ML20245D637
| ML20245D637 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 04/13/1989 |
| From: | Holahan G Office of Nuclear Reactor Regulation |
| To: | Tison Campbell ARKANSAS POWER & LIGHT CO. |
| References | |
| REF-GTECI-124, REF-GTECI-NI, TASK-124, TASK-OR NUDOCS 8905010081 | |
| Download: ML20245D637 (12) | |
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'o UNITED STATES j g. 8 NUCLEAR REGULATORY COMMISSION i -n E S' q, WASHINGTON, D. C. 20665 ,p# April 13,1989 g ' Docket No. 50-368 -{ Nr.'T. Gene Campbell .Vice President, Nuclear . Operations
- Arkansas Power & Light Company P. O. Box 551
- Little Rock, Arkansas 72203 l Dear Mr. Campbelli
SUBJECT:
PLANT-SPECIFIC BACKFIT FOR IMPROVED AUXILIARY FEE 0 WATER SYSTEM RELIABILITY AT ARKANSAS NUCLEAP. ONE, UNIT 2 (ANO-2) This letter. requests that a plant-specific backfit be implemented as the final resolution of NRC Generic Issue-(GI) 124, " Auxiliary Feedwater System Reliability," for ANO-2.. Previous' actions relative to this GI included a detailed NRC review group. reliability assessment for each of seven plants with a two-train auxiliary feedwater(AFW) system,includingANO-2. A final report of the staff's conclusions concerning the ANO-2 AFW system reliability was transmitted to Arkansas Power & Light Company (AP&L) on June 14, 1988. This report stated that the level of l AFW system reliability was not adequate on the basis of plant-specific data and . existing compensatory decay heat features such as the method of feeding the steam generators with the condensate pumps following loss of both main .feedwater pumps and both emergency feedwater (EFW) pumps. The transmittal letter requested AP&L's response to the findings and specific proposals to upgrade the AFW system reliability. On September 2,1988, you submitted a response to the assessment report. The response restated the AP&L position that the ANO-2 r.ethod of feeding the steam generators with condensate pumps was an ecceptable alternate-secondary side decay. heat removal method and satisfied the guidelines of SRP Section 10.4.9, and no upgrade to the existing AFW system was warranted. You also provided a detailed evaluation (modeling and fault f.ee analysis) of the ability of the condensate pump to perform the safety functions of the EFW pumps. The'NRR staff has fully evaluated your response and has not been persuaded to alter.its determination that the two-pump AFW system at ANO-2 needs to be . upgraded. I have therefore enclosed, as justification for backfit, an analysis for. improvement of the ANO-2 AFW system. The analysis indicates that substantial improvement in plant safety can be achieved by providing an additional means of supplying water to the steam generators in the event of loss of both main feedwater pumps and both emergency feedwater pumps, such as by adding an additional startup feed pump. You are therefore requested to implement improvements in the secondary decay heat removal capability for ANO-2 as resolution of GI 124 and to provide a schedule for completion of the recommended modifications within 60 days of 8905010003 g9043p DR ADOCK 05000368 PNU, [1
f fir. T. Gene Campbell ) receipt of this letter. If you choose to appeal this proposed backfit, the appeal should be addressed to the Director, Office of Nuclear Reactor Regulation. If you have any questions regarding this letter, please contact Mr. C. I;slusny, Project Manager for the Arkansas Nuclear One, Unit 2, plant. Sincerely, Asl Gary M. Holahan, Acting Director Division of Reactor Projects - III, IV, Y and Special Projects Office of Nuclear Reactor Regulation
Enclosure:
As stated cc W/ enclosure: See next page J DISTRIBUTION Docket File NRC PDR Loe,al PDR PD4 Reading T. Hurley J. Snfezek F. Miraglia G. Holahan L. Rubenstein J. Calvo P. Noonan C. Poslusny J. Craig A. Thadani L. Shao OGC-Rockville E. Jordan
- 8. Grimes ACRS(10)
PD4 Plant File i D. Crutchfield j
- SEEPREVIOUSCONCURRENC[S:
i JCalvo ilpf'l ADR4* (A)D:DRSP* (A)ADP* I PD4/D* M PD4/LA* PD4/PM* PNoonan CPoslusny:sr LRubenstein GHolahan SVarga 02/15/89 02/15/89 02/15/89 02/16/89 03/09/89 03/10/89 i SPLB* Tech. Ed.* OGC* ADT* DO JCraig Bac FMiraglia JS r1 02/15/89 02/16/89 02/17/89 03/09/89 04/ / 02/28/89
i Mr. T. Gene Campbell, receipt of this letter. If you chocse to appeal this proposed backfit, the appeal should be addressed to the Director, Office of Nuclear Reactor Regulation. If you have any questions reg 6rding this letter, please contact Mr. C. Poslusny, Project Manager for the Arkansas Nuclear One, Unit 2, plant. Sincerely, $ d} W '~ Gary M. Holahan, Acting Director Division of Reactor Projects - III, IV, V and Special Projects Office of Nuclear Reactor Regulation
Enclosure:
As stated cc w/ enclosure: See next pkge i l l L____.____..
1 l
- .1
~ _Mr.. T. Gene Campbell. receipt of this letter. If you choose to appeal this proposed backfit, the appeal should be addressed to the Director, Office of Nuclear Reactor Regulation. If you have any questions regarding this letter, please contact Mr. C. Poslusny, Project Manager for the Arkansas Nuclear One, Unit 2, plant. Sincerely, /5/ Gary M. Holahan, Acting Director Division of Reactor Projects - III, IV, V and Special Projects Office of Nuclear Reactor Regulation
Enclosure:
As stated cc w/ enclosure: See next page DISTRIBUTION <D0ChetiF11e 4 NRC PDR Local PDR PD4 Reading T. Murley J. Snfezek F. Miraglia G. Holahan L. Rubenstein J. Calvo P. Noonan C. Posiusny J. Craig A. Thadani L. Shao 0GC-Rockville E. Jordan B. Grimes ACRS.(10) PD4 Plant File D. Crutchfield
- SEE PREVIOUS CONCURRENCES:
PD4/D*A*$ JCalvo MI {Q ADR4* (A)D:DRSP* (A)ADP* PD4/LA* PD4/PM* PNoonan CPoslusny:sr LRubenstein GHolahan SVarga 02/15/89 02/15/89 02/15/89 02/16/89 03/09/89 03/10/89 SPLu* - Tech. Ed.* OGC* ADT* D0f(@ / JCraig Bac FMiraglia JSnTer f url 02/15/89 02/16/89 02/17/89 03/09/89 04/ 8 l 02/28/89
b 4 4 ^ Mr. T. Gene Campbell Arkansas Power &' Light Company Arkansas Nuclear One, 'Init 2 CC: Mr. Dan R. Howard, Manager Mr. Charles B. Brinkman, Manager Licensing Washington Nuclear Operations Arkansas Nuclear One. Combustion Engineering, Inc. P. O. Box 608 12300 Twinbrook Parkway, Suite 330 Russellville, Arkansas 72801 Rockville, Maryland 20852 Mr. James M. Levine, Executive Director Site Nuclear Operations Honorable William Abernathy Arkansas Nuclear One County Judge of Pope County P. O. Box 608 Pope County Courthouse Russellville, Arkansas 72801 Russellville, Arkansas 72801 Mr. Nicholas S. Reynolds Bishop, Cook, Percell & Reynolds 1400 L Street, N.W. _ Washington, D.C. 20005-3502 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission Office of Executive Director for Operations 611 Ryan Plaza Drive, Suite 1000 Arlington, Texas 76011 Senior Resident Inspector U.S. Nuclear Fegulatory Comiission 1 Nuclear Plant Road Russellville, Arkansas 72801 Ms. Greta Dicus, Director Division of Environmental Health Protection Arkansas Departroent of Health 4815 West Markam Street Little Rock, Arkansas 72201 Mr. Robert B. Borsum - Babcock & Wilcox Nuclear Power Generation Division l 1700 Rockville Pike, Suite 525 i Rockville, Maryland 20852 { 4
t PLANT-SPECIFIC CACKFIT ANALYSIS GENERIC ISSUE 124, AUXILIARY FEEDPATER SYSTEM RELIABILITY ARKANSAS NUCLEAR ONE, UNIT 2 As.a result of its review and resolution of the auyiliary feedWater system ' reliability in those plants with two-pump auxiliary feedwater systems (AFWSs) under Generic Issue (GI) 124, the staff has concluded that improven,ent in the secondary side. decay heat renoval capability is necessary at Arkansas Nuclear One, Unit 2 (ANO-2). TheStandardReviewPlan(SRP)Section10.4.9 unavailability criterion cf 10~4 to 10-5 per demand served as the goal for resolution of GI-124. The SRP criterion perrits a' greater AFWS unavailability if suitably reliable compensatory occay heat removal features are provided, and therefore the staff's review focused on this area. A suitably reliable compensatory fehture is one that provides an alternative means of supplying water to the steam generators. However, such an alternative capability has not been demon-strated for ANO-2. This action is being taken at this time in order to avoio a repetition of the significant delay in achieving secondary decay heat removal improvements such as occurred before th Davis-Pesse loss of all feedwater
- event, It is the staff's jucgment that a substantial safety improvement can be gained by providing additional means of decay heat renioval through the steam generators.
