ML20216C737

Safety Evaluation Supporting Amend 158 to License NPF-49

ML20216C737
Person / Time
Site:	Millstone
Issue date:	04/09/1998
From:	NRC (Affiliation Not Assigned)
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ML20216C729	List: ML20216C727 ML20216C737
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NUDOCS 9804150030
Download: ML20216C737 (5)

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UNITED STATES s

j NUCLEAR REGULATORY COMMISSION WASHINGTON, D.c. 30666 4 001 44.....,o SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION l

RELATED TO AMENDMENT NO. 158 TO FACILITY OPERATING LICENSE NO. NPF-42 NORTHEAST NUCLEAR ENERGY COMPANY. ET AL.

l MILLSTONE NUCLEAR POWER STATION. UNIT NO. 3 DOCKET NO. 50-423

1.0 INTRODUCTION

By letter dated November 11,1997, the Northeast Nuclear Energy Company, et al. (the licensee),

submitted a request for changes to the Millstone Nuclear Power Station, Unit No. 3 Technical Specifications (TS). Specifically, TS 3.9.1.2 would (1) be revised to require that the spent fuel pool (SFP) boron concentration be maintained greater than or equal to 1750 ppm whenever fuel assemblies are in the SFP, and (2) require sampling of the SFP every 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to ensure the boron concentration is greater than or equal to 1750 ppm, and that if the boron con entration is found to be less than 1750 ppm, the boron concentration must be restored to at least 1750 ppra within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. TS 3.9.13 would be revised to require that the licensee isolate and administratively control the opening of dilution pathways to the SFP in the event of an Operating Basis Earthquake (OBE) or load drop onto the top of the spent fuel racks and to perform an engineering evaluation (e.g., blackness testing) to determine whether soluble boron is required '.o control k,in the SFP.

2.0 BACKGROUND

Spent fuel from operation of the Millstone Unit 3 reactoris stored in a 61,600 ft pool cooled by S

two 100 percent redundant trains of SFP cooling. Each train of SFP cooling contains a pump and heat exchanger capable of maintaining the SFP coolant below 150 *F under full core offload conditions. The SFP cooling system is qualified to seismic Category I and Safety Class 3. The SFP cooling system is instrumented with high and low level alarms and a high fuel pool temperature alarm that indicate locally and in the control room. SFP levelis observed during j

operator rounds (Millstone Unit 3 currently uses 8-hour shifts). The licensee typically maintains j

an SFP boron concentration of 2700 ppm, although the current TS requires a minimum boron concentration of 800 ppm.

During normal SFP operation, spent fuel storage racks are capable of maintaining k, no greater than 0.95 in an unborated water environment due to the geometry of the rack spacing and the l

presence of the Boraflex neutron absorber. The recently performed analysis by the licensee has l

indicated that after a seismic event exceeding the OBE level, the Boraflex neutron absorber, i

used in the spent fuel racks for reactivity control, may be degraded to the point that it ceases to l

perform its design function.

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1 Boraflex consists of boron carbide particles embedded in a silicon matrix. Panels of this material are attached to the cell walls in the spent fuel racks by means of stainless steel wrappers. When these Boraflex panels are exposed to radiation fields for an extended period of tims, the material i

undergoes two types of degradation: at first it shrinks, causing formation of gaps in the Boraflex panels and later, with higher radiation doses accumulated, it becomes brittle. The licensee's analysis has shown that this brittle material will break during a seismic event and the spacing between the wrapper and the Boraflex panel is not tight enough to prevent its movement within the wrapper. As a result, its neutron absorbing capability becomes curtailed.

In the current design basis for the existing spent fuel racks, it is assumed that following a seismic event, the Boraflex neutron absorber remains intact and it can be credited in determining 4 However, since the results of the licensee's recent analysis have indicated that Boraflex will degrade, no credit for its presence can be taken. Therefore, the licensee proposed to increase the minimum soluble boron requirement in TS 3.9.1.2 to 1750 ppm to compensate for Boraflex degradation.

