ML20141J390
| ML20141J390 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf, Arkansas Nuclear, River Bend, Waterford  |
| Issue date: | 05/19/1997 |
| From: | Yelverton J ENTERGY OPERATIONS, INC. |
| To: | Callan L NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| References | |
| CNRO-97-00012, CNRO-97-12, NUDOCS 9705280062 | |
| Download: ML20141J390 (14) | |
Text
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=Entergy r:w" ~
Jackson. MS 39286-1995 Tel 6ui.4bM bbw Jerry W. Yelverton Execut:ve wce President and C%f Operahng OCcer May 19,1997 Mr. L. Joseph Callan Executive Director of Operations United States Nuclear Regulatory Commission Mail Stop P1-37
- Washington, DC 20r.55-0001 Subject Entergy Operations, Inc.
Design and Licensing Basis of Entergy Operations, Inc.'s Plants Concerning Appendix R Compliance and its Relation to Information Notice 92-18 and Multiple Spurious Actuations Arkansas Nuclear One Grand Gulf Nuclear Station Units 1 & 2 Docket No. 50-416 Docket Nos. 50-313 & 50-368 License No. NPF-29 License Nos. DPR-51 & NPF-6 River Bend Station Waterford 3 Steam Electric Station Docket No. 50-458 Docket No. 50-382 License No. NPF-47 License No. NPF-38 CNRO-97/00012
Dear Mr. Callan:
Entergy Operations, Inc. (EOl) is writing to address an issue concerning the NRC Staff's interpretation of fire protection requirements that would reflect a new position beyond the existing &mign and licensina bases for the EOl plants. At issue is the method used for evaluatin;, hot shorts" and associated spurious equipment operations under Appendix R to 10 CFR Part 50 and the associated fire protection program requirements. We firmly believo each of the EOl plants is in full compliance with.egulatory requirements and the design and licensing bases relavent to this issue. However, from recent interactions between the NRC Staff and the industry, EO! is concerned that the NRC might now consider methods we have i
used to evaluate hot shorts and spurious actuations at our plants for many years to be inadequate.
With a Fire Protection Functional inspection currently scheduled to begin in June 1997 at River Bend Station, and with some of our plants now in, or soon to be in, refueling outages,
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IN 92-18 and Multipl3 Spurious Actions M:y 19,1997
' CNRO-97/00012 l
Page 2 of 5 we believe it is important to clarify the regulatory uncertainty regarding this issue.
- Accordingly, in the interest of full and open communication, EOl wishes to document our position in this area and request reaffirmation of the previously accepted approaches for EOl sites.
Compliance with the fire protection regulations is a complex matter including the extent of the applicability of different requirements to individuallicensees. This complexity has led to the issuance of many generic NRC communications following promulgation of the fire protection rule in 1980. The complexity also resulted in the NRC requiring that all licensees provide detailed plant analyses for NRC review. Each EOl plant was subjected to 10 CFR 50 Appendix R/ fire protection program compliance inspections. These inspections included the methods the licensee credited for isolation of equipment from fire damage and the treatment of spurious actuations.
In 1992, the NRC issued Information Notice (IN) 92-18, " Potential for Loss of Remote Shutdown Capability During a Controi Room Fire," which addressed certain circuit failure modes that may impair the capability to achieve and maintain safe shutdown following a fire and referred licensees to Generic Letter 86-10, Enclosure 2, Section 5.3.1 (the guidance provided in this Generic Letter is discussed in detail in the attached). As discussed in IN 92-18, the potential for hot shorts during a control room fire that could adversely affect Motor Operated Valve (MOV) operation was found and reported by three licensees. We understand that following additional investigation at least one of these licensees withdrew their report when they determined that this failure mode was outside the scope of the fire protection analysis requirements for their plant.
Following issuance of IN 92-18, individual licensees, including EOi, addressed the failure j
mode described in IN 92-18 as part of their industry events review programs. EOl, In fact, discussed the applicability of the failure mode described in IN 97-18 with NRC inspectors.
For example, at Grand Gulf Nuclear Station (CGNS), utility personnel discussed the type of spurious actuation analysis performed and the applicability of IN 92-18 with the Appendix R alternate shuidown inspection team. The inspection team agreed with GGNS's position that assuming all possible functional failure states precluded the need to consider mechanistic damage as a result of specific circuit failure modes such as those described in IN 92-18.
