ML20077M547
| ML20077M547 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 01/04/1995 |
| From: | Stewart W ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR |
| To: | Chilk S NRC OFFICE OF THE SECRETARY (SECY) |
| References | |
| FRN-59FR52707, RULE-PR-50 59FR52707-00023, 59FR52707-23, NUDOCS 9501130101 | |
| Download: ML20077M547 (11) | |
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r DOCKET NUMBER 5y - A3 PROPOSED RULE (5 W g e) Dog 0 Arizona Public Service Company ...
P O BOr 53999 . PHOENIX. ARIZONA 8$07?-3999 ,
102-03217-WLS/JRP
$Uhf[,"O January 4,1995 OITICt U n Z i
DOCIEiiM r s.
Mr. Samuel Chilk, Secretary U. S. Nuclear Regulatory Commission !
ATTN: Docketing and Service Branch {
Washington, DC 20555 l l
Dear Mr. Chilk:
Subject:
Palo Verde Nuclear Generating Station (PVNGS) i Units 1,2, and 3 Docket Nos. STN 50-52f/529/530 Comments on Shotdown and Low-Power Operations for Nuclear Power Reactor Proposed Rule File: 95-056-026 These comments are being submitted by Arizona Public Service Company (APS), on behalf of itself and participants in the Palo Verde Nuclear Generating Station (PVNGS),
in response to the request for comments on the proposed rule, " Shutdown and Low l l
Power Operations for Nuclear Power Reactors," noticed in the Federal Register dated ]
October 19,1994, (Vol. 59, No. 201 Federal Register 52707). 1 APS is concerned that the proposed rule would not only adversely impact outaget durations but may have a negative impact on safety. The requirements that controls must reflect sufficient redundancy in systems, subsystems, components, and features i to ensure that, for the onsite electric power system in operation, safety functions can be accomplished, assuming a single failure for all conditions except refueling operations, will greatly restrict the time available for system level maintenance during refueling outages. By limiting options available during outages, all-important maintenance of significant safety related equipment may be jeapordized. The principle purpose of outages (safety related equipment maintenance) may be slighted, potentially leading to higher equipment failure rates during full power operations. l l
l Also, we do not believe the regulatory analysis has justified the proposed rule. Concerns on the inadequacy of the regulatory analysis include flawed assumptions, inaccurate cost estimates, and the assumption that there would be no increase in outage duration due to the proposed rule.
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With industry implementation of the Maintenance Rule and NUMARC 91-06 to improve '
shutdown safety, we believe the potential improvement from the proposed rule in safety is limited and the potential economic impact is significant. We suggest that alternative 1
1 I 9501130101 950104 l PDR PR 50 59FR52707 PDR D)D
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U. S. Nuclear Regulatory Commission i Comments on Shutdown and Low-Power Operations for Nuclear Power Reactor Proposed Rule j' Page 2 i
l methods (i.e., a performance based program) be considered as a way to achieve safe !
and economic performance of shutdown operations. l APS believes that maintenance is critical for the safe continued operation of the plant.- l Undue restrictions, with limited safety benefit, would add financial burden to the ;
operation of the plant, and would jeopardize continued viability of nuclear power. !
in summary, APS remains deeply concemed by the direction and content of the ;
proposed rule. Specific comments on the proposed rule and draft regulatory guide are :
i provided as an enclosure to this letter. In addition to the enclosed comments, APS supports NEl's industry comments as well as the CE Owners Group comments. !
We appreciate the opportunity to comment on the proposed rule and the Staffs !
consideration of our comments. l
(
Sincerely, ;
WLS/JRP/rv .
Enclosure j E
cc: L. J. Callan )
K. E. Perkins ;
B. E. Holian K. E. Johnston :
NEl l CEOG !
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2- m M
O P
ENCLOSURE COMMENTS ON SHUTDOWN AND LOW-POWER OPERATIONS FOR NUCLEAR POWER REACTOR PROPOSED RULE
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Proposed NRC Shutdown Rule introduction Section [pg.~52708]. _ {
The staff plans to revise the regulatory analysis performed in support of the proposed 1 shutdown rule. The revision willincorporate: (1) insights gained from the recent NRC ~ l
- PRA's Ibr shutdown and low-power operations at Surry and Grand Gulf; (2) industry l improvements made in outages; (3) comments received I am the ACRS, CRGR and the - 1 Commission, and 4) speci6c industry comments on the draft regulatory analysis. !
