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| Entered date | Event description | |
|---|---|---|
| ENS 46251 | 14 September 2010 15:04:00 | On September 14, 2010, at approximately 0815 PDT, a minor diesel fuel spill was discovered at the boat dock in the intake cove at the Diablo Canyon Power Plant. A rainbow sheen was observed on the water around the kelp harvester. Harvester operators immediately began deploying absorbent booms and absorbent pads to contain the sheen. It is estimated that less than 2 ounces of diesel fuel reached the water. Mechanics on scene discovered that a small hose clamp had failed on the diesel fuel return line. Repairs were made and the spill was contained. Absorbent pads were used to clean up the residual diesel fuel on the pontoons of the harvester. Repairs were complete and most of the diesel fuel has been absorbed by pads and booms. The licensee notified the NRC Resident Inspector. The licensee also notified the California State Office of Emergency Services, National Response Center, San Luis Obispo County Environmental Health and the Regional Water Quality Control Board. |
| ENS 45585 | 22 December 2009 11:14:00 | This notification is being made in accordance with 10 CFR 50.73(a)(i), which states, in part; that in case of an invalid actuation reported under 10 CFR 50.73(a)(2)(iv)(A), other than the actuation of the Reactor Protection System when the reactor is critical, the licensee may provide a telephone notification to the NRC within 60 days after discovery of the event instead of submitting a written Licensee Event Report. On November 21, 2009, at 2113 PST, EDG 2-1 automatically started, but did not load, due to an attempted replacement of an indicating light that caused a control circuit electrical short and opening the power supply fuse. EDG 2-2 and EDG 2-3 were unaffected by this event. Plant operators entered TS 3.8.1, AC Sources - Operating, due to the loss of the Startup Feeder indication circuit. No actual condition requiring the start of EDG 2-1 existed. The EDG 2-1 4kV Bus Start up Transfer Feeder Undervoltage Relay was placed in bypass (knife switch #10 for relay 27 HGU opened), the EDG was shutdown at 2147 PST and placed in standby operation at 2148 PST. This inadvertent start relay input is not a required safety function, but provides an anticipatory start of the EDG. The actuated relay input is not required for operability, thus the EDG was operable at 2148 PST. Electrical Maintenance replaced the affected sensing relay circuit fuse (52HG14 "UA" fuses), tightened the indicating light socket for SUT 2 2 Potential C A Phase, and reset 27HGU (Startup Feeder UV for 4kV Bus G). On November 22, 2009, at 0729 PST, TS 3.8.1 was exited. The consequences of this event were limited to the unplanned start of EDG 2-1. The EDG started and functioned in accordance with its design. Since no valid signal which required the EDG to start, and since the start occurred inadvertently as the result of a known maintenance action (resulting in a single component failure, a protective fuse opening), this event has been classified as an invalid actuation. The licensee has notified the NRC Resident Inspector. |
| ENS 44927 | 22 March 2009 20:02:00 | At 1334 on March 22, 2009, while Unit 1 was in Mode 3, replacement steam generator (RSG) 1-3 was conservatively determined to be in an unanalyzed condition in that seismic washer plates were found to have nonconforming gaps on two of the four steam generator support columns. A plant walk down discovered that the two washer plates were not seated in the column adapter due to an interfering weld on the interior recess of the column adapter. Because of this condition, Technical Specification 3.0.3 was entered for Unit 1. At 1536 on March 22, 2009, a shim was installed between the washer plate and the column adapter at each of the two non-conforming locations on RSG 1-3 of sufficient thickness to clear the weld metal interfering with washers. This action brought the support columns for RSG 1-3, support foot joints into compliance with the full design capacity. Technical Specification 3.0.3 was exited for Unit 1 at that time. This issue was discussed with US NRC DCPP Senior Resident. |
| ENS 44675 | 21 November 2008 14:08:00 | As part of the ongoing seismic monitoring program, PG&E (Pacific Gas & Electric) in conjunction with the US Geological Survey (USGS) is studying a pattern of seismic activity in close proximity to the Diablo Canyon Power Plant (DCPP). The discovered pattern of seismic activity suggests a potential offshore fault near DCPP. PG&E and the USGS were previously unaware of this potential fault. Initial evaluation shows that the potential fault is closer to DCPP and much smaller than the Hosgri fault, which is the current bounding seismic feature for DCPP. Initial assessment indicates that the ground motion from this potential fault is expected to be bounded by the existing seismic design basis for DCPP. The possible impact of this potential fault, including potential ground deformation is the subject of an ongoing evaluation. Given the available data, PG&E and the USGS estimate that it will take up to a year to determine if a seismic fault exists. This issue was discussed with US NRC Region IV and Office of US NRC Nuclear Reactor Regulation on November 21, 2008. PG&E is planning a media briefing. The licensee has notified the NRC Resident Inspector. |