In addition to the issues related to IN 92-18, during recent interactions with the Nuclear Energy Institute (NEI) and various licensees, the Staff has indicated that multiple spurious actuations during individual fire events must be considered in more cases than just high/ low pressure interfaces. EOl is concerned that the IN 92-18 insights and the consideration of multiple spurious actuations are being interpreted as requirements for compliance with 10 CFR 50 Appendix R/ fire protection program requirements for alllicensees. We believe this l
is inconsistent with previously issued generic guidance and the design and licensing basis of the EOl plants.
In the attachment, EOl discusses generic guidance previously provided by the NRC on the consideration of " hot shorts" and spurious actuations, as well as some of the plant-specific l
IN 92-18 and Multipla Spurious Actions May 19,1997
' CNRO-97/00012 i
Page 3 of 5 reviews of EOl's approach. The guidance discussed in the attachment includes that provided in Generic Letter 86-10 concerning spurious actuations which states:
"Per the criteria of Section Ill.L of 10 CFR 50 Appendix R a loss of offsite power shall be assumed for a fire in any fire area concurrent with the following assumptions:
- a. The safe shutdown capability should not be adversely affected by any one spurious actuation or signal [ emphasis added] resulting from a fire in any plant area; and
- b. The safe shutdown capability should not be adversely affected by a fire in any fire area which results in the loss of all automatic function (signals, logic) from the circuits located in the area in conjunction with one worst case spurious actuation or signal [ emphasis added] resulting from the fire; and
- c. The safe shutdown capability should not be adversely affected by a fire in any plant area which results in spurious actuation of the redundant valves in any one high-low pressure interface line [ emphasis added]."
Concerning the " hot shorts" issue, the NRC guidance discussed in the attachment h.:Nd es that provided in Generic Letter 85-01 and Generic Letter 86-10 which respectively identify:
4 "If the concern is spurious actuation of equipment, actual circuit failure modes could be bypassed by assuming all possible failure states [ emphasis added] for the equipment (valves could fail either open or closed)."
" Sections Ill.G.2 and Ill.L.7 of 10 CFR 50 Appendix R define the circuit failure modes as hot shorts, open circuits, and shorts to ground. For consideration of spurious actuation, all possible functional [ emphasis added] failure states must be evaluated, that is, the components could be energized or de-energized by one or more of the above failure modes. Therefore, valves could fail open or closed; pumps could fail running or not running; electrical distribution breakers could fail open or closed."
From a review of the guidance, it is clear that the NRC accepted the following approaches as satisfying the requirements of Appendix R:
i 1.
Perform a bounding evaluation of worst-case functional failure states without the need for analysis of snecific circuit failure modes and the resultant mechanistic damage, and 2.
Assume a single spurious operation during any fire event except in the case of high/ low pressure interfaces.
The functional failure state approach is very conservative and provides adequate assurance that safe shutdown conditions can be maintained. This approach conservatively assumes all possible functional failure states regardless of whether a credible cable fault could actually l
IN 92-18 and Multiple Spurious Actions May 19,1997 CNRO-97/00012 Page 4 of 5 cause such a failure state to occur. The evaluation of multiple spurious operations was first addressed in Generic Letter 81-12, but was limited to the effects on high/ low pressure interfaces. Similarly, Generic Letter 86-10 addressed the Appendix R requirement to consider hot shorts, open circuits, and shorts to ground, and indicated that only "one spurious actuation or signal" needed to be assumed.
EOl has implemented the functional failure state and single spurious actuation approaches since the early 1980s with previous Staff acceptance as described in the attachment.
Certainly, until recently, there was no NRC objection to EOl's approaches over the years. A review of the generic guidance going back over 15 years indicates that, until IN 92-18, the NRC did not articulate the position that specific circuit failure modes and the resultant mechanistic damage had to be evaluated in all cases or that multiple spurious actuations for more than the high/ low pressure interfaces needed to be assumed. This is compelling evidence that Appendix R was not previously interpreted to require such analyses.
Based on the previous NRC guidance and the plant-specific acceptances, EOl believes that its analytical approaches are consistent with the regulatory requirements. Under the circumstances, the NRC should not enforce the new positions requiring consideration of specific circuit failure modes in all cases instead of functional failure states and multiple spurious actuations for more than high/ low pressure interfcces. New Staff positions in this area have significant backfitting and policy implications that would require appropriate NRC management review and evaluation in accordance with 10 CFR 50.109. In addition, given the generic implications, these issues would seem appropriate for an independent review by the NRC's Committee to Review Generic Requirements (CRGR).