An aoditional compensatory feuture of this type can provide as ruch as an order of nagnitude decrease in.the likelihood of a loss of all feedwater. The staff recogr. ires the existence and availability of other means cf decay heet rerioval, such as the " feed-and-bleed" coaling rode and the use of condensate pumps. However, i the use of the " feed-and-bleed" mode is appropriate or.ly as a last rescrt in en emergency. Two factors form the basis for the staff's conclusion that the " feed-and-bleed" mede entcils great uncertainty as a decay heat removal feature at ANO-2. The first factor is the operator's inherent reluctance to initiate " feed-and-bleed" given the consequences of this action, as observed during the Davis-Besse loss of all feedwater event. " Feed-and-bleed" cooling intentiontily releases substantial ancunts cf reactor ccolant inte the containment. Plant restart felicwing " feed-and-bietd" cooling will be delayed because of (I) a potentially lengthy cleanup period, and (2) the necessity to correct those secondary heat sink deficiencies that required the use of the " feed-and-bleed" node. The
. second factor is the basic pressurized-water reactor (PWp) primary system design, which is not intended for direct decay heat removal at high pressure. The staff recognizes that ANO-2 has a unique " bleed" capability that permits rapid primaty system depressurization to the high pressure safety injection pump discharge pressure through a 3-inch vent path. However, even with this capability, the " feed-and-bleed" mode must be initiated in a timely manner l before steat generator dryout in order to be an effective mear,s of decay heat removal Lefore the core is uncovered. These factors preclude consideration cf the " feed-and-bleed" mode as a reliable compensatory decay heat removal feature. The use of a condensate pump fcr decay heat reraoval through the steam generators in the event of e loss of all main and auxiliary feedwater avoids the difficulties noted for initiati0n cf the " feed-and-bleed" mcde, but does net represent an adequate compensatory feature as claimed by the ANC-E licensee. The staff has for some time recognized the explicit use of condensate pumps as an emergency source of water for the steam generators. All plants have the capability of empicying a condensate pump te supply water flow tc the steam gererators once the seccndary sice pressure has been reduced sufficiently below the pump shutoff head. Although the staff r.otes that ANO-2 condensate purps bevc a narginally higher discharge pressure than c.ther piat.ts, as showr. by the licer.see, an action to depressurire the secondary side must still be taken. Therefore, the ANO-2 capability in this regard is siniilar to that of other PWR plants. To supplement the abeve qualitative evaluation, the staff performed a quantita-tive value impact assessment of the prcposed action. This assessment used tht licensee's estimate of AFW system unavailability per denand anc site-specific date to determine the person-rem release resulting from a postulated core melt and containment failure caused by a loss of decay heat removal. The assessment was based on an assumed range of success between 10 and 90 percent for the " feed-and-bleed" mode. The frequency of exter.ded loss of secondary heat sink in the value in. pact assessment assumes credit for condensate pump availability. The results indicated that considering cnly $1000/ person-rem for the proposed
. improvement in decay heat removal capability, the proposed action is cost-effective when a 10 percent success rate for the " feed-and-bleed" mode is assumed. The proposed action is only marginally cost effective when a 90 percent success rate for the " feed-and-bleed" mode is assumed. However, when considering the uncertainty in the use of the " feed-and-bleed" mode and other factors in the cost of recovery following its use (i.e., cleanup of the containment and cost of replacement power while the plant is down following the loss of all feedwater event), a substantially greater expenditure can be justified. For the reasons indicated above, the staff proposes the identified plant-specific backfit. The licensee is requested to implement improvement in the ANO-2 secondary decay heat removal capability and propose a schedule for completion of the necessary modifications. The following section addresses information required for a backfit analysts formatted in accordance with NRC Manual Chapter 0514. MC 0514 BACKFIT ANALYSIS INFORMATION The folicwing discussion supports the regulatory anhlysis of the proposed plant specific backfit and addresses the specific areas of consideration in the staff's guidelines, in accordance with NRC MC 0514. a. The objective of the proposed backfit is to improve secondary sido decay heat removal reliability for Arkansas Nuclear One, Unit 2 (ANO-2) by providing an additional means of delivering water to the steam generators following transient and accident conditions. Installation of a nonsafety-related startup feedwater pump or an additional auxiliary feedwater pump are suitable alternatives to satisfy this proposed action. Such a modifi-cation would provide substantial safety improvement by decreasing the likelihood of a loss of all feedwater by as much as one order of magnitude, and would significantly reduce reliance on the " feed-and-bleed" mode and the use of condensate pumps (which are part of the feedwater system) to preveat core damage from loss of all feedwater events.