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APS COMMENT: Rule making should be postponed until the regulatory analysis and 10 .-l CFR 50.109 backfit analysis are revised. Waiting ~ until the regulatory analysis is j complete will present a more accurate picture of areas that industry needs to focus on i to improve shutdown operations and show the benefit of implementation of the shutdown - 1 rule goveming low power'and shutdown operations. In addition, the actual cost benefit j analysis will be reflected in the regulatory analysis. The original cost benefit analysis ;
was in error.primarily due to under estimating the impact upon outage length due to j implementation of the proposed rule and over estimating the public risk reduction with !
the associated rule. l The proposed rule poses significant economic impact to outage operation. We believe other alternatives exist which will both minimize the economic impact to outages and l maximize safety. Through the industry implementation of Individual Plant Examination !
program and NUMARC 91-06 for shutdown operation, it is recognized that certain j maintenance activities that are typically conducted during outages, can be' performed :
safer while on-line. . This, in general, can be demonstrated using PRA for lower modes !
and for power operation. If this is technically justified, then certain Technical.
Specification allowed outage times may have to be re-evaluated. To ensure'overall l]
reliability and availability for structures, systems, and components are maintained, the I Maintenance Rule performance measures, which can be established for all modes, would t serve as an effective monitoring and compliance tool. ' We believe this alternative would i minimize economic impact and ensure that nuclear safety and reliability is assured for j all modes of operation. -l Proposed NRC Shutdown Rule introduction Section [pg. 52709]
"The results of the analysis of the dominant event sequences indicate potential l reductions in core-damage probability of greater than S.0E-05 per reactor-year for each !
PWR's improvement...." The staff further concedes that significant improvement in }
core-damage probability has already been achieved through recent industry actions ;
(e.g., NUMARC 91-06). The staff further comments that a regulatory " foot print" on -
outage safety and codify improvements made by industry to ensure that [1] reductions in risk already achieved are not eroded in the future and [2] consistency and uniform achievement of the safety improvements is realized throughout the industry.
APS COMMENT: We maintain that there is little benefit to be gained from a safety standpoint (reduction ln overall outage risk) for those utilities that have adopted NUMARC 91-06. To manage a successful outage (from a shutdown safety and Page 1 of 8
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,r s : economic standpoint) the licensees needs to have the flexibility in outage scheduling that
- may not be available through the implementation of a prescribed set of rules goveming equipment availability and containment integrity. : Licensees should have the option of- :
assessing the risk associated with the .various outage' periods and activities and ;
. assigning the appropriate level of defense in depth to ensure that the shutdown safety functions are maintained. For- example, the requirement.to maintain containment integrity vice containment closure will be costly.in terms of timing to complete the action ,;
and will most likely result in delays in staging equipment in containment which will impact : j critical path activities. Also the " single failure" requirement for onsite AC power sources . -i may add 'little value when compared to the more- dominant causes of a loss of a - a l
shutdown safety function. Defense in depth requirements may charm for licensees from what was originally committed to in the original NUMARC 91-06 e .Jorsement. If this is the case then each licensee should be able to defend the change from a risk standpoint 1 before a change is implemented. .;
Proposed NRC Shutdown Rule introduction Section [pg. 52708] .
"The NRC has observed that many shutdown operations may take place with the !
containment partially open. Therefore, cost-elfective regulatory actions are appropriate to ensure substantial reduction in core-damage probability, and an improvement in the -. .
likelihood of containment isolation, when necessary. These actions would substantially ;j increase the overallprotection of public health and safety."
APS COMMENT: The substantial reduction in core damage probability has already been l realized by the majority of the industry through the implementation of NUMARC 91-06. l Implementation of the proposed shutdown rule would not have the major reduction in ;
outage risk as described in the regulatory analysis. Also, there is little. description in the .l draft regulatory guide for the requirements for containment integrity. This leaves the licensee to assume that possibly the requirements for containment integrity as proposed i in the existing technical specifications is to be followed. This is a position that does not 'l'
. appear to be applicable for shutdown operations nor is this_ position supported by NUREG/CR-1449 " Shutdown and Low-Power Operation at Commercial Nuclear Power ;
Plants in the United States." With respect to fire protection, the draft regulatory guide seems inconsistent with the Rule as proposed in several areas. It needs to be revised to ensure that performance measures are defined. Unless clearly defined performance ;
measures are included in the Rule, the extent of regulatory expectations are unknown i until the final regulatory guide is published. Compliance may be required as soon as -
6 months from the publication date. This could be difficult to achieve in the short time ,
frame. .