3.0 EVALUATION The current Millstone Unit 3 TS 3.9.1.2 requires SFP boron concentration be maintained greater than or equal to 800 ppm. This was previously determined to be sufficient to maintain y less than or equal to 0.95, even in the event of a fuel handling or misloading event. Since the licensee has determined that a postulated seismic event greater than an OBE can cause

. extended Boraflex degradation, the seismic event is a more limiting accident condition and a higher concentration of boron is needed to maintain Q less than or equal to 0.95. Therefore, the licensee proposed to increase the minimum soluble boron requirement in TS 3.9.1.2 to 1750 ppm. In addition to the proposed change in boron concentration, the licensee is also modifying TS 3.9.1.2 to (1) require sampling of the SFP every 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to ensure the boron concentration is greater than or equal to 1750 ppm, and that if the boron concentration is found to be less than 1750 ppm, the boron concentration must be restored to at least 1750 ppm within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, and (2) reflect that the TS is applicable whenever fuel assemblies are in the pool. In addition, the licensee proposed a revision to TS 3.g.13 that requires the licensee to isolate and administratively control the opening of dilution pathways to the SFP in the event of an OBE or load drop onto the top of the spent fuel racks and to petform an engineering evaluation (e.g.,

blackness testing) to determine whether soluble boron is required to control 4 in the SFP.

3.1 Dilution of the SFP The licensee performed an evaluation to determine whether any piping in the fuel handling building could cause a dilution of the SFP following a seismic event greater than an OBE. The licensee identified fire protection, hot water heating, hot water preheating, domestic water, component cooling, and a portion of the roof drain as systems having piping in the fuel handling _

building near the SFP. An engineering evaluation of these systems revealed that, with the exception of portions of the hot water preheating system and the roof drain system, piping in these systems are leak tight and meet the licensee's commitment w seismic 11/l criteria up to and including a Safe Shutdown Earthquake.- The evaluation was performed consistent with the original design criteria for seismic 11/1 piping as documented in Section 3.9.2 of the Millstone Unit 3 Safety Evaluation Report, No. 4. In its letter of November 11,1997, the licensee committed to eliminate piping in the hot water preheating system and the roof drain system as dilution sources by modifying the hot water preheating system piping to meet seismic ll/l criteria and by isolating that portion of the roof drain system piping that runs in the vicinity of the SFP.

These commitments have since been completed.

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. Portions'of systems in the fuel building but not in the vicinity of the SFP were evaluated to determine whether leakage from these systems following a seismic event greater than an OBE could dilute the SFP. The licensee determined that some piping may leak following a seismic event greater than an OBE, but that the leakage would not reach the SFP due to the refueling building floor drains and the elevated curbs surrounding the SFP. Therefore, this leakage was not considered a possible dilution source for the SFP.

The licensee's evaluation concludes that the SFP can be maintained in a safe condition by requiring the presence of boron in the SFP following a seismic event to compensate for the potentialloss of Boraflex. The licensee ensures that at least the minimum required concentration of boron is present in the SFP by sampling every 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> and after makeup from nonborated sources. The staff finds that the combination of TS-controlled SFP minimum boron concentration, the 72-hour sampling requirements, alarms, and operator rounds should adequately detect a dilution event prior to the SFP reaching a boron concentration of 1750 ppm during system operation.

Should a seismic event greater than or equal to an OBE occur, the licensee's' evaluation has determined that (1) the piping in the vicinity of the SFP, with the completed modifications, will be leak tight and le therefore not a dilution source, and (2) leakage from other piping in the fuel handling building that may not be leak tight will not reach the SFP. The proposed TS changes also require that an engineering evaluation be performed to determine whether the Boraflex in the spent fuel racks has degraded due to the seismic event. This requirement will provide early

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indication of Boraflex degradation, confirmation that soluble boron is controlling SFP k,, and that increased attention to activities that may dilute the SFP boron concentration is necessary.

The staff finds that the proposed TS controls will maintain SFP boron concentration at or above i

1750 ppm. An SFP boron concentration of at least 1750 ppm will ensure k,is maintained less than or equal to 0.95 following a seismic event.

3.2 Effects of increased Boron Concentration The proposed increase in the minimum dissolved boron concentration from 800 ppm to 1750 ppm may affect performance of the SFP in two ways: it"may increase corrosion of the SFP materials and it may reduce its capability to retain radioactive iodine, released from the damaged fuel to the SFP water. The licensee addressed both these cases in its November 11,1997, submittal.

The licensee determined that all the metallic components in the Millstone Unit 3 SFP are fabricated from Type 300 series stainless steels, high nickel alloys such as inconels, and Zirconium alloys such as Zircaloy-4 or ZlRLO. All these materials are corrosion resistant in acidic environments and it is not expected that they will experience any corrosion problems when, due

. to a higher concentration of boric acid in the SFP, pH will decrease from approximately 5.0 to 4.7. In addition, the normally maintained concentration of boron in the SFP is higher than the i

required minimum. Typically, this concentration is about 2700 ppm and past experience has indicated that it has not caused any corrosion of the SFP components. Therefore, an increase in the minimum boron concentration from 800 ppm to 1750 ppm will not cause any corrosion problems.

