ML20149J337

Provides Update on 2.206 Petition That Recipient Submitted on 970410.Petition Requested NRC Take Actions Re Nuclear Facilities That Northeast Utilities Operates in Connecticut. Director'S Decision Expected to Be Issued Shortly

ML20149J337
Person / Time
Site:	Millstone, Haddam Neck  File:Connecticut Yankee Atomic Power Co icon.png
Issue date:	07/21/1997
From:	Mcdonald D NRC (Affiliation Not Assigned)
To:	Gunter P, Katz D CITIZENS AWARENESS NETWORK, NUCLEAR INFORMATION & RESOURCE SERVICE
References
2.206, NUDOCS 9707280172
Download: ML20149J337 (19)

Text

t UNITED STATES g ) j NUCLEAR RE'JULATORY C3MMISSION l

.  % t CASHIN2TCN, O.C. 20555 4001

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July 21, 1997 g - m /jqd s / W 3 1

Deborah Katz, President l Citizens Awareness Network l P.O. Box 83 l Shelburne Falls, MA 03170 Paul Gunter, Reactor Watchdog Project l Nuclear Information and Resource Service l 1424 16th Street, NW., 4th Floor Washington, DC 20036 l

Dear Ms. Katz and Mr. Gunter:

1 1

The surpose of this letter is to provide an update on the 2.206 Petition that l you 1 ave submitted. The initial update was provided by letter dated April 10, 1997. The Petition was filed pursuant to Title 10 of the Code of Federal Reaulations (10 CFR) Section 2.206 on November 25, 1996, and amended on December 23, 1996. The Petition requested that the U.S. Nuclear Regulatory Commission (NRC) take actions regarding the nuclear facilities that Northeast  ;

Utilities (NU or Licensee) operates in Connecticut. l The Petition was submitted by you on behalf o.f the Citizens Awareness Network ,

(CAN) and the Nuclear Information and Resource Service (NIRS) (Petitioners).

In your December 23, 1996, amendment to the Petition, you requested that the NRC provide copies of calculations to the Petitioners that were referred to by the Licensee at the November 1996, enforcement conference. The calculations were performed by the Licensee to determine the reactor vessel water level as the result of nitrogen inadvertently entering the reactor coolant system.

Actually, the presentation you refer to was a public predecisional enforcement conference held on Decmber 4,1996, at the Hillstone training building in Waterford, Connecticut. Ms. Katz confirmed, during a telephone conversation on July 17, 1997, that the calculations requested were the ones referred to by  !

the Licensee at the December 4, 1996, cor.ference.

By letter dated July 3,1997, the Licensee provided information, including the requested calculations, relating to the different methods used for determining the reactor vessel water level resulting from the nitrogen intrusion event.

This information has been placed in the NRC's Public Document Room and the ,

Local Public Document Ronm. l We are providing the enclosed calculations to you as a courtesy since the calculations are relevent to your concern, are not proprietary, and are in the public domain.

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'00043 i DFO\ i I NBC FRE CEMER W 9707280172 970721 PDR ADOCK 05000213 G PDR _

t Deborah Katz and Paul Gunter We are continuing our review of your Petition and expect to issue a Director's Decisi on shortly.

If you have any questions,-please contact me at (301) 415-1408.  ;

Sincerely, -

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Daniel G. Mcdonald Jr., Senior Project Manager Special Projects Office - Licensing Office of Nuclear Reactor Regulation

Enclosure:

As stated cc w/ enc 1: Rosemary Bassilakis, Researcher Citizens Awareness Network 54 Old Turnpike Road Haddam, Connecticut 06438 t

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Deborah Katz and Paul Gunter -2 July 21, 1997 We are continuing our review of your Petition and expect to issue a Director's Decision shortly.

If you have any questions, please contact me at (301) 415-1408.

Sincerely, Original signed by:

Daniel G. Mcdonald Jr., Senior Project ~ Manager Special Projects Office - Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-245, 50-336, 50-423 and 50-213

Enclosure:

As stated cc w/ encl: Rosemary Bassilakis, Researcher Citizens Awareness Network 54 Old Turnpike Road Haddam, Connecticut 06438 DISTRIBUTION:

Docket File" PUBLIC SP0-L Reading SP0 Reading WTravers PMcKee LBerry DMcDonald SDembek JAndersen MFairtile EHylton OCA RHoefling, OGC Licensee and Service List .

