ML12166A560
| ML12166A560 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 06/12/2012 |
| From: | Clark R Entergy Operations |
| To: | Kalyanam N Plant Licensing Branch IV |
| Kalyanam N | |
| Shared Package | |
| ML12166A553 | List: |
| References | |
| TAC ME8282 | |
| Download: ML12166A560 (28) | |
Text
License Amendment Request NFPA 805 Acceptance Review Arkansas Nuclear One Unit 2 June 12, 2012
NRC four areas of concern with the LAR The modifications for transition need to be described and, as appropriate, modeled in the PRA to properly estimate the change in risk associated with transition. The LAR needs to be supplemented with the descriptions of these modifications and provide adequate information to review the evaluations supporting these modifications.
About one third of the fire areas in the "Additional Risk of RAs column of Table W-2 of the LAR do not contain a quantitative risk result. The LAR needs to be supplemented with all of the quantitative Recovery Action risk estimates to demonstrate that the evaluations supporting the transition have been satisfactorily completed.
Attachment G of the LAR states that ANO-2 has no primary control Attachment G of the LAR states that ANO 2 has no primary control station, besides the Main Control Room (MCR), yet only eight Recovery Actions are identified for Fire Area G. It is also unclear how both the total change in risk and the additional risk from Recovery Actions is bounded by a risk estimate of "0.0." The LAR needs to be supplemented with additional discussion about the planned modifications and Recovery Actions, and how these are modeled in the PRA in sufficient detail to explain the unexpected results.
Two sensitivity studies compare the results based on one "unaccepted method" to results based on another "unaccepted method." The LAR needs to be supplemented with the risk results (in relation to the sensitivity analyses for non-suppression probability for long-term fires and adjustment factor for electrical cabinet ignition frequency) calculated using an acceptable analysis method.
1.
ANO has prepared more detailed modification descriptions. Draft changes available for discussion.
2.
ANO has prepared a draft analysis to address the risk estimates of the quantitative Recovery Actions (RA).
These draft RA risk values are available for discussion.
3.
ANO will explain the results in Fire Area G (Control Technical Acceptance Issues 3.
ANO will explain the results in Fire Area G (Control Room) and how the mods and RAs were modeled in the Fire PRA.
4.
ANO has drafted a new Sensitivity analysis in compliance with NUREG/CR-6850 for comparison to the current results. Further analysis is needed to accurately reflect the risk and minimize the need for unnecessary plant modifications.
The modifications for transition need to be described and, as appropriate, modeled in the PRA to properly estimate the change in risk associated with transition. The LAR needs to be supplemented with the Item No. 1 -
Modification Details LAR needs to be supplemented with the descriptions of these modifications and provide adequate information to review the evaluations supporting these modifications.
Item No. 1 -
Modification Details
- Detailed final plant configurations have been completed and will be discussed for all 16 modifications identified Th difi ti ill b l t d i
- The modifications will be completed in a manner that supports the assumptions of the Fire PRA
Insert Att. S Excerpt
Item No. 2 - Risk Estimates for Recovery Actions About one third of the fire areas in the "Additional Risk of RAs column of Table W-2 of the LAR do not contain a quantitative risk result. The LAR needs t
b l
t d ith ll f th to be supplemented with all of the quantitative Recovery Action risk estimates to demonstrate that the evaluations supporting the transition have been satisfactorily completed.
Item No. 2 - Risk Estimates for Recovery Actions
- The delta risk from recoveries are currently being drafted and preliminary results are available for review A
l f th i f ti t
b id d i
- An example of the information to be provided in the Supplement to the ANO-2 LAR is contained in the next slide
Example of the information to be provided in the Supplement to address the delta risk of recoveries Table W-2 ANO-2 Fire Area Risk Summary Fire Area Area Description NFPA 805 Basis Fire Area CDF Fire Area LERF VFDR (Yes/No)
Recovery Actions Fire Risk Eval CDF Fire Risk Eval LERF Additional Risk of RAs (CDF/LERF)
DD fire zones 2019-JJ, 2032-JJ, 2040-JJ, and 2068-DD (boric acid condensate tank room, spent resin storage tank room, corridor, and hot machine shop) 4.2.4.2 2.45E-06 2.76E-08 yes no
-2.85E-06
-9.64E-08 n/a EE-L fire zones 2055-JJ and 2084-DD (piping penetration rooms) 4.2.4.2 3.81E-07 7.53E-09 yes yes
-7.89E-07
-2.64E-08
-6.00E-09/1.51E-09 EE-U fire zone 2111-T (lower south electrical penetration room) 4.2.4.2 2.03E-06 4.81E-08 yes yes
-5.77E-06
-1.94E-07 2.00E-08/2.70E-09 FF fire zone 2025-JJ (motor-driven emergency feedwater 4 2 3 2 1 15E 08 3 66E 10 no n/a n/a n/a n/a Revised Column for delta risk of Recovery action only FF driven emergency feedwater pump room) 4.2.3.2 1.15E-08 3.66E-10 no n/a n/a n/a n/a G
fire zones 2199-G, 2119-H, 2136-I, 2137-I, 2150-C, 2098-C, and 2098-L (control room and other alternate shutdown areas) 4.2.4.2 2.64E-06 3.52-08 yes yes
-2.65E-06
-9.78E-08
-2.00E-08/1.60E-09 GG fire zones 2074-HH and 2081-HH (electrical equipment room and upper north and lower north piping penetration room).
