ML17320A193

NRC Public Meeting, Treatment of Mitigating Strategies in Risk Informed Decision Making

ML17320A193
Person / Time
Site:	Palo Verde
Issue date:	11/15/2017
From:	Powell M - No Known Affiliation
To:	Office of Nuclear Reactor Regulation
Schwab A
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ml17312a356	List: ML17320A146 ML17320A193 ML17320A200 ML17320A201
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Download: ML17320A193 (35)

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Palo Verde Use of NEI 16-08 & NEI 16-06 NRC Public Meeting

- Treatment of Mitigating Strategies in Risk Informed Decision Making November 15,2017 Michael Powell, Director Fukushima & Strategic Initiatives

Palo Verde Generating Station Example Risk Evaluation Using NEI 16

-08 Example Risk Evaluation Using NEI 16

-08 Deploying Portable 4 1 60V Diesel Generators During A Safety Related Diesel Outage

.

I Description Benefit Summary The purpose of this strategy i s to use FLEX diesel generators to prov i de a redundant source of 4 1 60V ac power to e ither of the emergency busses dur i ng evolut i ons where defense-i n-depth to the Medium V o ltage ac safety funct i on is challenged, such as a d iesel generator outage. The 4 160V ac portab l e generators and the cab l es to attach to the permanent plant. This strategy w i ll support the 4 160V ac e lectrical distr i but i on system and be used to prov i de defense-in-depth to the stat i on b lackout generator when a safety re lated d iesel is out of serv i c e. This will be reflected i n the PRA model used for the s i te's configurat i on risk management Risk reduction; Maintenance can be performed whi l e maint a ining a green risk w indow. This strategy will be reflected i n the PRA model used for the site's configurat ion risk management.

3 Feasibility Assessment Element Descript i on Summary I Identification of all equipment necessary for implementa t ion including permanently installed equipment Portable equipment necessary to emp l oy the 2MW 4 1 60V ac portable generators includes the generators themselves and the cab l es connec t i ng the generators to the p lant. Permanently installed equipment necessary for imp lementation includes transfer switches and supply breakers for the 4 1 60V ac busses.

I Identify important attributes of the strategy {e.g. pre dep loyment of equipmen t, plant mod ification s ,or procurement of additional portable equipment) that need to be established pr i or to the implementa t i on of the strategy.

Generators are requ ired to be pre-dep loyed and connected based on t i m i ng requ irements. P lant mod ificat i ons exist and all hardware has already been procured.

I Is the equipment adequate to meet the proposed strategy? Generator, cab les, and e lectr ical breaker performance capab i l i ty has been ver ified to be sufficient for necessary l oad s. E x isting overcurrent protect i on in the circuit was determ i ned to be suffic ient. I Id ent ify any power supply or fuel req u irements Refue l i ng of the generator d iesel fuel i s requ ired every 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> s. Can the eq u ipment be dep loyed, installed, and operated in time to perform the function?

The equ ipment is pre-dep loyed and connected to meet necessary time re q u irements. The system time w i ndow i s one hour. The necessary act i ons are procedura lized, uncomp l icated and crews are br iefed at the start of each shift. Hard Cards are pre-staged for easy to use proceduralized compliance.

Example Risk Evaluation Using NEI 16

-08 4 Are the cond i t ions w i t h i n the d es i gn capa b ilit i es of any support components such as hose s , p i p i n g , or va lve connect ions? Yes. Both the portab l e cab l es and installed permanent p l ant cab l es are capable of handl i ng the current and output of the porta b l e generator s. If condit i ons are outs i de of equipment performance requ irements , i s there any bas i s {e.g.,marg i n) to support the use dur i ng these con d i t ions? Not applicable, everyth i ng is w ithin equ ipment performance requ irements. Do connect i on po ints and rout i ng paths ex i st to connect the eq u ipment into the system be i ng supported?

Yes. Dep loyment paths are located near the connect i on po ints and routing of the temporary cables is "skill of the craft". Cab l es can be routed w ithout interfer i ng w i th other p lant activ ities. I Id ent i fy other requ ired system cons iderat i ons (e.g. va l ve a l ignment s , b ack pressure). N o n e. I Id e n t i fy req u i red suct ion sources

{e.g. t ank levels/capacit y , water qual i t y , and need f or stra iners). None. I Id ent i fy requ ired i nstrumentat i on and control to ensure the funct ional i ty of the e q u ipment. Permanent p l ant instrumentat i on e xists i n the control room to monitor the electrical output of the portable generators o n ce they are connected to the p lant. Local instrumentat i on e xists on the portab l e generators to monitor the i r operat i o n.

