Information Notice 2015-01, Degraded Ability to Mitigate Flooding Events

Degraded Ability to Mitigate Flooding Events

ML14279A268
Person / Time
Issue date:	01/09/2015
From:	Michael Cheok, Kokajko L Division of Construction Inspection and Operational Programs, Division of Policy and Rulemaking
To:
banic, merilee 415-2771
References
IN-15-001
Download: ML14279A268 (14)

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

OFFICE OF NEW REACTORS

WASHINGTON, D.C. 20555-0001 January 9, 2015 NRC INFORMATION NOTICE 2015-01: DEGRADED ABILITY TO MITIGATE FLOODING

EVENTS

ADDRESSEES

All holders of an operating license or construction permit for a nuclear power reactor under

Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Domestic Licensing of Production

and Utilization Facilities, except those that have permanently ceased operations and have

certified that fuel has been permanently removed from the reactor vessel.

All holders of and applicants for a power reactor early site permit, combined license, standard

design approval, or manufacturing license under 10 CFR Part 52, Licenses, Certifications, and

Approvals for Nuclear Power Reactors. All applicants for a standard design certification, including such applicants after initial issuance of a design certification rule.

PURPOSE

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to inform

addressees of recent operating experiences related to external flood protection where

deficiencies with equipment, procedures, and analyses relied on to either prevent or mitigate the

effects of external flooding at licensed facilities have resulted in degraded ability to mitigate

flooding events. Information from the following events may apply to the design and maintenance

of physical protection features such as flood barriers, the ability to effectively implement

abnormal operating procedures to mitigate the effects of external flooding, and the accuracy of

analyses that are used to determine design-basis flooding elevations, as well as flood water

inundation times. The NRC expects that recipients will review the information for applicability to

their facilities and consider actions, as appropriate, to avoid similar problems. However, suggestions contained in this IN are not NRC requirements; therefore, no specific action or

written response is required.

DESCRIPTION OF CIRCUMSTANCES

St. Lucie Plant, Unit 1

On January 9, 2014, St. Lucie Unit 1 was operating at 100 percent reactor power when the site

experienced a period of unusually heavy rainfall. Although this event was below the design

basis flood, St. Lucie declared an unusual event because of storm drain capacity degradation.

Blockage in the sites storm drain system caused water to backup within the emergency core

cooling system (ECCS) pipe tunnel outside of the Unit 1 reactor auxiliary building (RAB). Water

entered the RAB through two degraded conduits that lacked internal flood barriers. Operators

ML14279A268 managed the inflow of water into the RAB via operation of floor drain valves between the

affected elevation and the location of safety-related systems. An extent-of-condition review

identified four additional conduits on Unit 1 that lacked the required internal flood barriers. The

modification that had installed the conduits had not considered the need for internal flood

barriers for conduits installed below the design-basis flood elevation. Previous walkdowns at St.

Lucie, performed in 2012 using the guidance contained in Nuclear Energy Institute (NEI) 12-07, Guidelines for Performing Verification Walkdowns of Plant Flood Protection Features, dated

May 2012, had failed to identify the degraded conduit or the missing conduit internal flood

barriers. Additionally, St. Lucie determined that previous engineering evaluations used to

assess the results of the 2012 NEI 12-07 walkdowns did not account for the site flood inundation

times and therefore underestimated the volume of external flood leakage through degraded

flood barriers. The licensee implemented corrective actions that included installing qualified

internal water seals on all of the affected conduits. Additional information regarding this event is

available in Licensee Event Report (LER) 50-335/2014-001-00, dated March 10, 2014, and in

NRC Integrated inspection reports 05000335/2014009 and 05000389/2014009, dated

September 24, 2014.