EOl would be happy to meet with the Staff to discuss these issues. Please address any comments or questions regarding this matter to Steve Bethay at (601) 368-5758.
Sincerely, W2 JWY/SJB/BSF/baa attachment:
Design and Licensing Basis of Entergy Operations, Inc.'s Plants Concerning Appendix R Compliance and its Relation to information Notice 92-18 and Multiple Spurious Actuations (9 pages) cc:
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1 IN 92-18 and Multipla Spurious Actions May 19,1997 -
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cc:
Mr. J. L. Blount Mr. S. J. Collins L
Mr. J. G. Dewease l
Mr. J. N. Donohew l
Mr. C. M. Dugger l
Mr. J. J. Hagan i
Mr. C. R. Hutchinson Mr. G. Kalman Mr. J. R. McGaha Mr. C. P. Patel l
Mr. D. F. Stenger Mr. D. L. Wigginton U.S. NRC Document Control Desk i
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4 Attachment to CNRO-97/00012 Page 1 of 9 Design and Licensing Basis of Entergy Operations,Inc.'s Plants Concerning Appendix R Compliance and its Relation to information Notice 92-18 and Multiple Spurious Actuations A. BACKGROUND i
l Since promulgation of the fire protection rule in 1980, the rule has been officially interpreted in many generic NRC communications. Among those interpretations particularly important here are those in Generic Letter 81-12 and Generic Letter 86-10. In addition, to ensure that the fire protection requirements and associated NRC interpretations were correctly
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implemented, the NRC required that alllicensees provide detailed plant fire hazards analyses for NRC review. Additionally, each plant was subjected to 10 CFR 50 Appendix R/
l fire protection program compliance inspections which included a review of the proper treatment of spurious actuations and the isolation of equipment as required by the regulations. The EOl plant's have undergone fire protection implementation inspection (s) which included the treatment of spurious actuations and the methods of circuit isolation.
B. CONCEM i
10 CFR 50 Appendix R requires that where cables of redundant trains of systems necessary to achieve and maintain hot shutdown are located within the same fire area outside of primary containment (e.g., the control room), one of the redundant trains must remain free l
from fire damage, included in this population of cables are associated cables that could cause maloperation due to hot shorts, open circuits, and shorts to ground. In 1992, the NRC issued Information Notice (IN) 92-18, which identified a potential failure mechanism of motor operated valves in which a postulated fire could damage the valve control circuit in such a way as to bypass valve protective features such as limit switches, torque switches, or thermal overload devices and cause valve actuation. The resulting spurious operation of the valve could potentially result in physical damage to the valve operator or the valve itself.
During recent interactions with NEl and various licensees, the NRC has maintained that multiple spurious actuations during fire events must be considered in more cases than the high/ low pressure interfaces which had previously been the only cases for which this was required to be evaluated. This position is evidenced by the Unresolved item (URI) given to Arkansas Nuclear One (ANO) on November 12,1996 which stated: "The inspectors were concerned that the licensee had not considered the possibility that more than one motor-l operated valve may experience a hot short maloperation during a control room fire, as I
required by 10 CFR 50, Appendix R."
The IN 92-18 circuit failure mode and the consideration of multiple actuations have been the subject of correspondence and discussion between the Staff and the industry in recent months. This correspondence (References 1 and 2) and discussions with the Staff (e.g., the meeting between NEl and the NRC on February 7,1997 and the NEl Fire Protection Information Forum in March 1997) has led to the concern that the methods used to address
" hot shorts" and associated spurious equipment operations, which were previously deemed acceptable, may now be viewed by the Staff as inadequate.
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Attachment to CNRO-97/00012 Paga 2 of 9 The following sections summarize the generic guidance previously issued by the Staff upon which the EOl plants were licensed.
C. CIRCUIT FAILURE MODES The new Staff Interpretation of Appendix R goes far beyond the long established analysis method that has been considered an acceptable method by the NRC for demonstrating compliance with Appendix R. In accordance with Generic Letter 86-10, it has been acceptable for licensees to evaluate the consequences of all functional failure states due to a fire and as a result specific circuit failure modes were not required to be considered.
However, the new interpretation would in every case require detailed failure modes and affects analyses of the circuits in a fire area. Such a review would be costly, would not significantly increase fire safety, and would constitute a new Staff position for the reasons discussed below.
