ML24199A151

MD 8.3 Evaluation for Perry Rain Water Intrusion 06/19/2024

ML24199A151
Person / Time
Site:	Perry
Issue date:	06/21/2024
From:	Billy Dickson NRC/RGN-III/DORS/RPB2
To:
References
EN 57181
Download: ML24199A151 (1)

Text

MD 8.3 Evaluation Decision Documentation for Reactive Inspection (Deterministic and Risk Criteria Analyzed)

PLANT:

Perry Unit 1 EVENT DATE:

06/19/2024 DETERMINISTIC CRITERIA EVALUATION DATE:

06/21/2024 Brief Description of the Significant Operational Event or Degraded Condition:

On June 19, 2004, Perry Unit 1 experienced heavy rainfall that entered the Division 3 (HPCS) diesel generator (DG) room through the roof. This rainwater entered the electrical portion of the generator rendering the Division 3 DG inoperable. This resulted in an 8-hour non-emergency 50.72 notification (EN 57181).

The rainfall event was estimated at ~2.5 inches of rainfall within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />. During this time the DG building roof drains were unable to keep up with the rain, which allowed the water to start building up on the roof. At some point the water started to leak into the Division 3 DG room along the diesel exhaust manifold seal. At the peak of the leakage, it was not possible to determine the amount of water coming into the building. Several minutes after the initial water intrusion, the amount of water dissipated down to 300-400 drops per minute. During the peak leakage, water was observed to be running down the engine, down the turbo charger, and rolling off the turbo charger directly onto the generator. Once the leakage slowed, water continued to run onto the engine, turbo charger, and began to splash off the coupling guard and directly on the generator.

After the leakage subsided, the licensee isolated the DG, dried out the affected portions of the generator, inspected, tested, and restored the DG to operable. The licensee also installed sandbags around the DG exhaust manifold penetration on the roof to minimize water collection around the seal.

An event similar to this occurred previously in 2017. At that time, rainwater was also entering through the Division 3 DG exhaust piping penetration seal, but no equipment was impacted.

The licensee concluded that the condition was acceptable with deficiencies but it was not known if the licensee has completed any repair since then.

Y/N DETERMINISTIC CRITERIA N

1. Involved operations that exceeded, or were not included in, the design bases of the facility Remarks: The estimated 2.5/hr rainfall is within the peak PMP for the station (13.19/hr) and the standard projected storm (3.747/hr). Therefore, this did not involve operations that exceeded, or were not included in, the design bases of the facility. The leak is caused by a degraded exhaust manifold seal.

2 N

2. Involved a major deficiency in design, construction, or operation having potential generic safety implications Remarks: This event did not involve a major deficiency in design, construction, or operation having potential generic safety implications since it only involved a single DG exhaust manifold seal.

N

3. Led to a significant loss of integrity of the fuel, primary coolant pressure boundary, or primary containment boundary of a nuclear reactor Remarks: There was no loss of any fission product barriers.

Y

4. Led to the loss of a safety function or multiple failures in systems used to mitigate an actual event Remarks: This event led to the loss of the safety function of the Division 3 DG to provide power to the high-pressure core spray system used to mitigate an actual event. Although the high-pressure core spray system is still operable per Technical Specifications, the system will not be able to perform its function during a loss of offsite power (LOOP) event due to the loss of its emergency power source.

N

5. Involved possible adverse generic implications Remarks: No generic implication were identified.

Y

6. Involved significant unexpected system interactions Remarks: The external rain event adversely affected the Division 3 DG which resulted in the DG being declared inoperable with a non-emergency 50.72 issued.

Y

7. Involved repetitive failures or events involving safety-related equipment or deficiencies in operations Remarks: An event similar to this occurred previously in 2017. That event was not as severe as the rainwater did not enter any of the electrical components, nor impact any safety related equipment.

N

8. Involved questions or concerns pertaining to licensee operational performance Remarks: This issue did not involve questions or concerns pertaining to licensee operational performance. Operators performed as expected and per procedures.

3 CONDITIONAL RISK ASSESSMENT RISK ANALYSIS BY: Dariusz Szwarc DATE: 06/24/2024 Brief Description of the Basis for the Assessment (may include assumptions, calculations, references, peer review, or comparison with licensee=s results):

A regional Senior Reactor Analyst (SRA) performed an analysis of this condition using SAPHIRE 8, version 8.2.10, and the Perry SPAR model (Version 8.81). The SRA made the following assumptions:

The SRA modeled a base case for a weather-related loss of offsite power (LOOPWR).

The SRA modeled an initiating event for a LOOPWR (IE-LOOPWR) and a failure of the Division 3 DG. EPS-DGN-FS-DGC was set to TRUE.

There was a lot of uncertainty associated with this event as a LOOPWR did not occur.

However, during severe weather there is an increased likelihood of a LOOPWR occurring.

Precipitation Frequency Data was obtained from the National Oceanic and Atmospheric Administration (https://hdsc.nws.noaa.gov/pfds/?bkmrk=pa).

The conditional probability of a LOOP given the rain event was estimated as 0.1 (1E-1) based on a previous best estimate documented in ML15022A637.

Since the condition existed for more than a year an exposure period of 1.0 was used in accordance with the NRCs Risk Assessment of Operational Events (RASP) manual.

The formula for ICCDP used was:

ICCDP =

• CP * (conditional CCDP - baseline CDP)

• exposure period, where:

= the initiating event frequency for the rain event CP = the conditional probability of a LOOP given the rain event CDP = Core Damage Probability CCDP = Conditional Core Damage Probability ICCDP = Incremental Conditional Core Damage Probability The SRA evaluated two sensitivity cases: 1) precipitation of 2.5 inches in one hour to reflect the conditions on June 19, 2024, and 2) precipitation of 2 inches per hour to reflect the conditions in 2017.

Sensitivity 1 (2.5 inches of rain per hour):

ICCDP =

• CP * (conditional CCDP - baseline CDP)

• exposure period 9.1E-7 = 1E-2*1E-1*([1.01E-3]-[1.02E-4])*1 Sensitivity 2 (2 inches of rain per hour):

ICCDP =

• CP * (conditional CCDP - baseline CDP)

• exposure period 3.6E-6 = 4E-2*1E-1*([1.01E-3]-[1.02E-4])*1 The dominant sequences for this condition are a weather-related loss of offsite power along with the weather event causing the loss of HPCS.

4 The estimated incremental conditional core damage probability (ICCDP) is between 9.1E-7 and 3.6E-6 and places the risk in the range of no additional inspection and a special inspection.

RESPONSE DECISION USING THE ABOVE INFORMATION AND OTHER KEY ELEMENTS OF CONSIDERATION AS APPROPRIATE, DOCUMENT THE RESPONSE DECISION TO THE EVENT OR CONDITION, AND THE BASIS FOR THAT DECISION DECISION AND DETAILS OF THE BASIS FOR THE DECISION:

Region III has determined the degradation of the DG exhaust manifold seal and the resultant inoperability of the Division 3 DG due to rainwater intrusion should continue to be inspected under the baseline inspection program versus a special inspection (SIT). The basis for this decision is as follows:

1) the impact of the exhaust manifold seal degradation was limited to a single train of emergency power that affected HPCS only. All other systems (RCIC/ADS/CS/RHR) were available.

2) the resident inspectors have obtained a significant amount of information regarding potential cause of the degradation. It would be more efficient to continue the inspection.

3) licensee operational performance during and after the rainwater intrusion was as expected.

Based on these reasons, continued inspection in the baseline inspection program is the appropriate approach to resolving this issue.

BRANCH CHIEF: Thomas Hartman /RA/

DATE: 07/05/2024 SRA: Joshua Havertape for Dariusz Szwarc /RA/

DATE: 07/08/2024 DEPUTY DIVISION DIRECTOR: Billy Dickson /RA/

DATE: 07/12/2024 DIVISION DIRECTOR:

DATE:

RA (if reactive inspection is initiated)

DATE:

ADAMS ACCESSION NUMBER: ML24199A151 ADAMS PACKAGE ACCESSION NUMBER: ML24199A145 EVENT NOTIFICATION REPORT NUMBER (as applicable): 57181 Internal Distribution List is at the end of this document.

5 Decision Documentation for Reactive Inspection (Deterministic-only Criteria Analyzed)

PLANT:

Perry Unit 1 EVENT DATE:

06/19/2024 EVALUATION DATE:

06/21/2024 Brief Description of the Significant Operational Event or Degraded Condition:

On June 19, 2004, Perry Unit 1 experienced heavy rainfall that entered the Division 3 (HPCS) diesel generator (DG) room through the roof. This rainwater entered the electrical portion of the generator rendering the Division 3 DG inoperable. This resulted in an 8-hour non-emergency 50.72 notification (EN 57181).

