05000263/LER-2012-005, Regarding Partial Group II Isolation During Removal of Original Steam Dryer
| ML13014A124 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 01/11/2013 |
| From: | Schimmel M Northern States Power Co, Xcel Energy |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| L-MT-13-002 LER 12-005-00 | |
| Download: ML13014A124 (4) | |
| 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)(8) 10 CFR 50.73(a)(2)(viii)(8) 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)(8) 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)(8) 10 CFR 50.73(a)(2)(iv)(B), System Actuation |
| 2632012005R00 - NRC Website | |
text
Xcel Energy@
January 11, 2013 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Monticello Nuclear Generating Plant Docket 50-263 Renewed Facility Operating License No. DPR-22 Monticello Nuclear Generating Plant 2807 W County Road 75 Monticello, MN 55362 L-MT 002 10 CFR 50.73 LER 2012-005 "Old Steam Dryer Removal Results in Partial Group II Isolation" A Licensee Event Report (LER) for this occurrence is attached.
Summary of Commitments This letter contains no new commitments and no revisions to existing commitments.
Mark A. Schimmel Site Vice-President, Monticello Nuclear Generating Plant Northern States Power Company-Minnesota Enclosure cc:
Regional Administrator, Region III, USNRC Project Manager, Monticello Nuclear Generating Plant, USNRC Resident Inspector, Monticello Nuclear Generating Plant, USNRC
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 no required to respond to, the information collection.
- 3. PAGE Monticello Nuclear Generating Plant 05000 - 263 1 OF 3
- 4. TITLE Partial Group II Isolation during Removal of Original Steam Dryer
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED YEAR I SEQUENTIAL I REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR NUMBER NO MONTH DAY YEAR FACILITY NAME DOCKET NUMBER 11 12 2012 2012 - 005 - 00 01 11 2013
- 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)(i)(C)
D 50.73(a)(2)(vii) 1 D 20.2201 (d)
D 20.2203(a)(3)(ii)
D 50.73(a)(2)(ii)(A)
D 50.73(a)(2)(viii)(A)
D 20.2203(a)(1)
D 20.2203(a)(4)
D 50.73(a)(2)(ii)(8)
D 50.73(a)(2)(viii)(8)
D 20.2203(a)(2)(i)
D 50.36(c)(1)(i)(A)
D 50.73(a)(2)(iii)
D 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL D 20.2203(a)(2)(ii)
D 50.36(c)(1)(ii)(A)
~ 50.73(a)(2)(iv)(A)
D 50.73(a)(2)(x)
D 20.2203(a)(2)(iii)
D 50.36(c)(2)
D 50.73(a)(2)(v)(A)
D 73.71(a)(4) 100%
D 20.2203(a)(2)(iv)
D 50.46(a)(3)(ii)
D 50.73(a)(2)(v)(8)
D 73.71(a)(5)
D 20.2203(a)(2)(v)
D 50.73(a)(2)(i)(A)
D 50.73(a)(2)(v)(C)
D OTHER Specify in Abstract below or in D 20.2203(a)(2)(vi)
D 50.73(a)(2)(i)(8)
D 50.73(a)(2)(v)(D)
EVENT DESCRIPTION
During the 2011 refueling outage, the Monticello Nuclear Generating Plant (MNGP) replaced the original steam dyer which was then stored in the dryer separator pit on the refueling floor until November 2012 when it was removed and shipped offsite.
Prior to the event, the MNGP was in Mode 1 at approximately 100% power. There were no systems, structures, or components that were inoperable at the start of the event that contributed to the event.
On November 12, 2012 the steam dryer was prepared for transportation off site. As the steam dryer was moved East on the refuel floor, the "A" Refuel Floor Radiation Monitor [IL] reading increased as expected.
When the steam dryer was approximately 6 feet from the center of the equipment hatch, dose rates exceeded 50mR/hr on the Refuel Floor Radiation Monitor and the move was stopped per the work plan. At 1551 hours0.018 days <br />0.431 hours <br />0.00256 weeks <br />5.901555e-4 months <br />, the "A" Refuel Floor Radiation Monitor indication exceeded the trip setpoint. This resulted in the isolation of the drywell containment air monitor and the oxygen analyzer primary containment isolation valves [V]. The signal also resulted in a reactor building isolation, initiation of "A" Standby Gas Treatment [BJ], and transfer of Control Room Ventilation [VI] to the High Radiation Mode.
The steam dryer was then moved down the reactor building equipment hatch. When the steam dryer was at the center of the equipment hatch, dose rates dropped to approximately 42mR/hr and the Group II isolation was reset at 1610 hours0.0186 days <br />0.447 hours <br />0.00266 weeks <br />6.12605e-4 months <br />.
EVENT ANALYSIS
This event is being reported in accordance with 10 CFR 50.73(a)(2)(iv)(A) as an event or condition that resulted in manual or automatic actuation of any of the systems listed in paragraph 10 CFR 50.73(a)(2)(iv)(B) specifically, the Primary Containment Isolation (Partial Group II) actuation.
SAFETY SIGNIFICANCE
The Refuel Floor Radiation Monitors measure radioactivity on the refueling floor. They are designed to isolate the Reactor Building normal ventilation, and initiate operation of the Standby Gas Treatment System following a refueling accident. Trip settings for the monitors are based upon minimizing the amount of activity released during the refueling accident. During movement of the steam dryer, the Refuel Floor Radiation Monitors tripped, isolating Reactor Building ventilation and successfully initiating Standby Gas Treatment as designed.
Additionally, there was no release of radioactivity during the movement. Therefore, there was no significant impact on the health and safety of the public.
CAUSE
The apparent cause was determined to be the infrequently performed test or evolution process was not adequately tied to the risk management process to ensure that the high risk plans and validation of critical parameters were reviewed prior to execution.
CORRECTIVE ACTION
- 3. PAGE 30F3 The immediate corrective actions were to move the steam dryer away from the "A" Refuel Floor Radiation Monitor and reset the Partial Group II Isolation at 1610 hours0.0186 days <br />0.447 hours <br />0.00266 weeks <br />6.12605e-4 months <br /> on November 12,2012.
Corrective actions to address the apparent cause include updating the infrequently performed tests or evolutions process to institutionalize a review of the high risk plan and mitigating actions including validation of critical parameters prior to work.
PREVIOUS SIMILAR EVENTS
There were no previous similar licensee event reports in the past three years.
ADDITIONAL INFORMATION
Energy industry identification system (EllS) codes are identified in the text within brackets [xx].