ML20056D706
| ML20056D706 | |
| Person / Time | |
|---|---|
| Site: | Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png |
| Issue date: | 07/26/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20056D699 | List: |
| References | |
| TASK-06-04, TASK-6-4, TASK-RR NUDOCS 9308170344 | |
| Download: ML20056D706 (14) | |
Text
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1 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION CONTAINMENT ISOLATION SYSTEM CONNECTICUT YANKEE ATOMIC POWER COMPAN'T HADDAM NECK PLANT DOCKET NO. 50-213
1.0 INTRODUCTION
As part of the Systematic Evaluation Program (SEP) the NRC staff re-evaluated the containment isolation system for the Haddam Neck Plant (Ref. 1). The SEP was initiated by the Nuclear Regulatory Commission (NRC) in February 1977 to review the designs of older operating reactor plants and to confirm and document their safety. Among ths SEP objectives was showing how designs of the older plants compared to current criteria on significant safety issues and documenting the rationale for acceptable departure from these criteria.
Containment isolation was identified as SEP Topic VI-4 for the Haddam Neck Plant.
Reference 1 identified numerous deviations of the as-built containment t
isolation system from the current safety criteria. The significance of the identified deviations and recommendation of corrective measures was deferred to subsequent SEP integrated assessment of the Haddam Neck Plant.
In June 1983 the staff published " Integrated Plant Safety Assessment, Systematic Evaluation Program, Haddam Neck Plant" (Ref. 2). This evaluation resolved some of the previously identified deficiencies based partly on a limited scope probabilistic risk assessment (PRA). Specifically the conclusions and recommendations drawn by the staff in Ref. 2 as based on the previous staff evaluation and the PRA study were as follows:
1.1 Valve Location Some penetrations have both isolation valves outside containment instead of one inside and one outside, as required by either GDC 55 or 56.
Based on PRA little improvement could be seen in moving a valve inside containment. This is because the probability of failure of the pipe between the containment and the first valve was considered to be small compared to the probability of valve failure. Corrective modifications were not recommended. The staff concluded that the existing arrangement for these penetrations constitutes an acceptable alternate basis as permitted by the GDC.
1.2 Valve Type Some penetrations have check valves outside containment as isolation valves instead of a motor-operated valve as required by GDC 55 or 56.
Based on the PPA evaluation little improvement was concluded to be obtained by replacing the simple check valves with motor-operated valves because the failure 9308170344 930726 PDR ADOCK 05000213 P
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. probabilities of the two types of valves are not that different. Corrective measures were not recommended. The staff concluded that the existing valve type for these penetrations constituted an acceptable alternate basis as permitted by the GDC.
1.3 Automatic Isolation Valves GDC 55 and 56 specify that automatic isolation valves should, upon loss of actuating power, take the position that provides greater safety. Acceptable valve position depends on the function of the fluid system.
Insufficient information existed at the time for the staff to reach a conclusion in this area.
Connecticut Yankee Atomic Power Company (the licensee) proposed to evaluate the design of the isolation valves and, where necessary,' propose corrective actions to ensure that valves take the position of greatest safety upon a loss of power. The staff found this proposal acceptable.
1.4 Local Manual Valves The staff identified vent, drain and test lines containing local manual valves which serve as containment isolation barriers. The staff required these valves to be administratively controlled and locked closed and if need be that there be written procedures to be in effect governing their use during plant operation.
1.5 Number of Isolation Valves The staff noted that a number of penetrations had only a single barrier identified as a containment isolation boundary instead of two barriers as required by the GDC. The licensee proposed to evaluate the existing isolation capabilities for these systems in conjunction with an ongoing evaluation of containment leak testing provisions and methods. Based on the results of this evaluation, the licensee committed to propose corrective actions as necessary to ensure redundant isolation capability. The staff found this approach acceptable.
By letters dated January 16, 1991 and January 29, 1993, the licensee submitted additional justification (Refs. 3 and 4) for penetrations that had previously l
been judged to deviate from GDCs 54 through 57 and the seismic requirements of GDC 2.
