05000366/LER-2008-005, Edwin I Hatch Nuclear Plant, Unit 2, Re Main Control Room Environmental Control System Inoperable Due to System Tagout
| ML090291067 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 01/29/2009 |
| From: | Madison D Southern Nuclear Operating Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NL-09-0044 LER 08-005-00 | |
| Download: ML090291067 (5) | |
| 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 |
| 3662008005R00 - NRC Website | |
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Dennis R. Madison Southern Nue!ear Operating Company. Inc 11028 Hatch f'arkVVii\\f ~Jortl1 Baxley, GeorlJI2 31513 Tel 9125375859 Fax 912366.2077 SOUTHERN'\\.
COMPANY January 29, 2009 Docket No.:
50-366 NL-09-0044 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Edwin I. Hatch Nuclear Plant - Unit 2 Licensee Event Report Main Control Room Environmental Control System Inoperable Due to System Tagout Ladies and Gentlemen:
In accordance with the requirements of 10 CFR 50.73 (a)(2)(v)(D), Southern Nuclear Operating Company is submitting the enclosed report for a condition that occurred on February 21, 2008 and identified for reporting on December 5, 2008.
This letter contains no NRC commitments. If you have any questions, please advise.
Sincerely, iO~YYl~'
D. R. Madison Vice President - Hatch DRM/MJKldaj Enclosure: LER 2-2008-005 cc: Southern Nuclear Operating Company Mr. J. T. Gasser, Executive Vice President Mr. D. H. Jones, Vice President - Engineering RTYPE: CHA02.004 U. S. Nuclear Regulatory Commission Mr. L. A. Reyes, Regional Administrator Mr. R. E. Martin, NRR Project Manager - Hatch Mr. J. A. Hickey, Senior Resident Inspector - Hatch
NRC FORM 366 (9-2007)
PRINTED ON RECYCLED PAPER NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION (9-2007)
LICENSEE EVENT REPORT (LER)
APPROVED BY OMB: NO. 3150-0104 EXPIRES: 08/31/2010
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 1. FACILITY NAME Edwin I. Hatch Nuclear Plant Unit 2
- 2. DOCKET NUMBER 05000 366
- 3. PAGE 1 OF 4
- 4. TITLE Main Control Room Environmental Control System Inoperable Due to System Tagout
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL NUMBER REV NO.
MONTH DAY YEAR FACILITY NAME DOCKET NUMBER 02 21 2008 2008 005 0
01 29 2009 FACILITY NAME DOCKET NUMBER
- 9. OPERATING MODE 1
- 10. POWER LEVEL 99.7
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§: (Check all that apply) 20.2201(b) 20.2203(a)(3)(i) 50.73(a)(2)(i)(C) 50.73(a)(2)(vii) 20.2201(d) 20.2203(a)(3)(ii) 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(A) 20.2203(a)(1) 20.2203(a)(4) 50.73(a)(2)(ii)(B) 50.73(a)(2)(viii)(B) 20.2203(a)(2)(i) 50.36(c)(1)(i)(A) 50.73(a)(2)(iii) 50.73(a)(2)(ix)(A) 20.2203(a)(2)(ii) 50.36(c)(1)(ii)(A) 50.73(a)(2)(iv)(A) 50.73(a)(2)(x) 20.2203(a)(2)(iii) 50.36(c)(2) 50.73(a)(2)(v)(A) 73.71(a)(4) 20.2203(a)(2)(iv) 50.46(a)(3)(ii) 50.73(a)(2)(v)(B) 73.71(a)(5) 20.2203(a)(2)(v) 50.73(a)(2)(i)(A) 50.73(a)(2)(v)(C)
OTHER 20.2203(a)(2)(vi) 50.73(a)(2)(i)(B) 50.73(a)(2)(v)(D)
Specify in Abstract below or in NRC Form 366A
- 12. LICENSEE CONTACT FOR THIS LER FACILITY NAME Edwin I. Hatch / Kathy Underwood, Performance Improvement Supervisor TELEPHONE NUMBER (Include Area Code) 912-537-5931 CAUSE SYSTEM COMPONENT MANU-FACTURER REPORTABLE TO EPIX
CAUSE
SYSTEM COMPONENT MANU-FACTURER REPORTABLE TO EPIX
- 14. SUPPLEMENTAL REPORT EXPECTED YES (If yes, complete 15. EXPECTED SUBMISSION DATE)
NO
- 15. EXPECTED SUBMISSION DATE MONTH DAY YEAR ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)