Brunswick Steam Electric Plant, Units 1 and 2

On April 20, 2011, NRC inspectors identified that the emergency diesel generator (EDG) fuel oil

tank chamber (FOTC) enclosure contained openings that would adversely impact the ability to

mitigate external flooding of the EDG FOTCs in the event of a probable maximum hurricane

(PMH). The licensee subsequently performed extent-of-condition walk downs and identified

numerous examples of degraded or nonconforming flood protection features, the majority of

which were flood penetration seals. During walkdowns of flood protection features in

accordance with NEI 12-07 during August through September 2012, the licensee identified

additional degradation in the reactor buildings and the EDG building, specifically degraded flood

penetration seals, conduit seals, and a 7.6-centimeter (3-inch) gap in the weather stripping along

the bottom of the Unit 2 reactor building railroad door. This gap would have allowed leakage into

the reactor building during a PMH. The inspectors also identified an EDG rollup door that could

have allowed water intrusion into the EDG building during a PMH. Additionally, the licensee

identified unsealed shims under the base plates of the service water pumps (SWPs), as well as

leaking flood penetration seals and an unsealed conduit in the service water building (SWB) that

could have allowed flood water to enter the SWB during a PMH. The licensee also identified a

potential flood pathway from the intake canal into the SWB through unsealed SWP leak off hub

drains, a condition that had existed since construction of the plant. These conditions were

caused by a historical lack of a flood protection program at Brunswick. Multiple examples were

identified where credited flood mitigation equipment had no established preventative

maintenance program. Corrective actions included correcting the degraded seals, developing

and implementing an engineering program to mitigate consequences of external flooding, and

developing topical design basis for internal and external flooding. Additional information

regarding this issue is available in NRC inspection reports 05000324/2014011 and

05000325/2014011, dated May 29, 2014.

Sequoyah Nuclear Plant, Units 1 and 2

On December 12, 2012, the licensee at Sequoyah, Tennessee Valley Authority (TVA),

performed an inspection of an electrical manway and confirmed that inadequate electrical

conduit penetration seals provided an in-leakage path into the essential raw cooling water

(ERCW) pumping station. The condition had previously been identified and evaluated as a

degraded condition based on the fact that flood barriers were not installed to seal the subject electrical conduit penetrations as required by the pertinent design drawings. Subsequent

physical inspection of the conduits revealed that inadequate flood barriers were actually

installed. The licensee concluded that an external flooding event exceeding the elevation that

would impact the conduits would inundate the ERCW pumping station, with impacts to both Unit

1 and Unit 2. The nonconforming seals would have allowed flood waters to enter the pumping

station at a rate greater than the capacity of the sump pump and could have resulted in the

ERCW system being unavailable to perform its design function during a flood event below plant

grade. Based on a review of the supporting documents, the licensee determined that the

electrical conduit penetration seals were meant to be the flood barrier. However, there was no

clear identification of the flood barriers and their requirements. The licensee took corrective

actions that included installing qualified conduit seals and revising design-basis documents and

flood barrier drawings to identify flood boundaries and to include seal details. Additional

information regarding this issue is available in LER 05000327, 328/2012-001-00, dated

February 8, 2013, and in NRC inspection reports 05000327/2013011 and 05000328/2013011, dated June 4, 2013.

Watts Bar Nuclear Plant, Unit 1

In 2013, the licensee at Watts Bar (TVA) identified that it could not demonstrate the capability to

implement site external flood mitigation procedures in the time assumed between the notification

of an imminent design-basis flood event and flood waters reaching the Watts Bar site. The

design-basis flood event for Watts Bar would result in flooding above plant grade. Accordingly, the licensee relied on procedures used to reconfigure plant systems in preparation for site

inundation to ensure the ability to safely shut down the reactor and remove decay heat.

Examples of issues that challenged the assurance that the flood mitigation procedures could be

implemented within the available time included:

• Work activities in the implementing procedures were directed in a sequential manner, which added to the overall time required.

• Piping interferences and the lack of suitable rigging locations for inter-system spool

pieces.

• Mislabeled or missing equipment was used in the implementing procedures.

• The time to perform some of the more complex and coordinated work activities was

underestimated.

This issue resulted in a violation of technical specification for failure to establish adequate flood

mitigation procedures. The licensee took corrective actions that included revising the flood

mitigation procedures to add more detail, increasing the frequency of the training for the

procedures, and staging equipment and developing preventive maintenance activities to

periodically validate that the equipment is in place. Additional information regarding this issue is

available in NRC inspection report 05000390/2013009, dated June 4, 2013.

