ML032940114
| ML032940114 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 07/03/2003 |
| From: | Cotton S Entergy Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| EA-03-016, FOIA/PA-2003-0358, IR-01-006 | |
| Download: ML032940114 (4) | |
Text
-- EEntagy Entergy Operationswinc.
Russeliviffes AR 72802 Tel 501 858 5000 OCAN070302 July 3, 2003 U. S. Nuclear Regulatory Comimission Attn: pocument Control Desk Washiigton, DC 20555-0001 Subject Arkansas Nuclear One - Units 1 and 2 Docket Nos. 50-313 and 50-368 License Nos. DPR-51 and NPF-6 NRC Triennial Fire Protection Inspection Report 01-06; EA-03-016 Significance Determination Process Report
Dear Sir or Madam:
Attached is the subject Significance Determination Process Report that was performed for the apparent violation described in a Marcd 25, 2003, letter from Mr. Dwight D. Chamberlain to Mr.
Craig Anderson at Arkansas Nuclear One. The attached information will be discussed at the July 10, 2003, Regulatory Conference at Arlington, Texas.
Should you have questions or comments, please call Mr. Glenn Ashley at 479-858-4617.
There are no new commitments contained In this submittal.
Sincerely, Sherrie R. Cotton Director, Nuclear Safety Assurance SRCIRMC Attachment in formatin rn oh.;
ra w/
in accord Jo
cc:
Mr. Thomas P. Gwynn Regional Administrator (Acting)
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.P. Box 310 Lqndon, AR 72847 U. S. Nuclear Regulatory Commission Attn: Mr. John Minns Washington, DC 20555-0001 U. S. Nuclear Regulatory Commission Attn: Mr. Thomas Alexion Washington, DC 20555-0001
/j Summary Several parameters contribute to the extent and timing of fire damage in fire zone 99-M. These include:
- Size and profile of the initial fire, i.e., how fast the fire grows to its peak and how long it takes before it begins to decay
- The cable damage temperature. ANO verified through review of the original and current plant design and installation documents that the cables installed throughout the plant are predominantly thermoset. Thermoplastic cables are, however, used on a very limited basis. A'review byLthe..ANstaf identified othermopa i fire zones in unit I where this issues was examined for risk, namely, 99-M, lOON and 104S.
-- Therefore our assessment assumed damage and ignition temperature of oT7F tor cables min se fire zones.
- Size and location of any cable fire that may be initiated by the initialfire.
The following is a summary of the insights from the fire modeling:
- The maximum expected fire scenario in the room is an energetic arcing fire in the 4KV switchgear. This is for two reasons. First, this event is capable of the largest set of immediate circuit/equipment damage and; second, the event is capable of initiating secondary cable fires that can cause additional time-phased circuit/equipipent failures.
- A credible fire scenario cannot be postulated in this zone-which would result in an immediate damaging 7007F hot gas layer. A large -2MW fire is needed to produce a damaging 70fF HGL in this fire zone. Only cable fires in the room are capable of generating such intensity if enough cables are burning. Even if such a large cable fire can be sustained (unlimited oxygen) it will take about 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> for the cable fire to propagate to this size.
bLrg elevateifablrfiresihut contnue lo grow unabated can not be sustained due to oxygen limitation:
I) Cable fires can only burn inside the hot gas layer. Assuming no manual intervention, with either closed or open doors, the cable trays will be immersed in smoke because the height of the door is not high enough to allow for smoke movement from the top section of the room, and no automatic extraction system is in place. The fire eventually would be oxygen controlled if it keeps growing in such an environment.. CFAST results are consistent with this argument.
- 2) If the simulation is run with open doors, AND the fire is assumed at the elevation lower than the steady state position of the hot gas layer, the fire will have enough oxygen to burn at the stipulated intensity. Therefore, assuming open doors, and a cable fire located about I mn high growing up to 2 MW in 1.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> can generate a hot gas layer of 700 0F. All cable trays in fire zone 99-M are located above the steady state position ofthe hot gas layer, i.e., 6 ft. With closed doors, the smoke layer would reach the floor, and eventually the fire will be oxygen controlled.
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-p ep 11.2 Analysis of Operator Response and Reliability
.2.1 Information Collection and Simulation of Fire Scenarios 11.2.1.1 Purpose The Human Reliability Analysis (HRA) team of Bill Hannaman and Alan Kolaczkowski lead by Bijan Najafi visitbl the ANO-I site on April 14 through 1 8th to obtain input for the HRA task, and support other parts of the evaluation of a hypothetical fire in location 99-M. Parallel work on fire modeling was performed by, Francisco Joglar. The aim is to support a reevaluation of the CCDP for 99-M that includes the impact of realistic fire growth timing and fire damage on human actions. This work follows a significance determination evaluaiion by-the NRC. The significance determination process reached a conclusion that there was a lack-of adequate procedures and the strategy for implementing the manual actions was inadequate, which may result in a potential for a greater than green condition for ANO-l.
Additional information has been obtained to evaluate the potential for more clearly addressing the analysis assumptions used in modeling both the fire scenario (growth and damage of the fire),
and a crew's ability to manage the plant cooling from the control room and locally. To evaluate the feasibility of control room and manual actions the ANO-l plant simulator and local task walkdowns were used to evaluate the feasibility of performing local control actions.
11.2.1.2 Key activities The key activities accomplished for the HRA evaluation with ANO-I were to (1) Identify a set of rcalistic fire bIccidio sJ m Vzne-99-M-(2-lMentif-and-visift-eeations-in4hs-plant-wheelocl__
manual actions could be performed to maintain cooling and avoid core damage given a fire in 99-M, (3) Observe two simulations of a fire in 99AM originating in the A4 switchgear (one with the original procedures and one with new procedures that include pre-emptive actions, (4)
Review the ANO-I PRA model for addressing the fire issues in 99-M, (5) Adjust the HRA values (based on walkdowns and simulation observations) in the existing model to account for fire dependencies, (6) Identify actions that are fire unique that should be added to the model.
Then develop findings for the HRA.
11.2.1.3 Plant Support The HRA team was well supported by the plant operational personnel in this effort. Dale James, Engineering manager made arrangements and provided information as needed. Ron Rispoli, and Tom Robinson, fire protection, provided information and escort during the walkdowns, Mike Cooper, licensing, discussed elements of the work, Ron Hendrix, Dale Smith and Randy Kulbuth, electrical engineering, provided evaluations of circuits in the cable trays to support development of the component damage as a function of cable locations. Ken Canitz, provided integration of the fire growth damage model into the inputs of the simulator and testing of the 35