On December 5, 2008 at approximately 1119 EST, it was determined that a written report should have been made to report an instance where the Main Control Room Environmental Control System (MCREC) was inoperable on February 21, 2008. At the time the system was inoperable Unit 2 was in the Run mode at a power level of approximately 2796 CMWTh, 99.7 percent rated thermal power. On February 21, during refueling outage 1R23, work on Essential Cabinet 1B supply breaker was to begin and a tagout was authorized to provide a clearance boundary. Prior to de-energizing Essential Bus 1B, the tagout instructions required placing Instrument Bus 1B on alternate power supply. The A Air Handling Unit (AHU) had previously been tagged out and was still out of service. When Instrument Bus 1B was de-energized, the C AHU tripped, and the B AHU did not auto-start. The control room crew realized that no AHUs were operable and directed that Instrument Bus 1B be placed back on normal supply. This action took approximately 10 minutes. After power was restored to Instrument Bus 1B, the C AHU was restarted, and the B AHU could auto-start if required.
The direct cause of the inoperable MCREC system was determined to be an inadequate clearance and tagging review to identify plant response to removing Instrument Bus 1B from service.
The load list was revised to include more detail regarding response of the C AHU on de-energizing the instrument bus or breaker, and procedures were revised to include additional details regarding expected response of C AHU when the instrument bus is de-energized.
(If more space is required, use additional copies of NRC Form 366A)
PLANT AND SYSTEM IDENTIFICATION
General Electric - Boiling Water Reactor Energy Industry Identification System codes appear in the text as (EIIS Code XX).
DESCRIPTION OF EVENT
On February 21, during refueling outage 1R23, electrical PMs on 1R25-S037 Essential Cabinet B supply breaker (EIIS Code EC) were to begin and tagout 1-DT-1R23-1-DT-07-1R23-00511 was authorized to provide a clearance boundary. Prior to de-energizing Essential Bus 1B, the tagout instructions required placing Instrument Bus 1B (EIIS Code EC) on its alternate power supply. Approximately one week prior, the A AHU had been tagged out due to repairs on Plant Service Water (PSW) system (EIIS Code BI) components and was still out of service. During the transfer to the alternate power supply, Instrument Bus 1B was de-energized, which caused the C AHU (EIIS Code VI) to trip, and the B AHU failed to auto-start. At this time, the control room crew realized that no AHUs were operable and directed that Instrument Bus 1B be placed back on normal supply. An operator was directed to start the B AHU which was accomplished approximately 4-5 minutes after power had been lost. Instrument Bus 1B was placed back on its normal supply within approximately 10 minutes, during which time Unit 2 was required to enter Limiting Condition of Operation (LCO) 3.0.3 in accordance with Technical Specifications 3.7.4.E and 3.7.5.F. This action was required since all three AHUs were inoperable. After the B AHU was started, MCREC operability was restored, but LCO 3.0.3 was not exited until after power was restored to Instrument Bus 1B.
CAUSE OF EVENT
The cause of the inoperable MCREC system was determined to be an inadequate clearance and tagging review to identify plant response to removing Instrument Bus 1B from service. This resulted in making all of the AHUs for the MCREC system inoperable.