The rainfall event was estimated at ~2.5 inches of rainfall within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />. During this time the DG building roof drains were unable to keep up with the rain, which allowed the water to start building up on the roof. At some point the water started to leak into the Division 3 DG room along the diesel exhaust manifold seal. At the peak of the leakage, it was not possible to determine the amount of water coming into the building. Several minutes after the initial water intrusion, the amount of water dissipated down to 300-400 drops per minute. During the peak leakage, water was observed to be running down the engine, down the turbo charger, and rolling off the turbo charger directly onto the generator. Once the leakage slowed, water continued to run onto the engine, turbo charger, and began to splash off the coupling guard and directly on the generator.

After the leakage subsided, the licensee isolated the DG, dried out the affected portions of the generator, inspected, tested, and restored the DG to operable. The licensee also installed sandbags around the DG exhaust manifold penetration on the roof to minimize water collection around the seal.

An event similar to this occurred previously in 2017. At that time, rainwater was also entering through the Division 3 DG exhaust piping penetration seal, but no equipment was impacted.

The licensee concluded that the condition was acceptable with deficiencies but it was not known if the licensee has completed any repair since then.

REACTOR SAFETY Y/N IIT Deterministic Criteria N

1. Led to a Site Area Emergency Remarks: This event did not lead to a Site Area Emergency.

N

2. Exceeded a safety limit of the licensee's technical specifications Remarks: This event did not result in the licensees Technical Specification Safety Limit being exceeded.

6 N

3. Involved circumstances sufficiently complex, unique, or not well enough understood, or involved safeguards concerns, or involved characteristics the investigation of which would best serve the needs and interests of the Commission Remarks: The leak was from a roof seal. It did not involve any complex, unique, or not well understood phenomena.

Y/N SI Deterministic Criteria N

4. Significant failure to implement the emergency preparedness program during an actual event, including the failure to classify, notify, or augment onsite personnel Remarks: This event did not involve any failure to implement the emergency preparedness program.

N

5. Involved significant deficiencies in operational performance which resulted in degrading, challenging, or disabling a safety system function or resulted in placing the plant in an unanalyzed condition for which available risk assessment methods do not provide an adequate or reasonable estimate of risk.

Remarks: This event did not involve any deficiencies in operational performance.

7 RADIATION SAFETY Y/N IIT Deterministic Criteria N

1. Led to a significant radiological release (levels of radiation or concentrations of radioactive material in excess of 10 times any applicable limit in the license or 10 times the concentrations specified in 10 CFR Part 20, Appendix B, Table 2, when averaged over a year) of byproduct, source, or special nuclear material to unrestricted areas Remarks: This event did not involve in radiological release to unrestricted areas.

N

2. Led to a significant occupational exposure or significant exposure to a member of the public. In both cases, significant is defined as five times the applicable regulatory limit (except for shallow-dose equivalent to the skin or extremities from discrete radioactive particles)

Remarks: This event did not involve any occupational exposure or exposure to a member of the public.

N

3. Involved the deliberate misuse of byproduct, source, or special nuclear material from its intended or authorized use, which resulted in the exposure of a significant number of individuals Remarks: This event did not involve any deliberate misuse of byproduct, source, or special nuclear material that resulted in the exposure of individuals.

N

4. Involved byproduct, source, or special nuclear material, which may have resulted in a fatality Remarks: This event did not involve any byproduct, source, or special nuclear material, that resulted in a fatality.

N

5. Involved circumstances sufficiently complex, unique, or not well enough understood, or involved safeguards concerns, or involved characteristics the investigation of which would best serve the needs and interests of the Commission Remarks: The leak was from a roof seal. It did not involve any complex, unique, or not well understood phenomena.

Y/N AIT Deterministic Criteria N

6. Led to a radiological release of byproduct, source, or special nuclear material to unrestricted areas that resulted in occupational exposure or exposure to a member of the public in excess of the applicable regulatory limit (except for shallow-dose equivalent to the skin or extremities from discrete radioactive particles)

8 Remarks: This event did not involve a radiological release of byproduct, source, or special nuclear material to unrestricted areas.