10 CFR 50 Appendix R requires that where cables of redundant trains of systems necessary to achieve and maintain hot shutdown are located within the same fire area outside of primary containment, one of the redundant trains must remain free from fire damage.
Included in this population of cables are associated cables that could cause maloperation due to hot shorts, open circuits, and shorts to ground, in Generic Letter 86-10," Implementation of Fire Protection Requirements," dated April 24, 1986, the staff issued guidance conceming the regulatory requirements regarding the need to isolate fire-damaged circuits, mitigate spurious actuations, and retain functionality of the safe shutdown components after their transfer. Enclosure 2 to the Generic Letter provided a list of industry initiated questions and the corresponding NRC responses. In response to Question 3.8.4, " Control Room Fire Considerations," the staff stated,"[t]he damage to the systems in the control room cannot be predicted. A bounding analysis should be made to assure that safe shutdown conditions can be maintained from outside the control room." In addition, the staff stated, "[t]he analysis should demonstrate that the capability exists to manually achieve safe shutdown conditions from outside the control room by restoring a/c power to designated pumps, assuring that valve lineups are correct, and assuming that any malfunctions of valves that permit the loss of reactor coolant can be corrected before unrestorable conditions can occur."
Further in Generic Letter 86-10 the staff interpreted the term " free of fire damage." In," Interpretations of Appendix R," interpretation 3," Fire Damage," the staff stated, in part, that "the Commission has provided methods acceptable for assuring that necessary structures, systems and components are free of fire damage, that is, the structure system or component under consideration is capable of performing its intended function during and after the postulated fire as needed."
Generic Letter 86-10 also identified the circuit failures that must be considered in the j
response to Question 5.3.1. The industry question addressed as Question 5.3.1 is: "What circuit failure modes must be considered in identifying circuits associated by spurious actuation?" The NRC response states that " Sections Ill.G.2 and Ill.L.7 of 10 CFR 50 Appendix R define the circuit failure modes as hot shorts, open circuits, and shorts to ground. For consideration of spurious actuation, all possible functional [ emphasis added]
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Attachment to CNRO-97/00012 Pag 3 3 of 9 failure states must be evaluated, that is, the components could be energized or de-energized by one or more of the above failure modes. Therefore, valves could fail open or closed; pumps could fail running or not running; electrical distribution breakers could fail open or closed."
Clarification concerning the intent of the term " functional failure states" can be found in Generic Letter 85-01 and in the NRC Regional Fire Protection Workshop handouts for the questions and answers. As discussed in Generic Letter 86-10 these workshops and handouts formed the basis for Generic Letter 86-10. The Generic Letter 86-10 question identified above was discussed in the workshop handouts in Section Vill, " Safe Shutdown and Fire Damage," as Question A and in Generic Letter 85-01 as question and answer 5.3.1.
The industry question addressed was the same question previously discussed (i.e., "What circuit failure modes must be considered in identifying circuits associated by spurious actuation?"). To this question the NRC replied ".. If the concern is spurious actuation of equipment, actual circuit failure modes could be bypassed by assuming all possible failure states [ emphasis added] for the equipmW (valves could fait either open or closed)."
As discussed above the NRC's position during the development of the individual plant's Appendix R analysis was that during a control room fire "[t]he damage to the systems in the control room cannot be predicted. A bounding analysis should be made to assure that safe shutdown conditions can be maintained from outside the control room." Consistent with this position the Appendix R analysis of the plants made the bounding assumption that any and all safe shutdown components located in (or with cables routed in) a fire area fail to the worst possible functional failure state unless a specific circuit failure mode analysis was performed.
If the worst safe shutdown position for a valve is closed, the valve is assumed to be closed, regardless of whether a cable fault (including associated cables) can actually cause valve closure, except for certain three-phase AC and ungrounded DC circuits for which the failure was not considered credible.
The functiona failure state approach is conservative with respect to the fire damage evaluated in NUREG-0050," Recommendations Related to Browns Ferry Fire," February 1976. NUREG-0050 identifies that a total of 1611 cables were damaged or assumed damaged by the Browns Ferry fire and identifies that: *Except for cables, conduits, cable trays, and cable ladders, there is no evidence of significant equipment damage to electrical equipment." Consistent with the NUREG-0050 statement, we could not identify any documented occurrences of the IN 92-18 postulateo event where the hot short in the control circuitry caused mechanical damage to a valve located outside of the fire area. Therefore, this NUREG demonstrates that the functional failure state analysis performed provides adequate assurance that safe shutdown conditions can be maintained.
