Semantic search
| Start date | Reporting criterion | Title | Event description | System | LER | |
|---|---|---|---|---|---|---|
| ENS 52201 | 25 August 2016 20:23:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | Unanalyzed Condition Involving Potential Tornado Missile Damage | On August 25, 2016, Engineering staff were reviewing a proposed modification to install additional internal flooding protection for the Intake Building staircase down to the Raw Water Pump vault. Fort Calhoun Station determined that the existing Intake Building internal flooding and tornado-borne missile analyses did not sufficiently account for the potential of tornado-borne missiles striking Fire Protection piping in the Intake Building. A tornado-borne missile strike could potentially cause a double-ended rupture of Fire Protection piping in the vicinity of the stairwell down to the Raw Water Pump vault, which could cause flooding and subsequent failure of all four Raw Water Pump motors more quickly than bounded by the Engineering Analysis. The Engineering Analysis uses a postulated crack from a Moderate Energy Line Break per USNRC Branch Technical Position MEB 3-1, vice postulating a double ended pipe rupture. The resulting flow rate from this postulated crack is less than that possible from a tornado-borne missile strike. This condition creates a potential loss of safety function from the Fort Calhoun Station Raw Water System (ultimate heat sink). All four Raw Water Pump motors could potentially become inoperable from flooding caused by a tornado-borne missile impacting the Fire Protection System Piping near the Raw Water vault stairwell prior to operator action to secure both Fire Pumps. This condition is reportable per 10 CFR 50.72(b)(3)(ii)(B) for any event or condition that results in the nuclear power plant being in an unanalyzed condition that significantly degrades plant safety, and per 10 CFR 50.72(b)(3)(v)(D) for any event or condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident. Interim compensatory measures are to isolate the Fire Protection piping in the vicinity of the Raw Water Pump vault stairwell when severe weather is forecast. The NRC Resident Inspector has been notified. | ||
| ENS 51917 | 10 May 2016 16:38:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | Containment Cooling Water System Inoperable Due to Unanalyzed Condition | During scheduled maintenance, at 1138 CDT, the Fort Calhoun Station Shift Manager was notified via phone call and condition report of an unanalyzed condition which was the result of the maintenance on Shutdown Cooling Heat Exchanger valves. This condition could have led to the inability of the Component Cooling Water (CCW) system to perform its design function of providing a cooling medium for the Containment atmosphere under Loss of Coolant Accident (LOCA) conditions. This was identified by OPPD (Omaha Public Power District) staff engaged in Design Basis Reconstitution. As part of the maintenance, HCV-484, Shutdown Cooling Heat Exchanger AC-4A CCW Outlet Valve, and HCV-481, Shutdown Cooling Heat Exchanger AC-4B CCW Inlet Valve, were opened. Under these conditions, with the assumed single failure loss of DC control power and accident conditions of a LOCA, CCW would be allowed to flow through both shutdown cooling heat exchangers, effectively bypassing flow to the Containment Cooling Units. These conditions are not assumed under plant design basis calculations, and therefore placed the plant in an unanalyzed condition. Following clearance removal at 1535 CDT, both HCV-484 and HCV-481 were returned to service and the condition described above no longer exists. The licensee notified the NRC Resident Inspector.
Discovered 6/15/2016 at 1330 CDT: During the extent of condition review for the above ENS notification, it was discovered that the unanalyzed condition that occurred on 5/10/2016 also occurred five other times during the past 3 years. Details for these additional occurrences will be included in the 60-day Licensee Event Report associated with the original 5/10/2016 ENS notification. The licensee has notified the NRC Resident Inspector. Notified R4DO (Taylor). | Shutdown Cooling | |
| ENS 47359 | 20 October 2011 15:50:00 | 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Flood Barrier Penetrations Not Water Tight | During follow-up inspections of flood barrier penetrations into two rooms in the plant it was determined that some of the water tight conduit fittings were not filled with the material required to make them water tight. Inspection caps were removed from the fittings to perform the inspections. Three fittings into room 19 (auxiliary feedwater and plant air compressors) and fittings into room 56E (electrical switchgear) were found to contain no filling material. One additional fitting into room 56E that was thought to be capped was found to be open with a sheet metal box covering the inside access thereby obscuring inspections. All of the affected penetrations have modifications in progress to assure that they are modified and qualified for design basis flood levels. Of the 16 penetrations 6 have been verified to be made water tight by other means, specifically fire foam barrier installed in the conduit from the room 56E side. The remaining 10 penetrations will leak with a 1014 flood, although the plate will restrict flow to some degree. The stations auxiliary feedwater and safety related electrical switch gear could be affected. This eight-hour notification is being made pursuant to 10CFR50.72 (b)(3)(v). The licensee notified the NRC Resident Inspector. | Auxiliary Feedwater | |
| ENS 46965 | 16 June 2011 17:30:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | Additional Penetration Identified for Mitigation During Walkdown | Operations identified a potential flooding issue in the Intake Structure 1007 ft. 6 in. level. The area of concern is a the hole in the floor at the 1007 ft. 6 in. level where the relief valve from FP-1A discharge pipe goes through the raw pump bay and discharges into the intake cell. There is one penetration of concern. Flooding through this penetration could have impacted the ability of the station's Raw Water (RW) pumps to perform their design accident mitigation functions. Efforts are in progress to seal the penetration. This eight-hour notification is being made pursuant to 10 CFR 50.72 (b)(3)(v). The licensee notified the NRC Resident Inspector.
