05000324/LER-2011-003, Regarding Loss of Control Room Air Conditioning and Emergency Ventilation
| ML12046A835 | |
| Person / Time | |
|---|---|
| Site: | Brunswick  |
| Issue date: | 01/30/2012 |
| From: | Frisco J Progress Energy Carolinas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| BSEP 12-0009 LER 11-003-00 | |
| Download: ML12046A835 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 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)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3242011003R00 - NRC Website | |
text
Progress Energy JAN 0 2012 SERIAL: BSEP 12-0009 10 CFR 50.73 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001
Subject:
Brunswick Steam Electric Plant, Unit Nos. 1 and 2 Renewed Facility Operating License Nos. DPR-71 and DPR-62 Docket Nos. 50-325 and 50-324 Licensee Event Report 1-2011-003 Ladies and Gentlemen:
In accordance with the Code of Federal Regulations, Title 10, Part 50.73, Carolina Power
& Light Company, now doing business as Progress Energy Carolinas, Inc., submits the enclosed Licensee Event Report (LER). This report fulfills the requirement for a written report within sixty (60) days of a reportable occurrence.
Please refer any questions regarding this submittal to Mr. Lee Grzeck, Acting Supervisor -
Licensing/Regulatory Programs, at (910) 457-2487.
Sincerely, Joseph M. Frisco, Jr.
Plant General Manager Brunswick Steam Electric Plant LJG/ljg
Enclosure:
Licensee Event Report Progress Energy Carolinas, Inc.
Brunswick Nuclear Plant P.O. Box 10429 Southport, NC 28461
Document Control Desk BSEP 12-0009 / Page 2 cc (with enclosure):
U. S. Nuclear Regulatory Commission, Region II ATTN: Mr. Victor M. McCree, Regional Administrator 245 Peachtree Center Ave. N.E., Suite 1200 Atlanta, GA 30303-1257 U. S. Nuclear Regulatory Commission ATTN: Mr. Philip B. O'Bryan, NRC Senior Resident Inspector 8470 River Road Southport, NC 28461-8869 U. S. Nuclear Regulatory Commission (Electronic Copy Only)
ATTN: Mrs. Farideh E. Saba (Mail Stop OWFN 8G9A) 11555 Rockville Pike Rockville, MD 20852-2738 Chair - North Carolina Utilities Commission P.O. Box 29510 Raleigh, NC 27626-0510
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.
- 3. PAGE Brunswick Steam Electric Plant (BSEP), Unit 1 05000325 1 of 4
- 4. TITLE Loss of Control Room Air Conditioning and Emergency Ventilation
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED SFACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR BAEPT Nit 2 NUMBER NO.
BSEP, Unit 2 05000324 FACILITY NAME DOCKET NUMBER 12 01 2011 2011 - 003- 00 01 30 2012
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
EI 20.2201(b)
ED 20.2203(a)(3)(i)
ED 50.73(a)(2)(i)(C)
ED 50.73(a)(2)(vii)
E D 20.2201(d)
E] 20.2203(a)(3)(ii)
ED 50.73(a)(2)(ii)(A)
ED 50.73(a)(2)(viii)(A)
ED 20.2203(a)(1)
El 20.2203(a)(4)
ED 50.73(a)(2)(ii)(B)
ED 50.73(a)(2)(viii)(B)
__ 20.2203(a)(2)(i)
El 50.36(c)(1)(i)(A)
El 50.73(a)(2)(iii)
F-1 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL F1 20.2203(a)(2)(ii)
[-I 50.36(c)(1)(ii)(A)
FI 50.73(a)(2)(iv)(A)
El 50.73(a)(2)(x)
LI 20.2203(a)(2)(iii)
[L 50.36(c)(2)
El 50.73(a)(2)(v)(A)
El 73.71(a)(4) 100 EL 20.2203(a)(2)(iv)
[] 50.46(a)(3)(ii)
LI 50.73(a)(2)(v)(B)
El 73.71(a)(5)
El 20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A)
LI 50.73(a)(2)(v)(C)
LI 50.73(a)(2)(i)(B)
Z 50.73(a)(2)(v)(D)
Specify in Abstract below or in The temperature in the area of the dryer (i.e., the CB mechanical equipment room) was estimated to be approximately 60 degrees Fahrenheit (F) at the time of the failure of the instrument air system. This temperature is above the minimum operating temperature for the dryer, which is approximately 45 degrees F to 50 degrees F. Additionally, the ambient air temperature of the CB mechanical equipment room is checked once per shift, in accordance with the auxiliary operator daily rounds procedure. Ambient temperatures were not low enough to initiate any severe weather actions.
The investigation determined that the refrigerant pressure was at the bottom of the acceptable operating range at the time of the failure. The low refrigerant pressure is believed to be due to a very slight leak of the seals in the refrigerant circuit. Though temperature in the CB mechanical equipment room is checked once a shift, the refrigerant pressure of the dryer is monitored only once a quarter, as part of the System Engineers system trending. The slow leak in the refrigerant circuit over time caused the pressure in the dryer refrigerant system to decrease to the point that the saturation temperature of the refrigerant in the air dryer reached the freezing point. The combination of the lower room temperatures that occur in the winter months (i.e., in the CB mechanical equipment room) with the low pressure in the air dryer refrigerant system was enough to freeze the condensate that forms in the instrument air line. This caused an ice blockage in the supply instrument air line, resulting in a loss of control air and the CR isolation dampers failing closed. This rendered the CREV and Control Room AC systems inoperable.
Safety Assessment
The safety significance of this event is minimal. The condition existed for approximately 26 minutes. Plant staff took immediate actions to return the equipment to service. For the brief time the Control Room AC and CREV systems were inoperable, performance of plant personnel and equipment in the Control Room was not adversely affected. The maximum Control Room back panel temperature during this event was approximately 68 degrees Fahrenheit.
Corrective Actions
The following actions have been completed.
- Replaced the Control Building HVAC instrument air dryer with a new unit.
" As an interim action, a supplemental check has been added to the Operators daily rounds to verify adequate refrigerant pressure in the CB HVAC instrument air dryer.
The following corrective actions will be taken.
Revise operating procedure 201-03.4.3, "Unit 2 Turbine Building Auxiliary Operator Daily Check Sheets," to check CB instrument air dryer refrigerant system pressure once per shift, and bypass the dryer if a low pressure condition exists. This action is expected to be complete by June 28, 2012.
Previous Similar Events
A review of LERs and corrective action program condition reports (CRs) for the past three years identified the following similar previous occurrence.
" LER 1-2009-001, dated March 22, 2009, reported a loss of Control Room Air Conditioning and Emergency Ventilation System due to blockage of air flow through the Control Building instrument air dryer due to freezing of condensate within the cooling coil. The corrective actions to prevent recurrence included procedure revisions to ensure proper operation of the CB HVAC system during cold weather operation.
The resulting corrective action plan from the 2009 event did not prevent this event due to the fact that the direct cause was determined to be blockage of air flow through the Control Building instrument air dryer due to low temperatures in the CB mechanical equipment room. Corrective actions to prevent recurrence included revising appropriate procedures to include guidance for low temperature operation.
Ambient temperatures on December 1, 2011, were not low enough to initiate this guidance.
" LER 1-2011-001, dated June 2, 2011, reported a loss of CREV following a trip of the 480 VAC Emergency Bus E-7 main feeder breaker. The cause was determined to be a spurious actuation of the solid state trip unit on the E-7 breaker. The corrective action was to replace the E-7 breaker.
Commitments
No regulatory commitments are contained in this report.