The staff review of the SEP Topic concluded that the intent of the topic was to address only GDCs 54 through 57, dealing with the configuration of the penetrations. The seismic issue is not part of this SEP topic review.
In some cases PRA is utilized as justification for not meeting the GDC. The
-results of the licensee's PRA indicated that the risk to the public from piping and valve failure during a design basis accident is low for the as-built design. The occurrence of a seismic event concurrently with a design basis accident was not considered. The GDC require certain isolation barriers to be provided to protect the public. The NRC staff has not previously excused reduction in the number of these barriers based on the calculation of low risk. Although the simultaneous occurrence of a seismic event and a
. design basis accident would be unlikely, certain accident scenarios may require containment of fission products for an extended post-accident period increasing the need for seismic protection. The staff's review of the licensee's PRA analyses is discussed in Section 3.0.
Our evaluation compares the current status of each penetration as described by the licensee in Refs. 3 and 4 with the GDC and previous staff conclusions in Refs. I and 2.
In some cases the licensee has upgraded the penetrations so that they now meet the GDC or are acceptable on another basis as permitted by the previous staff evaluations.
In other cases, while the licensee has not complied with the GDCs, CYAPC0 has provided additional information on how they believe they meet the intent of the GDC.
2.0 EVALUATION P-3 Hiah Pressure Safety Iniection - HPSI Three check valves (SI-CV-862A, B, and C) and manual valve (SI-V-860) are in parallel arrangement.
The HPSI is a safety related system which is required to operate during accident conditions. The system is designed to function following a design basis earthquake (seismic category I) and has a design pressure higher than that of the containment. The HPSI system is leak tested in accordance with plant technical specifications (TS). The staff concludes that the isolation valve arrangement for this penetration is acceptable since double barrier protection is provided by the closed HPSI loop and the check valves and lock closed manual isolation valve. The licensee should confirm that they have instituted administrative controls for control of this manual valve as committed to in Ref. 2.
P-4 Pressurizer Relief Tank - PRT vent Isolation valves WG-TV-1845, WG-A0V-558 and WG-V-984A are arranged so there are two valves in series. The valves are both outside containment. Valve WG-A0V-558 has a remote manual operation switch but also has automatic closure which overrides the manual operation feature. This arrangement was_found to be acceptable by the NRC staff in Ref. 2.
The staff has determined that the isolation valve arrangement for this penetration has not changed and is still acceptable based on the original SE.
P-8 Charaina System There is a single check valve CH-CV-399 which provides isolation. The charging system is safety related and is required to operate during accid ~ent conditions. The. system is designed to function following a design basis earthquake (seismic category I) and has a design pressure higher than that of the containment. The charging system is leak tested in accordance with plant technical specifications. The staff concludes that the isolation provisions for this penetration are acceptable since double barrier protection is provided by the closed system and the check valve.
P-11 A. P-11B. P-11C and P-110 Reactor Coolant Samplina Single isolation valves SS-A0V-950, SS-A0V-955, SS-TV-960 and SS-TV-965 are located outside containment for each penetration.
Isolation provisions for these penetrations do not meet the GDC. Valves SS-A0V-950, SS-TV-960, and SS-TV-965 are normally closed and Valve SS-A0V-955 (Pressurizer Hydrogen Vent Line) is normally open and vented to the Chemical Volume and Control Tank, however, all four valves are automatically closed on high containment pressure. Valve SS-A0V-950 has a key locked remote manual switch which can override automatic closure. The licensee should confirm that they have instituted administrative controls for control of the key lock to assure that this valve is or can be closed when required as committed to in Ref. 2.
There is a second manual isolation valve (sample sink isolation valve) for each line which is not leak tested.
However, procedures for operation of the sampling i
line require that all isolation valves are confirmed closed before and after the sample is taken.
In addition, the sample sink isolation valves are pressurized when the sample isolation valves are opened. This provides a good indication that the sample sink isolation valves are leak tight. These are small lines (3/8") with the sample taps in a hooded area.
In addition, P-11B flow is restricted by 1/8" capillary tubing inside containment.
Any leakage through these lines would be filtered by the primary auxiliary building (PAB) filters when off-site power is available.
