IR 05000331/2020003

Integrated Inspection Report 05000331/2020003 and 07200032/2020001

ML20314A150
Person / Time
Site:	Duane Arnold
Issue date:	11/06/2020
From:	Billy Dickson NRC/RGN-III/DRP/B2
To:	Dean Curtland NextEra Energy Duane Arnold
References
IR 2020001
Download: ML20314A150 (20)

Text

November 6, 2020

SUBJECT:

DUANE ARNOLD ENERGY CENTER - INTEGRATED INSPECTION REPORT 05000331/2020003 AND 07200032/2020001

Dear Mr. Curtland:

On September 30, 2020, the U.S. Nuclear Regulatory Commission (NRC) completed an inspection at Duane Arnold Energy Center. On October 1, 2020, the NRC inspectors discussed the results of this inspection with you and other members of your staff. The results of this inspection are documented in the enclosed report.

No findings or violations of more than minor significance were identified during this inspection.

This letter, its enclosure, and your response (if any) will be made available for public inspection and copying at http://www.nrc.gov/reading-rm/adams.html and at the NRC Public Document Room in accordance with Title 10 of the Code of Federal Regulations 2.390, Public Inspections, Exemptions, Requests for Withholding.

Sincerely,

/RA/

Billy C. Dickson, Jr., Chief Branch 2 Division of Reactor Projects

Docket No. 05000331 and 07200032 License No. DPR-49

Enclosure:

As stated

Inspection Report

Docket Number:

05000331 and 07200032

License Number:

DPR-49

Report Number:

05000331/2020003 and 07200032/2020001

Enterprise Identifier: I-2020-003-0027 and I-2020-001-0144

Licensee:

NextEra Energy Duane Arnold, LLC

Facility:

Duane Arnold Energy Center

Location:

Palo, IA

Inspection Dates:

July 01, 2020 to September 30, 2020

Inspectors:

J. Beavers, Senior Resident Inspector

D. Childs, Resident Inspector

J. Corujo-Sandin, Senior Reactor Inspector

J. Dalzell, Health Physicist

R. Edwards, Senior Health Physicist

G. Hansen, Sr. Emergency Preparedness Inspector

C. Norton, Senior Resident Inspector

G. Roach, Senior Operations Engineer

D. Tesar, Resident Inspector

Approved By:

Billy C. Dickson, Jr., Chief

Branch 2

Division of Reactor Projects

SUMMARY

The U.S. Nuclear Regulatory Commission (NRC) continued monitoring the licensees performance by conducting an integrated inspection at Duane Arnold Energy Center, in accordance with the Reactor Oversight Process. The Reactor Oversight Process is the NRCs program for overseeing the safe operation of commercial nuclear power reactors. Refer to https://www.nrc.gov/reactors/operating/oversight.html for more information.

List of Findings and Violations

No findings or violations of more than minor significance were identified.

Additional Tracking Items

None.

PLANT STATUS

The Unit began the inspection period at 84 percent of rated thermal power. Power was limited to prevent turbine control valve oscillations. On July 8, 2020, the licensee lowered power to 77 percent to perform a control rod line adjustment. The licensee then slowly raised power, achieving 82 percent on July 10, 2020. On July 15, 2020, the licensee lowered power to 70 percent to perform a control rod line adjustment. The licensee slowly raised power, achieving 84 percent on July 17, 2020. On July 23, 2020, the licensee lowered reactor power to 74 percent in response to a moisture separator drain tank high level. The licensee returned the plant to 84 percent on July 25, 2020. On August 10, 2020, at 12:49 p.m., the plant experienced a weather-related loss of offsite power. The turbine tripped, and the reactor automatically shut down by design. The licensee placed the plant in cold shutdown on August 11, 2020. The plant remained in cold shutdown until the end of the inspection period. For a more detailed description of this weather-related event, see section 71153 of this report.

INSPECTION SCOPES

Inspections were conducted using the appropriate portions of the inspection procedures (IPs) in effect at the beginning of the inspection unless otherwise noted. Currently approved IPs with their attached revision histories are located on the public website at http://www.nrc.gov/reading-rm/doc-collections/insp-manual/inspection-procedure/index.html. Samples were declared complete when the IP requirements most appropriate to the inspection activity were met consistent with Inspection Manual Chapter (IMC) 2515, Light-Water Reactor Inspection Program - Operations Phase. The inspectors reviewed selected procedures and records, observed activities, and interviewed personnel to assess licensee performance and compliance with Commission rules and regulations, license conditions, site procedures, and standards.