i Through development of the Maintenance Rule, the NRC and industry have made significant progress towards performance based environment. In the future competitive >
energy service market, the nuclear industry can only compete with other energy producers and, in the meanwhile, maintain safe and reliable operation through effective allocation of resources on important structures, systems, and components. The Page 2 of 8
Maintenance Rule allows for effective monitoring of plant and SSC performance and direct effective allocation of resources. The Maintenance Rule, in conjunction with industry wide implementation of NUMARC 91-06, should form a reasonable basis for moriitoring industry performance during shutdown modes. Performance indicators would be maintaining each shutdown safety function (subcooling/ decay heat removal, RCS inventory, and reactivity control). The defense in depth technique as prescribed in NUMARC 91-06 would be applied to ensure that the performance indicators would be met. The appropriate defense in depth level would be a function of the current RCS configuration and time in the outage (days shutdown).
Proposed NRC Shutdown Rule Section (c)(1) [pg. 52713]
- Provide reasonable assurance that uncontrolled changes in reactivity, uncontrolled changes in reactor coolant inventory, and loss of subcooled state in the reactor coolant system when subcooled ccnditions are nonnally maintained will not occur when the plant is in either a shutdown or low power condition."
APS COMMENT: The scope of the proposed rule should be limited to Modes 5,6 and defueled conditions. Technical specifications currently cover (to the level of detail prescribed by the proposed shutdown rule) operation il modes 1-4 and adequately address the equipment requirements for control of reacdvity, reactor coolant inventory and decay heat removal. Modes 5,6 and defueled conditions that are not already addressed by the Technical Specifications should be in the scope of the rule in regards to event mitigating equipment identification and control.
Proposed NRC Shutdown Rule Section (c)(3)(i) [pg. 52713]
"The contmls must reflect sufficient redundancy in systems, subsystems, components, and features to ensure that, for the onsite electric power system in operation (assuming offsite poweris not available), safety functions can be accomplished, assuming a single failure, for all conditions except refueling operations (with water level above the reactor in excess of a lower limit established in applicable technical specifications or plant procedures)..... "
APS COMMENT: The single failure for all plant conditions with the exception of refueling operations is overly conservative. This will greatly restrict the time available for system level maintenance during refueling outages. This will compress the period for system level work with the potential to increase the possibilities for loss of a safety function and '
human errors. Licensees should be given the flexbility to manage plant activities according to the actual risk posed by each plant outage state with the highest levels of controls applied to those periods of the greatest risk. There are several factors which determine plant risk as well as varying strategies to reduce the risk to acceptable levels.
The guidance provided by NUMARC 91-06 provides this flexibility as well as allowing licensees to conduct effective outages from a cost effective standpoint.
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' Assumption on loss of offsite power for all shutdown conditions is unrealistic and overly. -l n prescriptive. Outage management plans availability of ALL power supplies. LOOP and : j
- " single failures" should be considered in the context of Probabilistic Risk Assessments' ;j so that the risks can be properly managed. This portion of the Rule should be written :
to specify an acceptable level (or acceptable measures) of safety. For example, NSAC !
203, dated April 1994, records show that there have been 26 LOOP events of more than
- one hour duration, in the' past 13 years which includes more than 1400 reactor years. jl Of these LOOPS, one half were weather related so that licensees were able to plan :
accordingly and take extra precautions as necessary. This potential risk seems l probabilistically insignificant and should be addressed accordingly. j i
This section refers to equipment that is required to be available for shutdown and low i power operation.~ They are not the same systems analyzed for Appendix R safe (hot) i shutdown. The analysis to identify all associated components including cable routings 'j (and associated circuits) would require significant time and resources. It is not clear that ;
the actual scope of work has been considered.
- l Proposed NRC Shutdown Rule introduction Section [pg. 52710] . l
" Requirements for specilfc equipment availability using plant procedures would be l established by the licensee in a way that provides maximum flexibility by permitting the
. Use of non-safety as weII as safety equipment to provide safety functions." l APS COMMENT: This statement appears to be in conflict with the~ requirement to ,
assume a loss of offsite power and single failure. Allowance for non-safety equipment i will allow licensees to credit their alternate AC power source installed as a result of the i SBO rule, however, most in-plant non-safety grade equipment is typically _ non-class l powered and hence would not be available if a loss of offsite power is assumed. -l i
Proposed NRC Shutdown Rule Section (c)(1) [pg. 52713] i
" Provide reasonable assurance that uncontroIIed changes in reactivity, uncontrolled l changes in reactor coolant inventory, and loss of subcooled state in the reactor coolant ;
system witen subcooled conditions are nom 1 ally maintained will not occur when the i plant is in either a shutdown or low power condition." l l
APS COMMENT: The requirement to maintain subcooling is overly restrictive in that i proven alternate decay heat removal methods such as reflux boiling in the steam generators and once through cooling (when the RCS is open) cannot be credited.