The staff concludes that while the isolation provisions for these penetrations deviate from the GDCs, there is adequate isolation (two closed valves) such that the staff can conclude that these isolation provisions do meet the intent of the GDCs for providing containment isolation.
P-12A Valve Stem Leak Off This penetration has been removed from service and is sealed with a welded cap outside of containment. This is the same configuration as all other spares.
The staff considers this issue closed.
P-12B NTS Sample This line contains one manual isolation valve SS-V-999A. A single isolation valve does not meet the isolation requirements of the GDC. Valve SS-V-999A is normally locked closed during plant operation. There is a locked _ closed manual valve (SS-V-999), which is tested in the reverse direction but is not credited as a containment isolation valve (CIV), in series with SS-V-999A.
When either valve is opened, administrative controls are implemented by TSs to provide for immediate closure if required.
In addition, this sampling line is a small line (3/8") and failure would result in low maximum leakage rate. The staff concludes that while the isolation provisions for this penetration deviate from the GDCs, there is adequate isolation (two closed valves) such that the staff can conclude that the isolation provisions for this penetration do meet the intent of the GDCs for providing containment isolation.
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I P-13 Containment Sumo Discharae This line contains two isolation valves (WD-HICV-1840 and WD-TV-1846) in series. The valves are both outside containment. This arrangement was found to be acceptable by the NRC staff in Ref. 2.
The staff has determined that the isolation valve arrangement for this penetration has not changed and is still acceptable based on the original SE.
P-14 Vapor Seal Head Tank Drain This line contains two isolation valves (DH-TV-1843 and DH-TV-1844) in series.
The valves are both outside containment. This arrangement was found to be acceptable by the NRC staff in Ref. 2.
The staff has determined that the isolation valve arrangement for this penetration has not changed and is still acceptable based on the original SE.
P-22 Space Heatina Condensate Return This line contains one manual isolation valve HC-V-2208. A single isolation valve does not meet the redundancy requirements of the GDC.
A single valve is acceptable for closed loop systems inside or outside of containment.- HV-V-220B is normally locked closed during plant operation and administratively controlled. There is a locked closed manual valve, which is tested in the reverse direction but is not credited as a CIV, in series with Valve HV-V-2208.
In addition, the Space Heating system is a closed system inside containment. The Space Heating system does not qualify as a containment barrier because it does not have the seismic and quality assurance (QA) t' requirements. However, it.would be a deterrent to containment leakage in case of an accident. The staff concludes that while the isolation provisions for this penetration deviate from the GDCs, there is adequate isolation (two closed valves and a closed system inside containment) such that the staff can conclude that the isolation provisions for this penetration do meet the intent of the GDCs for providing containment isolation.
P-23A Containment Leak Monitorina Subsequent to the staff's previous evaluations in Refs. I and 2, the licensee removed two containment isolation valves that were in one branch of this line and classified the line as part of the containment boundary. This position was accepted by the staff for another penetration (P-73A) in Ref. I because it-supplies safety related instrumentation for accident mitigation. The licensee states that at times when the plant is operating, manual root valves are utilized for isolation when instruments are calibrated. The root valves are not classified as containment isolation valves nor are they leak tested.- The licensee has confirmed that the root valves provide an isolation to containment for pressurization of the instrument. The calibration is done with the instrument in-line and containment boundary is never violated. The staff has determined that the containment isolation arrangement for this penetration has not changed and is still acceptable based on the original SE.
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i
. P-24A. P-248. P-24C and P-24D HPSI Recirculation Each of these lines contains a single manual isolation valve (SI-V-863A, B, C and D) located outside containment. A single isolation valve does not meet the redundancy requirement of the GDC. These are 3/4" lines which are used for the HPSI check valves flow test. This test can only be performed during plant shutdowns.
The valves are locked closed during operation and administratively controlled by TS Section 1.6.a.2, Containment Integrity. The TSs allow these valves to be opened for short periods of time for periodic-surveillance and diagnostic test. When these valves are open, a locally stationed operator will be in direct communication with the main control room.
