Semantic search
| Entered date | Event description | |
|---|---|---|
| ENS 42966 | 6 November 2006 04:57:00 | On 6 November 2006 at 0110 an automatic reactor scram was received. This report is being made under 10 CFR 50.72 (b)(2)(iv)(B), 'any event or condition that results in actuation of the reactor protection system (RPS) when the reactor is critical.' The plant also received Group 2, 3 and 4 isolations from the low level signal as reactor water dropped due to the reactor scram. The isolations are being reported under 10 CFR 50.72 (b)(3)(iv)(A), 'any event or condition that results actuation of any of the systems listed in paragraph (b)(3)(iv)(B) of this section.' The scram is believed to be the result of a turbine trip but is currently being investigated further. Main Turbine surveillance testing was in progress at the time but it is not known if the testing caused the turbine trip and subsequent Reactor Scram. Reactor pressure is currently being controlled by the turbine bypass valves and steamline drains. No actuations of Safety Relief Valves were required or occurred. Both Reactor Recirculation pumps tripped as part of RPT. The 'B' Recirc pump has been restarted. Reactor level dropped following the scram resulting in the isolations but was recovered and is currently being maintained by the normal feedwater systems. All isolations went to completion and have been reset at this time. The plant electrical buses transferred without incident and are currently in a normal shutdown alignment. The current plan is to remain in Mode 3 while investigations determine the cause of the turbine trip and reactor scram. All control rods fully inserted on the trip. Currently the plant is using offsite power but diesel generators are available. The licensee notified the NRC Resident Inspector. |
| ENS 42088 | 27 October 2005 17:38:00 | As part of an ongoing Appendix R assessment, it has been determined that Operator actions credited in the Fire Hazards Analysis (FHA) potentially would not be met in fire zones credited for post fire safe shutdown per 10 CFR 50 Appendix R. Specifically, the FHA credited the availability of two in plant operators to conduct two separate series of operator actions that are required to be performed simultaneously within the first 20 minutes. However, the site Fire Plan requires one of these in plant operators to respond to a plant fire as a Fire Brigade member. Since no barrier was put in place to compensate for the lack of the credited operator; this event is reportable as an unanalyzed condition that significantly degraded plant safety. The licensee notified the NRC Resident Inspector.
Further review has determined that adequate operator resources are and have been available to perform the required post fire safe shutdown actions. Therefore, this event is not an unanalyzed condition that significantly degrades plant safety and is being retracted. The licensee notified the NRC Resident Inspector. Notified R3DO (H. Peterson) |
| ENS 41012 | 2 September 2004 15:52:00 | On September 2, 2004 at 14:15 (CDT) the Duane Arnold Energy Center made notification to Mr. Mike Wade of the Iowa Department of Natural Resources regarding a release of free available oxidant (chlorine) to the Cedar River. Although, the initial indications show that this release did not exceed our NPDES discharge permit value, as stated by Mr. Wade of the IDNR, the notification to an outside government agency meets the criteria of a 4-hour notification to the NRC per 50.72(b)(2).(xi). The licensee notified the NRC resident inspector. |
| ENS 40995 | 28 August 2004 07:38:00 | At approximately 01:46 (CDT) on August 28, 2004, the Duane Arnold Energy Center plant process computer (PPC) failed due to a lost power supply. This computer system provides the control room with its Safety Parameter Display System (SPDS), the Emergency Response Data System (ERDS) and MIDAS. With the loss of the PPC, and specifically the subsequent loss of SPDS, ERDS, and MIDAS representing a major loss of emergency assessment capability, the reportability criteria of 10CFR50.72(b)(3)(xiii) was met. No other control room indications, or communication systems were affected by this computer outage. They expect to have a new power supply at the site by noon today and installed within two hours after arrival. The NRC Resident Inspector will be notified.
The Duane Arnold Energy Center plant process computer (PPC) power supply has been replaced and operation of the PPC has been restored. The licensee has notified the NRC Resident Inspector. |