DOCUMENT-NAME: G:\ MCDONALD \ PET.00' to w . ..n .e w. e.om..t. wa.. . w v wx: c . con woout .n.com.ou.nce.g r - con we .u.h.nf.new.or. v Nocopy 0FFICE SPO-L:PM SP0-l.:LAh M & OGC ///) /P~l SPO+L:DD / l l NAME DMcDonalV M /LBerry V,U rho $1tinf PMcKeb /

DATE 07/ Y7/97N'7' 07/n/97 \ 07/ 2[/97 07/4V97 07/ /97 0FFICIAL RECORD COPY

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Northeast Nuclear Energy Company Millstone Nuclear Power Station Units 1, 2, and 3 cc:

Lillian M. Cuoco, Esquire Mr. Wayne D. Lanning Senior Nuclear Counsel Deputy Director of Inspections Northeast Utilities Service Company Special Projects 0ffice P. O. Box 270 475 Allendale Road Hartford, CT 06141-0270 King of Prussia, PA 19406-1415 Mr. Kevin T. A. McCarthy, Director Mr. F. C. Rothen Monitoring and Radiation Division Vice President - Work Services Department of Environmental Northeast Nuclear Energy Company Protection . P.O. Box-128 79 Elm Street Waterford, CT 06385 Hartford, CT 06106-5127 Charles Brinkman, Manager Mr. Allan Johanson, Assistant Washington Nuclear Operations j Director .

ABB Combustion Engineering <

Office of Policy and Management 12300 Twinbrook Pkwy, Suite 330 i Policy Development and Planning Rockville, MD 20852 Division 450 Capitol Avenue - MS 52ERN Mr. D.-M. Goebel P. O. Box 341441. Vice President - Nuclear Oversight l Hartford, CT 06134-1441 Northeast Nuclear Energy Company l P. O. Box 128 Regional Administrator, Region I Waterford, CT 06385 U.S.~ Nuclear Regulatory Commission 475 Allendale Road Mr. M. L. Bowling, Jr.

King of Prussia, PA 19406 Recovery Officer - Millstone Unit 2 Northeast Nuclear Energy Company First Selectmen P. O. Box 128 Town of Waterford Waterford, CT 06385 Hall of Records 200 Boston Post Road Senior Resident Inspector Waterford, CT 06385 Millstone Nuclear Power Station c/o U.S. Nuclear Regulatory Commission i

Mr. J. P. McElwain P. O. Box 513 Recovery Officer - Millstone Unit 1 Nia:.ic, CT 06357

, Northeast Nuclear Energy Company P. O. Box 128 Mr. J. K. Thayer Waterford, CT 06385 Recovery Officer - Nuclear Engineering and Support Neil S. Carns Northeast Nuclear Energy Company Senior Vice President P. O. Box 128 and Chief Nucleaar Officer Waterford, CT 06385 NortNeast Nuclear Energy Company

, c/o Ms.. Patricia A. Loftus Director - Nuclear Licensing Services P.O. Box 128 Waterford, CT 06385

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4 Northeast Nuclear Energy Company Millstone Nutlear Power Station Units 1, 2, and 3 cc:

Mr. M. H. Brothers Little Harbor Consultants, Inc.

Vice President - Millstone Unit 3 Millstone - ITPOP Project Office Northeast Nuclear Energy Company P. O. Box 0630 P. O. Box 128 Niantic, Connecticut 06375-0630 Waterford, CT 06385 Mr. Evan W. Woollacott Mr. M. R. Scully, Executive Director Co-Chair Connecticut Municipal Electric Nuclear Energy Advisory Council Energy Cooperative 128 Terry's Plain Road 30 Stott Avenue Simsbury, Connecticut 06070 Norwich, CT 06360 Mr. Daniel L. Curry Mr. William D. Meinert Project Director l Nuclear Engineer .