.,. b. The licensee would be required to install an additional nonsafety-related pump and its associated piping and power supplies. Much of the required installation work could be achieved while the plant is at power. However, interconnectionofthenewpumptothewatersource(e.g., condensate - storage tank) and existing auxiliary feedwater system piping would require plant shutdown such as a refueling outage because such activity could leave the AFW system inoperable. An appropriate schedule to deal with this concern should be developed by the licensee, c. Implementation of this proposed backfit is consistent with existing staff guidelines for AFW system reliability contained in the Standard Review Plan (SRP)Section10.4.9. Nearly all other operating pressurized water reactors (PWRs) satisfy the SRP AFW reliability criterion and provide three pumps for delivery of water. to the steam generators following feedwater transients. The proposed additional pump contributes minimal corrplexity to plant design or operation since it is intended for use only during upset conditions and is manually initiated. The additional pump may in fact improve overall plant safety if the licensee chooses to use it for normal plant startup and shutdown because reliance on the existing safety-related AFW pumps for this purpose would no longer be necessary. Some additional operational complexity would be imposed by the need to perform periodic tests and surveillance on the third pump's availability. Installation of the pump could be in areas of the plant which do not contain safety-related equipment, and therefore, it should not impact plant safety functions. d. The proposed backfit is final and provides the final resolution of issues . involving AFW and secondary decay heat removal reliability under GI 124. e. Implementation of the proposed backfit provides significant benefit by reducing the risk to the public from accidental offsite releases of I L
h l., ? .- radioactive materials resulting from core damage events caused by loss of the heat sink. Based on an estimated cost of $2 million for a third startup feedwater pump, and assuming the licensee's estimate of AFW system unavailability per demand, the proposed backfit satisfies the $1000/ person-rem guideline and is, therefore, cost effective when a 10 percent success rate for the " feed-and-bleed" mode is assumed. Even with an increased " feed-and-bleed" success rate, other costs resulting from its use such as the cost of cleaning up containment and the cost of replacement power while the plant is shutdown following a loss of all feedwater event will justify a substantially greater expenditure in secondary decay heat removal capability. Overall, the proposed backfit provides approximately one order of magnitude reduction in the probability of a loss of all feedwater event and its associated risk. The proposed modification would affect the secondary side of the plant and, therefore, its installation would be in areas not expected to contain radiological contamination. Therefore, there should be no radiological exposure to facility employees either during the installation process or during periodic testing and operation over the lifetime of the plant. i For the most part, the installation of the modification could be completed 3 while the plant is operating. Some portions of the installation would l result in inoperability of the auxiliary feedwater system and should, j therefore, be accomplished during plant shutdown. However, this installa-tion would not increase plant downtime as it could be completed during a scheduled refueling outage. The staff estimates the total installation cost of the proposed modification to be approximately $2 million for a startup feedwater pump or comparable modification. Some continuing cost i of periodic testing and maintenance would also result. The cost of this I is estimated at $1 million over the plant lifetime. i The proposed backfit results in minimal resource burden on the NRC staff because a license amendment to cover its implementation would not be j I
l ..o d 1 necessary (see item 1 below).. Some staff resources would be required for the staff to meet with the licensee as necessary to discuss details of the installation and to perform the post-implementation inspection. I f. Operating events continue to point out the need for reliable secondary decay heat removal capability. Continuing. problems with turbine driven auxiliary feedwater (AFW) pumps indicate that improvements in secondary - decay heat removal reliability are necessary at. plants with two pump AFW l systems. The proposed backfit will provide the necessary improvement. l g. The need for the proposed backfit was originally identified by the NRC Office of-Research (RES) before transfer of GI 124 to NRR for resolution. The Committee to Review Generic Requirements (CRCR) and the Executive DirectorforOperations(EDO)alsohavebeeninformedoftheproposed
- action, j
h. Although while no specific implementation schedule has been identified, the staff expects the licensee to act promptly to perform the necessary 1 engineering, design procurement, installation and testing to incorporate ] the modification in second6ry side decay heat removal capaaility into the .l plant. Most of the installation can be completed while the plant is operating with the interconnections to existing piping and power supplies made during a subsequent scheduled refueling outage. The staff estimates that final implementation including procedure development and training could be completed within two refueling outages from the date of this letter. 1. The staff will meet with the licensee when appropriate to discuss details of the licensees proposed modification. However, a license amendment may not be necessary to incorporate the proposed change as it can be implemented under 10 CFR 50.59 as not being an unreviewed safety question and based on the fact that no technical specification change may be required. A post-implementation inspection will be performed by the NRC staff. )
' j. The issue of improved secondary side decay heat removal reliability is of major importance because of the significance of loss of feedwater events to the risk of core melt. The implementation schedule mentioned in item h. above is consistent with its importance when compared to other activities involving plant safety. k. The proposed plant-specific backfit is a result of resolution of Generic Issue 124. All other PWR licensees have demonstrated sufficiently reliable auxiliary feedwater systems and secondary decay heat removal capability in accordance with the guidelines of SRP Section 10.4.9 to resolve the concern. i f i 1 - - _ _ - _ - - - _ _}}