EP ISSUES FOR INDEPENDENT SPENT FUEL STORAGE AND DECOMMISSIONING FACILITIES. Scenario Development For Shutdown And Defueled Nuclear Power Stations

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1 EP ISSUES FOR INDEPENDENT SPENT FUEL STORAGE AND DECOMMISSIONING FACILITIES Scenario Development For Shutdown And Defueled Nuclear Power Stations Daniel F. McDavitt Duke Engineering and Services Abstract After a nuclear power station is shutdown and defueled, a defueled emergency plan, which reflects the reduction in the level of commitment consistent with the recognized reduced risk, is written. Within these plans there continues to be a need to demonstrate the capabilities of the station s emergency response organization (ERO) by conducting realistic drills and exercises. In this shutdown mode, potential postulated accident scenarios become limited to activities associated with decontamination, dismantlement and disposal. In order to fully demonstrate the ERO capabilities, scenarios normally involve the actual or potential impact on the major source terms remaining onsite (i.e., spent fuel or radioactive waste). These sources of radioactive material are usually protected from damage by strict engineering controls, which further limits types of credible accident scenarios available for use. Therefore, the development of a scenario and sequence of events that meet these limitations is very challenging. This paper will detail several accident scenarios that have met this challenge. Background In order to continue to meet the requirements of emergency preparedness programs after a plant has been shutdown and defueled, drills and exercise need to be developed and performed. Approach The first and most common scenario associated with a shutdown and defueled facility involves the spent fuel. A realistic scenario that was developed and performed during a drill has resulted in the most play by the emergency response organization initiated with a fire which effected the spent fuel electrical systems and culminated in a fuel drop during a postulated fuel movement activity. The assembly was dropped onto other assemblies. The extent of the damage to the spent fuel assemblies involved in the accident is unknown to the operator. This allowed the scenario developers the opportunity to adjust the resulting source term to a level that would drive the classification through alert, if necessary, and then to decrease the source term and secure from the drill. The scenario was further complicated by a medical emergency. A sequence of events which outlines this scenario follows: 36

2 Table 1. Fuel Handling Accident - Detailed Sequence of Events Scenario Events/Expected Actions Time 00:00 Exercise participants in the Control Room are given the scenario initial conditions (operational, radiological and meteorological data.) 00:02 A fire breaks out on a forklift truck in the Radwaste Reduction Facility (RRF) and the Control Room is immediately notified. 00:02+ The Operations Shift Manager (OSM) should immediately implement AOP x.x-xx, Station Fires. The procedure directs the following actions be taken:! Announce the fire over the Public Address System.! Sound the station annunciation alarm for approximately 15 seconds.! Notify the on-call Emergency Director and the Security Department.! Deenergize the Radwaste Reduction Facility.! Notify the off-site Fire Department.! Classify the fire using DEPIP x.x-x, Emergency Assessment Using Defueled EAL Tables. 00:12 The Fire Brigade Leader contacts the Operations Shift Manager with an initial assessment of the fire from the scene. 00:17 The Fire brigade Leader contacts the Operations shift Manager with a follow-up assessment of the fire from the scene. 00:17+ The OSM should declare and UNUSUAL EVENT based on initiating condition GU1, EAL 1- Fire in the Radiation Control Area (RCA) NOT Extinguished Within 15 Minutes of the Control Room Notification OR Within 15 Minutes of the Fire Alarm Actuation in the Control Room. The OSM becomes the Emergency Director and initiates his DEPIPs. The OSM can activate the Defueled Emergency Response Organization (DERO) for Unusual Events. 00:27 Issue the contingency message if 37

3 necessary that the Shift Manager should declare an Unusual Event, D-1 based on initiating condition GU1- EAL 1. 00:30 The Fire Brigade Leader contacts the OSM to inform him that the fire is out. 00:30 Following fire-fighting activities;! A Spent Fuel Pool High Level Alarm is received in the Control room. (It clears when the CR Operator pushes the reset button.)! The SFP camera also goes blank at this time.! 480 V ground occurs on Bus 4. 00:31 R-34, Spent Fuel Bridge Area Radiation Monitor is alarming. 00:32 The following radiation monitors are alarming:! Spent Fuel Bridge! New Fuel Storage Area! Stack Monitor! Wide Range Gas Monitor! RMS Computer High Radiation! Radiation Monitoring Channel Hi Activity 00:32+ The Shift Manager should declare an ALERT, C-1 based on initiating condition, RA1- EAL 1- Fuel Handling Accident Causing Damage to Spent Fuel Indicated by Fuel Building Radiation Monitors Alarming and Increasing. The Shift Manager implements his DEPIPs. DERO personnel should also implement their respective procedures at this time. 00:35 The SFP Crane Operator calls up from the PAB and tells the OSM that I pushed the up button on the crane and it stuck in, the crane up limit switch didn t stop the crane and the crane continued to roll the hook up on the drum. I left when the crane started making loud noises. I heard a big splash as I was running down the SFB stairs. 00:35+ The Operations Shift Manager (OSM) should implement AOP-x.x-xx, Fuel Handling and Spent Resin Cask Accidents. The procedure directs the following actions be taken:! Shutdown the control room ventilation. 38