REPORTABILITY ANALYSIS AND SAFETY ASSESSMENT This report is required by 10 CFR 50.73 (a)(2)(v)(D), Any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident. On December 5, 2008, it was determined that inoperability of the MCREC system met this criterion. Since the MCREC pressurization mode is a safety function needed to mitigate the consequences of an accident, the condition should have been reported via a phone notification to the NRC and followed by an LER at the time of the event. The condition met 2 reporting requirements with the first involving the question of whether entry into Technical Specification. 3.0.3 was reportable. The determination was correctly made at that time that no report was required since the condition was cleared within an hour and before power reduction began. Further down in NUREG 1022, Rev. 2, it states this conclusion and also adds
"... and no other 10CFR50.73 criteria apply. In this case 10CFR50.73(a)(2)(v) requires the report if the condition could have prevented the fulfillment of the safety function (going into the pressurization mode) of structures or systems to mitigate the consequences of an accident. Since this reporting requirement applied the necessary reports should have been made. (9-2007)
LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET U.S. NUCLEAR REGULATORY COMMISSION
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE YEAR SEQUENTIAL NUMBER REVISION NUMBER Edwin I. Hatch Nuclear Plant Unit 2 05000366 2008 005 0
3 OF 4
PRINTED ON RECYCLED PAPER The MCREC System provides a radiologically controlled environment from which the reactors can be operated safely following a design basis event. The system is designed in accordance with GDC 19 to maintain the control room environment for a 30 day continuous occupancy after a design basis accident without exceeding 5 rem whole body dose or its equivalent to any part of the body. A single MCREC subsystem will pressurize the control room to greater than or equal to 0.1 inches water gauge to prevent infiltration of air from surrounding buildings.
The MCREC System is a standby system, parts of which also operate during normal unit operation to maintain the control room environment. Upon receipt of the initiation signal(s) (indicative of conditions that could result in radiation exposure to control room personnel), the MCREC System automatically switches to the pressurization mode of operation to prevent infiltration of contaminated air into the control room. A system of dampers isolates the control room, and a portion of the recirculated air is routed through either of the two filter subsystems. Outside air is taken in at the normal ventilation intake and is mixed with the recirculated air before being passed through one of the charcoal adsorber filter subsystems for removal of airborne radioactive particles and gaseous iodines.
The safety related function of MCREC System includes two independent and redundant high efficiency air filtration subsystems for emergency treatment of recirculated air and outside supply air. Each subsystem consists of a prefilter, a high efficiency particulate air (HEPA) filter, an activated charcoal adsorber section, a second HEPA filter, a booster fan, and the associated ductwork and dampers. Prefilters and HEPA filters remove potentially radioactive particulate matter. The charcoal absorbers hold up gaseous iodines allowing time for decay.
As documented in the Hatch updated Final Safety Analysis Report (FSAR) section 15.3, the loss-of-coolant accident (LOCA) is the limiting event for radiological exposures to occupants of the control room.
Radiological exposures to control room occupants are documented in terms of whole body, skin and thyroid doses. Thyroid doses are the limiting doses for the Hatch control room.
An operator was directed to start the B AHU which was accomplished approximately 4-5 minutes after power had been lost. This action restored the automatic capability of the MCREC system to perform its safety function. The affected instrument bus was re-energized within approximately 10 minutes. Based on this short time of system inoperability and the low probability of a design basis LOCA occurring within this timeframe, it is concluded that this event had no adverse impact on nuclear safety.
CORRECTIVE ACTIONS
Load list A-10229 has been revised to clarify and include more detail regarding response of the C AHU on de-energizing the instrument bus or breaker 15.
Procedure 34SO-R25-001-1, 120/208 VAC Essential Power System, has been revised to include additional details regarding C AHU response when 1R25-S065 is de-energized.
Procedure 34AB-R25-002-1, Loss of Instrument Buses, has been revised to include additional details regarding expected response of C AHU when the instrument bus is de-energized. (9-2007)
LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET U.S. NUCLEAR REGULATORY COMMISSION
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE YEAR SEQUENTIAL NUMBER REVISION NUMBER Edwin I. Hatch Nuclear Plant Unit 2 05000366 2008 005 0
4 OF 4
PRINTED ON RECYCLED PAPER
ADDITIONAL INFORMATION
Other Systems Affected: No systems other than those already mentioned in this report were affected by this event.
Failed Components Information
None Commitment Information: This report does not create any permanent licensing commitments.
There are no previous similar events in the last two years, since February 2008, in which the MCREC system was inoperable due to a tagout: