Event Notification Report for December 03, 2009

AGREEMENT STATE REPORT - UNPLANNED EXPLOSION DAMAGING MIXTURE OF 400 MILLICURIES OF CARBON 14

This information was emailed from the state as follows:

During a routine health and safety inspection, the [state] inspector learned that an explosion had occurred at the facility on December 3, 2009. An Authorized User was quenching a mixture containing 400 milliCuries of Carbon-14 at the time of the explosion. The individual showered and was taken to the emergency room. The individual had several bioassays done prior to returning to work. The licensee decontaminated the area of concern within the lab. Iowa Item Number: IA100005

Sources that are "Less than IAEA Category 3 sources," are either sources that are very unlikely to cause permanent injury to individuals or contain a very small amount of radioactive material that would not cause any permanent injury. Some of these sources, such as moisture density gauges or thickness gauges that are Category 4, the amount of unshielded radioactive material, if not safely managed or securely protected, could possibly - although it is unlikely - temporarily injure someone who handled it or were otherwise in contact with it, or who were close to it for a period of many weeks. For additional information go to http://www-pub.iaea.org/MTCD/publications/PDF/Pub1227_web.pdf

This source is not amongst those sources or devices identified by the IAEA Code of Conduct for the Safety & Security of Radioactive Sources to be of concern from a radiological standpoint. Therefore is it being categorized as a less than Category 3 source

MANUAL REACTOR TRIP AFTER LOSS OF INSTRUMENT AIR TO CONTAINMENT

"On December 3, 2009 at approximately 04:30 Mountain Standard Time (MST) Palo Verde Unit 3 operators manually tripped the reactor from approximately 100% rated thermal power due to loss of Instrument Air (IA) to Containment. This loss was apparently caused by a failure (closed) of the outboard IA Containment Isolation Valve (CIV) solenoid valve. Loss of IA to Containment resulted in closure of the inboard Reactor Coolant Pump (RCP) controlled seal bleedoff CIV. The RCP seal bleedoff was then being diverted via relief valve to the Reactor Drain Tank (RDT) inside Containment.

"Following the manual reactor trip all CEAs [Control Element Assemblies] fully inserted into the reactor core. All 4 RCPs were stopped to allow for isolation of bleedoff to the RDT. Upon completion of Standard Post Trip Actions, the crew entered the Optimal Recovery Procedure for Loss of Forced Circulation. No emergency classification was required per the Emergency Plan. No automatic ESF actuations occurred and none were required. Safety related buses remained energized during and following the reactor trip. The Emergency Diesel Generators did not start and were not required. The offsite power grid is stable. LCO 3.6.3 was entered due to failure of the IA CIV. No major equipment was inoperable prior to the event which contributed to the need for manual reactor trip."

The reactor was manually tripped for equipment preservation. No safety or relief valves lifted other than noted above. After the trip, decay heat was being removed using the turbine bypass valves and steam generator level was being maintained with the auxiliary feedwater pumps. The licensee also entered LCO 3.4.5, "RCS Loop Operability" because the RCPs were stopped.

The licensee notified the NRC Resident Inspector.