ML032940116

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Appendix R, Regulatory Conference
ML032940116
Person / Time
Site: Arkansas Nuclear  Entergy icon.png
Issue date: 07/10/2003
From:
Entergy Operations
To:
Office of Nuclear Reactor Regulation
References
FOIA/PA-2003-0358
Download: ML032940116 (21)
v • d • e


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ARKANSAS NU APPENE CLEAR ONE

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1 REGULATORY C ONFERENCE

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OPENING REMAR A,

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Craig Anderson ti Vice President, ANO I;

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Sherrie dotton Nuclear Safety Ass 4J7/lLL A {L-iL.i /@

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es Problem Statement 6

NRC Conclusions ANO's reliance on manua lozgwlt

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%bJ ANO's strategy for implenr inadequate actions In in features r cA lieu o-is in violation enting manual actions is

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Risk Assessment Overview 7

NRC's preliminary SDP eviluation d

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unacceptable (greater than damage frequency

  • Key assumptions in NRC e preliminary assessment Heat release rate Human error probability Subsequent site-specific 'in Results incorporated into derive ACDF green) increase in core valuations vs ANO's

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Ris strategy for Zone 99M 8

Simulator Scen Developmen 3rio Circuit Analysis &

Location Evaluation 99M Procedure Development 99M

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NRC

  • 4250 F cable failure temperature 0

e Zone wide prompt damage 0

I ANO 700° F cable failure temperature Limited time phased damage Plant specific HRA Scenario specific operator actions evaluated

  • Generic HRA Based on zone wide prompt damage Included LOOP No LOOP Green finding
  • Greater than Green finding 0

Summary 12 In our analysis we will show that!I Damage to equipment and instruments nleeded for safe shutdown will be limited to portions of the room Failures will occur over a period iof time, and No credible fire can be postulated that leads to zone-wide damage

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)om (fire zone 99M) 16 99M - south view Load center Dry-type transformer A.

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i Typical ANO switchgear cabinet wiring, control cubicle

Fire Characteriz atio 21 Electrical cabinet fires The heat release rate data profile is based on the best available fire test HRRProfle data 120

87/88) and VTT (Valtion Teknillinen Tutkimuskeskus, 94/96) in Finland 80

  • Same test used in the NRC SDP analysis x

60 The ANO HRR is based on the highest

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40 peak of ST5 (unqualified, open 1 10 20 KBTU loading) and all qualified, vertical 2.0 cabinets (excluding PCT6 and test 23 0

with 1.5 MBTU loading) 0 5

10 15 20

^ The NRC HRR is based on test 23 (qualified, open 1.47 MBTU loading) and me [min) test 24 (unqualified, open, 1.44 MBTU)

Time-to-peak is based on the average Tests are based on control panels The switchgear, MCC's and load centers are encl9sed wvith sealed

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Used for scenarios la, 2 - 5

Fire Characterization (c ig F

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High-energy Switchgear

  • The damage/ignition zone of the inil from US nuclear experience (next si EPRI Fire PRA Guide)
  • Ensuing electrical cabinet fires (the to its arcing fault) follow the same b electrical cabinet fires Potential ensuing cable fires spread vertically through cable tray stacks
  • Observations:

Experience of the US nuclear indus damaging/severe switchgear fires t tault ype ial pressure phase is derived ide) (EPRI SU105928 Supp to witchgear or others exposed havior as the non-energetic horizontally and spread faster try indicates that

,nd to be of the energetic arcing Used in scenario l b

Fire Characterization (co

/OE of the High-energy Sh01vitchgear Ari re24 Iva d hga Adong NM I3I a

goy Cable trays are offset as indicated in top view

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Fire Modeling:

3 28 Target Damage/ignition' Assumed cables inside metal conduits damaged at the same critical temperature, but will not contribute to room heat-up High-energy arcing fire Assumed raceways and cabinets in the gone-of-influence are damaged with exposed cables (trays) ignited Assumption conservative for the conduit§ (if stainless or galvanized steel pipes) where they are likely to survive the short-lived (seconds) initial pressure spike Spurious operation of damaged circuits were modeled.

I-n some cases, the likelihood,of the spurious actuation was obtained from the EPRI Expert Elicitation report (EPRI 1006961) which was estimated in part based on the data from EPRI/NEI circuit failure characterization fire tests

Kesults:

Frequency of Fire Scenarios -in Fire one 99M ANO SDP Analysis Results 9.

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artaoratio sae event for a plant Pns by l

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u ae f8ratio Senry l severe personnel fire Results Fr~ny weighting wihig Itseuislent Fco switchgear or flre brigade factor) facto fires) fire watch 18 Fire In the A4 svAldcgear.

Nominal value. 100 KW fire 1.60E-02 2.50E-01 5.88E-Ol.

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t.20EO1 2.50E01 1.OOE+00 1.00E+O0 6.62E-05 lb r

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ii tIhe A4 switchgear bmake* cubicles 1

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2 Fire Inhe 655 MCC. Nominal 100 KW fire. Fires hInnverter Y28 arm,boundedby this scenario.