Sequoyah Nuclear Plant, Units 1 and 2; Watts Bar Nuclear Plant, Unit 1; and Browns Ferry

Units 1, 2 and 3

On July 28, 2009, TVA determined that computer modeling inconsistencies predicting the

performance of dams located in the watershed upstream of the Sequoyah, Watts Bar, and

Browns Ferry sites adversely affected the probable maximum flood (PMF) design-basis analyses. Corrections to those issues identified that there would be less flow through the dam

spillways at the high headwater elevation during a PMF event and would result in over-topping

the earthen portions of the affected dams. Failure of the dams was assumed if their earthen

portions over-topped. Based on these results, TVA determined that the PMF elevations may

exceed the original design-basis flooding elevations at the Watts Bar, Sequoyah, and Browns

Ferry nuclear sites. On April 8, 2013, TVA determined that the issue was reportable as an

unanalyzed condition and submitted LERs to the NRC for each of the three affected sites. One

of the root causes for the event was over-confidence in the design-basis analyses, which

allowed latent computer modeling errors to remain undetected. An additional contributing cause

was that formal process controls were not established to ensure that the flood protection

program protected critical safety systems. Additional information regarding this issue is available

in NRC inspection reports 05000327/2013011, 05000328/2013011, and 05000390/2013009, dated June 4, 2013. The NRC is currently reviewing the circumstances associated with this

issue at the Browns Ferry site.

Three Mile Island Station

On August 2, 2012, while observing the licensee flooding walkdowns at Three Mile Island

Station in accordance with Temporary Instruction (TI) 2515/187, Inspection of Near-Term Task

Force Recommendation 2.3 Flooding Walkdowns, NRC inspectors noted degradation on

several conduit couplings in the air intake tunnel. The air intake tunnel provides a source of air

for safety-related ventilation systems and also contains both safety- and nonsafety-related

electrical conduits. The couplings, which by design should have been injected with sealant to

provide a barrier to design-basis flooding events, showed signs of exposure to wet

environments, indicating that the sealant was missing. The licensee eventually determined that

43 conduit couplings were missing sealant. The original construction deficiency had not been

identified by the licensee during a comprehensive review performed in 2010. Without adequate

protection from flooding (flood seals), flood water could have bypassed all flood barriers through

the conduits and impacted the operability of decay heat removal equipment. The licensee

implemented prompt compensatory actions, including staging extra sandbags and earth moving

equipment to restore operability of the flood barriers. The licensee implemented permanent

corrective actions that included sealing the conduits by injecting watertight qualified sealant

material into the associated cable conduits. Additional information regarding this issue is

available in NRC inspection report 05000289/2012005, dated February 11, 2013.

R.E. Ginna Nuclear Power Plant

On May 29, 2013, while performing flooding walkdowns in accordance with NEI 12-07, the

licensee at R.E. Ginna Nuclear Power Plant discovered two penetrations that appeared to be

unsealed leading to one of the battery rooms. Although the licensee determined that drains in

the manhole would prevent the water level from reaching the unsealed penetrations, NRC

inspectors raised questions about the operability of these drains, since they were not included in

any maintenance or test program. In response to these questions, the licensee tested the drains

and determined that they were not capable of draining enough water to prevent a design-basis

flood from reaching the unsealed penetrations and flooding battery room B. Battery room A

would also be flooded by a non-watertight fire door that connects it with battery room B. The

potential existed to also lose offsite power leading to the loss of all alternating current power to

the site and an unrecoverable station blackout. In 1983, as part of the Systematic Evaluation

Process, the licensees design basis was changed to include additional external flooding events

and the flood protection level was agreed to by the licensee at a level that was above the elevation of the manhole. The licensee did not evaluate the potential for flooding through the

manhole and, therefore, did not seal the cable penetrations that were at an elevation below

the new level. The licensee took corrective actions that included installing permanent

hydrostatic seals in both penetrations between the manhole and the battery room. Additional

information regarding this issue is available in NRC inspection report 05000244/2013005, dated

February 14, 2014.