This ensures that these valves are capable of being closed within 60 seconds of a containment isolation actuation signal (CIAS). During an accident these lines would most likely be pressurized by the HPSI flow and any leakage would tend to be into containment rather than out. During Cycle 16 refueling outage, CYAPC0 installed an Appendix J test boundary valve in each of these lines inside con ^ainment. CYAPC0 has committed to close and maintain close these valves 6. ring Modes 1 through 4.
In addition there is a locked closed valve (SI-V-865) in line with the 862A-D valves after they come to a common header.
Even though the test valves are tested in the wrong direction, the Type C test would provide some indication of leak integrity of the test valves and the test valves provide an additional deterrent to containment leakage.
The staff concludes that while the isolation provisions for this penetration deviates from the GDCs, there is adequate isolation (two closed valves and system pressure) such that the staff can conclude that these isolation provisions for this penetration do meet the intent of the GDCs for'providing containment isolation.
P-28 and P-29 Component Coolina Water - CCW to and from the Reactor Coolant Pumo-RCP Oil Coolers Single isolation valves CC-TV-1411 and CC-CV-853 are located outside containment.
Isolation provisions for these lines do not meet the redundancy requirements of the GDC. A single valve is acceptable for closed loop systems inside or outside of containment. The CCW system is a closed system inside and outside containment. The CCW system does not qualify as a containment barrier because it does not have the seismic and QA requirements. However, it would be a deterrent to containment leakage in case of an accident. The staff
-concludes that while the isolation provisions for this penetration deviate from the GDCs, there is adequate isolation (one valve and a closed system inside and outside containment) such that the staff can conclude that these isolation provisions for these penetrations do meet the intent of the GDCs for providing containment isolation.
P-33 Refuelino Cavity Purification This penetration has two isolation valves (PU-V-242A and PU-V-242) in series.
They are located outside containment. This arrangement was found to be acceptable by the NRC staff in Ref. 2.
The staff has determined that the isolation valve arrangement for this penetration has not changed and is.still acceptable based on the original SE.
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i P-34 CCW from RCP Thermal Barrier This line contains a single remote manual isolation valve (CC-FCV-608) located outside containment. The valve receives an automatic closure signal on high containment pressure which overrides the manual setting. A single isolation valve does not meet the redundancy requirement of the GDC. A single valve is acceptable for closed loop systems inside or outside of containment. The CCW system is a closed system inside and outside containment. The CCW system does not qualify as a containment barrier because it does not have the seismic and l
QA requirements. However, it would be a deterrent to containment leakage in case of an accident.
The staff concludes that while the isolation provisions for this penetration deviate from the GDCs, there is adequate isolation (one i
valve and a closed system inside and outside containment) such that the staff can conclude that these isolation provisions for these penetrations do meet the intent of the GDCs for providing containment isolation.
P-39 Purae Air Exhaust and P-40 Containment Purae Air Supply The Purge Air exhaust (P-39) single isolation barriers are provided by two locked closed isolation valves (VS-V-1B and VS-HCV-1101) and a blind flange arranged in parallel. At the supply (P-40) a single isolation valve (VS-V-1A) is provided. A single isolation barrier does not meet the redundancy requirement of the GDC. The CIVs are locked closed during operation as required by TS 3/4.6.1.7.
Reference 2 required that the licensee propose corrective actions to ensure redundant isolation capability. These penetrations are 42" lines that provide containment purge and exhaust.
By letter dated July 1, 1993, CYAPCO committed to provide a second barrier against leakage for both these penetrations.
For P-40, the purge supply penetration, a blank flange will be put in-place on this piping just inside the containment wall. This flange will be maintained in series with the manual CIV during Modes I through 4.
For P-39, the purge exhaust penetration, CYAPC0 is reviewing two options, either providing a flange inside or outside of containment.
CYAPC0 in its letter dated July 2, 1993, stated that it will make a decision, regarding this P-39, by November 30, 1993 and implement the modification during the next outage.
In addition, any leakage past these valves is filtered by the HEPA/HECA filters in the primary ventilation system.
The staff has reviewed CYAPCO's commitment and concludes that with the installation of these flanges the plant will be in conformance with the GDCs.