N

7. Involved the deliberate misuse of byproduct, source, or special nuclear material from its intended or authorized use and had the potential to cause an exposure of greater than 5 rem to an individual or 500 mrem to an embryo or fetus Remarks: This event did not involve a deliberate misuse of byproduct, source, or special nuclear material.

N

8. Involved the failure of radioactive material packaging that resulted in external radiation levels exceeding 10 rads/hr or contamination of the packaging exceeding 1000 times the applicable limits specified in 10 CFR 71.87 Remarks: This event did not involve a failure of radioactive material packaging.

N

9. Involved the failure of the dam for mill tailings with substantial release of tailings material and solution off site Remarks: This event did not involve a failure of the dam for mill tailings.

Y/N SI Deterministic Criteria N

10. May have led to an exposure in excess of the applicable regulatory limits, other than via the radiological release of byproduct, source, or special nuclear material to the unrestricted area; specifically occupational exposure in excess of the regulatory limits in 10 CFR 20.1201 exposure to an embryo/fetus in excess of the regulatory limits in 10 CFR 20.1208 exposure to a member of the public in excess of the regulatory limits in 10 CFR 20.1301 Remarks: This event did not involve any exposure via the radiological release of byproduct, source, or special nuclear material to the unrestricted area.

N

11. May have led to an unplanned occupational exposure in excess of 40 percent of the applicable regulatory limit (excluding shallow-dose equivalent to the skin or extremities from discrete radioactive particles)

Remarks: This event did not involve an unplanned occupational exposure.

N

12. Led to unplanned changes in restricted area dose rates in excess of 20 rem per hour in an area where personnel were present or which is accessible to personnel Remarks: This event did not involve an unplanned change in restricted area dose rates where personnel were present or was accessible to personnel.

9 N

13. Led to unplanned changes in restricted area airborne radioactivity levels in excess of 500 DAC in an area where personnel were present or which is accessible to personnel and where the airborne radioactivity level was not promptly recognized and/or appropriate actions were not taken in a timely manner Remarks: This event did not involve an unplanned change in restricted area airborne radioactivity levels in an area where personnel were present or was accessible to personnel.

N

14. Led to an uncontrolled, unplanned, or abnormal release of radioactive material to the unrestricted area for which the extent of the offsite contamination is unknown; or, that may have resulted in a dose to a member of the public from loss of radioactive material control in excess of 25 mrem (10 CFR 20.1301(e)); or, that may have resulted in an exposure to a member of the public from effluents in excess of the ALARA guidelines contained in Appendix I to 10 CFR Part 50 Remarks: This event did not involve an uncontrolled, unplanned, or abnormal release of radioactive material to the unrestricted area.

N

15. Led to a large (typically greater than 100,000 gallons), unplanned release of radioactive liquid inside the restricted area that has the potential for groundwater, or offsite, contamination Remarks: This event did not involve an unplanned release of radioactive liquid inside the restricted area that had the potential for groundwater, or offsite, contamination.

N

16. Involved the failure of radioactive material packaging that resulted in external radiation levels exceeding 5 times the accessible area dose rate limits specified in 10 CFR Part 71, or 50 times the contamination limits specified in 49 CFR Part 173 Remarks: This event did not involve a failure of radioactive material packaging.

N

17. Involved an emergency or non-emergency event or situation, related to the health and safety of the public or on-site personnel or protection of the environment, for which a 10 CFR 50.72 report has been submitted that is expected to cause significant, heightened public or government concern Remarks: This event did not involve an event that was expected to cause significant, heightened public or government concern.

10 SAFEGUARDS/SECURITY Y/N IIT Deterministic Criteria N

1. Involved circumstances sufficiently complex, unique, or not well enough understood, or involved safeguards concerns, or involved characteristics the investigation of which would best serve the needs and interests of the Commission Remarks: This event did not involve any complex, unique, or not well enough understood, or safeguards concerns.

N

2. Failure of licensee significant safety equipment or adverse impact on licensee operations as a result of a safeguards-initiated event (e.g., tampering).

Remarks: This event did not involve a safeguards-initiated event.

N

3. Actual intrusion into the protected area Remarks: This event did not involve an intrusion into the protected area.

Y/N AIT Deterministic Criteria N

4. Involved a significant infraction or repeated instances of safeguards infractions that demonstrate the ineffectiveness of facility security provisions Remarks: This event did not involve any instances of safeguards infractions.