1 SOE2 2.50E-01 s.s8E-02 !1lE.00E 0I 1.20E1

.0015E+00 1.00E+00 1.00E+00 2.65E-05 3

Fre hn the B65 MCC. Nominal 100 KW fire 1.50E.02 E-0Eo1 -s88E 02 [l t.OOE+OO 1.20E.-01 t.OOE+00 t.OOE+00 I.AA +00 2.65E405 4

Fire in theWM22 Invarter. Basse case. 100 KW fire. Fires In Y24

. and Y 25 are bounded by this l

iscnarIe t.6CE2 2.60E-01 5.88E 02 t.WE+00 1.20E-Ot,

1.00E+00 1.00E+W0 5.00E-01 1.32E-O5 5

FireIn the Load Ceiter Be.'

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11 itominal HRR.

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2.501i-5.t8-02 !.OOE+OO 1.20E-Q.

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1.0QE+00 2.OOE-O1 5.29EW6 so Translent fire In areas of the room

.where cable trays rre exposed to a 1itoor1bsed firet. Nominal Value.

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3.8E 2.00E+W t0E-oi 1.00E-1.E t.OOE+0 SOE-Ot 1.OOE+00 t.48E-05

.Sb Cable ire caused by weldin end cuttin n inreas of the room where.,

cable trays are exposed to a floor-based fire. Nominal Value of 250KW.

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.00E.0-01' 1.0OE+00 1.00E+00 S.OOE-2 1.00E+00 2.SOE.OT NRC SDP Analysis Results (May 15, 2003 SuppIen iental Letter Page 25)

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.Source Frequency Electrical cabinets 2.3E-04 Transformers I,

1.6E-05 IVentilation Subsystems I.

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-Summary of Procedural Guiclance "94 10=1 - -.I - -,,.. --..

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3 Starting EFW P-7A manually and positioning associated valves Ine previous procedures discuss tmis in 1 detail. Spurious and false indicators are mentioned which could delay operator response.

rema not Discussion in new procedure includes functional indicators.

Conerollinproceduresr discussrothisomlocalon r

Lack of adequate and correct indication is

~Controlling EFW (A orB1) contrvols prooactdre ion.

ti ocl directly discussed in the new procedure to prevent overfill which makes this action more likely in the new procedure.

Local closing of bus A3 This action not explicitly discussed inlth switchgear for p-713 arid, normal operating procedures but is disr ssed new procedure explicitly addresses HPI A (egg., in'.erter fires) in Altemate Shutdown.

l locally closing these breakers.

Discussed in previous procedures. The timing of this action depends on When letdown is Tlie new procedure addresses the Starting HPI Makeup isolated.

possibility of starting the HPI pump locally.

Isolation of letdown to In both the previous and new procedures, this In both the previous and new procedures, aMid needing.HPI action is discussed and can be performed in this action is discussed and can be (Makeup) sooner the control room.'

perfdormed in the control room.

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67 Switch to recirculation long-term, cooling In both the previous and new procedure, this action is discussed and can be performrd In the control room.-

In both the previous and new procedures, this action is discussed and can be performed In the control room.

ok ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~1-it EPRI Calculator Industry sponsored method prov keeping HRA evaluations I

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53 ides a process for book Addresses HRA requirements in ASME PRA Standard 2002 Includes several methods for quantification Industry and-NRC sponsored

~-j~nericd.~taquantitatively diffei

,- probabilities (HEP's) for key cha entiate human error racteristics of procedures and man machine interface

  • HRA analyst judgment is still required

HFEsn 99M fire Fire in 99M increases human failure event (HF initial internal events PRA from zero to a valu scenarios and conditions If action is not feasible, then HFE assessment Very small difference in impact of previous ye Comparison of previous and new procedures o a

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A "baseline with 56 E) for typical feasible actions over in range of 3E-3 to 4E-2 for various

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Unit Ri Total Urnit Risk 65 0

0 The assessment of fire risk in 99M was extrapolated to tv other Unit 1 fire zones:

Each was assessed with walkdol wn and examination of the potential fire scenarios threatening the other train raceways (e.g., red train raceway in a green train room)

Unit 1 A3 4KV switchgear room (1 OON)

  • Similar to 99Mmn combustibles and fire sources
  • Considerably less redundant train cable routed through zone Unit 1 electrical equipment room (1 04S)
  • Lack of high energy switchgear
  • Considerably less redundant tralin cable routed through zone r0
  • Each zonfe is bounded by the re Conservative estimated fire risk
  • Unit 1 < 6.6E-07/yr I~tA

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sults of 99M (ACDF) for this condition

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Overall Summary 69 1 9

  • ~-Detailed analysis of zone 99M X

Credible fires result in time-phasedIfailures without zone-wid damage (700 0F damage temperature for thermoset cables) letailed circuit analysis indicates there is not a loss of offsite power

{ from any fire scenario Simulator scenarios provided realistic data for assessment of operator reliability in the use of previous and. new-procedures ACQF for 99M is 2.2E-07/yr

  • Total Unit Risk Two additional zones considered risk significant for Unit 1 Risk assessment of zone 99M conservative with respect to other zones-Conservative estimate of total unit ACDF is < 6.6E-07/yr
  • The significance of the use of manual actions to achieve safe shutdown has very low safety significance and should be characterized as GREEN
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