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Entered date | Event description | |
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ENS 55122 | 4 March 2021 04:00:00 | At time 0323 (EST) on March 04, 2021, it was determined that the Reactor Coolant System (RCS) pressure boundary did not meet the acceptance criteria under ASME, Section XI IWB-3600, "Analytical Evaluation of Flaws." This condition will be resolved prior to plant start up. This event is being reported as an eight hour non-emergency notification per 10 CFR 50.72(b)(3)(ii)(A). There was no impact on the health and safety of the public or plant personnel. The NRC Resident has been notified. |
ENS 50502 | 1 October 2014 15:07:00 | At 0750 EDT on October 1, 2014, the Shift Manager was notified that site Information Technology (IT) personnel were being mobilized to investigate a potential voice and network loss at the Emergency Operations Facility (EOF) and Joint Information Center (JIC). Site IT personnel were notified by offsite IT resources at 0727 EDT on October 1, 2014 of the issue that was first identified by IT monitoring software at 0124 on October 1, 2014. The site IT personnel that responded to the EOF and JIC reported to site Control Room and Emergency Preparedness (EP) personnel at 0845 that connectivity to the Exelon network and the internet was unavailable at both the EOF and the JIC. This loss of connectivity would prevent the ability of the EOF Emergency Response Organization (ERO) personnel to directly monitor key plant parameters via the site's Plant Process Computer (including the Site Parameter Display System) and other network-based plant parameter display systems. Site IT and EP personnel determined that the following communications equipment was not impacted by the connectivity issue: - Dedicated Offsite Agency Phones (primary method for contacting state and local agencies) - Commercial Phones and dedicated bridge line (primary method for contacting other site Emergency Response Facilities) - FTS-2001 Phones (e.g., ENS and HPN lines) - ERDS Additionally, EP personnel verified with Dose Assessment Office personnel that dose assessment and dose monitoring functions from the EOF could still be performed without delay. Site IT personnel reported to the Control Room at 1135 that connectivity to the Exelon network and the internet had been restored to a fully functional status. While site and fleet IT personnel continue to address and verify all appropriate corrective actions have been taken to prevent recurrence of the connectivity issue, the site has employed appropriate compensatory measures to ensure that the verbal transmission of key plant parameters from the site (Technical Support Center or Control Room) to the EOF is recognized and maintained. The NRC Resident Inspector has been notified.
This update retracts Event Report #50502, which reported that a loss of connectivity to the Exelon network and internet at the Emergency Operations Facility (EOF) and Joint Information Center (JIC) had impacted the ability of staff in these facilities to directly monitor key plant parameters via the site's Plant Process Computer and other network-based plant parameter display systems. Subsequent to the identification of this event, further investigation by site and fleet staff determined that adequate direction was included in applicable Emergency Response Organization (ERO) procedures to respond to data display system failures of this type. Specifically, the checklist (procedure) for the Operations Communicator in the EOF provided adequate direction for this ERO member to obtain required plant data from the Operations Communicator located in the Control Room via alternate methods (e.g., over the phone - phone lines remained functional throughout the time that the loss of computer connectivity condition existed). Therefore, this event did not result in a major loss of emergency assessment capability and was not reportable to the NRC under 10CFR50.72(b)(3)(xiii). The NRC Resident Inspector has been notified. Notified R1DO (Bickett) and Cyber Assessment Team via email. |
ENS 49754 | 22 January 2014 00:33:00 | Dual Unit Trip due to loss of '21' 13 KV bus . All safety functions are met for both units. Unit 1 remained with normal heat removal. Unit 2 lost power to its normal heat sink and is stable on Auxiliary Feed water and Atmospheric Dump Valves for temperature control. Both trips were automatic trips. Due to loss of power a Under Voltage actuation occurred on both units ('14' and '24' 4Kv bus). Due to loss of main feed on Unit 2 a Auxiliary Feed water Actuation System (AFW) actuation occurred on Unit 2. Cause is under investigation. All control rods fully inserted on the loss of power to the Control Rod Drive Mechanisms (CRDMs). Both Units Reactor Coolant Pumps (RCPs) remained running during the transient. The normal Unit 2 heat sink was unavailable due to the loss of the operating circulating water pumps resulting in a loss of condenser vacuum. The Unit 2 AFW actuation included one of two steam-driven pumps and the motor-driven pump. Both Units Emergency Diesel Generators started and loaded and have since been secured. Both Units are stable and will remain in mode 3 (Hot Standby) pending the results of the investigation. The licensee will inform the NRC Resident Inspector. |
ENS 47699 | 26 February 2012 20:15:00 | Calvert Cliffs will be performing planned maintenance to the U-1 Plant Process Computer to install isolation transformers. This maintenance window was expected to start at 2100 (EST) today, 2/26/2012, but the U-1 Plant Process Computer failed at 1546 this afternoon and it was decided to commence the planned maintenance window at that time versus spending resources to attempt recovery of the computer for just a short time period. The planned maintenance window is expected to be 54 hours long and end February 28, around 2300. This will impact the Unit 1 data dissemination to the Safety Parameter Display System (SPDS), TSC Computer. PI (Plant Trending Software) and ERDS will also be out of service for both Unit-1 and Unit-2. Should an emergency be declared during this period, the Control Room will continue to have the capability to retrieve plant data inputs to assess plant conditions and perform core damage assessment. Control Room Emergency Response Organization personnel will use backup methods already captured in emergency response procedures to disseminate plant parameter data to the effected Emergency Response Facilities and NRC during the plant data network outage. MIDAS (Meteorological Data) will continue to be operational at the site. Applicable Reporting Requirement: 10 CFR 50.72 (b) (3) (xiii); 8 Hour report. The licensee notified the NRC Resident Inspector.
