ML20205G019
| ML20205G019 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 03/17/1999 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20205G009 | List: |
| References | |
| NUDOCS 9904070091 | |
| Download: ML20205G019 (8) | |
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pR CEO k UNITED STATES g
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t"JCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20565-0001
- * * * *,o SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION l
RELATED TO AMENDMENT NO.168 TO FACILITY OPERATING LICENSE NO. NPF-49 NORTHEAST NUCLEAR ENERGY COMPANY. ET AL.
MILLSTONE NUCLEAR POWER STAT!ON. UNIT NO. 3 DOCKET NO. 50-423 -
1.0 INTRODUCTIOE By letter dated April 1,' 1998, as supplemented May 29, June 26, and August 4,1998, the Northeast Nuclear Energy Company, et al. (the licensee), requested a change to the Millstone Nuclear Power Station, Unit No. 3 licensing basis. The requested change would revise the Millstone Unit 3 licensing basis by adding a new sump pump subsystem to address groundwater inleakage through the containment basemat. The May 29, June 26, and August 4,1998, letters provided clarifying information that did not change the initial proposed no significant hazards consideration determination.
2.0 BACKGROUND
In its submittals dated April 1, May 29, June 26, and August 4,1998, the licensee provided information regarding a design change for Millstone Unit 3 involving the addition of a new j
sump pumping subsystem to address groundwater inleakage through the containment basemat. While the previous Final Safety Analysis Report (FSAR) concluded that significant amounts of groundwater were not expected and no safety-related dewatering system was required, the licensee determined that the waterproof membrane was degraded and groundwater inleakage could potentially jeopardize the integrity of the containment liner and affect the operability of both trains of the recirculation spray system (RSS). Without the new safety-related sump pumping subsystem to pump cut groundwater inleakage when the engineered safety features (ESF) building is inaccessible, the existing nonsafety-related sump pumps could fail resulting in flooding of the ESF building where the RSS pumps are located.
The proposed amendment involves a revision to the plant FSAR, including a description of the functional design of the new subsystem, its construction and quality attributes, the necessary surveillance requirements, and the operating requirements.
2.1 Gystem Description The containment structure at Millstone Unit 3 has a 10-foot thick reinforced concrete basemat
' founded on rock. Between the foundation rock surface and the underside of the basemat are two porous concrete subfoundation layers which are separated by a waterproof membrane designed to preclude the inteakage of groundwater. Porous concrete pipes are installed in the 9904070091 990317 PDR ADOCK 05000423 P
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I upper porous concrete layer to collect and drain the groundwater into one of the RSS cubicle sumps inside the ESF building in the event of the degradation of the membrane.
The new safety-related pumping subsystem consists of one train (an air-driven pump, piping, j
fittir.gs, valves, and supports) for each of the RSS cubicle sumps. The sump liners have also
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been upgraded to assure the sumps remain isolated from potentially contaminated RSS i
system fluids. Motive air for the pumps is supplied by portable diesel compressors which are required to be connected to the permanently installed air supply connections outside the ESF building during sump pump operation. The air-driven pumps discharge the sump water to temporary storage tanks also located outside the ESF building. Any equipment accessible for repair (such as the portable diesel compressors) is nonsafety-related. Although located in different cubicles, either air-driven pump is capable of removing groundwater inleakage from both cubicles since the two sumps communicate hydraulically, The safety function of this subsystem is the long-term removal of groundwater, post accident, to preclude flooding the RSS cubicles which could ultimately jeopardize the integrity of the containment steel liner and the operability of the RSS pumps.
2.2 NRC Inspection Activities Following the installation of the new sump pumping subsystem, the NRC performed an inspection of the system design and installation. As a result of the inspection activities, it was discovered that there were some significant deficiencies in the design and qualification of the sump pumping subsystem and its ability to accomplish its safety function of removing groundwater from the RSS cubicle sumps for the required time period following a licensing basis large-break loss-of-coolant accident (LOCA). As a result, the licensee performed additional qualification testing and evaluation in order to assure the pumping system function, and some of the important subcomponents of the system had to be augmented. The results of the NRC inspection are discussed in Inspection Report (IR) 50-423/98-208. One of the unresolved items in this inspection report is that the FSAR revisions need to be reviewed by
' the Office of Nuclear Reactor Regulation (NRR) staff. The results of the NRR review are provided below.