P-51. 52. 53. and 54 Service Water from Containment Air Recirculation Fans i
These lines contain single locally operated manual ball valves for containment isolation outside containment. The valve numbers for these valves are SW-V-264, 266, 268, and 270. The containment fan coolers and associated service water piping is a safety related system which is required to operate during accident conditions. The system is designed to function following a design basis earthquake (seismic category I). This system qualifies as a closed system which would require one remote manual valve.
In Ref. I the staff required that these lines be equipped with power operated remote manual isolation valves.
Remote isolation capability has not yet been added by the
, licensee. Automatic isolation is not appropriate for these line:: since they have a post accident safety function. CYAPC0 has stated that each month an operational inspection is conducted at the system operating pressure. The acceptance criterion for this inspection is "zero leakage." This provides the licensee with a monthly indication of the service water piping integrity.
In
- addition, the service water lines have flow instrumentation that will provide control room annunciation of a service water line break for each service water line. The service water lines low flow indication is provided from a flow transmitter inside containment and therefore will provide an indication of a break inside containment. Upon an indication of a service water line break during a design basis event, an operator would be dispatched to the primary auxiliary building to manually close the discharge isolation valve. However, the accessibility of the discharge isolation valves will be determined based on actual conditions at the time.
Based on the above, the staff has concluded that the licensee has provided additional assurances of pipe integrity and while remote operation is desirable, the plant will be able to detect and isolate a service water line break inside containment during a design basis event. The staff concludes that while the isolation provisions for these penetrations deviate from the GDCs, there is adequate indication and procedures to manually isolate a service water line break inside containment such that the staff can conclude that these isolation provisions for these penetrations do meet the intent of the GDCs for providing containment isolation.
P-55. 56. 57. and 58 Service Water to Containment Air Recirculation Fans These lines contain a single check valve inside containment for containment isolation. These are SW-CV-271A, B, C and D.
Since the SW system is seismically qualified inside containment double barrier protection is provided. Automatic isolation for these lines is not appropriate since they have a post accident safety function.
Service water pressure at this penetration is higher than containment' maximum design and any leakage would be from the service water into containment. The staff concludes that while the isolation provisions for these penetrations deviates from the GDCs, there is adequate isolation (one valve, system pressure, and a closed system inside containment) such that the staff can conclude that these isolation provisions for these penetrations do meet the intent of the GDCs for providing containment isolation.
P-61 Component Coolina Water - CCW from Neutron Shield Tank (NST) Cooler A single isolation valve CC-TV-1831 is located outside containment.
Isolation provisions for this line do not meet the redundancy requirements of the GDC and the staff required that the isolation provisions be upgraded to meet the GDC in Ref. 1.
A single valve is acceptable for closed loop systems inside or outside of containment. The CCW system is a closed system inside and outside containment.
The CCW system does not qualify as a containment barrier because it does not have the seismic and QA requirements. However, it would i
be a deterrent to containment leakage in case of an accident. The staff concludes that while the isolation provisions for this penetration deviate
1 t
' i from the GDCs, there is adequate isolation (one valve and a closed system inside and outside containment) such that the staff can conclude that these isolation provisions for these penetrations do meet the intent of the GDCs for providing containment isolation.
P-62 Service Air to Containment A single isolation valve (SA-V-413) is located on this line outside containment.
Isolation provisions for this line do not meet the redundancy requirements of the GDC therefore the staff required that the isolation provisions be upgraded to meet the GDC in Ref. 1.
This penetration contains two check valves (one inside and one outside of containment) downstream of the CIV. These check valves are not leak tested but would provide a deterrent to containment leakage in case of an accident. The staff concludes that while the isolation provisions for this penetration deviate from the GDCs, there is adequate isolation (one valve and two check valves) such that the staff can conclude that these isolation provisions for this penetration do meet the intent of the GDCs for providing containment isolation.
P-64 Air Monitor Samole from Containment This line contains two isolation valves (VS-TV-1848 and VS-S0V-12-1) in series outside containment. Valve VS-SOV-12-1 receives an automatic closure signal on high containment pressure. The arrangement of two isolation valves in series outside containment was found to be-acceptable by the NRC staff in Ref.
2.
In addition, the Containment Air Sampling system is a closed system outside containment. The Containment Air Sampling system does not qualify as a containment barrier because it does not have the seismic and QA requirements.
However, it would be a deterrent to containment leakage in case of an accident. The staff concludes that while the isolation provisions for this penetration deviate from the GDCs, there is adequate isolation (two valves and a closed system outside containment) such that the staff can conclude that these isolation provisions for these penetrations do meet the intent of the GDCs for providing containment isolation.
P-65 Air Monitor Samole to Containment This line can be isolated by two check valves in series (VS-CV-1103 outside containment and SV-CV-1104 inside containment). Having a check valve outside containment instead of a motor operated valve was found to be acceptable by the NRC staff in Ref. 2.
In addition, the Containment Air Sampling system is a closed system outside containment. The Containment Air Sampling system does not qualify as a containment barrier because it does not have the seismic and QA requirements. However, it would be a deterrent to containment leakage in case of an accident. The staff concludes that while the isolation provisions for this penetration deviate from the GDCs, there is adequate isolation (two valves and a closed system outside containment) such that the staff can conclude that these isolation provisions for these penetrations do meet the intent of the GDCs for providing containment isolation.
N P-66 CCW to Drain Cooler
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i This 'iine is provided with a single check valve (CC-CV-731) for isolation inside containment.
Isolation provisions for this line do not. meet the redundancy requirements of the GDC therefore the staff required in Ref. I that.
.i the isolation provisions be upgraded to meet the GDC. A single valve-is acceptable for closed loop systems inside or outside of containment. The CCW system is a closed system inside and outside containment. The CCW system does not qualify as a containment barrier because it does not have the seismic and QA requirements. However, it would be a deterrent to containment leakage in i
case of an accident. The staff concludes that while the isolation provisions for this penetration deviate from the GDCs, there is adequate isolation' (one valve and a closed system inside and outside containment) such that the staff' can conclude that the isolation provisions for these penetrations do meet the intent of the GDCs, for providing containment isolation.
P-67 CCW from Drain Cooler l
f A single isolation valve (CC-FCV-611) is located 'on this line outside containment. The valve has a remote manual operating switch which is overridden by an automatic closure signal on high containment pressure.
l Isolation provisions for this line do not meet the redundancy requirements of the GDC therefore the staff required in Ref. I that the isolation provisions ba upgraded to meet the GDC. A single valve is acceptable for closed loop p
systems.inside or outside of containment. The CCW system is a closed system i
ir, side and outside containment. The CCW system does not qualify as a containment barrier because it does not have the seismic and-QA requirements.
I However, it would be a deterrent to containment leakage in case of an.
accident. The staff concludes that while the isolation provisions for this penetration deviate from the GDCs, there is adequate isolation (one valve.and i
a closed system inside and outside containment)-such that the staff can i
conclude that these isolation provisions for these penetrations do meet the intent of the GDCs for providing containment isolation.
P-68 Primary Water Sucolv
.q This line can'be isolated by two check valves in series (PW-CV-139.outside' containment and PW-CV-140 inside containment). Having a check valve-'outside containment instead of a motor operated valve was found to' be. acceptable in Ref. 2.
The staff has determined that the isolation valve arrangement for-i this penetration has not changed and is still acceptable based on the original SE.
i P-69 RCS Loen Fill This line-is provided with a single check valve inside containment for isolation. The containment penetration piping is seismic category-I. The connection to the reactor system for this line provides a' potential' leakage path for containment atmosphere or reactor coolant to escape the containment with single failure of the check valve. The GDC require.that two isolation
i barriers be provided.
Each branch line downstream of the check valve contains a normally closed MOV.
In addition, there is a pressure transmitter between the check valve and the MOVs which will provide a reasonable indication that the MOVs are leak tight. The staff concludes that while the isolation provisions for this penetration deviate from the GDCs, there is adequate isolation (two valves) such that the staff can conclude that these isolation provisions for these penetrations do meet the intent of the GDCs for providing containment isolation.
P-72A Containment Leak Monitorina This line contains no isolation valves. This was accepted by the staff in Ref. I since the line contains safety related instrumentation for accident mitigation and the line is classified as part of the containment boundary.
ine licensee states that at times when the plant is operating, manual root valves are utilized for isolation when instruments are calibrated. The root valves are not classified as containment isolation valves nor are they leak tested. The licensee has confirmed that the root valves provide an isolation to containment for pressurization of the instrument. The calibration is done with the instrument in-line and containment boundary is never violated. The staff has determined that the containment isolation arrangement for this penetration has not changed and is still neeptable based on the original SE.
P-74. 75. 76 and 77 RCP Seal Water Iniectiot Check valves (CH-CV-405A, B, C and D) are prt vided on each of these lines inside containment. Seal water injection is provided by the charging system.
The charging system is safety related and is required to operate during accident conditions. The system is designed to function following a design basis earthquake (seismic category I) and has a design pressure higher than that of the containment. The charging system is leak tested in accordance with plant technical specifications. The staff concludes that the isolation provisions for this penetration are acceptable since double barrier protection is provided by the closed system and the check valve.
P-78 PRT Drain This line has two isolation valves in series (DH-TV-1844 and DH-TV-554). Both valves are outside containment. Valve PH-TV-554 has a remote manual operation switch but also has automatic closure which overrides the manual operation feature. This arrangement was judged to be acceptable in Ref. 2.
The staff l
has determined that the isolation valve arrangement for this penetration has not changed and is still acceptable based on the original SE.
P-80 Auxiliary Containment Soray This line contains a single isolation valve (RH-MOV-31) outside containment.
Isolation provisions for this line do not meet the redundancy requirements of the GDC. There is a check valve inside containment which does provide another containment boundary even though it is not leak tested. The staff concludes i
c
. that while the isolation provisions for this penetration deviate from the GDCs, there is adequate isolation (two valves) such that the staff can conclude that these isolation provisions for this penetration does meet the intent of the GDCs for providing containment isolation.
3.0 PROBABILISTIC RISK ANALYSIS 3.1 Introduction As part cf the NRC Systematic Evaluation Program, Topic VI-4, Containment Isolation System, the staff reviewed the isolation provisions for lines penetrating the primary containment against regulatory requirements in Appendices A and J to 10 CFR Part 50, as implemented by Section 6.2.4 of the Standard Review Plan (NUREG-0800, July 1981) and Regulatory Guides 1.11 and 1.141.
In a letter dated April 5,1984, from D. G. Eisenhut (NRC) to W. G.
Counsil (Northeast Utilities), the staff noted that not all containment penetrations at the Haddam Neck Plant are designed or tested in accordance with the requirements in Appendices A and J.
The staff concluded that it was acceptable to defer implementation of specific Appendices A and J modifications until an integrated assessment could be performed.
In report NUSC0149, " Connecticut Yankee Probabilistic Safety Study," February 1986, the licensee identified a number of containment penetrations thht do not meet the requirements of Appendix A, Appendix J, or both.
The licensee performed a probabilistic risk assessment of these containment penetrations and calculated the risk in terms of man-rem for each of the penetrations.
As part of the NRC Integrated Safety Assessment Program, the Science Applications International Corporation, an NRC contractor, has reviewed the licensee's report and issued its findings in report SAIC-87/3004, " Review of Risk-based Evaluation of Integrated Safety Assessment Program Issues for the Haddam Neck Plant," May 29, 1987. The contractor concluded that upgrading penetration P-10 would result in risk reduction benefits that would justify ranking this modification as medium in the implementation priority of the Integrated Safety Assessment Program. Upgrading of the other containment penetrations to meet Appendix A or Appendix J or both is ranked as drop. The contractor's implementation priority ranking was based solely on the evaluation of the licensee's probabilistic risk assessment.
The staff has reviewed the Haddam Neck Plant under the Integrated Safety Assessment Program and issued the findings in report NUREG-1185, " Integrated' Safety Assessment Report, Haddam Neck Plant," July 1987. For Topic 1.03, Containment Penetration Evaluations, the staff rated the implementation priority of upgrading the containment penetrations to meet Appendix A or Appendix J or both to be medium, except for penetration P-10 which was rated high. The rating of these implementation priorities was based in part on the Commission's policy to ensure the philosophy of defense-in-depth.
