Headquarters Daily report APRIL 11, 1994 *************************************************************************** REPORT NEGATIVE NO INPUT ATTACHED INPUT RECEIVED RECEIVED HEADQUARTERS X REGION I X REGION II X REGION III X REGION IV X *************************************************************************** PRIORITY ATTENTION REQUIRED MORNING REPORT - REGION I APRIL 11, 1994 Licensee/Facility: Notification: Vermont Yankee Nuclear Power Corp. MR Number: 1-94-0044 Vermont Yankee 1 Date: 04/11/94 Vernon,Vermont Dockets: 50-271 BWR/GE-4 Subject: REACTOR SCRAM Reportable Event Number: 27068 Discussion: On 4/10 at 1:22 a.m., the reactor scrammed from 98% of rated power following a turbine trip that was initiated by a high level in the turbine's "C" moister separator (MS). The high level in this MS was caused by equipment problems with level control components that operate the drain tank's normal and emergency dump level control valves. Plant response to the trip was normal, however the licensee is investigating an issue involving anomalous plant computer data for control rod scram insertion timing. Routine weekly turbine valve and control system surveillance was being conducted prior to the scram. This testing would, under normal conditions and proper equipment performance, result in exercising the MS's drain tank normal level control system without challenging its emergency dump valve. The licensee's investigation determined that a shift in the output of the level transmitter that corresponds to the low level setpoint of the drain tank normal level control system had occurred, which caused the tank's normal level control valve to not respond to increasing level. Additionally, a failure in the level controller for the emergency dump valve caused it to not respond adequately to an increasing drain tank level. Corrective actions consisted of adjusting the setpoint on the normal level transmitter and replacing the emergency level controller. Simultaneous failure of both level control valves to operate properly and result in a high MS trip has not been a recurrent problem. Regarding scram insertion timing, this issue is of heightened concern to the licensee because of prior scram pilot valve performance concerns (LER 50-271/93-05). An initial review by licensee personnel of the computer output data for scram insertion times identified the potential for the insertion times to not meet the technical specifications. A high level of attention was focused on the issue by the licensee's organization. Subsequently, the contractor responsible for new computer software that generates control rod drive performance data (derived from plant trip conditions) identified a software error in the calculation of insertion times from raw data. As of 8:00 a.m., 4/11, the reactor is in hot standby and a plant start-up is pending verification that no control rod drive equipment performance issues exist. Regional Action: Resident inspector followup. Contact: R. Conte (610)337-5183 PRIORITY ATTENTION REQUIRED MORNING REPORT - REGION IV APRIL 11, 1994 Licensee/Facility: Notification: Entergy Operations Inc. MR Number: 4-94-0026 Arkansas Nuclear 2 Date: 04/11/94 Russelville,Arkansas Resident Inspector Telecon Dockets: 50-368 PWR/CE Subject: UNIDENTIFIED HOT PARTICLE Reportable Event Number: N/A Discussion: On April 7, 1994, the licensee began decontaminating the refueling cavity and, while vacuuming the bottom of the containment sump to remove residual water, a 300 R/Hr hot spot was detected in a cyclone separator vacuum used to dewater the sump. The flowpath was from the refueling cavity to the containment sump to the cyclone separator vacuum and then to the auxiliary building sump. The licensee monitored the movement of the hot spot to the auxiliary building sump. During this water movement, an HP technician reported 1000 R/Hr and 250 R/Hr contact readings in the HPSI A room. Further flushing moved this hot spot to the auxiliary building sump. The licensee did followup surveys on the flush line and did not find any further hot spots. With the water as shielding, the radiation level on top of the auxiliary building sump rose from less than 1 mR/Hr to approximately 17 mR/Hr. [The auxiliary building sump top is at floor level and extends down 7 feet, 8 inches. The water level in the sump was about 30 percent, or approximately 2 feet.] The licensee pumped the auxiliary building sump to the spent resin storage tank on April 8, 1994. Followup evaluation by the licensee has concluded that the 1000 R/Hr reading is highly suspect. The instrument had pegged high and a corresponding reading at 30 cm was 1.8 R/Hr. Back calculations conducted on the source particle in the cyclone separator, auxiliary building sump, and containment to auxiliary building sump drain line do not support a source term of 1000 R/Hr. The licensee has also evaluated the most probable source of the particle and considers that it did not originate this refueling outage but had been in the containment sump since the last refueling outage when leaking fuel was removed from the core. Regional Action: The resident inspectors have monitored the licensee's action to date and a radiation specialist will be onsite today to review the event. Contact: T. F. Stetka (817)860-8247 PRIORITY ATTENTION REQUIRED MORNING REPORT - REGION IV APRIL 11, 1994 Licensee/Facility: Notification: Arizona Public Service Co. MR Number: 4-94-0027 Palo Verde 2 Date: 04/11/94 Wintersburg,Arizona TELECON WITH LICENSEE AND NRR Dockets: 50-529 PWR/CE80 Subject: UNIT 2 EMERGENCY DIESEL GENERATOR Reportable Event Number: N/A Discussion: On April 9, 1994, Region IV granted a Notice of Enforcement Discretion (NOED) to the licensee to extend the Unit 2 emergency diesel generator (EDG) "B" outage by 18 hours to allow for the completion of maintenance and testing activities. A 72-hour Technical Specification allowed out-of-service time would have expired at 12:45 p.m. MST on April 9. The licensee completed repairs and testing and declared EDG B operable at 12:52 a.m. on April 10. On April 6, during monthly testing of EDG B, the licensee noted an unusual noise in the diesel's 4L cylinder. They found that the cylinder's intake valve crosshead roller, which transfers the cam lobe profile to the push rod, had seized. The licensee replaced the crosshead assembly and performed several inspections. On April 8, during post-maintenance testing, the licensee discovered that the 4L cylinder was not firing. During subsequent inspection, the licensee found that the exhaust valve crosshead was stuck in the inserted position, holding the exhaust valves open. The licensee removed the 4L cylinder head and replaced it with an identical assembly from the Unit 3 EDG B. Unit 3 is currently in a refueling outage and the EDG B was out-of-service for maintenance on the B spray pond pump. The original 4L cylinder was quarantined for root cause evaluation. At 5:46 a.m. on April 9, EDG B tripped as a result of a spurious overspeed signal during post-maintenance testing. At 8:00 a.m. the licensee initiated enforcement discretion discussions with Region IV and NRR. The licensee requested 18 hours to troubleshoot and correct the overspeed trip system problems, to perform final inspections of the EDG, and to test the EDG. At 12:15 p.m. Region IV granted the NOED with the understanding that if the inspections of the EDG identified unexpected debris or if the testing was not successful, the licensee would reconsider their actions. Subsequently, the licensee determined that the trip was caused by a loose bracket on a limit switch in the EDG's overspeed trip system. The bracket was readjusted and successfully tested. The licensee subsequently completed EDG testing and declared the EDG operable. Regional Action: Routine resident followup. Contact: Stu Richards (510)975-0283