ML030420101

Arkansas, Units 1 and 2, Significance Determination Process Technical Information

ML030420101
Person / Time
Site:	Arkansas Nuclear
Issue date:	02/03/2003
From:	Cotton S Entergy Operations
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
FOIA/PA-2003-0358, OCAN020302
Download: ML030420101 (9)

Text

Entergy Operations, Inc.

Lhteigy1448 SR 333 Russellville, AR 72802 Tel 501 858 5000 0CAN020302 February 3, 2003 U. S. Nuclear Regulatory Commission Attn; Document Control Desk Washington, DC 20555-0001

Subject:

Arkansas Nuclear One - Units 1 and 2 Docket No. 50-313; 50-368 License No. DPR-51; NPF-6 Inspection Report 50-313; 368/01-06 Significance Determination Process Technical Information

Dear Sir or Madam:

Inspection Report 50-313; 368/01-06, Triennial Fire Inspection, dated August 20, 2001, and subsequent Nuclear Regulatory Commission (NRC) correspondence dated April 15, 2002, determined that Arkansas Nuclear One (ANO) is in non-compliance with 10CFR50, Appendix R III.G.2. The non-compliance concerns the use of manual actions on ANO-1 to achieve safe-shutdown conditions should a fire occur in an area outside the control room. In the April 15, 2002, letter this item was reclassified as an Apparent Violation pending the NRC's assessment of the risk significance associated with the finding.

In a telephone conference between representatives of Entergy and NRC Region IVstaff on January 15, 2003, Entergy determined that additional technical information should be provided to the NRC for consideration in the Significance Determination Process (SDP). contains this technical information and we request it be considered prior to any final decision being made concerning the risk significance of the manual action issue.

This may not be the only additional technical information necessary to get a realistic characterization of the risk significance of this finding. Over the last year Entergy has attempted to engage the staff in discussions concerning the assumptions and models used to perform the assessment of risk. Additional information was provided where it was identified that the model assumptions did not accurately reflect conditions in the plant. To more effectively utilize both NRC and Entergy resources we encourage the NRC to provide Entergy the opportunity to review the Staffs risk evaluation and allow the inclusion of updated information as necessary.

-A 0 (

0CAN020302 Page 2 There are no new commitments identified in this submittal. Should you require additional information please contact Mr. Glenn Ashley at 479-858-4617.

Sincerely, Sherrie R. Cotton Director, Nuclear Safety Assurance SRC/RMC attachments

0CAN020302 Page 3 cc: Mr. Ellis W. Merschoff Regional Administrator U. S. Nuclear Regulatory Commission Region IV 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011-8064 NRC Senior Resident Inspector Arkansas Nuclear One P.O. Box 310 London, AR 72847 U.S. Nuclear Regulatory Commission Attn: Mr. Tom Alexion Washington, DC 20555-0001 U.S. Nuclear Regulatory Commission Attn: Mr. William D. Reckley Washington, DC 20555-0001

Attachment to 0CAN020302 Page 1 of 6 ATTACHMENT 1 FIRE SDP TECHNICAL INFORMATION The following information is provided for input into the SDP associated with Inspection Report 50-313; 368/01-06.

1) Cable Data - the following table contains a list of cables with the applicable insulation type. The listed cables (with one exception) were determined to have thermoset insulation which has a failure temperature of 700 degrees F. The one exception is cable RCB5721 D1 (component P64A) that was installed in the 1990's. The work package that recorded the cable reel number has not been located; however, the other listed instances of this cable type (i.e. R74) are thermoset cables; therefore, we believe that this cable also has thermoset insulation.

Cable Equipment Cable Type Type A308 RCA308G R34 Thermoset A3 RCD1104A R12 Thermoset RCD1104B R12 Thermoset P36A RCA306D R34 Thermoset B5 RCB512C R54 Thermoset P64A RCB5721D1 R74 RCB5721D R74 Thermoset P64B B801B1 714 Thermoset B801B 714 Thermoset K4A RCA11C R34 Thermoset RCA11D R34 Thermoset RCE11C R54 Thermoset CV2680 RCB5124F R74 Thermoset RCB5124G R54 Thermoset CV2620 RCD1514D R74 Thermoset RCD1514E R54 Thermoset CV2627 RCD1522D R74 Thermoset RCD1522E R54 Thermoset CV2646 RJ1423A1 R2S Thermoset CV2648 RJ1423B1 R2S Thermoset CV2800 RCB5173E R74 Thermoset D15 RPD0121A1 R25 Thermoset RPD0121A2 R25 Thermoset P7A (RS2) GCY2200A G12 Thermoset GCY2200B G12 Thermoset GCD0242AA G120 Thermoset GCD0242AB G120 Thermoset

Attachment to 0CAN020302 Page 2 of 6

2) Cable Routing - For the cables listed in the above table, the associated raceways in Zone 99-M are listed below.

Equipment Cable Raceways in 99M A308 RCA308G EC1175 EC1237 EC1236 A3 RCD1104A EC1175 ECI 190 ECI 176 RCD1104B EC1175 EC1 190 EC1176 P36A RCA306D EC1258 ECI190 EC1 275 B5 RCB512C EC1258 EC1237 EC1257 P64A RCB5721D1 EC 088 EC 093 RCB5721D EC1175 EC1163 P64B B801B1 EC1 088 EC 093 B801B ECl175 EC1165 EC1164 K4A RCAI C EC1175 EC1 236 EC1237 RCAI ID EC1175 EC1236 EC1237 RCE11C EC1258 EC1 236 EC1237 CV2680 RCB5124F EC1 504 RC85124G EC 504 CV2620 RCD1514D EC1 504 RCD1514E EC1 504 CV2627 RCD1522D ECI 504 RCD1522E EC1 504 CV2646 RJ1423A1 EJ1004 CV2648 RJ1423B1 EJ1004 CV2800 RCB5173E EC1 530 D15 RPDO121A1 EC 589 RPDO121A2 EC1 589 P7A(RS2) GCY2200A EC2184 GCY2200B EC2184 GCD0242AA EC2212 EC2213 GCD0242AB EC2212 EC2213

Attachment to 0CAN020302 Page 3 of 6

3) Raceway Layout - This following sketch identifies the location of the raceways of interest in Zone 99-M.

Raceways Located in Zone 99-M 4

North EC2184, EC1163 EC1093 EC1165 EC1088 EC1237 EC1190

2. JB344

9. JB459

10. TB1054

Attachment to 0CAN020302 Page 4 of 6

4) Ignition Sources - This sketch identifies the relative locations of the electrical cabinets located in Zone 99-M.

Attachment to 0CAN020302 Page 5 of 6 Items to Consider Note: Focus has been placed on Zone 99-M (vs. 98-J) since there is no suppression system installed. Most of the listed cables are also routed through Zone 98-J. Similar consideration should be given to Zone 98-J.

1) During the teleconference on January 15, 2003, we determined that the current SDP fire models do not predict a hot gas layer reaching 700 degrees F in any of the modeled scenarios. Accordingly, all components will not 'fail' due to development of a hot gas layer. Instead, dependent on which ignition source is modeled, a certain set of components may incur damage (due to plume or ceiling jet effects) whereas others will not experience damage temperature due to the location of the circuits within the room. Without having run specific fire models, we would theorize the potential damage of circuits routed in raceways along the west wall of Zone 99-M (i.e. those associated with Emergency Feedwater

[EFW]), whereas those routed in the eastern half of the room (i.e. associated with High Pressure Injection [HPI]) would not incur damage. Conversely, if the ignition sources are on the eastern half of the room, we would theorize damage to HPI related cabling, whereas EFW cabling in the western half of the room would not incur damage. With one success path undamaged by fire, the Human Reliability Analysis (HRA) values for performing any manual actions will be positively impacted.

2) For those components that do incur damage, there is a finite amount of time available prior to failure. Those closest to the ignition source would fail first, whereas those further away would fail sequentially as the fire progresses to the least severe exposure. Availability of the systems during this interval could have a significant impact on the amount of time available to perform manual actions.

For example, assume the EFW valves do not fail closed for approximately 15 minutes. A considerable amount of decay heat can be removed by the EFW system during this 15 minute time span. This will positively impact the amount of time available to manually reestablish EFW and potentially impact the HRA values.

3) When preparing the IPEEE submittal, ANO assumed that the Main Feedwater System (MFW) would be unavailable in all fire scenarios. As a result, the PSA model built to support the IPEEE (and utilized for this SDP) assumed that a fire caused a loss of all MFW. In the process of evaluating this SDP, we have determined that one flow path of MFW will be available. Thus, the associated MFW pump will continue to operate until failures occur in the support systems (e.g. loss of cooling water for the lubrication system). Similar to Item 2 above, the availability of MFW to remove decay heat will impact the time available to perform recovery actions to restore EFW.

4) One of the conclusions of NUREG/CR-6776 Cable Insulation Resistance Measurements Made During Fire Test was that in the observed test cases, when a cable failure occurred, the failure ultimately resulted in the conductors shorting to ground. There are two flow paths from the motor driven EFW pump (i.e. P7B) to the steam generators. In order to lose a flow path (i.e. fail a valve closed), the controller for the solenoid valve (i.e. CV2646 or CV2648) must receive a spurious close signal. To fully close the valve, the close signal must be approximately 20mA (vs. a 4mA [or less] signal that results in a fully open valve). The valve position signal is provided by the Emergency Feedwater Initiation Control (EFIC) system and is normally a 4 mA signal (i.e. valve is normally open). With all

Attachment to 0CAN020302 Page 6 of 6 related related conductors ultimately failing to ground in a fire scenario, the prospect of maintaining a 20mA signal for an indefinite period of time is unlikely. The NUREG/CR notes that the duration of hot shorts (for thermoset cable) is limited to a matter of minutes after the onset of cable damage. Thus, while one (or both) flow path(s) from the EFW pump may be temporarily impacted by fire damage, ultimately the flow control valve will reopen and allow EFW flow to the steam generators.

These factors increase the availability of a method for removing decay heat, without requiring the performance of recovery manual actions during the initial stages of the fire event.