4.2.4.2 1.03E-06 2.17E-08 yes yes
-1.12E-05
-3.82E-07
-9.27E-06/3.20E-09 HH fires zones 2063-DD, 2072-R, 2073-DD, 2096-M, 2106-R, and 2107-N (sample room, VCT room, 2B-62 room, 2B-63 room, degasifier vacuum pump room, and corridor) 4.2.4.2 3.11E-06 4.65E-08 yes yes
-5.80E-07
-2.18E-08
-1.13E-06/1.23E-08 II fire zone 2101-AA (north switchgear 2A-3 room) 4.2.4.2 2.90E-06 9.31E-08 yes yes
-1.33E-04
-4.52E-06
-2.70E-07/6.80E-09 JJ fire zone 2109-U (corridor) 4.2.4.2 2.70E-06 7.97E-08 yes yes
-3.78E-06
-1.21E-07
-1.50E-07/1.24E-08 K
fire zones 16-Y and 2020-JJ (clean waste receiver tank room and boron holdup tank vault) 4.2.3.2 6.47E-10 1.44E-11 no n/a n/a n/a n/a
Example of the information to be provided in the Supplement to address the delta risk of recoveries Table W-2 ANO-2 Fire Area Risk Summary Fire Area Area Description NFPA 805 Basis Fire Area CDF Fire Area LERF VFDR (Yes/No)
Recovery Actions Fire Risk Eval CDF Fire Risk Eval LERF Additional Risk of RAs (CDF/LERF)
DD fire zones 2019-JJ, 2032-JJ, 2040-JJ, and 2068-DD (boric acid condensate tank room, spent resin storage tank room, corridor, and hot machine shop) 4.2.4.2 2.45E-06 2.76E-08 yes no
-2.85E-06
-9.64E-08 n/a EE-L fire zones 2055-JJ and 2084-DD (piping penetration rooms) 4.2.4.2 3.81E-07 7.53E-09 yes yes
-7.89E-07
-2.64E-08
-6.00E-09/1.51E-09 EE-U fire zone 2111-T (lower south electrical penetration room) 4.2.4.2 2.03E-06 4.81E-08 yes yes
-5.77E-06
-1.94E-07 2.00E-08/2.70E-09 FF fire zone 2025-JJ (motor-driven emergency feedwater 4 2 3 2 1 15E 08 3 66E 10 no n/a n/a n/a n/a Zero delta risk removed and actual delta risk incorporated to show negative delta risk FF driven emergency feedwater pump room) 4.2.3.2 1.15E-08 3.66E-10 no n/a n/a n/a n/a G
fire zones 2199-G, 2119-H, 2136-I, 2137-I, 2150-C, 2098-C, and 2098-L (control room and other alternate shutdown areas) 4.2.4.2 2.64E-06 3.52-08 yes yes
-2.65E-06
-9.78E-08
-2.00E-08/1.60E-09 GG fire zones 2074-HH and 2081-HH (electrical equipment room and upper north and lower north piping penetration room).
4.2.4.2 1.03E-06 2.17E-08 yes yes
-1.12E-05
-3.82E-07
-9.27E-06/3.20E-09 HH fires zones 2063-DD, 2072-R, 2073-DD, 2096-M, 2106-R, and 2107-N (sample room, VCT room, 2B-62 room, 2B-63 room, degasifier vacuum pump room, and corridor) 4.2.4.2 3.11E-06 4.65E-08 yes yes
-5.80E-07
-2.18E-08
-1.13E-06/1.23E-08 II fire zone 2101-AA (north switchgear 2A-3 room) 4.2.4.2 2.90E-06 9.31E-08 yes yes
-1.33E-04
-4.52E-06
-2.70E-07/6.80E-09 JJ fire zone 2109-U (corridor) 4.2.4.2 2.70E-06 7.97E-08 yes yes
-3.78E-06
-1.21E-07
-1.50E-07/1.24E-08 K
fire zones 16-Y and 2020-JJ (clean waste receiver tank room and boron holdup tank vault) 4.2.3.2 6.47E-10 1.44E-11 no n/a n/a n/a n/a
Item No. 3 - Recovery Actions Credited for Control Room Abandonment Attachment G of the LAR states that ANO-2 has no primary control station, besides the Main Control Room (MCR), yet only eight Recovery Actions are identified for Fire Area G. It is also unclear how both the total change in risk and the additional risk from g
Recovery Actions is bounded by a risk estimate of "0.0." The LAR needs to be supplemented with additional discussion about the planned modifications and Recovery Actions, and how these are modeled in the PRA in sufficient detail to explain the unexpected results.
