05000397/LER-2011-004, Regarding Secondary Containment Low Differential Pressure Due to Ice Buildup
| ML12055A390 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 02/08/2012 |
| From: | Sawatzke B Energy Northwest |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| G02-12-022 LER 11-004-00 | |
| Download: ML12055A390 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 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)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3972011004R00 - NRC Website | |
text
Bradley J. Sawatzke Columbia Generating Station ENERGY iP.O.
Box 968, PE08 Richland, WA 99352-0968
ý; NORTHW EST Ph. 509.377.43001 F. 509.377.4150 bjsawatzke @energy-northwest.com February 8, 2012 G02-12-022 10 CFR 50.73 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001
Subject:
COLUMBIA GENERATING STATION, DOCKET NO. 50-397 LICENSEE EVENT REPORT NO. 2011-004-00
Dear Sir or Madam:
Transmitted herewith is Licensee Event Report No. 2011-004-00 for Columbia Generating Station. This report is submitted pursuant to 10 CFR 50.73(a)(2)(v)(C) and 10 CFR 50.73(a)(2)(v)(D). The enclosed report discusses items of reportability and corrective actions taken related to an event which occurred December 10, 2011 that caused secondary containment differential pressure to exceed Technical Specification limits for a short period of time due to ice buildup and subsequent release from reactor building air filters.
There are no commitments being made to the NRC by this letter. If you have any questions or require additional information, please contact Mr. ZK Dunham at (509) 377-4735.
Respectfully, BJ Sawatzke Vice President, Nuclear Generation & Chief Nuclear Officer Attachment: Licensee Event Report 2011-004-00 cc: NRC Region IV Administrator NRC NRR Project Manager NRC Senior Resident Inspector/988C RN Sherman - BPA/1 399 WA Horin - Winston & Strawn
- - NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 EXPIRES 10/31/2013 (10-2010)
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
i 3. PAGE Columbia Generating Station 05000397 1 OF3
- 4. TITLE Secondary Containment Low Differential Pressure due to Ice Buildup
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED I
FAIIYNAEDCETNME MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR FAITYNMDOKTUBE NUMBER NO.
_____i 05000 IFACILITY NAME DOCKET NUMBER 12 10 2011 2011 -004 -00 02 08 2012050
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) 1 El 20.2201(b)
El 20.2203(a)(3)(i)
El 50.73(a)(2)(i)(C)
[I 50.73(a)(2)(vii)
El 20.2201(d)
El 20.2203(a)(3)(ii)
El 50.73(a)(2)(ii)(A)
El 50.73(a)(2)(viii)(A)
C3 20.2203 (a)(1)
[I 20.2203(a)(4)
El 50.73(a)(2)(ii)(B)
El 50.73(a)(2)(viii)(B) 20.2203(a)(2)(i)
[I 50.36(c)(1)(i)(A)
Cl 50.73(a)(2)(iii)
El 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL El 20.2203(a)(2)(ii)
El 50.36(c)(1)(ii)(A)
[I 50.73(a)(2)(iv)(A)
[I 50.73(a)(2)(x) 100 [1 20.2203(a)(2)(iii)
El 50.36(c)(2)
El 50.73(a)(2)(v)(A)
El 73.71 (a)(4)
[I 20.2203(a)(2)(iv)
El 50.46(a)(3)(ii)
El 50.73(a)(2)(v)(B)
El 73.71(a)(5)
El 20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A) 0 50.73(a)(2)(v)(C)
El OTHER El 20.2203(a)(2)(vi)
[E 50.73(a)(2)(i)(B) 0 50.73(a)(2)(v)(D)
Specify in Abstract below or in =
Plant Conditions
At the time of the event, the plant was in Mode 1 and 100 percent; power. There were no structures, systems, or components that were inoperable at the start of the event that contributed to the-event. Reactor building exhaust [VL] was in a normal alignment with REA-FN-1A, one of two 100 percentcapacity exhaust fans [FAN],
running with REA-FN-11B in standby condition. Reactor building exhaust filters [FLT] had been observed to be icing over due to adverse environmental conditions (the area had been under a deep freeze since 12/8/11 and humidity was approximately 90 percent for this same time period) and steps had been taken to monitor the filters and advance roll filters on a more frequent basis.
Event Description
The control room received a high secondary containment differential pressure alarm on 12/10/11 at 04:43. The pressure excursion resulted in a peak pressure of approximately 0.03 inches water gauge and an unplanned entry into LCO 3.6.4.1A. In response to the alarm, Operations swapped from REA-FN-1A and ROA-FN-1A to REA-FN-1 B and ROA-FN-1 B. Reactor Exhaust Air (REA) Differential Pressure (DP) controller [VA], REA-DPIC-1A was then able to maintain Reactor Building pressure below the Technical Specification (TS) limit of -
0.25 inches water gauge after two minutes, as designed.
This event is reportable as an event that could have prevented fulfillment of a safety function needed to control the release of radiation and mitigate the consequences of an accident per 10 CFR 50.73(a)(2)(v)(C) & 10 CFR 50.73(a)(2)(v)(D). A 10 CFR 50.72(b)(3)(v)(C) and 10 CFR 50.72(b)(3)(v)(D) notification was made via Event Number 47516. Note that the original Event Notification incorrectly listed the event time as 04:56, review of plant data after the fact confirmed the actual time the TS limit was exceeded was 04:43.
Immediate Corrective Actions
The shift manager authorized a verbal procedure change to SOP-COLDWEATHER-OPS to allow for cutting of the roll filter of Reactor Building Outside Air (ROA) during extreme cold conditions when it was recognized that existing guidance in the procedure was insufficient to counter the ongoing conditions.
Assessment of Safety Consequences
This event resulted in an unplanned entry into LCO 3.6.4.1A. Containment pressure was above -0.25 inches water gauge for approximately two minutes. The actual pressure response of secondary containment [NH]
during this event was bounded by existing drawdown and dose analyses and thus there are no actual safety consequences to this event.
Cause of Event
The DP decrease was caused by buildup and subsequent release of ice on the ROA filter and bird screen allowing an increased amount of air to be pulled into the Reactor Building [NG] in a short amount of time. The resulting rapid pressure transient was on a time scale shorter than that which the flow controllers [TC] could respond.
26158 R5
Similar Events
A search of corrective action documents back to 2004 revealed only two instances of noted icing on outside air filters. Both events occurred in December 2008, but neither resulted in exceeding TS allowable differential pressure on secondary containment.
Further Corrective Actions Additional corrective actions will formalize enhancements to SOP-COLDWEATHER-OPS made as immediate corrective actions as well as to include precautions about conditions of high humidity and low temperatures and to lower the threshold for advancing roll filters with observed icing.
Energy Industry Identification System (EIIS) Information codes from IEEE Standards 805-1984 and 803-1983 are represented in brackets as [XX] and [XXX] throughout the body of the narrative.
26158 R5