Starting on March 20, 2020, in response to the National Emergency declared by the President of the United States on the public health risks of the coronavirus (COVID-19), resident inspectors were directed to begin telework and to remotely access licensee information using available technology. During this time the resident inspectors performed periodic site visits each week and during that time conducted plant status activities as described in IMC 2515, Appendix D; observed risk significant activities, and completed on-site portions of IPs. In addition, resident and regional baseline inspections were evaluated to determine if all or a portion of the objectives and requirements stated in the IP could be performed remotely. If the inspections could be performed remotely, they were conducted per the applicable IP. In some cases, portions of an IP were completed remotely and on-site. The inspections documented below met the objectives and requirements for completion of the IP.

71111.01 - Adverse Weather Protection

Seasonal Extreme Weather Sample (IP Section 03.01) (1 Sample)

(1) The inspectors evaluated planned preparations for seasonal extreme weather conditions prior to the onset of cold weather for the following:

[turbine building, reactor building, intake structure and pump house]

Impending Severe Weather Sample (IP Section 03.02) (1 Sample)

(1) The inspectors evaluated the adequacy of the overall preparations to protect risk-significant systems from impending severe weather from a storm with potential damaging high winds on August 28, 2020

71111.04 - Equipment Alignment

Partial Walkdown Sample (IP Section 03.01) (2 Samples)

The inspectors evaluated system configurations during partial walkdowns of the following systems/trains:

(1)

'A' and 'B' standby diesel generators starting air sub systems on July 7, 2020

(2) Emergency service water on August 15, 2020

Complete Walkdown Sample (IP Section 03.02) (1 Sample)

(1) The inspectors evaluated system configurations during a complete walkdown of the offsite power supply to the electrical safety buses on August 15, 2020

71111.05 - Fire Protection

Fire Area Walkdown and Inspection Sample (IP Section 03.01) (4 Samples)

The inspectors evaluated the implementation of the fire protection program by conducting a walkdown and performing a review to verify program compliance, equipment functionality, material condition, and operational readiness of the following fire areas:

(1) Reactor Building 833 zone 5-C on July 21, 2020

(2) Turbine Building Elevation 780 on July 22, 2020

(3) Control Building Elevation 786 on July 24, 2020

(4) Reactor Building Elevation 786 on September 2, 2020

71111.06 - Flood Protection Measures

Inspection Activities - Internal Flooding (IP Section 03.01) (1 Sample)

The inspectors evaluated internal flooding mitigation protections in the:

(1) Southeast corner room ['A' core spray and 'A' residual heat removal subsystem] on July 28, 2020

71111.07A - Heat Sink Performance

Annual Review (IP Section 03.01) (1 Sample)

The inspectors evaluated readiness and performance of:

(1) The 'B' emergency service water system on September 21, 2020

71111.11Q - Licensed Operator Requalification Program and Licensed Operator Performance

Licensed Operator Performance in the Actual Plant/Main Control Room (IP Section 03.01) (1 Sample)

(1) The inspectors observed and evaluated licensed operator performance in the Control Room during a minor reactor water level transient on July 7, 2020

Licensed Operator Requalification Training/Examinations (IP Section 03.02) (1 Sample)

(1) The inspectors observed and evaluated requalification of a reactor operator on July 24, 2020

71111.12 - Maintenance Effectiveness

Maintenance Effectiveness (IP Section 03.01) (3 Samples)

The inspectors evaluated the effectiveness of maintenance to ensure the following structures, systems, and components (SSCs) remain capable of performing their intended function:

(1) Availability of the 'C' well water sub-system on July 2, 2020

(2) Availability of the electric fire pump on July 8, 2020

(3) Recirculation system inboard sample valve on September 30, 2020

Quality Control (IP Section 03.02) (1 Sample)

The inspectors evaluated the effectiveness of maintenance and quality control activities to ensure the following SSC remains capable of performing its intended function:

(1) Quality control of the activities associated with the welding of the lid on to the independent spent fuel storage installation dry storage container on July 14, 2020

71111.13 - Maintenance Risk Assessments and Emergent Work Control

Risk Assessment and Management Sample (IP Section 03.01) (1 Sample)

The inspectors evaluated the accuracy and completeness of risk assessments for the following planned and emergent work activities to ensure configuration changes and appropriate work controls were addressed:

(1) Emergent work and elevated risk associated with replacing the diaphragm on the 'B' moisture separator normal drain valve on July 30, 2020

71111.15 - Operability Determinations and Functionality Assessments

Operability Determination or Functionality Assessment (IP Section 03.01) (2 Samples)

The inspectors evaluated the licensee's justifications and actions associated with the following operability determinations and functionality assessments:

(1) CR 02364570, Unexpected Alarm on Core Spray Sparger Low Differential Pressure on August 6, 2020

(2) CR 02365031, 'B' Emergency Service Water Strainer Plugged Requiring to be Bypassed on August 11, 2020