One of the functions of the SFP is to contain the radioactive iodine, which may be accidentally

. released from the damage fuel. Retention of iodine in the SFP water is pH dependent and lower pH favors its release to the environment. The licensee addressed this concem by referring to NRC Safety Guide 25, which recommends a value of 100 for the iodine decontamination factor n

. (DF) be used in the SFP safety analyses. However, the tests performed with boric acid solutions having a pH between 5.0 and 4.3 indicated that a DF as high as 760 could be achieved and the value of 100 is, therefore, a very conservative estimate. Since at 2700 ppm of boron pH stays above 4.3, the increase of minimum boron concentration from 800 ppm to 1750 ppm will not cause the DF for SFP to exceed the value used in the existing SFP safety analyses. Therefore, the proposed increase of boron concentration will not cause any excessive release of iodine to the environment.

- The staff evaluated the effects of this increased boron concentration on corrosion of the SFP components and on the release of radioactive iodine to the environment. The staff concludes that the analysis performed by the licensee provides an acceptable justification for its claim that higher boron concentration will not affect safety-related functions of the SFP.

3.3 SFP Reactivity During normal SFP operation, the storage racks are capable of maintaining 14less than or equal to 0.95 in an unborated water environment due to the geometry of the rack spacing and the presence of the Boraflex neutron absorber. However, due to radiation induced embrittlement, there is a possibility that the Boraflex absorber could degrade following a seismic event greater in magnitude than an OBE. The licensee has, therefore, reanalyzed the reactivity of the SFF by taking credit for some of the soluble boron in the pool water to maintain the spent fuel rack (

less than or equal to 0.95. Because of the difficulty in predicting the final configuration of th a Boraflex following a seismic event greater than an OBE, the reanalysis conservatively assun'ed that there was no Boraflex in the storage racks.

Westinghouse performed a criticality analysis for this degraded condition and determined that 1500 ppm of soluble boron is required to maintain 19 at less than or equal to 0.95 with no credit for any Boraflex and with a loss of SFP cooling resulting in boiling conditions in the SFP. If,...

addition to the above, a single misplaced fuel assembly is postulated, then a minimum of 1750 ppm boron is required. Therefore, the licensee has proposed to increase the minimum soluble boron requirement in TS 3.9.1.2 to 1750 ppm. In addition, the TS would be revised to reflect that it is applicable whenever fuel assemblies are in the pool, that if the boron concentration is less than 1750 ppm it must be restored to at least 1750 ppm within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, and that the boron concentration must be verified to be at least 1750 ppm every 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

Based on the fact that the proposed value of 1750 ppm is well below the 2700 ppm of soluble boron typically present in the pool, and that if all Boraflex is lost and a concurrent fuel assembly handling accident involving either a dropped or misplaced fuel assembly occurs, the ly of the spent fuel storage racks will remain less than or equal to 0.95, the proposed changes are acceptable.

3M' Overall 3

Based on (1) the TS controls that maintain SFP boron concentration of at least 1750 ppm under normal operations, (2) the determination that higher boron concentration will not effect the safety-related functions of the SFP (3) the results of the licensee's evaluation of the systems with piping capable of diluting the SFP following a seismic event of a magnitude greater than an OBE, and (4) the TS actions following an OBE or drop of a load on the spent fuel racks, the staff i

concludes that the proposed changes to Millstone Unit 3 TS 3.9.1.2 and 3.9.13 are acceptable

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and ensure that SFP ly is maintained less than or equal to 0.g5.

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4 5-The staff notes that the licensee stated that this a temporary condition, which is not expected to go beyond the year 2001. The licensee stated that they will replace spent fuel storage racks containing Boraflex prior to the start of the eighth operating cyr se. The licensee expects to perform the rack replacement during the seventh operating cycle, which is currently scheduled for years 1999-2001.

4.0 STATE CONSULTATION

in accordance with the Commission's regulations, the Connecticut State official was notified of the proposed issuance of the amendment. The State official had no comments.

5.0 -

ENVIRONMENTAL CONSIDERATION

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The amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes surveillance requirements. The NRC staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be r

released offsite, and that there is no significant increase in individual or cumulative occupational l radiation exposure. The Commission has previously issued a proposed finding that the amendment involves no significant hazards consideration, and there has been no public comment on such finding (62 FR 63980 dated December 3,1997). Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). ' Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.