The functional failure state approach assumed all possible functional failure states regardless of whether a cable fault could actually cause the failure state to occur. The failure states are " functional" failure states and as a result the equipment was assumed to be recoverable following isolation from the fire area. Since all possible failure states were evaluated, as discussed in the guidance of Generic Letter 85-01, the plant was not required to determine and analyze the specific circuit failure modes. The condition described in IN 92-18 can only be identified by performing a detailed analysis of the circuits which are in a fire area and reviewing them from a fire damage assessment approach. This type of analysis is
Attachment to CNRO-97/00012 Paga 4 of 9 beyond the requirements of the functional failure state approach previously accepted by the Staff.
D. MULTIPLE SPURIOUS ACTUATIONS The need to address multiple spurious actuations is a new Staff interpretation. In accordance with Generic Letter 86-10, licensees have evaluated all spurious actuations, one at a time, except for high/ low pressure interfaces. The new interpretation would require the consideration of multiple spurious actuations, contrary to the established practice.
As discussed previously,10 CFR 50 Appendix R lll.G and Ill.L both require that where cables of redundant trains of systems necessary to achieve and maintain hot shutdown are located within the same fire area outside of primary containment, one of the redundant trains must remain free from fire damage. Included in this population of cables are associated cables that could cause maloperation due to hot shorts, open circuits, and shorts to ground.
The concept of evaluating multiple spurious operations was first addressed in Generic Letter 81-12. However, the evaluation was limited to the effects on high/ low pressure interfaces. Enclosure 2, Item 2 states :
"It is our concern that this single fire could cause the two valves to open resulting in a fire-initiated LOCA through the subject high-low pressure system interface. To assure that this interface and other high-low pressure interfaces are adequately protected from the effects of a single fire, we require the following information;"
The document continued by specifying what information needed to be provided such that the staff could perform an adequate review of the subject scenario. This position was reiterated in the subsequent clarification letter to Generic Letter 81-12, again with the focus on high-low pressure interfaces.
The response to Generic Letter 86-10, Question 5.3.10 addressed what the 10 CFR 50 Appendix R requirements to consider hot shorts, open circuits, and shorts to ground meant in terms of the spurious actuation of equipment associated with the fire area being evaluated for more than just the high/ low pressure interfaces. This Generic Letter specifically indicates that only one spurious actuation signal is required to be postulated for any single fire event.
Question 5.3.10, Design Bases Plant Transients, states "What plant transients should be considered in the design of the alternative or dedicated shutdown systems?" The NRC's response was "Per the criteria of Section Ill.L of 10 CFR 50 Appendix R a loss of offsite power shall be assumed for a fire in any fire area concurrent with the following assumptions:
- a. The safe shutdown capability should not be adversely affected by any one spurious actuation or signal [ emphasis added] resulting from a fire in any plant area; and
- b. The safe shutdown capability should not be adversely affected by a fire in any fire area which results in the loss of all automatic function (signals, logic) from the circuits located in the area in conjunction with one worst case spurious actuation or signal (emphasis added] resulting from the fire; and i
Attachment to CNRO-97/00012 Pags 5 of 9
- c. The safe shutdown capability should not be adversely affected by a fire in any plant area which results in spurious actuation of the redundant valves in any one high-low pressure interface line [ emphasis added]."
The purpose of the NRC response to Question 5.3.10 was to specify the plant transients that licensees should consider in their analysis. Since the Requirements for Ill.G and Ill.L are the same in the regulations with regards to hot shorts, open circuits, and shorts to ground the guidance provided in the response 5.510 is applicab'.e to all fire areas. This response provides the spurious actuations which must be considered for equipment associated with the fire area being evaluated. Spurious action of equipment which does not interact with the fire area (including equipment isolated from the area)is not credible and, therefore, not assumed.
Generic Letter 85-01 also included the Generic Letter 86-10 question and answer discussed above. Additionally, one of the enclosures to Generic Letter 85-01 included minutes from the third meeting of the Fire Protection Policy Steering Committee. A discussion conceming the scope of review for alternate shutdowns was led by a representative of Auxiliary Systems Branch and yielded the fo!!owing :
"With respect to the associated circuits analysis it was indicated that the evaluation assured, assuming offsite power loss, that safety could be demonstrated assuming one spurious signal (emphasis added] a loss of all automatic signals, and spurious operation of motor operated valves in the high/ low pressure interface."