4 ! Direct fuel-handling personnel to place the affected assembly in a safe condition, If possible. Check the RMS indicators to determine if a radiological release is occurring.! Announce the fuel handling accident over the Public Address System.! Sound the station annunciation alarm for approximately 15 seconds.! Repeat the announcement. Verify SFB exhaust fan is operating with suction aligned through the charcoal filter. 00:42 Issue contingency message that ED should declare an Alert, C-1 based on initiating condition RA1-EAL 1. 00:42+ DERO personnel should arrive at the TSC and begin activating the facility, if not initiated at the UE, in accordance with DEPIP x.x-xx, TSC Activation. The decision to activate will be conducted in accordance with the applicable sections of the DEPIPs. 01:10 Following the completion of relocation and accountability it is determined that the Health Physics (HP) Technician who was providing radiation protection coverage of the fuel handling activities is unaccounted for. Search and Rescue activities should be implemented. 01:10+ The HP Technician, once located, will be found to be unconscious and have suffered a mild concussion. 01:20+ A Radiological Monitoring Team should be assembled and dispatched from the TSC to verify the downwind location and magnitude of the release. 02:15 The drill is terminated. This sequence allowed the controller organization to maintain control of the drill. The magnitude and duration of the release of radioactive material was elevated to drive the classification to an Alert. The medical aspects were added to provide additional play and satisfy medical drill requirements and objectives. It also allowed the players to respond to a fire, classify an emergency, notify internal and external organizations, activate their facilities, communicate within their facilities and demonstrate the use of their procedures. 39

5 The second and most challenging scenario involves the response to the release of spent resins from a reactor coolant system decontamination activity. The most limiting scenario resulting from this source involved a fire, which drove the dispersion of this source term from the facility. This scenario required the controllers to provide a survey reading to the players to drive the proper classification and for players to assume the worst dose assessment results because of the unmonitored nature of the release. A sequence of events which outlines this accident follows: Table 2. Resin Fire Accident Sequence of Events Scenario Events/Expected Actions Time 00:00 Exercise participants in the Control Room are given the scenario initial conditions (operational, radiological and meteorological data). 00:02 The Control Room is notified that the next poly HIC liner of resin beads are being transferred from the Ion Exchange Pit to the cask transport truck. 00:05 The Control Room is notified that the poly HIC liner that was being transferred drops onto a forktruck parked adjacent to the transport truck. This causes the resin to spill and the propane tank on the forktruck to be ruptured causing a large fire to break out. 00:05+ The Operations Shift Manager (OSM) should immediately implement AOP x.x-xx, Fuel Handling and Spent Resin Cask Accidents. The procedure directs the following actions be taken:! Announce the spill and fire over the Public Address System.! Sound the site relocation alarm for approximately 15 seconds.! Notify the on-call Emergency Director and the HP Department. 00:05+! The OSM should also immediately implement AOP x.x-xx, Station Fires. The procedure directs the following actions be taken:! Announce the fire over the Public 40

6 Address System.! Sound the station annunciation alarm for approximately 15 seconds.! Repeat the announcement.! Notify the on-call Emergency Director and the Security Department.! Classify the fire using DEPIP x.x-x, Emergency Assessment Using Defueled EAL Tables. 00:05+ The following radiation monitors will increase:! Spent Fuel Bridge! New Fuel Storage Area! PAB Passageway! S/G Sample Blowdown Area! Containment Personnel Hatch 00:20 The HP Technician calls the Control Room from the Radwaste Reduction Facility (RRF) and informs them that there is smoke from the fire in the RRF that has been reading 6 mr/hr since the fire began approximately 15 minutes ago. 00:20+ The Shift Manager should declare an Alert, C-1 based on initiating condition OA1, EAL 2, Measured Plume Dose Rate On-site > 5 mr/hr for > 15 minutes of the category, Off-site Releases. The Shift Manager should implement his DEPIPs. 00:20+ Through a controller inject the Shift Manager will be requested to make an announcement activating the remainder of the pre-designated Defueled Emergency Response Organization (DERO), if necessary. 00:30 Issue contingency message that ED should declare an Alert, C-1 based on initiating condition OA1, EAL 2. 00:35 The Fire Brigade has extinguished the fire. 00:40+ DERO personnel should arrive at the TSC and begin activating the facility in accordance with DEPIP x.x-xx, TSC Activation. DERO personnel should also implement their respective procedures at this time. 00:40+ Health Physics personnel should have roped and posted the area. If HP have not 41

7 yet done so, they should be directed to do so at this time. 01:05+ A Radiological Monitoring Team should have assembled and dispatched from the TSC to verify the downwind location and magnitude of the release. 01:05+ Planning should have been initiated for cleaning up the spilled resins. If they have not done so, they should be directed to do so at this time. 02:00 Terminate the drill. This sequence allowed the controller organization to control the drill but limited the ability of the players to perform mitigative actions and was therefore limited in demonstrable objectives. It also allowed the players to respond to a fire that they could extinguish, classify an emergency, notify internal and external organizations, activate their facilities, communicate within their facilities and demonstrate the use of their procedures. Conclusion The development of these scenario and sequence of events that have met the limitations of a shutdown and defueled facility was very challenging, however, they served the purpose of demonstrating and maintaining the capabilities of the station s emergency response organization. Acknowledgements I would like to acknowledge the Haddam Neck Plant Operations Department and Radiological Assessment Branch for their support in generating these scenarios. References 1. Haddam Neck Plant Defueled Emergency Plan and Implementing Procedures. 2. Haddam Neck Updated Final Safety Analysis Report. 3. Haddam Neck Plant Administrative Operating Procedures. Mr. Daniel F. McDavitt received his Bachelor of Science Degree in Radiological Health Physics from the University of Lowell in Mr. McDavitt has over 19 years of experience in the nuclear power industry, 17 years of which have been in emergency preparedness and planning. Most recently his experience has involved developing defueled emergency preparedness programs at the Yankee Nuclear Power Station in Rowe, Massachusetts and the Haddam Neck Nuclear Power Station in Haddam Neck, Connecticut. dfmcdavi@dukeengineering.com 42