Boiling in containment does not necessarily mean that an offsite dose in excess of 10 ;
CFR 100 limits will result. The requirement for decay heat removal should state that _
j adequate core cooling must be maintained so that fuel design limits can be maintained. !
i Proposed NRC Shutdown Rule Section (c)(4)(i) [pg. 52713]
" evaluate realistically available fire protection features and the outage plan forpossible
... l fires stemming from activities conducted during cold shutdown or refueling conditions, {
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and determine realistically whether such fires could prevent accomplishment of nomial ,
decay heat removal capability during cold shutdown or refueling conditions. If the evaluation shows that such fires would prevent accomplishment of normal decay heat removal capability, the licensee must either (A)...."
APS COMMENT: The intent to be realistic is commendable. However t.he phrases
" realistically available" and " determine realistically whether" are, at best, nebulous. The Rule should prescribe an acceptable level of safety performance consistent with NUMARC 91-06 philosophy. Each licensee should use defense-in-depth techniques to assure that their respective outage management plan achieves the predetermined level of safety performance.
Supplementary information published in the Federal Register indicates that the fire protection portion of the Rule is intended only to address shutdown decay heat removal.
This section addresses normal decay heat removal which appears to unintentionally expand the scope of the Rde. SECY 93-190 dated July 12,1993 and the statements of considerations published in ihe Federal Register state that only decay heat removal requires analysis. Section (c) (4) appears to require that changes in reactivity, reactor coolant inventory and level, loss of subcooled state and containment integrity be analyzed. The rule should be revised in accordance with the stated intent to address fire risk only for decay heat removal systems. ;
Proposed NRC Shutdown Rule introduction Section [pg. 52709] l The proposed rule and Reg. Guide prescribe that each licensee maintain containment
" integrity" or maintain the ability to re-establish containment " integrity" to prevent. i releases in excess of 10 CFR 100 limits. l l
APS COMMENT: We acknowledge the additional flexibility for establishment of this radiological barrier between the RCS and the environment. It is most likely that some degree of core damage would need to occur before 10 CFR 100 limits would be !
challenged. However, containment " integrity" has a very specific technics.1 specification definition normally associated with operations in modes 1-4. It is unnecessary to apply 1 these stringent requirements to modes 5 or 6 where the accidents progress at a much lower rate and energy level when compared to power operations. The guidance for containment structural requirements contained in Generic Letter 88-17 appear to be ;
more representative of the requirements for shutdown operations to mitigate an off-site release as a result of an accident which initiates from modes 5 or 6.
l Proposed NRC Shutdown Rule Reg. Guide Section C. Guidance [pgs. 4-5]
The Reg. Guide states that "The entire list of equipment need not be available; rather, sufficient equipment from the controlled list must be maintained in a " capable" and "connectable" status in order to protect the stated safety functions.
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3 APS COMMENT: There is no need to' introduce _ new terms to replace the! term -
."functional" currently in use by the industry. We acknowledge the concem of the sta*f with .the varying equipment configurations used by licensee's during ~ outages for
.." functional"_ systems. The intent of the terms " capable" and "connectable" should be :
incorporated into each licensee's definition of equipment functionality to ensure that only_
equipment Qat is truly availabie for event mitigation'is credited for safety function -
support.
Proposed NRC Shutdown Rule Section (d) [pg. 52713] .
"Alllicensees of pressurized water reactors must provide instrumentation Ibr monitoring waterlevelin the RCS during midloop operation. The accuracy of the instrumentation shall not be affected by changas in pressure in the RCS or connected systems. The-installed instrumentation shallunclude visible and audible indications in the controlroom to alert operators belbre wat'ar level falls below a prescribed limit."
APS COMMENT: The Reg. Guide [pgs 7-8] states that ultrasonic devices or other local measurements, such as pressure differential across the hot leg can be used to meet the RCS water level instrumentation requirement. Other ways of level monitoring, such as the use of available heated junction thermocouples (HJTC), should be allowed to meet this requirement. The HJTCs are not susceptible to the effects of pressure differentials l and provide a range of coverage in both the reactor vessel head and hot leg area.