3.0. EVALUATION The staff review of the FSAR revisions included a review of the component quality as determined by the licensee's quality group classification. Component quality and functional capability for long duration operation is especially important under conditions of inaccessibility,
. such as exist for the design basis function for this system. As a result, the staff identified concerns about the licer.see's quality group classification of many of the system components as other than American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code Class 1,2, or 3, and the staff requested additional information from the licensee in a letter dated April 30,1998. The licensee's response dated May 29,1998, provided the licensee's basis for the classification of the various components. While the components in this pumping system are not classified as ASME Code Class, the licensee provided information to justify the adequacy of the quality assurance of the various components. Further, the licensee provided a comparison of the component qualification and construction quality provided for various components against that which would be required had the components been ASME Code Class. While not ASME Code Class, the pumping subsystem components in the
. inaccessible portion of the system are listed as American Nuclear Society (ANS) Safety Class
. 3 and are QA Category I and Seismic Category 1. Based on this information, the staff has concluded that the provided qualification and construction quality are similar to those required for ACME Code Class components in important aspects and are acceptable for the limiting service conditions expected.
In the submittal dated August 4,1998, the licensee also provided the vendor test report for the qualification and dedication of the new sump pumps. This report documents the functional testing and seismic and environmental qualification performed. During the functional testing, several anomalies were observed, which ultimately resulted in the augmentation of several of the pump subcomponents, as discussed in IR 50-423/98-208. Based on the review of the August 4,1998, submittal, the staff identified no additional issues and concludes that the test report adequately demonstrates that the currently configured safeiy-related pumps are capable of performing their safety function.
The diesel-powered compressors are not classified as safety-related since they are not required to operate until approximately 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> post accident and are only required to operate intermittently to remove collected inleakage. Due to the relatively long time period before operation is necessary, the staff finds that this is acceptable since the licensee has ample time to take corrective action to repair or replace an inoperable compressor air supply, Since the nonsafety-related compressors and associated equipment provide motive air to the safety-related sump pumps, one additional area of concern is that the compressors could have some adverse effect on pump operation. However, this concern has been adequately addressed as a result of the NRC inspection activity referenced above (IR 50-423/98-208).
Specifically, the issues addressed in the inspection report include: the oiling of the pump air motors by the air compressor supply, the regulation of the pressure of the air supply to prevent overpressurization of the air motors, and the need for an air line filter. As a result, the staff J
concludes that the issue of possible adverse effects of the nonsafety-related compressors on j
the operation of the sump pumps, has been adequately addressed.
j Because the RSS cubicle sump pumping subsystem performs a safety function, the staff also reviewed the period,'c testing performed on the system components. The plant inservice testing program for ASME Code Class pumps and valves does not include these components; however, the plant Technical Requirements Manual has been revised to provide periodic testing of both trains of compressors and sump pumps. The licensee also stated that the pumps will be operated yarterly per the preventive maintenance program. The staff finds that this is acceptable for periodically assuring the functional capability of this subsystem.
In a request for additional information dated April 30,1998, the staff requested information related to the method, and ground motion input, used in the seismic qualification of the sump pumps. In its letter dated May 29,1998, the licensee stated that it has qualified the pumps using biaxial dynamic test results from an outside vendor, and that the test response spectra conservatively enveloped the required response spectra at elevation (-) 34 feet,4 inches (which is approximately the floor elevation of the ESF building). The licensee further stated that the pump support is attached directly to the building, and therefore, no additional seismic interaction (amplification) effects are considered in this case. This general procedure for obtaining the seismic input is acceptable to the NRC staff.
' 3.1 Overall Based on the review of the information provided by the licensee, the staff finds that the licensee has demonstrated the adequacy of the new RSS cubicle sump pumping subsystem.
Further, the staff concludes that the proposed FSAR revisions and the associated license amendment, which adds this new subsystem, are acceptable.
