ML16285A319
| ML16285A319 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 10/12/2016 |
| From: | Mary Anderson NRC/NRR/DIRS/IPAB |
| To: | |
| Anderson M,NRR/DIRS,301-415-8744 | |
| References | |
| Download: ML16285A319 (4) | |
Text
FAQ 13-03 Quad Cities Animal Intrusion (NRC Final Response)
Page 1 of 3 10/18/2013 Plant: Quad Cities Date of Event: June 5, 2013 Submittal Date: August 16, 2013 Licensee
Contact:
Jason Smith Tel/email: jason.smith@exeloncorp.com NRC
Contact:
Brian Cushman Tel/email: brian.cushman@nrc.gov Performance Indicator: Unplanned Power Changes per 7,000 Critical Hours (IE03)
Site-Specific FAQ (Appendix D)? No FAQ requested to become effective: when approved Question Section Question #1 -What is considered reasonable for prevention of animal intrusion? Would turning off the lights in a switchyard without motion sensors and an intact boundary still be considered reasonable to prevent animal intrusion?
Question #2 - When does the anticipated outcome of an event apply for PI reporting? If during the review of an event, new information is discovered that validates plant response during the event, can that new information be applied to consider the plant response anticipated even though operators were challenged by unanticipated plant response at the time?
NEI 99-02, Rev. 7 Guidance needing interpretation (include page and line citation):
Page 15, line 19-28 19 Anticipated power changes greater than 20% in response to expected environmental problems 20 (such as accumulation of marine debris, biological contaminants, or frazil icing) which are 21 proceduralized but cannot be predicted greater than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> in advance may not need to be 22 counted unless they are reactive to the sudden discovery of off-normal conditions. However, 23 unique environmental conditions which have not been previously experienced and could not 24 have been anticipated and mitigated by procedure or plant modification, may not count, even if 25 they are reactive. The licensee is expected to take reasonable steps to prevent intrusion of 26 marine or other biological growth from causing power reductions. Intrusion events that can be 27 anticipated as part of a maintenance activity or as part of a predictable cyclic behavior would 28 normally be counted unless the down power was planned 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> in advance.
Page 16, line 39-43 39 For an environmental event to be excluded, any of the following may be applied:
40 If the conditions have been experienced before and they exhibit a pattern of 41 predictability or periodicity (e.g., seasons, temperatures, weather events, animals, etc.),
42 the station must have a monitoring procedure in place or make a permanent modification 43 to prevent recurrence for the event to be considered for exclusion from the indicator. If Event or circumstances requiring guidance interpretation:
On June 5, 2013 an animal (raccoon) caused a fault on a 13.8 kV bus located in the Quad Cities switchyard near Transformer 82, when the animal contacted one phase and part of the metal structure. The Unit 2 reserve aux transformer (RAT) tripped from service, as expected, and a fast bus transfer occurred to
FAQ 13-03 Quad Cities Animal Intrusion (NRC Final Response)
Page 2 of 3 10/18/2013 preclude a load trip due to undervoltage. This fault resulted in the loss of a bus in the switchyard. By procedure, when this bus is lost, operators are directed to reduce Unit 2 to approximately 85% power for transformer loading concerns on the unit auxiliary transformer (UAT). During the downpower, in response to the loss of the transformer, reduced feedwater temperature was observed by the control room operators. In response to the reduced feedwater heating, power was reduced to about 60% in accordance with approved procedures. Operator monitoring and response was consistent with their training and in accordance with approved station procedures.
Licensee management has determined that this event is not reportable because the transient was initiated by an animal intrusion event and the lower than anticipated final power was not the result of an equipment failure or human performance error.
The NRC resident inspectors consider this event reportable because the licensee began turning off the lights in the switchyard at night. Without lighting, the conditions in the switchyard were no longer reasonable to prevent animal intrusion. Also, by training and annunciator response, the anticipated power reduction for a loss of the Unit RAT would be about 85% power. The loss of feedwater heating, which was unanticipated for this event at the time, was an additional 25% downpower that should be reported as a separate PI occurrence.
If licensee and NRC resident/region do not agree on the facts and circumstances explain:
The licensee and the NRC agree on the facts. The NRC and the licensee disagree on the applicability of reporting under the PI.
The Licensee s Position:
Reasonable steps were taken to prevent the animal intrusion. The switchyard fence was in good repair and the gates were secured. Operations personnel perform a weekly walkdown of the switchyard and daily rounds in the switchyard on T82. This would identify degraded conditions and any signs of animal intrusion.
