05000254/LER-2018-001, Secondary Containment Differential Pressure Momentarily Lost Due to Fuel Pool Radiation Monitor Spike

Secondary Containment Differential Pressure Momentarily Lost Due to Fuel Pool Radiation Monitor Spike

ML18089A154
Person / Time
Site:	Quad Cities
Issue date:	03/30/2018
From:	Ohr K Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
SVP-18-021 LER 2018-001-00
Download: ML18089A154 (6)

LER-2018-001, Secondary Containment Differential Pressure Momentarily Lost Due to Fuel Pool Radiation Monitor Spike

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i)
2542018001R00 - NRC Website

text

March 30, 2018 SVP-18-021 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555 Quad Cities Nuclear Power Station, Units 1 and 2 Renewed Facility Operating License Nos. DPR-29 and DPR-30 NRG Docket Nos. 50-254 and 50-265 10 CFR 50.73

Subject:

Licensee Event Report 254/2018-001-000 "Secondary Containment Differential Pressure Momentarily Lost Due to Fuel Pool Radiation Monitor Spike" Enclosed is Licensee Event Report (LER) 254/2018-001-00, "Secondary Containment Differential Pressure Momentarily Lost Due to Fuel Pool Radiation Monitor Spike, for Quad Cities Nuclear Power Station, Unit 1 and 2.

This report is submitted in accordance with 1 O CFR 50.73 (a){2)(v)(C) which requires the reporting of any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to control the release of radioactive material.

There are no regulatory commitments contained in this letter.

Should you have any questions concerning this report, please contact Mark Humphrey at (309) 227-2800.

Res/?/

Kenneth S. Ohr Site Vice President Quad Cities Nuclear Power Station cc:

Regional Administrator-NRG Region Ill NRG Senior Resident Inspector - Quad Cities Nuclear Power Station

NRC FORM 366 (02-2018)

1. Facility Name U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)

(See Page 2 for required number of digits/characters for each block)

(See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)

APPROVED BY OMB: NO. 3150-0104 03/31/2020 EXPIRES:

Estimated burden per response to comply with this mandatory collection request: 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />. Reported lessons learned are incorporated into the licensing process and fed back to industry. Send comments regarding burden estimate to the Information Services Branch (T*2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to infocollects.Resource@nrc.gov, and to the Desk Officer, Office of lnfonnation and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, WashUigton, DC 20503. If a means used to impose an information collection dces not display a currently valid OMB ccntrol number, the NRG may not ccnduct or sponsor, and a person is not recuired to respond to, the infonnation ccllection.

2. Docket Number 3.Page Quad Cities Nuclear Power Station Unit 1 05000254 1

OF 5

4. Title Secondary Containment Differential Pressure Momentarily Lost Due to Fuel Pool Radiation Monitor Spike

5. Event Date

6. LEA Number

7. Report Date

8. Other Facilities Involved Facility Name Docket Number Month Day Year Year I Sequential IR N

M th Number I' ev o.

on Day Year Quad Cities Nuclear Power Station Unit 2 05000265 01 31 2018 2018 001

- 00 03 30 2018 Docket Number N/A Facility Name N/A

9. Operating Mode

11. This Report is Submitted Pursuant to the Requirements of 10 CFR §: (Check all that apply)

D 20.2201(b)

D 20.2203(a)(3)(i)

D 50. 73(a)(2)(ii)(A)

D 50.73(a)(2)(viii)(A)

D 20.2201(d)

D 20.2203(a)(3)(ii)

D 50. 73(a)(2)(ii)(B)

D 50.73(a)(2)(viii)(B)

D 20.2203(a)(1)

D 20.2203(a)(4)

D 50.73(a)(2)(iii)

D 50.73(a)(2)(ix)(A)

D 20.2203(a)(2)(i)

D 50.36(c)(1 )(i)(A)

D 50.73(a)(2)(iv)(A)

D 50.73(a)(2)(x) 1 o. Power Level D 20.2203(a)(2)(ii)

D 50.36(c)(1 )(ii)(A)

D 50.73(a)(2)(v)(A)

D 13.11 (a)(4)

D 20.2203(a)(2)(iii)

D 50.36(c)(2)

D 50.73(a)(2)(v)(B)

D 13.11(a)(5l D 20.2203(a)(2)(iv)

D 5o.46(a)(3)(ii)

[gj 50.73(a)(2)(v)(C)

D 13.11(a)(1) 100 D 20.2203(a)(2)(v)

D 50.73(a)(2)(i)(A)

D 50.73(a)(2)(v)(D)

D 13.77(a)(2)(ii)

D 20.2203(a)(2)(vi)

D 50.73(a)(2)(i)(B)

D 50.73(a)(2)(vii)

D 13.11(a)(2)(iii)

D 50.73(a)(2)(i)(C)

D Other (Specify in Abstract below or in

C. CAUSE OF EVENT

SEQUENTIAL NUMBER 001 REV NO.

00 The cause of the 2B fuel pool radiation monitor spike was a detector failure. The most likely potential causes of a detector failure are due to a manufacturing defect resulting in loss of quench gas in the Geiger-Mueller tube or a defective Geiger-Mueller tube. The failed detector was sent to Exelon PowerLabs for failure analysis. The specific failure mode of the detector has not been determined.

D. SAFETY ANALYSIS

System Design

The function of the secondary containment is to contain, dilute, and hold up fission products that may leak from primary containment following a Design Basis Accident (DBA). In conjunction with operation of the Standby Gas Treatment System (SBGTS) and closure of certain valves [V] whose lines penetrate the secondary containment, the secondary containment is designed to reduce the activity level of the fission products prior to release to the environment, and to isolate and contain fission products that are released during certain operations that take place inside primary containment, when primary containment is not required to be operable, or that take place outside primary containment.