Monticello Nuclear Generating Plant

During an inspection from September 12, 2012, to May 15, 2013, NRC inspectors identified that

the Monticello Nuclear Generating Plant site failed to maintain a flood mitigation procedure such

that it could support the implementation of flood protection activities within the 12-day timeframe

credited in the updated safety analysis report (USAR) to protect against a PMF event. The

inspectors made this observation while watching the licensee perform flooding walkdowns in

accordance with TI 2515/187. The licensee believed that flood mitigation actions for the

protected area could be taken within the 12 days specified in the USAR by citing an independent

engineering assessment performed in 2001. However, the licensee did not perform a

verification walkthrough of the activities in the procedure and, therefore, did not identify

vulnerabilities in its flood plan. NRC inspectors noted that according to that evaluation, construction of a bin wall around vulnerable portions of the site would take 12 days to complete, assuming that two crews were operating and all the materials were available on site. The

evaluation also specified a total time of 25 days for bin wall construction, including procurement

of bin wall materials. Although the timeframe for constructing a levee could be reduced to less

than 12 days with two crews operating, the licensee had not taken actions to support that

reduction. The licensee took corrective actions, which included revising its procedure to add

more detail, as well as pre-staging materials necessary to complete the bin wall in the timeframe

cited in the USAR. Additional information regarding this issue is available in NRC inspection

report 05000263/2013008, dated June 11, 2013.

Point Beach Nuclear Plant

In March 2013, inspectors found that the Point Beach Nuclear Plant licensee failed to establish

procedural requirements to implement external wave run-up protection design features as

described in the final safety analysis report (FSAR). The inspectors made this observation while

watching the licensee perform flooding walkdowns in accordance with TI-2515/187. Flood

protection procedures directed installation of concrete jersey barriers to protect the turbine

building and pumphouse from flooding. While performing the flooding walkdowns, the licensee

discovered that it did not have enough jersey barriers to cover the full length of the area that

needed to be protected. Furthermore, when the barriers were installed, gaps were created and

there were no provisions in the procedure for using sandbags to protect the openings in the

jersey barriers or the gaps between the barriers and the ground. The licensee also had failed to

consider the time that would be required to erect the barriers. The licensee took corrective

actions, including modifying existing jersey barriers to eliminate openings, revising the procedure

to direct the installation of jersey barriers in conjunction with sandbags, and pre-staging

additional sandbags and jersey barriers. Additional information regarding this issue is available

in NRC inspection report 05000266/2013002, dated May 13, 2013.

Dresden Nuclear Power Station, Units 2 and 3

In August 2012, while observing licensee simulations for executing flood protection procedures

as part of the NEI 12-07 walkdowns, NRC inspectors noted that the procedures did not account for reactor coolant system (RCS) inventory losses. The procedures assumed flood duration

of 4 days, during which time systems that provide normal and makeup capacity to the RCS

would be flooded and unavailable. The licensee calculations accounted for the 5-gallon per

minute (gpm) maximum technical specification allowance for unidentified RCS leakage, but it did

not account for inventory losses from identified leakage, which could be as high as an additional

20 gpm. The licensee strategy did not originally provide for a method to maintain RCS inventory

above the top of active fuel for RCS leakage rates that were allowable under technical

specifications. The licensee took corrective actions, including modifying procedures to provide

makeup capacity and to isolate the reactor recirculation loops during flood conditions when

reactor vessel makeup capabilities are limited so that sources of identified leakage would no

longer impact the reactor vessel level. Additional information regarding this issue is available in

NRC inspection report 05000237/2013002, dated May 7, 2013.

Fort Calhoun Station

In September 2009, during a component design basis inspection, NRC inspectors identified that

the licensee at Fort Calhoun Station failed to maintain adequate procedures to protect the intake

structure and auxiliary building during external flooding events. These procedures described

stacking and draping sandbags on top of installed floodgates to protect the plant up to the flood

elevation described in the USAR. When inspectors asked plant staff to demonstrate this

procedure, they were unable to complete the procedure as written because the cross section on

the top of the floodgates was too small to accommodate enough sandbags to retain a 5-foot (1.5 meter) static head of water. The inadequate procedure was caused by the licensee missing

several opportunities to implement appropriate corrective actions when new external flood

information became available. During the extent of condition review, the licensee identified

unsealed penetrations below the licensing basis flood elevation that could cause the intake

structure to be vulnerable during an extreme flooding event. The licensee took corrective

actions that included revising the procedures, redesigning and installing selected flood

protection features such that they would not require the use of sandbags, and sealing the

affected penetrations. Additional information regarding this issue is available in NRC inspection

report 05000285/2010007, dated July 15, 2010.