Also, the switchyard is in a frequently traveled area next to the security checkpoint. A vegetation management program in also in place, which sprays the switchyard to prevent overgrowth. Consistent with the guidance in NEI 99-02 (referenced above) a plant modification was installed after this event. This change added wildlife deterrent devices to both transformers 81 and 82. These devices should prevent recurrence of animal intrusion. Given the level of human activity in the area, material condition of the switchyard, and a history of no animal intrusion issues, the licensee maintains that reasonable steps were taken and in place to prevent animal intrusion.
Of note, the decision to turn off lights in the switchyard was vetted with key stakeholders prior to implementation.
The loss of feedwater heating was due to the voltage transient on the instrument bus, as a direct result of the fault caused by the raccoon. The momentary lowering of voltage caused various feedwater heater solenoid valves to trip, resulting in feedwater heater level control valves unlatching. Operators responded to the transient in accordance with approved procedures.
The loss of feedwater heating could be expected to occur during a fault in the switchyard, depending on where the fault occurs. There have been faults in the past where all heaters have remained latched, and some faults where a partial loss of feedwater heating has occurred. In this event, the fault was sufficient to cause enough of a voltage transient that the feedwater heater latching solenoids dropped out. Operators
FAQ 13-03 Quad Cities Animal Intrusion (NRC Final Response)
Page 3 of 3 10/18/2013 are trained on the loss of a Unit RAT and also trained on loss of feedwater heating. The operator responses for these two events are governed by approved procedures. There were no malfunctions of equipment or human performance errors that led to the additional 25% downpower.
The NRCs Position (Resident Inspectors Comments):
The NRC concurs that the switchyard fence was in good repair and there was no food or other materials in the switchyard. Licensee management made a decision to turn the lights in the switchyard off except for times of maintenance. There are no motion detectors in the switchyard. Lights have been on in the switchyard during the night for the purpose of theft deterrent. Licensee management did not assess if the lights in the switchyard also provided a deterrent to the local wildlife. Licensee management made this change to the switchyard lighting during the weekend of June 1, 2013, and on June 5, 2013, an animal causes a switchyard fault.
The NRC agrees that no equipment failed and no human performance errors occurred during this event that contributed to the extra 25% downpower. Indications were received by the control room operators for a loss of a Unit RAT. The additional loss of feedwater heating was unexpected and not anticipated to occur coincident with the loss of a Unit RAT. This fault occurred on the bus that feeds the transformer which resulted in the unlatching of several feedwater level control valves. This new information will be incorporated into operator response procedures and training materials.
It is the position of the NRC that prior to this event, the anticipated final plant condition for a loss of the Unit RAT is 85% power. For future events, with the inclusion of the possibility of partial loss of feedwater heating incorporated, the expected final power level may be lower. But for the purposes of reporting under this PI, the additional 25% power reduction should be reported as an unplanned power change.
Potentially relevant existing FAQ numbers:
ID 237-The response details taking actions outside of pre-planned activities.
Response Section Proposed Resolution of FAQ Proposed answer #1 - An intact switchyard fence in a frequently traveled area can be viewed as a reasonable barrier for the prevention of animal intrusion, with or without switchyard lighting being illuminated.
Vegetation management practices were in place to ensure there was not an adequate habitat for raccoons or their food source to exist.
Proposed answer #2 - Since the reduction in power was solely due to an animal intrusion event, this event should not be reported, regardless of when the validation of plant response is determined. The plant operated as expected during the transient and the operators responding to the event took appropriate actions in accordance with approved procedures.
NRC Final Response The staff reviewed IEEE Standard 1264-1993 (R2009), IEEE Guide for Animal Deterrents for Electrical Power Supply Substations to identify reasonable methods to prevent animal intrusion. The main methods identified in the standard are physical barriers, increased insulation, and other deterrents (fake predatory animals, disturbing noises, chemical repellents, and screening). The staff agrees that
FAQ 13-03 Quad Cities Animal Intrusion (NRC Final Response)
Page 4 of 3 10/18/2013 an intact switchyard fence in a frequently traveled area can be viewed as a reasonable barrier for the prevention of animal intrusion, with or without lighting.
Since the event has not been experienced previously at Quad Cities and the intrusion event could not have been anticipated 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> in advance, the following exclusion in NEI 99-02 is applicable:
NEI 99-02, Revision 7 (Page 15, Lines 19-25)
Anticipated power changes greater than 20% in response to expected environmental problems (such as accumulation of marine debris, biological contaminants, or frazil icing) which are proceduralized but cannot be predicted greater than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> in advance may not need to be counted unless they are reactive to the sudden discovery of off-normal conditions. However, unique environmental conditions which have not been previously experienced and could not have been anticipated and mitigated by procedure or plant modification, may not count, even if they are reactive.
The staff agrees that this event should not be counted against the PI. The licensee is expected to take adequate corrective action to prevent similar intrusion events in the future.
This FAQ is effective immediately (11/20/2013).