71111.18 - Plant Modifications

Temporary Modifications and/or Permanent Modifications (IP Section 03.01 and/or 03.02) (1 Sample)

The inspectors evaluated the following temporary or permanent modifications:

(1) Throttling the 'A' drywell cooling supply valve to reduce drywell leakage on July 9, 2020

71111.19 - Post-Maintenance Testing

Post-Maintenance Test Sample (IP Section 03.01) (2 Samples)

The inspectors evaluated the following post maintenance test activities to verify system operability and functionality:

(1) Proper operation and no air leakage following maintenance on the 'B' instrument air dryer, on July 29, 2020

(2) Proper operation of emergency service water system following troubleshooting of the

'B' emergency service water heat exchanger on August 18, 2020

71111.22 - Surveillance Testing

The inspectors evaluated the following surveillance tests:

Surveillance Tests (other) (IP Section 03.01)

(1)

'B' River Water Supply and Screen Wash System Vibration Measurement and Operability Test on July 15, 2020 (2)

'B' Reactor Water Level and Pressure Instrument Calibration on July 21, 2020

FLEX Testing (IP Section 03.02) (1 Sample)

(1) 'A' 480 VAC FLEX Diesel functional test on July 1, 2020

71114.06 - Drill Evaluation

Drill/Training Evolution Observation (IP Section 03.02) (1 Sample)

The inspectors evaluated:

(1) Unusual Event declaration on August 10,

71152 - Problem Identification and Resolution

Annual Follow-up of Selected Issues (IP Section 02.03) (2 Samples)

The inspectors reviewed the licensees implementation of its corrective action program related to the following issues:

(1) Corrective actions associated with bypassing emergency service water strainers

(2) Effectiveness of licensee's corrective actions for loss of offsite power event

71153 - Follow-up of Events and Notices of Enforcement Discretion Event Follow-up (IP Section 03.01)

(1) The inspectors evaluated the weather-related loss of offsite power (LOOP) event and Notice of Unusual Event (NOUE) declaration on August 10, 2020, as well as the licensee's immediate follow-up response.

On August 10, 2020, a widespread, long-lived, straight-line windstorm associated with a band of rapidly moving thunderstorms (derecho) moved through Iowa and other parts of the Midwest. The National Weather Service later estimated 80 to 100 miles per hour (mph) wind speeds for more than 30 minutes with gusts of up to 130 mph.

During the derecho, Duane Arnold Energy Center (DAEC) experienced a LOOP. The licensee declared a NOUE (an emergency classification defined by the NRC as one which indicates that a potential degradation in the level of safety of the plant is in progress or has occurred). After approximately 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, with the restoration of one of six offsite power lines, the site exited the LOOP and NOUE. The inspectors evaluated the event to verify that it resulted in no radiological consequences.

During this event follow-up inspection, the inspectors assessed the immediate actions and short-term considerations regarding potential challenges to plant stability, verified the safety barriers' integrity, and evaluated potential radiological impacts. In addition to the above considerations, the inspectors assessed the events' sequence, including equipment performance, procedure adherence, and personnel performance, for potential challenges to plant stability. The loss of offsite power event was the dominant nuclear safety risk-contributor at the DAEC. Inspectors independently reviewed event response records, site Emergency Plan, site emergency preparedness implementing procedures, and interviewed site emergency preparedness staff to evaluate the site's compliance with regulatory requirements and implementation of the site's emergency plan to protect the health and safety of the public during NOUE. Additionally, the NRC inspectors reviewed the licensee's post-event evaluation report in which the licensee identified areas for improvement and entered those items into the site's corrective action program. Based on the independent review, the site demonstrated, with reasonable assurance, the ability to effectively implement the site's emergency plan to protect the public's health and safety during the NOUE that they declared on August 10, 2020.

The overall integrated inspection effort for this event included the conduct of multiple baseline inspection samples documented throughout this report under the following inspection procedure: 71111.01, 71111.04, 71111.07, 71111.15, 71152, and 71153.

See the Inspection Results section of this report for any inspection-related observations and assessments made during this inspection.

Event Report (IP Section 03.02) (1 Sample)

(1) LER 05000-331/2020-0001, Notice of Unusual Event and Unit Trip Due to Loss of Offsite Power Due to High Winds, submitted on September 14, 2020. The inspectors determined that it was not reasonable to foresee or correct the weather-related cause discussed in the LER, therefore, no performance deficiency associated with the event was identified and the inspectors did not identify a violation of NRC requirements. On September 30, 2020 the licensee submitted LER 05000-331/2020-0001-01 which revised the LER to report that a small cut in secondary containment caused by the high winds had rendered secondary containment inoperable while in a mode of applicability, that is, from the time of the reactor scram until the unit was placed into cold shutdown. All required actions for the inoperable secondary containment were met within their required completion times. While preparing the LER revision, the licensee corrected verbal information provided to the NRC in the first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> following the event, that secondary containment was not made inoperable by the wind event. As the secondary containment function was maintained, the inaccurate information concerning operability would not have changed the NRC's response to the event.

Personnel Performance (IP Section 03.03) (1 Sample)

(1) The inspectors evaluated the licensees performance during and following the 'A' moisture separator drain tank high level occurrence on July 23,

OTHER ACTIVITIES

- TEMPORARY INSTRUCTIONS, INFREQUENT AND ABNORMAL

60855.1 - Operation of an Independent Spent Fuel Storage Installation at Operating Plants Operation of an Independent Spent Fuel Storage Installation at Operating Plants

(1) The inspectors evaluated the licensees independent spent fuel storage installation cask loading from August 31 - September 3, 2020. Specifically, the inspectors observed the following activities:

• Fuel selection and fuel loading

• Heavy load movements of a loaded transfer cask out of the spent fuel pool, and movement of the transfer cask from the processing area to the transfer trailer

• Drying and backfill evolutions

• Closure welding and non-destructive weld evaluations including helium leak testing

• Transfer and transport evolutions

• Radiological field surveys

The inspectors evaluated the following change reviews:

• Program changes associated with loading to Certificate of Compliance 1004, Amendment

INSPECTION RESULTS

Assessment 71152 Assessment of Licensee Corrective Actions for Loss of Offsite Power Event:

The inspectors evaluated the licensees overall corrective actions and response to the loss of off-site power (LOOP) and Notification of Unusual Event (NOUE) emergency classification on August 10, 2020 (described in more detail in section 71153 of this report). In particular, this section describes the inspectors observations and assessment related to the performance attributes discussed in Section 03.06 of NRC inspection procedure 71152.

Plant initial conditions on August 10, 2020, before the event, included the following: DAEC was operating at 80 percent of rated thermal power due to degraded drywell cooling capacity.

Major equipment out of service prior included the B train of the low-pressure coolant injection (LPCI) system, which was inoperable for surveillance testing but available for injection, and the diesel fire pump, which was unavailable due to planned maintenance. A leaking fuel element in the southeast core quadrant was also actively under power suppression at the time. Finally, spent fuel handling was in progress for a dry cask storage campaign with a loss of cooling time to boil in the spent fuel pool at 64 hours7.407407e-4 days <br />0.0178 hours <br />1.058201e-4 weeks <br />2.4352e-5 months <br />. The station probabilistic risk assessment (PRA) status was green for both core damage frequency and large early release frequency.

Event Narrative:

At 11:38 a.m. (all times in Central Daylight Time), the National Weather Service declared a severe thunderstorm watch. The licensee entered the abnormal operating procedure for severed weather.

At 12:02 p.m., the severe thunderstorm watch was upgraded to a warning. The severe weather risk option was selected in the plant risk model. Plant risk incurred a fractional change, but overall risk remained green. The senior responsible manager directed fuel handling operations to be placed in a safe condition and secured.

At 12:35 p.m., as the storm approached, an electrical grid perturbation occurred, which initiated the logic for the auto start feature of the two emergency diesel generators (EDG);however, the logic was not met to close the diesel output breakers to their respective safety buses and the diesels remained running but unloaded.

At 12:49 p.m., the site lost offsite power from the electrical grid. The LOOP initiated an automatic main turbine trip due to load reject and an automatic reactor scram. Since the EDGs were already running, immediately following the LOOP, the diesel output breakers closed to maintain power to the plant's two electrical safety buses. The flywheels on the 120-volt alternating current reactor protection system (RPS) motor-generators held RPS voltage and frequency during the power transfer. The unit did not lose the RPS system.

Since RPS is the power supply to the main steam isolation valve (MSIV) solenoids, the MSIVs remained open following the LOOP. At 12:58 p.m., the licensee declared an NOUE due to all offsite AC power lost to both safety buses for greater than 15 minutes (SU1.1).

Emergency Operating Procedure (EOP)-1, RPV [reactor pressure vessel] Control, was entered on low water level and high pressure. The reactor water level initially lowered rapidly to level 2 (lo-lo) due to the loss of feedwater. Reactor core isolation cooling (RCIC) and high-pressure coolant injection (HPCI) systems automatically initiated and restored the reactor water level until it reached Level 8 (hi trip). Both systems automatically tripped, per design.

The operators placed both systems in manual control, and they maintained the reactor water level with RCIC injecting. Operators bypassed both RCIC and HPCI Level 8 trips to keep the reactor water level above Level 8 and below the main steam lines to promote natural core circulation.

Reactor pressure initially rose rapidly due to the turbine trip. Two safety relief valves lifted for approximately 10 seconds each and lowered pressure. Coincidentally, the initial reactor coolant injection from Level 2 to Level 8 added a significant mass of colder water and provided a short-term reduction in reactor pressure. After reactor pressure stabilized between 800 and 1155 psi, the operators maintained reactor pressure primarily with main steam line drains and the use of RCIC as a steam load. The operators slowly lowered the pressure band over the day until they placed shutdown cooling in service on August 10, 2020.

At 10:30 p.m., HPCI was used in pressure control mode to reduce pressure below the final shutdown cooling pressure interlock reset. On August 11, 2020, at 2:30 a.m., the operators established cold shutdown. A reactor coolant temperature band of 150 to 212 degrees was set.

During the 14-hour cooldown, the heat-up/cooldown rates exceeded the 100 degrees per hour limit (delineated in Technical Specification 3.4.9 and EOP-1) on three separate occasions. At 3:05 p.m. on August 10, 2020, the reactor pressure vessel experienced a 140 degree per hour cooldown rate on the bottom head drain due to stratification. At that time, the recirculation pumps were unavailable. At 4:00 p.m. on August 10, 2020, the reactor pressure vessel experienced a 112 degrees per hour cooldown rate due to added cooling from the control rod drive mini purge to the recirculation pump seals. At 9:15 p.m. on August 10, 2020, the reactor pressure vessel experienced a 162 degree per hour heat-up rate on the bottom head drain due to mixing caused by starting HPCI in the pressure control mode to facilitate starting shutdown cooling. Despite the cooldown rate exceeding technical specifications limits, the inspectors concluded that no violation occurred since the required actions for exceeding the limits were for the licensee to determine that the RCS was acceptable for operation before starting up.

On August 10, 2020, at 12:53 p.m., the licensee entered EOP 3, Secondary Containment Control, on a high steam tunnel temperature of 160 degrees. The licensee exited EOP-3 upon confirmation that high temperatures were due to loss of ventilation and not a steam leak. At 3:00 p.m., with a 60-hour spent fuel pool time to boil, the licensee re-entered EOP 3 on low spent fuel pool level because the 'B' fuel pool cooling pump tripped. Although the 'B' pump tripped and failed to restart due to a blown fuse caused by the grid disturbance and LOOP, operators started the standby 'A' fuel pool cooling pump without issue and exited EOP-3 after the level returned to normal.

On August 10, 2020, at 7:45 p.m., EOP 2, Primary Containment Control, was entered on torus water level greater than 10.4 feet due to safety relief valve and RCIC system operation.

At 9:54 p.m., the licensee re-entered EOP 2 on torus water temperature greater than 95 degrees F. These EOP entries were not unexpected. The licensee took appropriate actions.

On August 10, 2020, at 10:40 p.m., the 'B' emergency service water pump discharge strainer developed a high differential pressure, and the operators placed the strainer in bypass.

Emergency service water cools the diesel generators and other safety-related equipment the inspectors' observations concerning this occurrence are in the following 71152 Observation section of this report.

In coordination with the grid operator, the licensee took steps to clear debris and lineup breakers in the switchyard to facilitate the return of the 161kv Vinton line. The licensee repaired damaged transformers to ensure they were ready to receive offsite power when it became available. On August 11, 2020, at 11:26 a.m., the grid operator restored the Vinton line to the switchyard, and the licensee lined up offsite power to essential and non-essential electrical busses. The licensee terminated the NOUE at 4:00 p.m. on August 11, 2020. The grid operator restored all six offsite power lines by August 17, 2020.

On August 12, 2020, the licensee identified a 0.75 square inch gap in the Northwest corner of the 5th-floor reactor building secondary containment. At 11:12 p.m., the licensee performed the secondary containment integrity test and demonstrated that it could perform its safety function of preventing a ground-level release. This test bounded both identified and unidentified secondary containment gaps that may have resulted from the storm.

The licensee noted additional building damage. Specifically, the storm damaged the roof of the North FLEX building. The licensee declared the North FLEX building and the FLEX equipment inside inoperable. The FLEX function was maintained by the South FLEX building and the equipment inside. Additionally, there was damage to non-credited structures, including the collapse of the non-safety-related cooling towers and the loss of large turbine building siding sections.

Assessment:

Although this event did cause multiple failures to offsite power availability (all six offsite power sources were lost to the site) with damage to area power lines and the on-site switchyard, the inspectors determined that offsite power is not assumed to be available in any design basis analyses and is not safety-related. The EDGs, the system designed to mitigate this actual event's consequences, functioned satisfactorily, thereby maintaining this safety function until the licensee restored offsite power approximately 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> later. Concerning damaged cooling towers, they are not safety-related, nor a part of the safety-related ultimate heat sink.