Arkansas Nuclear One, Units 1 and 2

On March 31, 2013, following the collapse of a temporary lifting rig carrying the Unit 1 main

turbine generator stator, a rupture in the fire water system resulted in water leakage past floor

plugs in the auxiliary building and subsequent accumulation of water inflow in the safety-related

decay heat removal room B through a room drain pipe. This event overlapped the timeframe in

which the licensee was assessing flood mitigation features in response to Fukushima-related

orders issued by the NRC. The extent of condition reviews by the licensee related to this event

and those discrepancies identified during flood mitigation response efforts found numerous other

pathways that were not effectively sealed against flooding in the auxiliary building and

emergency diesel fuel storage buildings. These conditions were not identified during the

licensees initial flooding walkdowns in accordance with NEI 12-07.

The licensees failure to design, construct, and maintain the Unit 1 and Unit 2 auxiliary and

emergency diesel fuel storage buildings so that they would protect safety-related equipment

during design-basis flood events caused the overall condition. The unsealed penetrations were

not identified during the walkdowns because of incomplete information on flooding barriers, some information not being kept current, and inadequate oversight of the contractor performing

the flood protection walkdowns. The licensee took corrective actions that included re-performing the reviews of essential flood protection features, identifying those features that were initially not

identified, completing the missed portions of the walkdowns, and submitting corrected

information to the NRC. In this event, an internal flooding event resulted in the licensee

discovering external flooding vulnerabilities. Additional information regarding this issue is

available in NRC inspection reports 05000313/2014009 and 05000368/2014009, dated

September 9, 2014.

BACKGROUND

Related NRC Generic Communications

NRC IN 2012-002, Potentially Nonconservative Screening Value for Dam Failure Frequency in

Probabilistic Risk Assessments, dated March 5, 2012. The NRC issued this IN to alert

addressees of a potentially nonconservative screening value for dam failure frequency that

originated in 1980s reference documents which may have been referenced by licensees in their

probabilistic risk assessment (PRA) for external events.

NRC IN 2009-006, Construction-Related Experience with Flood Protection Features, dated

July 21, 2009. The NRC issued this IN to alert addressees of construction-related operating

experience involving inadequate flood protection features.

NRC IN 2007-001, Recent Operating Experience Concerning Hydrostatic Barriers, dated

January 31, 2007. The NRC issued this IN to alert addressees of deficient hydrostatic barriers

that allowed water to leak into rooms that contained safety-related equipment.

NRC IN 2005-030, Safe Shutdown Potentially Challenged by Unanalyzed Internal Flooding

Events and Inadequate Design, dated November 7, 2005. The NRC issued this IN to alert

addressees to the importance of establishing and maintaining the plant flooding analysis and

design, consistent with NRC requirements and principles of effective risk management, to

ensure that internal flooding risk is effectively managed.

NRC IN 2005-011, Internal Flooding/Spray-Down of Safety-Related Equipment due to Unsealed

Equipment Hatch Floor Plugs and/or Blocked Floor Drains, dated May 6, 2005. The NRC

issued this IN to alert addressees of the possibility of flooding safety-related equipment as a

result of (1) equipment hatch floor plugs that are not water tight, and (2) blockage of the

equipment floor drain systems that are credited to mitigate the effects of flooding in the FSAR

and plant design-basis calculations.

NRC IN 2003-008, Potential Flooding through Unsealed Concrete Floor Cracks, dated

June 25, 2003. The NRC issued this IN to alert addressees of observed flooding in a room

containing safety-related panels and equipment as a result of fire water seepage through

unsealed concrete floor cracks.

NRC IN 1994-027, Facility Operating Concerns Resulting from Local Area Flooding, dated

March 31, 1994. The NRC issued this IN to alert addressees to emergency preparedness, equipment operability, and radiological control problems that may result from local area flooding.

DISCUSSION

The examples provided by this IN are operating experience related to deficiencies with

equipment, procedures, and analyses that prevent or mitigate the effects of external flooding. These issues directly contributed to periods of time where the affected sites were vulnerable to

the impact of a flood event. Note that some cases involved actual external events (e.g., St.

