

THE LEAK RATE AND SPIKING AT MP2 ARE NOT SIMILAR TO EVENTS THAT OCCURRED AT OTHER PLANTS PRIOR ~TO TUBE RUPTURE THE-EVENTS OF APRIL 28TH WERE THE FIRST INDICATIONS OF DIRECT PRIMARY TO SECONDARY LEAKAGE THE IMPACT ON THE GENERAL PUBLIC FROM THE LEAK RATE AND SPIKING EVENTS IS MINIMAL e

9 s 0

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