By letters dated April 26, 1989, January 16, 1991, and May 7, 1992, the licensee indicated that a number of the containment penetrations either have been capped or modified to meet Appendix J requirements, or will be modified during_the 1993 refueling outage to meet Appendix J requirements.
In
w : to the letter dated January 16, 1991, the licensee provided the justification for deviation of the remaining containment penetrations from meeting GDC 54 through 57, The justification was based on the probabilistic risk assessment of the containment penetrations.
3.2 Evaluation The licensee used identical methodology of the probabilistic risk assessment in the January 16, 1991, letter as in NUSC0149 to calculate the risk of each contairment penetration. The NRC contractor has reviewed the methodology and generally concurred with the licensee's assumptions in the probabilistic risk assessment.
The calculated risks of the individual containment penetrations that are listed in Attachment 2 to the January 16, 1991, letter are essentially-the same as those presented in NUSC0149. The calculated risks range from 9 to 5 E-04 (5 times 10 raised to minus fourth power) man-rem. These risks are ranked as drop in the implement: tion priority under the Integrated Safety Assessment Program. Additional penetrations are identified and their calculated risks are comparable to those given in NUSC0149. The staff notes that penetration P-10 has been modified to meet the GDC and was removed from the list of containment penetrations that do not meet the NRC requirements.
The staff has determined that the licensee provides the same methodology for the probabilistic risk assessment and that the calculated risks for the individual containment penetrations are essentially the same as or comparable to those previously reviewed. Therefore, the staff finds that the same conclusion, drawn earlier by the contractor on the basis of its review of the licensee's probabilistic risk assessment, can and should apply to the present evaluation.
On the basis of the above evaluation, the staff finds that the implementation priority for upgrading the containment penetrations at the Haddam Neck Plant to meet the requirements of Appendices A and J for Topic 1.03, Containment Penetration Evaluations, should be ranked as drop under the Integrated Safety Assessment Program. The above conclusion is based on a re-review of the NRC contractor's evaluation of the licensee's probabilistic risk assessment of the containment penetrations, performed during the ISAP review, to assure that the methodology and assumptions assumed are still valid.
4;0 CONCLUSION The staff found that to a large extent the licensee does not comply with the GDC as noted in previous staff SEs for containment' isolation.
For many.
i penetrations double barrier protection is not provided. However, the staff has concluded that for~most of these penetrations, the valve configuration does meet the intent of the GDCs 54 through 57.
In addition, based on the low risk indicated by the licensee's PRA studies, the staff agrees that conformance with the GDCs 54 through 57 would provide minimal safety improvement to the plant. The staff notes that the licensee has previously agreed to provide the following:
o
. 1.
For those valves which do not receive an automatic closure signal the licensee should describe the administrative controls to ensure that the valves are locked closed or procedurally controlled during use. The licensee has previously committed to perform this study in Ref. 1.
The results of this analysis should be provided and where necessary propose corrective actions to ensure that the local manual valves credited for containment isolation are administratively and physically locked closed to ensure containment integrity.
2.
Evaluate the design of isolation valves to assure the valves take the position of greatest safety upon the loss of power.
4.0 REFERENCES
1.
D. M. Crutchfield letter to D. M. Counsil transmitting " Evaluation Report on SEP Topic VI-4, Containment Isolation System, for the Haddam Neck Nuclear Power Plant, Unit 1 Docket No. 50-213," December 13, 1982.
2.
NUREG-0826, " Integrated Plant Safety Assessment, Systematic Evaluation Program, Haddam Neck Plant," June 1983.
3.
E. J. Mroczka letter transmitting " Containment Isolation Valves (CIVs) in Connecticut Yankee Penetrations Differing From 10CFR50 Appendix A General Design Criteria (GDC)," January 16, 1991.
4.
J. F. Opeka letter transmitting "SEP Topic VI-4, Containment Isolation System," January 28, 1993.
Principal Contributors:
A. Wang J. Wing W. Jensen Date:
,