6.0 CONCLUSION

The Commission has concluded, based on the considerations discussed above, that: (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.

Principal Contributors: C. Gratton L. Kopp J.Ma K. Parczewski Date:

April 9, 1998

l Northe:st Nuclear Energy Company Millstone Nuclear Power Station Unit 3 cc:

Lillian M. Cuoco, Esquire Mr. William D. Meinert Senior Nuclear Counsel Nuclear Engineer Northeast Utilities Service Compan;<

Massachusetts Municipal Wholesale P. O. Box 270 Electric Company Hartford, CT 06141-0270 P.O. Box 426 Ludlow, MA 01056 Mr. Kevin T. A. McCarthy, Directu Monitoring and Radiation Division Joseph R. Egan, Esquire Department of Environmental Protection Egan & Associates, P.C.

79 Elm Street 2300 N Street, NW Hartford, CT 06106-5127 Washington, DC 20037 Regional Adminis'rator, Region'l Mr. F. C. Rothen t

U.S. Nuclear Regulatory Commission Vice President - Work Services 475 Allendale Road Northeast Utilities Service Company i

King of Prussia, PA 19406 P. O. Box 128 Waterford, CT 06385 First Selectmen Town of Waterford Emest C. Hadley, Esquire Hall of Records 1040 B Main Street 200 Boston Post Road P.O. Box 549 Waterford, CT 06385 West Wareham, MA 02576 Mr. Wayne D. Lanning Mr. John Buckingham Deputy Director of Inspections Department of Public Utility Control Special Projects Office Electric Unit i

475 Allendale Road 10 Liberty Square King of Prussia, PA 19406-1415 New Britain, CT 06051 Mr. M. H. Brothers Mr. James S. Robinson, Manager Vice President - Operations Nuclear investments and Administration Northeast Nuclear Energy Company New England Power Company P.O. Box 128 25 Research Drive Waterford, CT 06385 Westborough, MA 01582 Mr. M. R. Scully, Executive Director Mr. D. M. Goebel Connecticut Municipal Electric Vice President - Nuclear Oversight Energy Cooperative Northeast Utilities Service Company 30 Stott Avenue P. O. Box 128 Norwich, CT 06360 Waterford, CT 06385 Mr. David Amerine Deborah Katz, President Vice President - Nuclear Engineering Citizens Awareness Network and Support P.O. Box 83 Northeast Utilities Service Company Shelburne Falls, MA 03170 P. O. Box 128 Waterford, CT 06385 i

N:rth::st Nucle:r En:rgy Comprny Millstone Nuclear Power Station Unit 3 cc:

Mr. Allan Johanson, Assistant Director Mr. Don Schopfer Office of Policy and Management Verification Team Manager I

Policy Development and Planning Sargent & Lundy Division

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55 E. Monroe Street 450 Capitol Avenue - MS# 52ERN Chicago,IL 60603 P. O. Box 341441 Hartford, CT 06134-1441 Mr. J. P. McElwain Vice President (Acting)- Millstone 3 Citizens Regulatory Commission Northeast Nuclear Energy Company ATTN: Ms. Susan Perry Luxton P.O. Box 128 180 Great Neck Road Waterford, CT 06385 Waterford, CT 06385 Mr. G. D. Hicks The Honorable Terry Concannon Unit Director-Millstone Unit 3 Nuclear Energy Advisory Coundi Northeast Nuclear Energy Company Room 4035 P.O. Box 128 Legislative Office Building Waterford, CT 06385

. Capitol Avenue Hartford, CT 06106 Senior Resident inspector Millstone Nuclear Power Station -

Legislative Office Building clo U.S. Nuclear Regulatory Commission Captiol Avenue P. O. Box 513 Hartford, CT 06106 Niantic, Connecticut 06357 Mr. Evan W. Woollacott Co-Chair Nuclear Energy Advisory Council 128 Terry's Plain Road Simsbury, CT 06070 Little Harbor Consultants, Inc.

Millstone -ITPOP Project Office P.O. Box 0630 Niantic, CT 063S7-0630 Mr.9.O. Kenyon i

Chief Nuclear Officer-Millstone Northeast Nuclear Energy Company P.O. Box 128 Waterford, CT 06385 l

Mr. Daniel L. Cuny I

Project Director i

Parsons Power Group inc.

2675 Morgantown Road Reading, PA 19607