The cooling towers were not required to mitigate the consequences of an accident, nor were they needed for the reactor to shut down, cool down, or remain shut down. For the loss of the 'B' fuel pool cooling pump, the time to boil on the spent fuel pool was 60 hours6.944444e-4 days <br />0.0167 hours <br />9.920635e-5 weeks <br />2.283e-5 months <br />, and operators restored the system to service within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />. The licensee restored redundancy to the system when they identified and replaced a blown fuse in the 'B' pump control power circuit.

In summary, the inspectors evaluated the licensee's immediate and follow-up corrective actions to this event. The inspectors' evaluation considered equipment, processes, personnel performance issues, and the risk-significant post-initiator human error probabilities in the probabilistic risk assessment and bases. The assessment did not identify any loss of the plant's three fission product barriers (the fuel cladding, the reactor coolant system, and the containment system) or the key safety functions supporting them. Inspectors verified that no radiological impact resulted from this event. The inspectors determined that all equipment responded as expected with the exceptions noted above, and operators followed appropriate response procedures. The inspectors determined that the licensee's corrective actions to address this complex event were appropriate to the circumstances and commensurate with the potential safety significance.

Observation: Corrective Actions Associated with Bypassing Emergency Service Water Strainers 71152 On August 10, 2020 at 12:49 p.m., Duane Arnold experienced a derecho and a Loss of Off-site Power (LOOP). During the LOOP event, both emergency diesel generators (EDGs)started automatically to provide power to essential loads. The emergency service water (ESW) pumps auto started to provide cooling to the EDGs and other essential loads.

At 10:40 p.m., the licensee bypassed the 'B' ESW strainer due to high strainer differential pressure and declared 'B' ESW and 'B' EDG inoperable but available. The strainer remained bypassed until the plant was no longer in a mode of applicability for ESW (Mode 4, cold shutdown). After the operators bypassed the strainer, the licensee increased the monitoring of the 'B' EDG. The licensee identified no adverse effects on the 'B' EDG during this monitoring activity. The inspectors observed that the licensee took no action to minimize the time they bypassed the ESW strainer. The inspectors, concerned over potential fouling of safety-related equipment with the ESW strainer bypassed, reviewed previous licensee corrective actions associated with bypassing the ESW strainers.

The inspectors reviewed action request (AR) 295476, initiated on September 21, 2002, to re-evaluate acceptability of operating ESW with the strainer bypassed. The inspectors referenced an evaluation for operating the residual heat removal service water system (RHRSW) with its strainer bypassed for consideration. The Duane Arnold AR Review Committee recommended that ESW operation not be allowed with the strainer bypassed without performing a further evaluation, discussed below.

• The inspectors reviewed OTH025491; an engineering evaluation completed March 20, 2003, which identified several design basis requirements for the ESW System to supply debris-free water to prevent equipment or system fouling or plugging. In this evaluation, the licensee determined that because of the differences in heat exchanger tube diameters between the RHRSW system and the ESW system, the analysis that permits operating RHRSW with the strainer bypassed cannot be applied to all equipment cooled by ESW without additional actions.

• The inspectors reviewed OTH027041, completed May 07, 2003, to determine appropriate compensatory measures after bypassing the ESW strainer. The evaluation concluded that the operators should consider some of the components cooled by ESW inoperable when they bypass the ESW strainer.

• Evaluation OTH029100, completed on December 10, 2003, re-evaluated the acceptability of operating ESW with the strainer bypass valve open. This engineering evaluation concluded that declaring the ESW subsystem inoperable when running with the strainer bypass valve open was an adequate compensatory measure because ESW subsystem inoperability cascades to supported subsystems.

Based on these three engineering evaluations' conclusions, the licensee showed that they could not justify the operability of an ESW subsystem with its strainer bypassed. Hence, on August 10, 2020, per station procedures and the current design basis, the licensee declared the 'B' ESW subsystem and the 'B' EDG inoperable when operators bypassed the strainer due to high strainer differential pressure. Although inoperable, the licensee left the 'B' ESW subsystem in operation as the subsystem and supported subsystems still functioned. Had 'B' ESW or any of the supported subsystems failed to perform, the operable 'A' ESW subsystem was in operation to maintain ESW and supported system functions. Therefore, the inspectors observed that licensee actions were in accordance with the current design and licensing basis of the plant.

EXIT MEETINGS AND DEBRIEFS

The inspectors verified no proprietary information was retained or documented in this report.