Item No. 3 - Recovery Actions Credited for Control Room Abandonment
- Fire Area G contains several zones including the Control Room
- A fire in Fire Area G may result in control room abandonment room abandonment
- Mods and operator actions outside the Control Room have been credited for Core Damage Mitigation
Proposed Control Room Modifications for Transition to NFPA-805
- Modification to eliminate potential spurious operation
- 2CV-1002 ADV Block valve 2CV 1052 ADV Bl k
l
- 2CV-1052 ADV Block valve
- 2CV-4698-1 ECCS Vent Valve
- AFW Modification
Human Recovery Actions Credited for Control Room Abandonment Scenario
- Operator action to Isolate blowdown
- Operator action to Isolate Letdown Flow
- Operator action to trip RCPs at the switchgear
- Operator action to start and align AFW
- Operator action to stop Charging Pumps
- A specific location is used by the Shift Manager to monitor process instrumentation and coordinate operations activities
Control Room Analysis Discussion
- RCS integrity and primary to secondary heat removal are evaluated crediting the proposed mods and recoveries
- Additional Defense in Depth actions will enhance p
plant control and reduce the likelihood of equipment damage
- CDF = ~2.6E-06 (Crediting mods and recovery actions)
Control Room Analysis Discussion (Contd)
- Spurious Operation of equipment has been considered in the Fire PRA analysis.
Pump start with no suction HPSI - mini-recirc capability LPSI - spurious pump start EDG and support systems assumed failed
Control Room Analysis Discussion (Contd)
Compliant Case Analysis Methodology Control Room Variance from Deterministic Requirements (VFDR)
Compliant Case Analysis Methodology Single success train for plant control and mitigation RG 1.205: The deterministically compliant plant has been referred to as an ideal l
t th t t
i t b
f ibl i
plant that may not exist or be feasible in practice.
Modeling configuration assumed
- RCS remains intact
Delta Risk Analysis Zone Scenario Description IGF NSP SF CCDP CDF CLERP LERF
(/rx-yr)
(/rx-yr)
(/rx-yr) 2199-G Compliant Case 3.79E-05 1.0 1.0 1.40E-01 5.29E-06 3.50E-03 1.33E-07 2199-G Post Transition Case 3.79E-05 1.0 1.0 6.97E-02 2.64E-06 9.29E-04 3.52E-08 Results Delta CDF
-2.65E-06 Delta LERF
-9.78E-08
Item No. 4 - Sensitivity Study Two sensitivity studies compare the results based on one "unaccepted method" to results based on another "unaccepted method." The LAR needs to be supplemented with the risk to be supplemented with the risk results (in relation to the sensitivity analyses for non-suppression probability for long-term fires and adjustment factor for electrical cabinet ignition frequency) calculated using an acceptable analysis method.
Item No. 4 - Sensitivity Study
- Electrical Panel Propagation Factors are removed from the original analysis to comply with 6850 methodology.
- CDF Analysis
- Multi-compartment/Hot Gas Layer (MCA/HGL) screening
- This will meet the NRC expectation for 6850 compliance
- Draft results show an increase in risk from that reported in Attachment W of the LAR
- CDF increased from 4.3E-05/yr to
~6 0E-05/yr Core Damage Frequency 6.0E 05/yr
- LERF increased from 8.3E-07/yr to
~1.3E-06/yr
- Results will be provided in the LAR Supplement
Multi-compartment/Hot Gas Layer Draft results show that less than 2% of 1955 previously screened scenarios will no longer screen The list of unscreened fire scenarios will The list of unscreened fire scenarios will be provided in the LAR Supplement
Additional Level of Effort
- Efforts have begun to perform fire modeling.
- This effort is expected to more accurately calculate the risk of a y
MCA/HGL as well as reduce the increase in CDF
- The refined results will be provided once this additional level of effort is completed
- Scenario (2098-C) was chosen to analyze the impact of additional walkdowns and fire modeling
- 2098-C is the Core Protection Calculator Room
- This room uses Halon for fire suppression Example Case
- Low voltage electrical panels are contained within this room
- Current analysis assumes full room burnup
- The new fire modeling shows that a fire in this room will not generate a hot gas layer.
- This new information will be used to refine the risk results for fires in this zone
Impact on ANO-1 LAR
- ANO 1 has similar issues identified for
- ANO-1 has similar issues identified for ANO-2
- The ANO-1 LAR submittal is scheduled for August 31, 2012
Summary ANO-2 supplemental response will be provided by the July 11 deadline
Questions ??