4.0 REQUEST FOR INTERVENTION A request for intervention was received from the Citizens Regulatory Commission (CRC). On September 2,1998, the NRC Atomic Safety and Licensing Board (ASLB) ruled that the CRC did not have standing in its intervention request (LBP-98-22). Accordingly, the CRC's intervention petition was denied and the proceeding terminated. On September 11,1998, the CRC appealed the ASLB's decision to the Commission. On October 23,1998, the Commission affirmed the ASLB's decision to deny the intervention petition (CLl-98-20).
5.0 FINAL NO SIGNIFICANT HAZARDS CONSIDERATION
DETERMINATION The Commission's regulations in 10 CFR 50.92 state that the Commission may make a final determination that a license amendment involves no significant hazards consideration (SHC) if operation of the facility, in accordance with the amendment, would not: (1) Involve a significant increase in the probability or consequences of an accident previously evaluated; or (2) Create the possibility of a new or different kind of accident from any accident previously evaluated; or (3) Involve a significant reduction in a margin of safety. As required by 10 CFR 50.91(a), the licensee has provided its analysis of the issue of no significant hazards consideration, which is presented below:
- 1. Involve a significant increase in the probability or consequences of an accident previously evaluated.
The current FSAR credits the waterproof membrane for assuring that groundwater inleakage is not significant and would have no impact on safety related structures and components. However, degradation of the waterproof membrane has been detected, and it is now concluded that groundwater inteakage can be significant in that it could affect the operability of the RSS pumps. The original plant design had only nonsafety-i related RSS sump pumps available for pumping the groundwater from the RSS sumps.
I These pumps are not powered from the emergency busses and would not be I
accessible during a design basis LOCA. Two independent safety-related air-driven sumo pumps have been installed to eliminate the potential for groundwater inleakage tha ould affect the RSS pumps.
Air-ariven sump pumps have been installed with the air supply line routed to a connection outside the ESF building. This allows the installation of an air compressor i
in an area that is accessible during a design basis accident such as a LOCA. Two air compressors have been staged in designated locations, and will be maintained and pdodically tested to ensure their availability. Periodic testing of the sump pumps will l
also be performed. The surveillance requirements have been incorporated into the Technical Requirements Manual.
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- m. EOP (Emergency Operating Procedure) 35-ES1.3 has been modified to add a step to install the compressors and start the sump pumps. It is estimated that these sump pumps would be needed approximately ten hours after a design basis accident. Thus, there is sufficient time for the operators to perform this action. Since sufficient time is available, the action has been incorporated into procedures and the environmental conditions allow access to the area, it is concluded that credit for operator action can be taken.
Thus, the new system is single failure proof and meets the requirements of Standard Review Plan 3.4.1 which states the following:
"If safety-related structures are protected from below-grade groundwater seepage by means of a perrnanent dewatering system, then the system should be designed as a safety-related system and meet the single failure proof criterion."
This provides assurance that the RSS pumps and other safety-related structures and components will perform the required safety function as assumed in the accident analysis.
The current nonsafety-related RSS sump pump system will continue to provide protection from groundwater inleakage during normal operation. Thus, there is no impact on the probability of occurrence of a transient because of equipment or structural failure due to groundwater inleakage. In addition, the new safety-related RSS sump pump system provides additional assurance that groundwater inleakage would not affect structures or equipment during an extended loss of offsite power or a design basis accident. Thus, it is concluded that there is no impact on the probability of occurrence of any previously evaluated accident.
The change results in the use of the new air-driven sump pumps to remove groundwater in-leakage from the RSS cubicles. To preclude the possibility for radiological contamination of the groundwater, all sources of liquid radiological contamination to the sumps have been eliminated. The RSS cubicle floor drains leading to Sumps 7A/78 have been plugged. Drains from equipment determined Dot to be a potential source of radiological contamination continue to drain to Sumps 7A/7B (sources include CCP [ component cooling water) and Servico Water relief valves) and are covered with splash guards to prevent the entrance of Nmminated spray. The Hydrogen Recombiner area floor drains and the drain from the / ASS (post accident sampling system] sample sink, all of which are nonsafety-related, have been isolated from the indirect waste receptor which drains to Sump 78. Sumps 7A and 7B have been cleaned and the existing nonsafety-related sump pumps replaced to remove any existing residual contamination. The nonsafety-related pumps (3DAS-P8A/B) discharge to ESF Building sump 3DAS-SUMP 10. To preclude any potential siphoning from the potentially contaminated Sump 10 back to Sumps 7A/7B, the lines of the existing nonsafety-related pumps have been shortened to discharge above the water levelin Sump 10.