Parsons Power Group, Inc. l Massachusetts Municipal Wholesale 2675 Morgantown Road Electric Company Reading, Pennsylvania 19607 P. O. Box 426 j Ludlow, MA 01056 Mr. Don Schopfer i Verification Team Manager Ernest C. Hadley, Esq. Sargent & Lundy 1040 B Main Street 55 E. Monroe Street P. 0. Box 549 Chicago, Ilinois 60603 West Wart. ham, MA 02576 Joseph R. Egan, Esq.

Egan & Associates, P.C.

2300 N Street, NW Washington, D.C. 20037 Citizens Regulatory Commission ATTN: Ms. Susan Perry Luxton 180 Great Neck Road Waterford, Connecticut 06385 4 The Honorable Terry Concannon Co-Chair -

Nuclear Energy Advisory Council Room 4035 Legislative Office Building

. Capitol Avenue Hartford, Connecticut 06106

Northeast Utilities Service Company Haddam Neck Plant Docket No. 50-213 cc:

Lillian M. Cuoco, Esq. Resident Inspector Senior Nuclear Counsel Haddam Neck Plant Northeast Utilities Service Company c/o U.S. Nuclear Regulatory Commission P. O. Box 270 361 Injun Hollow Road Hartford, CT 06141-0270 East Hampton, CT 06424-3099 Mr. Kevin T. A. McCarthy, Director Mr. James S. Robinson Monitoring and Radiation Division Manager, Nuclear Investments and Department of Environmental Administration Protection New England Power Company 79 Elm Street 25 Research Drive Hartford, CT 06106-5127 Westborough, MA 01582 Mr. Allan Johanson Mr. G. P. van Noordennen Assistant Director Manager - Nuclear Licensing Office of Policy and Management Northeast Utilities Service Company Policy Development and Planning 362 Injun Hollow Road Division East Hampton, CT 06424-3099 450 Capitol Avenue-MS#52ENR P. O. Box 341441 Hartford, CT 06134-1441

. Mr. F. C. Rothen Vice President - Work Services Northeast Utilities Service Company I

, P. O. Box 128 i Waterford, CT 06385 Mr. D. M. Goebel I

, Vice President - Nuclear Oversight L Northeast Utilities Service Company .

P. O. Box 128 j Waterford, CT 06385 <

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Mr. J. K. Thayer Recovery Officer, Nuclear Engineering and Support Northeast Utilities Service Company P. O. Box 128 Waterford, CT 06385 4

Regional Administrator

. Regioitl

i. U.S. Nuclear Regulatory Commission 475 Allendale Road King of Prussia, PA 19406

! Board of Selectmen .

Town Office Building Haddam, CT 06438 f

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Docket No. 50-213 .

!- CY-97-041 : ,

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e Attachment 3  :

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'Haddam Neck Plant j

- Additi onalInformati on For The Nitrogen Intrusion Event Analysis Of The Nitrogen Intrusion Event

. Utilizing RELAPS/ MOD 3 l

- July 1997 1 g ' i )

Enclosure

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U. S. Nucinr Regul: tory Commission

. CY-97-041/ Attachment 3/Page 1 .

Analysis Of The Nitrogen Intrusion Event Utilizing RELAPS/ MOD 3 The inadvertent nitrogen intrusion vent was simulated with the RELAPS/ MOD 3 code in November 1996 to determine the maximum accumulation of nitrogen in the vessel and

'to calculate the resultant displacement of the vessel inventory from the reactor vessel 1 into the pressurizer. Given the rate of the nitrogen inflow to the primary side and the >

vent line resistance to nitrogen outflow from the pressurizer and the reactor, it is q possible to calculate with a system code the minimum level at which the two flows l balance.

The RELAPS/ MOD 3 model of the Haddam Neck Plant (HNP) included the detailed vessel representation, the pressurizer and part of the hot leg. The Icops were not represented since they were isolated during the event. The relative elevations among i the regions have been preserved in the model. The top of the vessel and the pressurizer were connected to a common vent header which provided the release path ,

for the nitrogen and served as the pressure boundary for the system. )

l Nitrogen injection was simulated by a separate junction connected to the top of the downcomer. The junction was supplied by a time-dependent volume representing the i

nitrogen supply tank. The downcomer communicated with the upper head through a small flow path which normally allows some cooling flow into the upper head during power operations. The fuel assemblies in the core were modeled as part of the overall I vessel flow resistance, but the actual decay heat was not simulated. The head vent pipe sizes were based on the 0.5 inch diameter Schedule 80 pipe for the reactor vessel vent, and on 0.75 inch Schedule 80 for the pressurizer vent.