I If th e porta b l e equ ipment cannot fully meet the funct ional re q u irement s , can it be util ized to prov i de add i t ional marg i n that may be beneficia l? Not applicable.

Example Risk Evaluation Using NEI 16

-08 5 E n g i neeri n g An a l ysis Element Descr i pt i o n Su m m a r y Ide nti f y specif i c eng i n e er i n g d o c u m e nta t i o n r e f er e n c e s an d a na l ysis met h od o l ogie s (e.g., MAA P , RE TRAN, GOTH I C , CE N T S , an d b a t t er y d eple t io n ca lculatio n s). O ve r c u rr en t p r o te c t i on ha s been e v a l u a t e d an d d o c u m en t ed i n an eng i n eeri n g w o r k orde r (EW O). J u stifi ca t i o n fo r th e E qu i pm en t Ou t o f Se r vice (E O OS) m o de l change s has bee n e v al u a t e d a n d d o c u m en t ed i n the e n g in e e r i n g wo r k o r d er a s well. EOO S m odel i m pa c t an d t h e i n co r p o r a t i o n o f t h e 4 1 60 V a c p o r t a b l e g e n e ra t o rs i n t o th e P R A m odel ha v e bee n e v a l u a t e d i n th e EWO. Ar e th e e q u ipme n t f l o w rate s an d p r e s s u r e s ad e q u a t e? No t a p p l i c a b l e Identi f y t h e timin g f o r spec i fi c o pe r at o r act i o n s re q ui r e d t o i mplem e nt. Th e e q u i p m en t i s pr e-d ep l o y ed a n d connected t o m ee t nec e s s ar y t ime requi re ments. T h e s y s t e m ti m e wi n do w i s o n e hou r. The ne c es s ary actions a r e procedurali z e d , u n co m p l icat ed a n d cre w s a r e briefe d a t the star t o f eac h sh i ft. I dent i f y t h e requ i r e d miss i o n t imes Th e porta b l e E D G is on l y be i n g c r e di t e d t o m i t i ga t e i n tern al ev e n t s. Therefo r e , a m i ss i o n t i m e o f 2 4 h o u r s i s assum e d c onsist en t w ith n o rm a l PR A pra c t ices. Ar e t h e el e ct r i c a l p o we r re q ui re m e n t s satisf i e d (e.g., voltag e , a m p s a nd f' r e q u e n c y)? Y es , e n g i n e er i n g calc ulation s ha ve been d o n e t o e nsur e re q u i r em e nts ar e satisfied, th e y ar e in c l ud e d in t h e Engineer i ng Wor k O rder. Ca n adeq u a t e temperatu r e limit s b e met? No t ap plica b l e I s adequa t e vo l um e a n d qual i t y of wate r av a i l abl e? No t app l ic a b l e Example Risk Evaluation Using NEI 16

-08 6 Can expected env ironmental parameters for the equ ipment funct ional i ty support the strategy? The portable generators are dep loyed on s e i s m ic pads. They have been purchased to operate in an external env i ro nmental temp e rature of 130F. No other env i ro nmental factors need to be cons idered. I s there a refuel i ng plan being implemented to meet the miss i on time of the strategy? Refueling of the gen e rator is required as the fuel will last 1 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> s. A procedure e xists for refuel i ng the portable equipment Example Risk Evaluation Using NEI 16

-08 7 Staffing and Tra i n i ng Assessment E lement Descr i pt i on Summary Does the ex ecut i on of the strategy impact the ability of operators to perform the i r ded icated dut i es (e.g. safe shutdown act i on s , F i re Br igade respons e , and local/offs ite communicat ions)? No. Th i s strategy provides a backup source of ac power as a cont ingency for loss of normal ac power. No additional act ions are required by operato r s un less an event occurs wh i ch requ ires the use of the portable generato

r. What other work groups or departments (e.g., eng i neer i n g, ma intenanc e ,secur ity) d i r ected by operators can perform the act ions? The connect ions are bo lted and have torque requirements so ma intenance is required to make the connections.

The fire department is needed to perform the refue ling of the portab l e diesel generator when i t is operat i ng. How many personnel are necessary to perform the act ions? Two a u x iliary operator are requir e d , one to start both d iesels and one to rack in the tran sfer switch. Does runn i ng portab l e e q u ipment n eed to be staffed cont i nuous l y? f no t , at what per i od icity do round s , refuelin g ,etc. need to be performed?