In reference to RCS water level instrumentation installed as a result of GL 88-17, NUREG 1449 [pg. 7-4] states that...."PWR licensees have added level instrumentation to cover shutdown operation in response to GL 88-17 and, in PWRs, level indications have generally improved in the last 3 years. However, events in PWRs continue _to occur (e.g., -Prairie Island,1992) in which axisting methods for monitoring water level have failed to adequately indicate a level too low to support DHR pump operation."_ We contend that consideration should be given to how the. water level instrumentation (installed as a result of GL 88-17) is operated from the standpoint of reliability. The Prairie Island event occurred as a result of errors associated with a nitrogen overpressure maintained in the pressurizer as the plant drained to mid-loop. Some licensees drain to mid-loop with a vented RCS system thereby minimizing the potential for errors as a result of pressure differentials. Licensees should not be required to install an additional water level indicating system if there is no clear benefit to the licensee. _ If a licensee can demonstrate that the existing system meets the requirement of GL 88-17 and has a proven reliable loss of shutdown cooling mitigating strategy with the existing RCS water level instrumentation, then the Licensee should have the option of installing additional RCS water level indication.
Proposed NRC Shutdown Rule introduction Section [pg. 52711]
i The proposed rule solicits information from licensees as to the steps already taken to reduce risk during shutdown and low-power operations.
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- APS COMMENT: Palo Verde has taken various steps to reduce the risk associated with L :
- shutdown operations. Palo' Verde 'is committed to meeting : the NUMARC . g1-06' _ l guidelines for all. shutdown. operations. .Equiprnent requirements.and controls are !
" i described and implemented through the use of administrative procedures. The following are representative of some of the actions and requirements that are in place which have .,
resulted in lower risk during shutdown operations. ~!
i n * - Outage . schedules receive .both ~ an intemal- (Outage Management). and l
independent extemal (multi-discipline team) safety review.
I
- Changes during the course of an outage which potentially impact the prescribed defense in depth requirements are reviewed by a member of the shutdown risk . ;
assessment team, Outage Manager and Operations Manager. 1
- Defense in depth is maintained for electrical power sources supplying Class 1E AC systems- (procedural requirements more stringent than Technical !
Specifications for all Moda 5-6 conditions except when the core is defueled or the !
RCS is at refueling wabr level).
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- Alternate sources of electrical power are available to the shutdown unit through l cross-tying electrical power to another unit or use the alternate AC power source -l (gas turbine generator).
- A structured review and approval process is used to control switchyard and i electrical work while the plant is shut down. ' Switchyard off-site power' sources j are typically not worked during unit outages.
- Strict control of work activities, augmented control room staffing, arid additional {
management oversight during reduced inventory /mid-loop operations.
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- Redundant RCS makeup flow paths (defense in depth) are maintained available j for all RCS draindown configurations (RCS level <23' above the vessel flange). j
- Gravity feed flowpath is available any time the RCS is opened (large hot leg 'l vent) and the steam generators are not available. Analysis has been performed i to identify any restrictions on gravity feed. These restrictions are accounted for~ l in the outage schedule primarily in determining when the steam generators can ;
be removed from service. The intent is to minimize the time period when an i alternate means of decay heat removal (other than shutdown cooling) are not available.
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- Two means of decay heat removal are available whenever the core is off-loaded to the spent fuel pool. During some outages this has necessitated the installation
, of a temporary cooling system to provide backup cooling.
- - Backup ' nitrogen is maintained available to the spent fuel pool gate seals
.whenever an air outage occurs that could potentially impact air to the gate seals ~
and whenever the core is.off-loaded to the spent fuel pool.-
- A permanent refuel cavity pool seal is being installed in all three units.
installation of the refueling pool seal will result in lower man-rem accumulation during outages and lower the probability of loss of inventory due to refueling pool ,
seal failures.
- Personnel are specifically trained and staged to close the containment equipment ,
hatch.whenever the RCS is breached and fuel is in the core. Additionally a temporary AC generator is installed to allow the hatch to be closed if non-class power is lost. ,
a Fire Induced Vulnerability Evaluation (FIVE) insights (corridor building, breezeway vulnerabilities) pertaining to offsite power have been incorporated in the station's i
administrative control procedures, s
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