At 1000 (EST) this morning planned maintenance was completed to the Unit 1 plant process computer. All plant assessment capabilities have been restored. The licensee informed the NRC Resident Inspector. Notified R1DO (Ferdas). |
ENS 46292 | 30 September 2010 09:39:00 | At 0650 (EDT) on September 30, 2010, site personnel were notified by multiple Calvert County residents of a single siren activation (Siren C21) at 0645 (EDT) for approximately 2-3 minutes. Following a detailed review of the site's Alert and Notification System, the site identified multiple activations of the siren in addition to the first inadvertent activation of the siren that occurred at 0645 (EDT). The multiple siren activations were not related to any condition or event at Calvert Cliffs. The siren has experienced multiple losses of power as a result of the effects from heavy rain and wind associated with the passing of Tropical Storm Nicole. Each time the power had restored to the siren, it performed a full cycle test as opposed to the standard silent test. County Officials were notified and are taking actions to communicate to Calvert County residents concerning the inadvertent siren actuation. Site maintenance locally deactivated the siren at 0827 (EDT) and will further investigate the extent of issue with the siren once the Tropical Storm Nicole has passed. In response to deactivating the siren, Calvert County has implemented the back-up method of route alerting in the event that actual siren activation is required. The NRC Resident Inspector has been informed of the activations. |
ENS 45709 | 18 February 2010 11:47:00 | Both U-1 and U-2 automatically tripped due to valid actuation of the Reactor Protection Systems (RPS). U-1 due to loss of 12B Reactor Coolant Pump (RCP) which resulted in a RCS Low Flow RPS Trip. Cause for loss of 12B RCP is currently not known but is suspected to be related to the electrical transient that occurred on U-2. U-2 tripped due to Loss of Load RPS Trip when the main turbine tripped due to an electrical malfunction and partial loss of offsite power. The electrical malfunction resulted in loss of power to all 4 Kv buses on U-2 with the exception of 21 4Kv bus (ZA train power) (Lost 22-26 4Kv buses) and the loss of 14 Kv bus (ZB train power) on U-1. All the buses lost are powered from the same in house service transformer, P-13000-2, which was lost due to the electrical transient. Cause of the electrical transient is being pursued but is unknown at this time. Loss of the 14 4Kv bus on U-1 and the 24 4Kv bus on U-2 resulted in an Engineered Safeguards Actuation System (ESFAS) valid actuations on both units due to Under Voltage (UV) conditions on those buses. The 1B (Diesel Generator) DG started automatically due to the 14 bus UV and is carrying that bus. The 2B DG received an automatic start signal due to the 24 bus UV but failed to start as expected. No other system actuations occurred. Both units are currently stable in Mode 3 at normal operating temperature (532 degrees) and pressure (2250 PSIA) with no other significant equipment malfunctions. Due to the loss of P-13000-2 (transformer), U-2 sustained a loss of normal heat removal due to loss of the main condenser cooling and the loss of secondary pumps. U-2 is removing heat with auxiliary feedwater pumps and (Steam Generator) SG atmospheric dump valves without issues. Current plans are to cool U-2 down to 445 degrees to maintain RCP seals cool until RCP's can be restarted. A decision on U-1 cool down has not yet been made. There is no primary to secondary leakage. U-2 is currently in a 12 hour LCO due to the partial loss of offsite power and 2B DG failing to start. The licensee has notified the NRC Resident Inspector. |
ENS 44874 | 25 February 2009 09:33:00 | Actual introduction of contraband into a vital area. The licensee notified the NRC Resident Inspector. Contact the Headquarters Operations Officer for additional details. The licensee informed the NRC Resident Inspector. |