N

5. Involved repeated instances of inadequate nuclear material control and accounting provisions to protect against theft or diversions of nuclear material Remarks: This event did not involve any nuclear material control and accounting provisions.

N

6. Confirmed tampering event involving significant safety or security equipment Remarks: This event did not involve a tampering event.

N

7. Substantial failure in the licensees intrusion detection or package/personnel search procedures which results in a significant vulnerability or compromise of plant safety or security Remarks: This event did not involve a failure in the licensees intrusion detection or package/personnel search procedures.

11 Y/N SI Deterministic Criteria N

8. Involved inadequate nuclear material control and accounting provisions to protect against theft or diversion, as evidenced by inability to locate an item containing special nuclear material (such as an irradiated rod, rod piece, pellet, or instrument)

Remarks: This event did not involve any inadequate nuclear material control and accounting provisions.

N

9. Involved a significant safeguards infraction that demonstrates the ineffectiveness of facility security provisions Remarks: This event did not involve a safeguards infraction.

N

10. Confirmation of lost or stolen weapon Remarks: This event did not involve any lost or stolen weapon.

N

11. Unauthorized, actual non-accidental discharge of a weapon within the protected area Remarks: This event did not involve a discharge of a weapon.

N

12. Substantial failure of the intrusion detection system (not weather related)

Remarks: This event did not involve a failure of the intrusion detection system.

N

13. Failure to the licensees package/personnel search procedures which results in contraband or an unauthorized individual being introduced into the protected area Remarks: This event did not involve a failure to the licensees package/personnel search procedures.

N

14. Potential tampering or vandalism event involving significant safety or security equipment where questions remain regarding licensee performance/response or a need exists to independently assess the licensees conclusion that tampering or vandalism was not a factor in the condition(s) identified Remarks: This event did not involve tampering or vandalism.

12 RESPONSE DECISION USING THE ABOVE INFORMATION AND OTHER KEY ELEMENTS OF CONSIDERATION AS APPROPRIATE, DOCUMENT THE RESPONSE DECISION TO THE EVENT OR CONDITION, AND THE BASIS FOR THAT DECISION.

DECISION AND DETAILS OF THE BASIS FOR THE DECISION:

Region III has determined the degradation of the DG exhaust manifold seal and the resultant inoperability of the Division 3 DG due to rainwater intrusion should continue to be inspected under the baseline inspection program versus a special inspection (SIT). The basis for this decision is as follows:

1) the impact of the exhaust manifold seal degradation was limited to a single train of emergency power that affected HPCS only. All other systems (RCIC/ADS/CS/RHR) were available.

2) the resident inspectors have obtained a significant amount of information regarding potential cause of the degradation. It would be more efficient to continue the inspection.

3) licensee operational performance during and after the rainwater intrusion was as expected.

Based on these reasons, continued inspection in the baseline inspection program is the appropriate approach to resolving this issue.

BRANCH CHIEF: Thomas Hartman /RA/

DATE: 07/05/2024 SRA: Joshua Havertape for Dariusz Szwarc /RA/

DATE: 07/08/2024 DEPUTY DIVISION DIRECTOR: Billy Dickson /RA/

DATE: 07/12/2024 DIVISION DIRECTOR:

DATE:

ADAMS ACCESSION NUMBER: ML24199A151 ADAMS PACKAGE ACCESSION NUMBER: ML24199A145 EVENT NOTIFICATION REPORT NUMBER (as applicable): 57181 Distribution: Michelle.Simmons@nrc.gov; Scott.Morris@nrc.gov; Jason.Carneal@nrc.gov; John.Giessner@nrc.gov; Mohammed.Shuaibi@nrc.gov; Blake.Welling@nrc.gov; Ray.McKinley@nrc.gov;Mark.Franke@nrc.gov; Gregory.Suber@nrc.gov; LaDonna.Suggs@nrc.gov; Laura.Pearson@nrc.gov; Jason.Kozal@nrc.gov; Billy.Dickson@nrc.gov; David.Curtis@nrc.gov; Jonathan.Feibus@nrc.gov; Geoffrey.Miller@nrc.gov; Michael.Hay@nrc.gov; Thomas.Briley@nrc.gov; Doris.Chyu@nrc.gov; Joshua.Havertape@nrc.gov; Dariusz.Szwarc@nrc.gov; NRR_Reactive_Inspection.Resource@nrc.gov; Thomas.Hartman@nrc.gov;