On May 7,1986, members of the NRC staff met to discuss SECY-85-306, Staff Recommendations Regarding the implementation of Appendix R to 10CFR50. The meeting minutes, as published by Leon Whitney (August 11,1986) contained the following statements :
"It was noted that the three assumptions of Question and Answer 5.3.10 are meant for independent use Chat is, only one assumption applies for any given configuration in a reactor plant). These assumptions are therefore consistent with the established NRR review practice of requiring licensees to analyze for any and all spurious actuations or failures where no two such spurious actuations or failures occur simultaneously"
[ emphasis added by NRC).
This position is reflected in NRC Inspection Procedure 64100, Post Fire Safe Shutdown, Emergency Lighting, and Oil Collection Capability at Operating and Near Term Operating Reactor Facilities, paragraph 03.01.e.2.f. specifically emphasizes the fact that:
"These assumptions (from GL 86-10, Question 5.3.10] are therefore consistent with the established NRR review practice of requiring licensees to analyze for any and all spurious l
actuations or failures where no such spurious actuations or failures occur l
simultaneously"[ emphasis added by NRC].
In order to comply with the requirements of 10 CFR 50 Appendix R, hot shorts must be assumed for unprotected cables / control circuits in the fire area under evaluation. The effect of the possible spurious operation for any unprotected circuit in the fire area must be l
Attachm nt to CNRO-97/00012 Pag 3 6 of 9 evaluated. However, only one spurious operation need be assumed during any fire event except in the case of high/ low pressure interfaces where multiple spurious operations can occur.
E. PREVIOUS NRC CONCLUSIONS EOl has implemented the functional failure state and single spurious actuation approaches since the early 1980s with previous Staff acceptance. Certainly, until recently, there was no NRC objection to the EOl's approaches over the years. In fact, a review of the generic guidance going back over 15 years indicates that, until IN 92-18, the NRC never articulated the position that specific circuit failure modes had to be evaluated or that multiple spurious actuations for more than the high/ low pressure interfaces needed to be assumed. This is compelling evidence that Appendix R was never previously interpreted to require such analyses.
To ensure that the fire protection requirements and associated NRC interpretations were correctly implemented, the NRC required that all licensees provide detailed plant fire hazards analyses for NRC review. Additionally, each EOl plant was subjected to 10 CFP. 50 Appendix R/ fire protection program compliance inspections which included a review of the proper treatment of spurious actuations and the isolation of equipment as required by the regulations. The NRC conclusions related to these issues include the following:
" Enclosure 1 provides our Safety Evaluation regarding the safe shutdown capability in the event of fire for Arkansas Nuclear One, Units 1 and 2 (ANO-1&2). The safe shutdown capability for ANO-1&2 was evaluated against the requirements of Sections Ill.G and Ill.L of Appendix R to 10 CFR 50. Our Safety Evaluation (Enclosure 2) concludes that ANO-1&2 are in accordance with Appendix R, items Ill.G.3 and Ill.L except where an exemption to the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> shutdown requirement has been granted (NRC letter dated May 11,1983) to ANO-1 and subject to the requirement that a source range neutron flux monitoring capability electrically independent of the control room be provided at the Safety Parameter Display System for both units."
Additionally, the NRC stated:
"The Licensee has considered all such situations in his fire zone analysis and has either proposed modifications or requested exemptions. In regard to the control room and cable spreading room, the Licensee has determined that there are no spurious operation conditions which could affect safe shutdown except for the following high-low pressure interfaces."
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- 2. Grand Gulf Nuclear Station l
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Attachment to CNRO-97/00012 Pags 7 of 9 Inspection report 50-416/85-16 which in sec%n b, " Associated Circuits of Concern,"
concludes:
"Except for the items identified by the licensee, associated circuits of concem appeared satisfactory for Appendix R, Sections Ill.G.2, Ill.G.3, and lli.L. The licensee has identified these associated circuits of concern areas, has taken exceptions, and specified modifications to bring these areas into compliance with their current understanding of the literal requirements of Appendix R."