ENS 44856 | 17 February 2009 11:16:00 | At 04:05 hours EST, on February 17, 2009, the Plant Process Computer System was removed from service to perform a planned maintenance on the inverter power supply. The plant computer provides monitoring capability for the Safety Parameter Display System (SPDS). The expected duration of plant computer inoperability is approximately 16 hours. The loss of the plant computer requires alternate methods, as described in plant procedures, to be used. Therefore, appropriate assessment of plant conditions, notifications and communications can still be made, if required, during the time that the plant computer is inoperable. This report is being made in accordance with 10 CFR 50.72(b)(3)(xiii) which is any event that results in a major loss of emergency assessment capability, offsite response capability or offsite communications capability. As previously stated, alternate means remain available to assess plant conditions, make notifications and accomplish required communications, as necessary. An additional notification will be provided when plant computer operability is restored. The NRC Senior Resident Inspector has been notified.
The SPDS was restored at 1545 EST. The licensee informed the NRC Resident Inspector. Notified R1DO (Jackson). |
ENS 44708 | 10 December 2008 13:02:00 | This notification of a system actuation is provided in accordance with 10 CFR 50.73(a)(2)(iv)(A). The Licensee is providing a telephone notification to the NRC Operations Center in accordance with 10 CFR 50.73(a)(1) instead of submitting a written Licensee Event Report, as the system actuation was invalid and was not the result of an actuation of the reactor protection system when the reactor was critical. The event involved the invalid actuation of 'Emergency AC electrical power systems, including: emergency diesel generators' as discussed in 10 CFR 50.73(a)(2)(iv)(B). At 1827 on November 16, 2008, with Calvert Cliffs Unit 2 operating at approximately 100% power, the Train A (2A) Emergency Diesel Generator (EDG) automatically started from the standby condition. The automatic start was caused by a degraded switch in the start circuit for the EDG. The 2A EDG successfully started and functioned properly, but did not automatically connect to the associated bus ('21' 4KV Bus) because no bus undervoltage signal was present. The 2A EDG start is considered to be invalid, as the start signal was not generated in response to actual plant conditions or parameters satisfying the requirements for initiation of the EDG start. The start was also not the result of an intentional manual action. The 2A EDG was removed from service and the Station Blackout diesel generator was aligned to '21' 4KV Bus. Following replacement of the degraded switch, the 2A EDG was tested and returned to Service at 2030 on November 17, 2008. The 2B EDG remained operable during this event. The licensee notified the NRC Resident Inspector. The degraded switch was in the EDG room and had degraded resulting in high resistance i.e. simulated an open circuit, which started the diesel. |
ENS 43830 | 8 December 2007 07:54:00 | On December 8, 2007 at 0050, during plant maneuvers to return Unit Two from 84% to 100% reactor power following main turbine control valve testing, the two-minute instantaneous thermal power was inadvertently increased above the accident analysis thermal power limit of 2735.1 thermal megawatts while adjusting main turbine load to maintain Reactor Coolant temperature on program. The maximum power level attained was 2741 thermal megawatts. This is a potentially unanalyzed condition. Prompt operator action was taken to restore reactor power to within limits. Reactor thermal power was restored to within limits (below 2735.1 thermal megawatts) eight minutes later at 0058. The two-minute instantaneous thermal power was restored to below 2700 thermal megawatts (100% rated thermal power) at 0105. The licensee notified the NRC Resident Inspector.
Based on the results of an evaluation of the event, the licensee concluded that Unit 2 operated at a maximum power level of 2741 MWth (101.5 percent rated thermal power (RTP)). The maximum analyzed steady-state reactor core power levels, including uncertainties, are 102 percent of RTP or 2754 MWth. The unit was not in an unanalyzed condition. Therefore, this event is not reportable. Based on this evaluation, the associated non-emergency notification made on December 8, 2007, is retracted. Licensee has notified the NRC Resident Inspector. Notified R1DO (Perry). |