A list of additional parameters is found in Table 1. The noding diagram of the HNP REl.APS/ MOD 3 modelis shown in Figure 1.

RELAP Simulation The simulation was performed in two steps. In the first part, the goal was to achieve a steady-state condition inside the vessel for a given nitrogen injection flow rate. The steady state is defined as the condition characterized by a stable water level inside the vessel, balanced by a column of water inside the pressurizer. Once the levels were stable, the next step was to isolate the N 2. injection and refill the vessel in several steps to match the operator actions over the period of three hours.

U. S. Nucirr R:gulatory Commission CY-97-041/ Attachment 3/Page 2 Before starting the nitrogen injection in the analysis, the initial water levels in the vessel and the pressurizer were allowed to come to a hydrostatic equilibrium with the head vent lines open. With the vessel full, the pressurizer registered the equilibrium levet just above the lower level tap. Once the balance was achieved, the nitrogen injection was initiated into the downcomer. The gas began to flow into the upper head and collected at the highest point, displacing the water from the vessel into the pressurizer. As the level in the pressurizer increased on the way to a new hydrostatic balance, a controller was activated in the code to maintain the level 160 inches above the hot leg by draining off some of the inventory. The code kept track of the discharge volume by integrating the discharged volume. The data shows that the operators drained some 5,000 to 6,000 gallons from the primary side as the level increased in the pressurizer.

In summary, the simulation was tuned to two basic assumptions:

• That the steady-state pressurizer level with nitrogen injection is at 345 inches on the level taps and that the tolerance associated with this readi! g is negligible, and e That the volume of water discharged from the Reactor Coolant System (RCS) is between 5,000 and 6,000 gallons when the steady-state pressurizer level of 345 inches is reached.

The unknown factors in the analysis are:

• The average nitrogen in-leakage rate, and j e The flow resist ~ance of the head vent lines.

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" _ U. S. Nuclecr R:gulatory Commission

. CY-97-041/ Attachment 3/Page 3  :

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1 Results

A. ' Steady State

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_Two' separate. cases _were analyzed, the first assuming the nitrogen injection rate of

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~4 CFM and the second case, which assumed the increased rate of 7 CFM. The higher flow rate is the maximum possible rate calculated from the_ inventory of the gas used by g the plant;over the ,three-day period (30,000 cubic feet), assuming that all of it was L ilnadvertently injected through the charging system into the primary side. Each case was  :

[ run_twice, with a different form loss K-factor to bound the head vent line resistance, F which was not known. The' vent lines typically. hooked up to the vessel and the r pressurizer for refueling. activities are temporary Tygon tubes (see Figure 2 for the diagram of the temporary vent connections). The analysis assumed that the' K-factor

'b equal to 100 would bound the resistance of the vent lines. A lower K-factor, equal to -

ISO was also used The lower number is similar in magnitude to the value calculated for the permanent head _ vent.line, which calculated the frictional losses through the lines. ,

Both vent lines used the same K-factor.

Case 1: 7 CFM N2injection rate and K=50 The results indicate that at this rate the level in the vessel would drop below the hot leg nozzle elevation and the pressurizer would fill up completely. Nitrogen ingestion into the Residual Heat Removal System, which takes suction at the mid-point of the hot leg, would most likely occur. The operators would have.to drain much more than the 5,000 gallons bro the RCS to maintain the level on scale. Since the recorded plant  ;

data shows that O was not the case, it can be concluded that the 7 CFM was not a realistic rate t- M late. -

Case 2: -4 CFM N 2injection rate and K=SO The steady state was achieved after approximately 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> of transient time simulation.

The RCS pressure stabilized at 19 psia in the upper head. The integrated volume of the water discharged from the primary side to maintain the pressurizer level at 345 inches was approximately 5000 gallons. The level inside the vessel stabilized 62 inches above the top of the hot legs.