- 3. River Bend Station Inspection report 50-458/85-41 which in section 2, " Followup on Previous inspection Findings," concludes:
"(Closed) Open item (458/8527-07): This item required the revision of the licensee's fire hazards analysis (FHA) to account for fire-induced spurious signals in all lil.G.2 areas. The NRC inspector reviewed Revision 3 of the fire hazards analysis, dated June 14,1985, and found spurious signals have been adequately addressed. This item is considered closed."
Inspection report 50-458/90-02 which in section 2.4, " Associated Circuits Review,"
concludes:
"The associated circuits analysis dated June 14,1985, provided the basis of the modifications which were made to comply with 10 CFR Part 50, Appendix R.... The inspectors concluded that the licensee's analysis of associated circuit concems is satisfactory and meets the requirements of Appendix R, Section Ill.L."
Subsequently, River Send Station elected to perform detailed circuit failure mode analyses for the post-fire safe shutdown analysis as a method of compliance with the requirements. As a result, when a circuit failure mode analysis identifies a failure mode of concern, design and procedural enhancements are implemented as needed.
Inspection report 50-458/93-30 reviewed this analysis and identified issues. This report also identified in section 2.2.2," Evaluation of Spurious Signals Analysis," the following:
"In the event of fire in the main control room, all circuits required for safe rhutdown were electrically isolable from the control room by isolation transfer switches. In addition to providing protection for potential spurious components within a credited system, the analysis performed by the licensee for each fire area also conservatively assumed one ' worse-case' spurious actuation of a non-credited system as a result of fire."
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Inspection report 50-458/93-30 concluded:
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"The reverification of potentiali puricus equipment operations was found to be based on acceptable assumptions anil suitable evaluation methods (Section 2.2.2)."
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- 4. ' Waterford 3 Steam Electric Station i
Attachment to CNRO-97/00012 Pag 3 8 of 9 1
Inspection report 50-382/88-29 which in " Associated Circuits Review," discusses:
"The Associated Circuits Analysis dated November 30,1984, provided the basis of the modifications which were made to comply with 10 CFR 50, Appendix R. This analysis was developed for LP&L by Ebasco (AE) as a result of an April 1984, NRC Audit."
Further the report concludes:
"The licensee's treatment of associated circuit concerns is considered to be satisfactory to meet the requirements of Appendix R, Section Ill.L."
F. CONCLUSION EOl believes that the clarifications of Generic Letter 81-12, the 1984 Workshops, Generic Letters 85-01 and 86-10 and several other documents were attempts to establish some standards for evaluating possible fire damage. These generic documents endorsed the methodology of performing a bounding analysis which assumed all possible functional failure states as an alternate to performing specific circuit failure mode analysis. Further the guidance identified that since all possible failure states were evaluated, the plant was not required to determine and analyze the specific circuit failure modes and the resultant mechanistic damage. The guidance also identified only one spurious operation need be assumed during any fire event except in the case of high/ low pressure interfaces.
The fundamentalissue is treatment by NRC of the IN 92-18 recommendations as regulatory requirements. The NRC staff interpretations of IN 92-18 guidance as regulatory requirements is not consistent with the intent of the regulations as previously understood by EOI. The IN positions and subsequent correspondence with NEl differ from previous NRC positions documented in generic NRC guidance. in particular, the IN implies that MOV failure modes other than the functional failure modes articulated in Generic Letter 86-10 must be considered.
EOl believes that the approaches of evaluating functional failure states thereby bypassing analysis of the specific circuit failure modes and only assuming one spurious operation during any fire event except in the case of high/ low pressure interfaces is consistent with the previously issued NRC guidance. As a result, EOl believes that the enforcement by the Staff of consideration of specific circuit failure modes in all cases and the consideration of multiple spurious actuations for more than high/ low pressure interfaces should only be undertaken after the appropriate review in accordance with 10 CFR 50.109 of these new interpretations.
G. REFERENCES
- 1. Letter from Ralph E. Beedle, Senior Vice President and Chief Nuclear Officer Nuclear Generation Nuclear Energy Institute, to Mr. Frank J. Miraglia, Jr., Acting Director Office l
of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission, dated January 14, j
1997.
Attachment to CNRO-97/00012 Pags 9 of 9 l'
- 2. Letter from Samuel J. Collins, Director Office of Nuclear Reactor Regulation U. S.~
Nuclear Regulatory Commission, to Letter from Ralph E. Beedle, Senior Vice President and Chief Nuclear Officer Nuclear Generation Nuclear Energy Institute, dated March 11, i
1997.
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