• On October 1, 2020, the inspectors presented the integrated inspection results to Mr. D. Curtland, Director of Site Operations, and other members of the licensee staff.

• On September 4, 2020, the inspectors presented the Independent Spent Fuel Storage Installation cask loading inspection results to Mr. D. Curtland, Director of Site Operations, and other members of the licensee staff.

DOCUMENTS REVIEWED

Inspection

Procedure

Type

Designation

Description or Title

Revision or

Date

60855.1

ALARA Plans

20 Dry Fuel Storage Campaign #3 ALARA Plan

Calculations

CAL-F19-002

Fuel Selection for DAEC ISFSI Campaign III

Corrective Action

Documents

Selected Corrective Action Documents Created Since 2017

Engineering

Changes

2.48 Screen EC 2428

EAL Radiation Monitoring Setpoint Change

2.48 Screen

EC290544

DAEC ISFSI Loading Campaign III

2.48 Screen

PCR2228558

Revision to ACP 1412.2 for Removal of Combustibles in

ISFSI Area

EC 289927

Update DBD-F16-001 to Reflect Revision 1 of CoC 1004

Amendments 8 and 9 and Associated Tech Specs

EC 289927

Adopt Revision 1 of CoC 1004 Amendments 8 and 9

EC 290544

DAEC ISFSI Loading Campaign III

EC 292428

EAL Radiation Monitoring Setpoint Change

EC-290544

DAEC Haul Path Engineering Evaluation and Haul Path

Repair Recommendations

Miscellaneous

Response for FME Question

09/01/2020

Selected 10 CFR 72.48 Screenings and Evaluations

Duane Arnold Energy Center Design Basis Document for the

Dry Spent Fuel Storage Program

DAEC ISFSI Campaign III Fuel Selection - October 16(1)

2019 Annual Radiological Environmental Monitoring Report

DBD-F16-001

Duane Arnold Energy Center Design Basis Document for the

Dry Spent Fuel Storage Program

E-56554

20 DAEC P2P - Training Matrix

07/14/2020

E-56559

Haul Path Repair Recommendations

05/15/2020

E-56576

20 DAEC P2P - Welders Documentation

05/27/2020

E-56592

20 DAEC P2P - OS197-1 Yoke Equipment Use Certificate

04/15/2020

E-56621

20 DAEC P2P - NDE Certifications

04/21/2020

E-56994

DAEC Haul Path Evaluation (New Trailer Weight)