Does not need to be staffed continuous ly. Consumption rates need to be verified period ically so that s uff i c i ent time i s avai l ab l e for refuel ing. The tank ho l ds 1 2 ho u rs of fuel. Does the execut i on of the strategy affect the staffing of the other un i ts on s ite? s add i t i onal staff i ng requ ired to i mp lement the strategy for mu l t i p l e un its? No. And the strategy cannot be i mp lemented at mult iple uni t s beca u s e there are on l y two 4 1 60V a c ge n erators available.

Example Risk Evaluation Using NEI 16

-08 8 Can pre-dep loyment reduce staff i ng requirements when the strategy i s needed to be executed?

The d iesel s are being pre-dep loyed to meet the ti me req u irements for the ir use as a backup to the station b lackout (SBO) generators

. Can supplemental personnel be utilized to augment site personnel dur i ng the execution of the strategy? Not applicable.

Are there any changes to train i ng programs required to be implemented?

No changes to the formal train i ng program are req u ired. Exist i ng tra i n i ng on the use of the portab l e d iese l s for acc i dent mit igat i on i s suffic i ent for this applicat i on. However, sh ift lead br iefs to each oncom i ng operat i ng crew are necessary to ma inta i n a he ightened awareness of the short time to start the portab l e d iesel generators if needed. Example Risk Evaluation Using NEI 16

-08 9 Addressing Unintended Consequences Element Descript i on Summary Can the strategy create the potential to cause a reactor scram? No, sufficient overcurrent protection and breaker protection i s prov i ded i n the circuit to prevent the portable generator from tr i pp i ng the p lant. Can the strategy create the potent i al for inadvertent actuat i on or failure of a system? No, sufficient overcurrent protection and breaker protect i on i s provided i n the circu i t. Does the implementation of the strategy prevent the successful operat i on of normally required permanently installed plant equipment?

No, because of the way the equ ipment is connected to the plan t ,normal equipment is unaffected by the operat i on of the portab l e equ ipment. Does the equipment meet the scop i ng requirements of 10CFR50.65(b) (i.e., The Maintenance Rule)? No, the strategy is not i n the EOPs, but i n an operat i ons ma intenance procedure, referred to from an a larm response procedure (ARP). A l s o ,because of the overcurrent protect i on breakers, a fai lure of the portab l e equipment cannot cause failure of the safety re lated eq uipmen t , or cause a p lant tr i p. Can the implementat i on of the strategy impact compliance with p l ant programs (e.g., FLEX progra m , 8.5.b ,Appendix R, and NFPA-805, barrier control)? This is not FLEX equ ipment or B.5.b equ ipmen t ,so those programs are not impacted. They are not located in a fire area (they are outs i de) and the combust ible fuel could not cause damage to any other p l ant equipment.

Can the implementat i on of the strategy impact the effect iveness of the phys ical security plan? No, security barr iers and security access are unaffected by the pre-dep loyment of the portab l e d iesel generator s. Example Risk Evaluation Using NEI 16

-08 10 Are there digital controls on the portable equipment that cou ld impact cyber security?I f so, how was that addressed?

There are digital control s ,they are not considered as cr itical digital assets. Does the implementat i on of the strategy impact the s ite emergency plan? No. There is no special access or egress, no spec ial requirement for use of the generator s , or impact on staffing of e-p l an personnel.

No Emergency Action Levels are affected by dep loyment of the portab l e d iesel generators

. Example Risk Evaluation Using NEI 16

-08 11 12 NEI 16-06 Evaluation Process

Backup Information

- Example Risk Reduction Evaluation Using NEI 16-06 *Two 2MW 4160VAC portable generators deployed and connected to 4160VAC FLEX distribution box 3

14 2MW 4.16KV Temporary Generators

15 2MW 4.16KV Temporary Generators

16 4.16KV Bus FLEX Connection

17 5.1.2 - Function Applicability Criteria Evaluation The function met by the portable generators is restoration of a single Class 1E 4160V AC bus given a loss of power to the bus.

Supported loads are the same as those supported by a single Station Blackout Generator (SBOG) per the documented engineering evaluation.