Lucie) or events that indicated a potential external flood vulnerability (e.g., ANO). Several cases

indicate the existence of potential cliff edge effects, as described in the report Near Term Task

Force Review of Insights from the Fukushima Daiichi Accident. Other cases indicated the

existence of a deficiency at levels below the existing licensing bases flood. The causal factors

involved failure to comply with original design requirements, failure to maintain plant design

basis, failure to implement adequate procedures to mitigate the effects of flooding, inadequate

barrier control programs, inadequate flood protection programs, and inadequate modeling of the

effects of design-basis flood events. Some of the issues had previously been entered into the

site corrective action program but were not adequately resolved in a timely manner. In some

cases, there was a lack of sensitivity by the licensee organization in understanding the potential

impact of flooding events to safety-related equipment and structures. It should be noted that the

examples discussed here are a subset of the operating experience which highlights the main

insights gained. Although not explicitly discussed in this IN, there are additional examples of

issues related to degraded external flood protection.

The examples discussed in this IN illustrate the importance of an effective flood protection

program. Regulations in 10 CFR Part 50, Appendix A, General Design Criterion 2, Design

Bases for Protection Against Natural Phenomena, requires that structures, systems, and

components important to safety be designed to withstand the effects of natural phenomena such

as floods without loss of capability to perform their safety functions.

Regulations in 10 CFR Part 50, Appendix B, Criterion III, Design Control, requires that

measures shall be established to assure that applicable regulatory requirements and the design

basis as specified in the license are correctly translated into specifications, drawings, procedures, and instructions.

GENERIC IMPLICATIONS

Flood protection vulnerabilities can be a significant contributor to risk at nuclear power facilities.

They have the potential to make multiple trains of safety-related equipment and support

equipment simultaneously inoperable. They also have a significant impact on operator recovery

actions, as demonstrated by the 2011 earthquake and tsunami that affected the Fukushima

Dai-ichi facility in Japan. In 2012, the NRC issued a request for information to all power reactor

licensees directing them to submit reevaluated flooding hazards report for their sites to confirm

the appropriateness of the hazards assumed and to perform walkdowns to confirm their ability to

protect against these hazards. The licensees completed their walkdowns by November 2012, and NRC inspectors performed follow-up inspections. The NRC staff is currently reviewing the

results of these actions to determine whether additional regulatory actions are necessary to

provide additional protection against the updated hazards.

CONTACT

S

This information notice requires no specific action or written response. Please direct any

questions about this matter to the technical contact listed below or the appropriate Office of

Nuclear Reactor Regulation project manager.

Michael C. Cheok, Director /RA/ Lawrence E. Kokajko, Director /RA/

Division of Construction Inspection Division of Policy and Rulemaking

and Operational Programs Office of Nuclear Reactor Regulation

Technical Contact:

Shane Sandal, RII Jesse Robles, NRR

404-997-4513 301-415-2940

E-mail: Shane.Sandal@nrc.gov E-mail: Jesse.Robles@nrc.gov

Note: NRC generic communications may be found on the NRC public Web site, http://www.nrc.gov, under Electronic Reading Room/Document Collections.

ML14279A268 *concurred via e-mail TAC MF4827 OFFICE TECH EDITOR BC(Acting)* RII/DRP* NRR/DRA/* NRR/DRA* NRR/DRA*

• RII/DPR/RPB3 NAME CHsu SSandal JMunday FFerrante Chung JGitter

DATE 10/30/2014 11/13/2014 11/13/2014 11/17/2014 11/20/2014 11/17/2014 OFFICE RES/DRA/ETB* NRR/DSS/SBPB* D: NRR/DPR/PGCB NRR/DPR/PGCB NRR/DPR/PGCB

NRR/DSS*

NAME WOtt GCasto TMcGinty CHawes MBanic SStuchell

DATE 11/13/2014 11/17/2014 11/18/2014 11/21/2014 11/24/2014 11/24/2014 OFFICE NRO/DCIP NRR/JLD NRR/DPR NRR/DPR

NAME MCheok JMcHale AMohseni LKokajko

DATE 12/8/2014 12/22/2014 12/18/2014 01/9/2015