Case 3: 4 CFM N2injection rate and K=100 The steady. state was reached after 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> of transient time. The pressure in the upper head leveled off at 19.2 psia. The integrated volume of the discharged water

- was 6300 gallons. The water level inside the vessel stabilized at 31 inches above the top of the' hot legs.

-. __ _a __. v _ _ _ - - _ - E_

V I U. S. Nucl::ar Regul tory Commission CY-97-041/ Attachment 3/Page 4 B. Refill of the Vessel The second part of the analysis involved refilling the vessel from the Refueling Water Storage Tank. The data shows that the operators cycled the refill valve six times over approximately a three-hour period. The duration of each cycle and the injection flow rates were scaled from the recorded plant data and the scaled data repiotted on Figure 3 (the time scale is not absolute but is referenced to the time the operators begaii the refill process on the morning of September 1,1996). In RELAP, the cycles were approximated by assuming that each refill cycle lasted two minutes and injected 1,200 gallons, for a total of 7,200 gallons. For conservatism, only Case 3 was analyzed, since the results of the steady state showed the largest inventory loss from the vessel.

Some of the pertinent results from this case, combined with the steady state, are plotted in Figures 4,5, and 6. Figure 4 shows the pressure in the upper head. The end of the steady state is at 12,000 seconds (the times are not related to the operator actions) when the nitrogen injection is isolated. immediately the level starts to decrease in the vessel because of the sudden hydrostatic imbalance, and the pressure begins to decrease. The level comes to rest at 316 inches in the calculation (compared to 321 inches in the data). After 20 minutes, there is an additional nitrogen injection because of the valve cycling by the operator. Forty minutes after the N2 isolation, the operators begin the refill process. As can be seen on the plot, the first cycle increases the RCS pressure by 1.5 psi (compared to approximately 2 psi on the data chart). The subsequent refill cycles show comparable pressure spikes.

Figure 5 shows the pressure plot in the pressurizer. There is very little repressurization, beyond temporary spikes," because the vent line on the pressurizer is larger and capable of venting more gas.

Figure 6 is the integrated mass of water drained from the RCS during the code initiation to steady state (to convert to gallons, multiply by 0.12), which on the data chart is 345 inches on the pressurizer level indicator.

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. 1 U. S. Nucimr Regulatory Commission

-CY-97-041/ Attachment 3/Page 5 Summary

. The inadvertent N 2intrusion event was simu!ated with RELAPS/ MOD 3, which has the non-condensable gas modeling capability. Results of the simulation were compared to I the available plant data recorded during the transient. The analysis shows that the most probable nitrogen average in-leakage rate was 4 CFM.

The resistance of the head vent line was bounded by assuming a lower K-factor equal to 50 and an upper K-factor of 100. Using these values, the level inside the vessel was calculated ' be as low as 31 inches above the top of the hot legs and as high as 62 inchc; above the hot legs The level was sufficient to preclude ingestion of nitrogen into the RHR line.

1 Finally, the refill cycles were dynamically simulated. The actual plant response in terms i of the pressure and level was reasonably predicted. Based on the simulation, an l I

estimated 5,000 to 6,300 gallons of water would have to be drained from the RCS to match the recorded data.

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. CY-97-041/ Attachment 3/Page 6 Table 1 Parameters Used in The RELAP/ MOD 3 Analysis Minimum Pressurizer Level in Steady State 345 inches Elevation Of Hot Leg Center Line 185 inches l

Vent Header Pressure 14.3 psia (10" H2O vacuum) i Temperature inside The Vessel 95"F l

' Loops isolated N2Injection Rate 4 CFM and 7 CFM Vent Line Resistance (Form And Friction) 50 and 100 (2 Cases)

Volume Control Tank (VCT) Pressure 30 psig  !

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U. S. Nuclear Regulatory Commission

- CY-97-041/ Attachment 3/Page 7 Figure i The HNP RELAPS/ MOD 3 Model Configuration For The N 2 Intrusion Event T

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. CY-97-041/ Attachment 3/Page 8 Figure 2 Simplified Air Purge Containment Pipmg Diagram Tyson Wnometer Leops Beed Yunt 10 ladas H2O T

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..CY-97-041/ Attachment 3/Page 9 l Figure 3 I

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