Updated Final Safety Analysis Report (UFSAR) Section 6.2.3.1 provides that the safety objective of the secondary containment system, in conjunction with other engineered safeguards and nuclear safety systems, is to limit the release of radioactive materials so that off site doses resulting from a postulated DBA will remain below 1 O CFR 100 guideline values.

The SBGTS is designed to maintain the RB (RB is common to both Units 1 and 2) at a negative pressure and to filter the exhaust of radioactive matter from RB spaces to the environment (by particulate filtration and halogen adsorption) in the unlikely event of a DBA, including the Loss of Coolant Accident (LOCA) and the refueling accident. It is also instrumental in maintaining the integrity of secondary containment during a primary to secondary containment instrument line break. Two parallel trains are provided, each of which is capable of producing greater than 0.25 inches water negative pressure required in the RB while processing 4000 cubic ft /min of exhaust air.

Safety Impact When the fuel pool radiation monitor spiked high due to an invalid actuation, the Unit 1 and Unit 2 RB ventilation system isolated which caused the differential pressure of the shared secondary containment to be momentarily lost.

TS 3.6.4.1, Action A.1, requires restoration of secondary containment to operable status within four hours. This Completion Time provides a period of time to correct the problem that is commensurate with the importance of maintaining secondary containment during Modes 1, 2, and 3, since the probability of an accident occurring during this short period when secondary containment is inoperable is minimal.

SEQUENTIAL NUMBER 001 REV NO.

00 The primary purpose of the secondary containment is to minimize the ground level release of airborne radioactive materials and to provide a controlled, elevated release of the building atmosphere under accident conditions. An engineering analysis was performed to demonstrate that during the time that secondary containment differential pressure increased to positive for approximately one (1) minute, there would be a negligible effect on the resulting dose calculations. Secondary containment would have sufficiently contained radioactive materials during a LOCA such that all current dose limits would remain to be met. Secondary containment would have been able to perform its safety function. Therefore, the dose consequence from postulated releases from the reactor building during this short duration would be bounded by the existing design basis LOCA dose analysis. The safety significance of this event was minimal.

An engineering analysis demonstrated this event did not constitute a Safety System Functional Failure (SSFF).

(Reference NEI 99-02, Revision 7, Regulatory Assessment Performance Indicator Guideline, Section 2.2, Mitigating Systems Cornerstone, Safety System Functional Failures, Clarifying Notes, Engineering analyses.) As such, this event will not be reported in the NRC Performance Indicator (Pl) for safety system functional failures.

Risk Insights The plant Probabilistic Risk Assessment (PRA) model gives no credit to Reactor Building (Secondary Containment) effectiveness for mitigating fission product releases to the environment and does not include it in the model, hence the as-found conditions did not contribute to an increase in risk. In addition, the physical integrity of the secondary containment structure was never compromised and the primary containment function was never lost.

Although a secondary containment loss of function (loss of differential pressure) occurred momentarily when the invalid fuel pool radiation monitor spike caused the Unit 1 and Unit 2 RB ventilation system to isolate, there was no OBA condition in progress, and secondary containment function was restored within one (1) minute when operation of the SBGTS restored the required differential pressure to the RB (secondary containment).

In conclusion, the overall safety significance and impact on risk of this event were minimal.

E. CORRECTIVE ACTIONS

Immediate:

1.

An initial investigation was conducted. Troubleshooting determined the detector had failed.

2.

Replaced the failed 2B fuel pool radiation monitor detector (sensor/converter) with a new detector to restore function.

Follow-up:

1.

The failed detector was sent to Exelon Powerlabs for failure analysis.

2.

Additional actions will be determined pending the results of failure analysis.

F.

PREVIOUS OCCURRENCES

The station events database, LERs, and INPO Consolidated Event System ICES (EPIX) were reviewed for similar events at Quad Cities Nuclear Power Station.

This event was a momentary loss of secondary containment differential pressure resulting from an invalid Unit 1 and Unit RB ventilation system isolation due to a fuel pool radiation monitor failure. Based on the conditions of this event, causes, and associated corrective actions, two SEQUENTIAL NUMBER 001 REV NO.

00 events described below are specifically applicable given that a sensor/converter failure caused a spurious signal and in one case resulted in a loss of secondary containment differential pressure.

Station Issue Report (IR) 1690135, Received Unexpected U2 Fuel Pool Channel B Hi Rad Alarm (08/07/14) -

Due to detector failure/Geiger-Mueller (G-M) tube failure. All automatic equipment actuations responded as expected and the Reactor Building differential pressure was maintained during the event. The G-M tube failure was due to loss of quench gas. The loss of quench gas is considered a manufacturing defect.

LERs - A review of LERs at Quad Cities Nuclear Power Station over the past 10 years identified LER 2014-001-00 (03/04/2014) as a similar event.

Due to a sensor I converter (detector) Geiger-Mueller (GM) tube manufacturing defect, the GM tube was double pulsing, causing an increase in sensor/converter output with a resulting isolation of reactor building ventilation and secondary containment differential pressure increase.

G. COMPONENT FAILURE DAT A Failed Equipment: Radiation Monitor Component Manufacturer: General Electric Component Model Number: 194X927G016 Component Part Number: 194X927G016 (Range 1 to 106 mR/hr)

This event has been reported to ICES. Page_5_ of _5_