NEI 16-06 Evaluation Example

18 5.1.3 - Equipment Capability Criteria Evaluation An evaluation was performed by Design Engineering to evaluate the electrical capability of the portable generators to ensure they could meet the PRA mission as defined by the evaluation. Initial fueling of the DGs provides approximately 9 hours1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br /> of operation, with additional fuel provided by a portable truck under control of the Fire Department. The Fire Department is continuously present at the station and is notified by a step in 40MT

-9ZZ01. NEI 16-06 Evaluation Example

19 NEI 16-06 Evaluation Example

20 5.2.2 - Reliability, Testing and Maintenance Criteria Evaluation Equipment Reliability Engineering Template (ERET) documents the engineering basis for the Palo Verde FLEX program testing and maintenance

. NEI 16-06 Evaluation Example

NEI 16-06 Evaluation Example 21 22 5.3 - Time Availability and Margin Criteria Evaluation A Human Reliability Assessment (HRA) assessment is documented in an Engineering Evaluation (EE), which demonstrates that the available time (75 mins) is adequate to support employing the portable generators, given that they are initially staged and connected to the FLEX distribution box. There is 15 min of margin based on the HRA.

NEI 16-06 Evaluation Example

23 NEI 16-06 Evaluation Example

24 NEI 16-06 Evaluation Example

25 5.4.3 - Staffing and Communications Criteria Evaluation Human Reliability Assessment (HRA) assessment which is documented in the Engineering Evaluation (EE) demonstrates that there are available staff, and their ability to communicate is adequate to employ the portable generators. The HRA is based on operations input.

NEI 16-06 Evaluation Example

26 NEI 16-06 Evaluation Example

27 7.1 - Initiating Events Criteria Evaluation An Engineering Evaluation (EE) documents that the portable generators can be modeled as a backup to the Station Blackout Generators (SBOGs). The connection of the portable generators to the class 1E bus requires closure of a manual transfer switch and breaker. All temporary equipment associated with the use of the portable generators is outside safety related structures. Postulated fires from the temporary generators have been evaluated and found to not impact safety related equipment.

NEI 16-06 Evaluation Example

28 7.2 - Accident Sequence Modeling Criteria Evaluation An Engineering Evaluation (EE) documents that the portable generators can be modeled as backup to the Station Blackout Generators (SBOGs).

NEI 16-06 Evaluation Example

29 7.3 - Success Criteria Criteria Evaluation An Engineering Evaluation (EE) documents that the portable generators can be modeled as backup to the Station Blackout Generators (SBOGs) with the same success criteria.

NEI 16-06 Evaluation Example

30 7.4 - System Analysis Criteria Evaluation An Engineering Evaluation (EE) documents that the portable generators can be modeled as backup to the Station Blackout Generators (SBOGs). The postulated Equipment failures associated with use of the portable generators were all evaluated and found to be very small compared to the human reliability failure contribution.

NEI 16-06 Evaluation Example

31 7.5 - Human Reliability Assessment Criteria Evaluation An Engineering Evaluation (EE) documents that the Human Reliability Assessment (HRA). The HRA to start and align the portable generators was determined to have a mean value of 0.3 using the EPRI HRA calculator. As the random failure rates are dominated by the magnitude of the HRA, it was decided for modeling simplicity to group the generators, transfer switches, and human action in a single undeveloped event with a value of 0.56. The 0.5 value includes margin to account for the uncertainty associated with both the random failures and the HRA. NEI 16-06 Evaluation Example

32 7.6 - Data Analysis Criteria Evaluation An Engineering Evaluation (EE) documents a quantitative analysis of vendor and industry reliability data pertaining to the portable generators. The failure rates selected for equipment (e.g., portable generators, switches, breakers) were taken from the NRC Reliability and Availability Data System (RADS). The failure rate of the portable generators were assumed to be consistent with station blackout (SBO) diesel generators. The equipment failure rates combined were all very small compared to the calculated human reliability analysis failure probability.

NEI 16-06 Evaluation Example

33 7.7 - Quantification Criteria Evaluation An Engineering Evaluation (EE) documents uncertainties associated with the system modeling of the portable generators via sensitivity analyses. The failure rates and their corresponding error factors were determined by data analysis and HRA. The highest error factor for basic events bounded by the undeveloped event is 4.2, which is associated with the fail

-to-run failure rate. A single undeveloped event set at 5E-1 was used in the EOOS model to capture the equipment random failure rates, the HRA, and a safety factor to address uncertainties.

NEI 16-06 Evaluation Example

34 NEI 16-06 Evaluation Example

NEI 16-06 Evaluation Example

Conclusion:

The 2MW 4160VAC portable generators deployed and installed meet the evaluation criteria in NRC Regulatory Issue Summary 2008-15 and NEI 16

-06 in order to credit in configuration risk assessments.

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