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$s The walls of Sumps 7A/78 have been extended to protect from a Limited Passive Failure and Pipe Break in the RSS cubicles. The expected flooding height is 6.6 inclies
[]. The sump cubicle height was extended to 3 ft. above the cubicle floor, we!! above this height. The sumps are covered with a vented hood to protect from pipe break spray and miscellaneous overhead leaks to further assure the sumps remain isolated from potentially contaminated RSS system fluids.
The existing SLCRS [ supplementary leak collection and release system] boundary has been extended to the isolation valves located outside of the ESF building. Additionally, when the sump level is reduced while using the air driven pump, the pumps are designed to prevent air from being discharged through the pump discharge outside of the ESF building.
Thus, use of the new sump pumps would not affect the offsite doses following a design basis accident.
Therefore, the proposed revision does not involve a significant increase in the probability or consequence of an accident previously evaluated.
- 2. Create the possibility of a new or different kind of accident from any accident previously evaluated.
The current nonsafety-related RSS sump pump system will continue to provide protection from groundwater inleakage during normal operation. This will continue to provide assurance there is no potential for a transient because of equipment or structural failure due to groundwater inleakage. In addition, the new safety-related RSS sump pump system provides additional assurance that groundwater inleakage i
would not affect structures or equipment during an extended loss of offsite power or a design basis accident.
Therefore, the proposed revision does not create the possibility of a new or different kind of accident from any accident previously evaluated.
3< Involve a significant reduction in a margin of safety.
The current FSAR credits the waterproof membrane for assuring that groundwater inleakage is not significant and would have no impact on safety related structures and components. However, degradation of the waterproof membrane has been detected and it is now concluded that groundwater inleakage can be significant in that it could affect the operability of the RSS pumps. Original design had only nonsafety-related RSS sump pumps available for pumping the groundwater from the RSS sumps.
These pumps are not powered from the emergency busses and would not be accessible during a design basis LOCA. Thus, it is assumed that they would not be available to mitigate a design basis accident. Two independent safety-related air-driven sump pumps have been installed to eliminate the potential for groundwater inleakage that would affect the RSS pumps. The new system is single failure proof and meets the requirements of Standard Review Plan 3.4.1.
6 Use of the new system requires operator action to install pre-staged air compressors to provide power for the new air-driven sump pumps, it is estimated that these sump pumps would be needed approximately ten hours after a design basis accident. Thus, j
there is sufficient time for the operators to perfr m this action. Since sufficient time is available, the action has been incorporated into procedures and the environmental conditions allow access to the area, it is concluded that credit for operator action can be taken.
With credit for the new single failure proof air-driven sump pumps and operator action to install pre-staged compressors to provide power for the pumps, the new subsystem provides the required assurance that the RSS pumps will not be affected by groundwater inleakage. Thus, it is concluded that the RSS pumps would be operable for long term accident mitigation and there is no impact on the margin of safety as defined in the basis of the Emergency Core Cooling Technical Specifications or any other Technical Specification.
Therefore, the proposed revision does not involve a significant reduction in a margin of safety.
In conclusion, based on the information provided, it is determined that the proposed revision does not involve an SHC.
Based upon the above considerations, the NRC staff concludes that the amendment meets the three criteria of 10 CFR 50.92. Therefore, tha staff has made a final determination that the proposed amendment does not involve a significant hazards consideration.
6.0 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.
7.0 ENVIRONMENTAL CONSIDERATION
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. 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 released offsite, and that there is no significant increase in individual or cumulative occupational 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 (63 FR 19974). 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.
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I 8.0 CONC 8.USION 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 w;ll not be inimical to the common defense and security or to the health and safety of the pub 3c.
Principal Contributors: R. Pichumani G. Hammer Date: March 17,1999 4
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