06/17/2020

Inspection

Procedure

Type

Designation

Description or Title

Revision or

Date

MTF Plan No. 20-

016

ISFSI Campaign III Dry Storage Canister #6

06/09/2020

NUH-06-106.62

R1 OS197-1

Yoke Maintenance Package

2/20/2020

NDE Reports

Report No. 6007-

19-167A1-0478

Non-Destructive Examination Reports for Canister No. 22

09/01/2020

Report No. BOP-

MT-19-009

Magnetic Particle Examination Reactor Building Crane Hook

01/20/2020

Procedures

Crane-H046-02

Harnischfeger Reactor Building Crane & Ederer Trolley

Inspections

DFS 201A

Dry Shielded Canister / Transfer Cask Preparation for Fuel

Loading Operations

DFS 203A

Dry Shielded Canister Sealing Operations

DFS 301A

Loaded Dry Shielded Canister / Transfer Cask from

Refueling Floor to ISFSI Operations

DFS 302A

Dry Shielded Canister from Transfer Cask to Horizontal

Storage Module Transfer Operations

HPP 3104.13

Dry Cask Storage Job Coverage and Decontamination

Radiation

Surveys

PDA-M-

200826-10

DFS3 Post DSC29 Insertion Inside of Transfer Cask

08/26/2020

Self-Assessments

Level 1 Assessment for LICA 02338906-01 2020 NRC ISFSI

Pre-Inspection Self-Assessment

05/26/2020

PDA 19-003

Duane Arnold Nuclear Assurance Report

05/29/2019

Work Orders

PM Task 02

Reactor Building Crane Inspection

04/24/2020

71111.01

Procedures

AOP 903

Severe Weather

NG 270K

Plant Winterization Checklist

71111.04

Drawings

BECH-M 132 <1>

P. & I.D. Diesel Generator System

BECH-M 132<2>

P. & I.D. 1G031 Standby Diesel Generator

71111.05

Drawings

PFP-RB-786

Reactor Building Elevation 786

Fire Plans

PFP-CB-786

Pre-Fire Plan Control Building El. 786

PFP-TB-780

Turbine Building Elevation 780

Procedures

PFP-RB-833

Pre-Fire Plan Reactor Building El. 833

71111.07A

Work Orders

WO 40736544

Flow Test 'B' ESW Cooled Components

08/18/2020

Inspection

Procedure

Type

Designation

Description or Title

Revision or

Date

71111.11Q Miscellaneous

ESG 2020B-01E

Evaluated Scenario

Procedures

AOP 644

Feedwater / Condensate Malfunction

71111.12

Corrective Action

Documents

CR 02360701

Good Catch/Use of Fundamentals in Mechanical

Maintenance

06/23/2020

CR 02362459

CV4639 Closed Unexpectedly

07/11/2020

Engineering

Evaluations

EVT-64.01-2020

CV4639 Closed with No Apparent Cause

07/28/2020

Miscellaneous

Shift Log

08-Jul-2020 0824

Shift Log

08-Jul-2020 0832

Procedures

DFS 203A

Dry Shielded Canister Sealing Operations

HTPT-DSC-

ORANO

Duane Arnold

6007-00

SPM 9.2-1

Services Program Manual, NUHOMS 61BTH Type 1 and 2

DSC Closure Weld Traveler

Work Orders

WO 40684334

1P048 Analyze Upper and Lower Bearing Oil Samples

07/08/2020

WO 409599461

Well Water Pump 1P58C Discharge Check Valve

06/30/2020

71111.13

Procedures

Valvop M120-01

Masoneilan Camflex II Valve and Operator Repair

Work Orders

WO 40734241

CV 1065B-O, Replace Diaphragm

07/24/2020

71111.15

Corrective Action

Documents

CR 02364570

Unexpected Alarm on Core Spray Sparger Low Differential

Pressure

08/05/2020

CR 02365031

'B' Emergency Service Water Strainer Plugged Requiring to

be Bypassed

08/11/2020

Procedures

Annunciator

1C03A C-8

'A' Core Spray Sparger LO D/P

71111.18

Procedures

MA-AA-100-1011-

F01

Equipment Troubleshooting

OP-001

Operator Challenge and Clearance Audit

OP-AA-100-1000

Clearance and Tagging

OP-AA-100-1000

Conduct of Operations

OP-AA-100-102

Plant Status Control

Work Orders

WO 40720786

High Drywell Leakage

05/11/2020

71111.19

Procedures

OI 518.1

Instrument

Service and Breathing Air System

107

Inspection

Procedure

Type

Designation

Description or Title

Revision or

Date

STP NS540002B

'B' Emergency Service Water Operability Test

71111.22

Miscellaneous

ML19092A212

Clinton Power Station - Final Significance Determination of

White Finding with Assessment Follow-Up and Notice of

Violation; NRC Inspection Report No. 05000461, /2018092

04/01/2019

Procedures

NS100102B

B River Water Supply and Screen Wash System Vibration

Measurement and Operability Test

STP 3.3.3.2-09B

Reactor Water Level and Pressure Instrument (Loop B)

Calibration

STP NS240502A

FLEX 480VAC Diesel Generator 1G101A Functional Test

71152

Corrective Action

Documents

AR 295476295476019545 Re-Evaluate Acceptability of Operating ESW With

Its Strainer Function Bypassed

09/21/2002

Engineering

Evaluations

OTH 025491

Re-Evaluate Acceptability of Operating ESW With Its

Strainer Function Bypassed

03/20/2003

OTH 027041

Re-Evaluate Acceptability of Operating ESW With Its

Strainer Function Bypassed

OTH 029100

Re-Evaluate Acceptability of Operating ESW With Its

Strainer Function Bypassed

2/12/2003

Procedures

OI-454

Emergency Service Water System

71153

Corrective Action

Documents

CR 02365031

1S089B ESW Strainer Plugged Requiring to be Bypassed

08/11/2020

CR 02365115

Note-05 for Unusual Event was 1 Minute Late

08/11/2020

CR 02365642

Inaccuracies in Notification Form

08/17/2020

Drawings

Bech M103<2>

P.& I.D. Main Steam Moisture Separators and Reheaters

Miscellaneous

BECH-MRS-

M305-S

Technical Specification for Self-Cleaning Strainers (ASME

VIII) Safety Related for the Duane Arnold Energy Center ff

the Iowa Electric Light and Power Company Cedar Rapids,

Iowa

DBD-E13-001

Emergency Service Water Design Bases Document

SD-454

System Description Emergency Service Water

SD-880

Reactor Vessel Instrumentation System

SD-880

Reactor Level Instrumentation System

Shift Log

2-Jul-2020 2155

UFSAR/DAEC-1

9.2

Water Supply Systems

Procedures

1C07B A-5

MSR Drain Tank 1T-93A Hi level

Inspection

Procedure

Type

Designation

Description or Title

Revision or

Date

IPOI 4

Shutdown (Fast Power Reduction)

141