The penetration in question is not an external penetration and is not within the scope of the CLB (Current Licensing Basis) and therefore the condition is not reportable. The penetration is internal to the intake structure and does not affect internal flooding. The failure to retract this notification in a timely fashion was identified while reviewing flood related station notifications from 2011 and has been entered into the corrective action system. The licensee has notified the NRC Resident Inspector. Notified R4DO (Werner). | ||
| ENS 46893 | 26 May 2011 05:15:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Potential Flooding Path Discovered | Operations identified a potential flooding issue in the Intake Structure 1007' 6" level. The areas of concern are the holes in the floor at the 1007' 6" level where the screen wash header penetrates the ceiling of the Raw Water Vault. There are five of these penetrations of concern. Flooding through the penetrations could have impacted the ability of the station's Raw Water (RW) pumps to perform their design accident mitigation functions. This eight-hour notification is being made pursuant to 10 CFR 50.72 (b)(3)(v). A one foot sandbag berm has been placed around each penetration of concern. The licensee notified the NRC Resident Inspector.
Following additional review of the reported condition, it has been determined that the Raw Water pumps are adequately protected during flooding conditions and that the open penetrations would not impact the ability of the Raw Water pumps to perform their design accident mitigation functions. The licensee notified the NRC Resident Inspector. Notified R4DO (Haire). | ||
| ENS 46747 | 12 April 2011 14:15:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Unsealed Flood Barrier Penetration | During investigations of flood barrier penetrations, a flood barrier sealing a diesel driven fire pump exhaust was found to be cracked. This exhaust pipe penetrates the west wall of the intake structure. Flooding through the penetration could have impacted the ability of the station's raw water pumps to perform their design accident mitigation functions. This eight-hour notification is being made pursuant to 10 CFR 50.72 (b)(3)(v). The penetration is at an approximate elevation of 1012 feet mean sea level (MSL). The river level has been less than 997 feet MSL since prior to December 1, 2010. The raw pumps are operable. There are not any indications of conditions that might result in a flood. Actions are in progress to plug the penetration. The NRC Resident Inspector has been notified.
This event is being retracted. Additional review and evaluation determined that the seal flaw is above the station design flood level of 1014 feet mean sea level, and is therefore, not reportable. The NRC Resident Inspector has been notified. Notified R4DO (Hay). | ||
| ENS 46741 | 8 April 2011 15:24:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Unsealed Flood Barrier Penetration | During investigations of flood barrier penetrations, one approximately 4 inch conduit has been identified that is not sealed. Reducers are installed in the conduit on the exterior side. This conduit penetrates the auxiliary building into room 56. Flooding through the penetrations could have impacted the ability of the station's safety related equipment in the auxiliary building to perform their design accident mitigation functions. During investigations of flood barrier penetrations, a drain flow path from the CARP building into Room 23 of the Auxiliary Building (was identified). There is no specific procedural guidance to isolate this flow path in the event of a flood above 1007 feet. Flooding through this flow path could have impacted the ability of the station's safety related equipment to perform their design accident mitigation functions. This eight-hour notification is being made pursuant to 10 CFR 50.72 (b)(3)(v)(D). The penetrations and CARP building drains are at an approximate elevation of 1007 feet. The river level has been less than 997 feet Mean Sea Level (MSL) since prior to December 1, 2010. The safety related equipment is currently operable. There are not any indications of conditions that might result in a flood. Compensatory actions have been identified. The NRC Resident Inspector has been notified. | ||
| ENS 46723 | 4 April 2011 20:00:00 | 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Scaffolding Affecting Safety Related Equipment | At 1500 (CDT), a concern was raised with regard to scaffolding that had been constructed around safety related equipment in the Auxiliary Building which contains both trains of safety injection and containment spray. As a result T.S. 2.0.1 was entered (which is the Fort Calhoun equivalent to standard T.S. 3.0.3). The scaffolding in question was removed and the equipment was returned to operable status and T.S. 2.0.1 was exited at 1726 (CDT). The NRC Resident Inspector has been notified.
Following the initial report, Fort Calhoun performed a seismic analysis of the impact of the scaffolding previously reported to determine if the equipment in the room would be capable of performing its required safety functions. The evaluation determined that the safety related function of the affected equipment would be able to be accomplished. Therefore, this event is being retracted. Notified R4DO (Haire). The licensee has notified the NRC Resident Inspector of this retraction. | Containment Spray | |
| ENS 46716 | 1 April 2011 02:26:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Identified Unsealed Flood Barrier Penetrations | During investigations of flood barrier penetrations, two approximately 4 inch conduits have been identified that are not sealed. These conduits penetrate the south wall of the auxiliary building near the transformers into room 19. Flooding through the penetrations could have impacted the ability of the station's auxiliary feedwater (AFW) pumps to perform their design accident mitigation functions. This eight-hour notification is being made pursuant to 10 CFR 50.72 (b)(3)(v). The penetrations are at an approximate elevation of 1007 (feet). The river level has been less than 997 feet Mean Sea Level (MSL) since prior to December 1, 2010. The AFW pumps are operable. There are not any indications of conditions that might result in a flood. Actions are in progress to plug the penetrations. The NRC Resident Inspector has been notified. | Auxiliary Feedwater | |
| ENS 46690 | 22 March 2011 18:08:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Potential Flooding of Raw Water Pump | During ongoing investigations of flood barrier penetrations at the station, a weakness in the flood protection strategy that would prevent protection of the raw water pumps for floods above 1007'-6" Mean Sea Level (MSL) was discovered. Cell in-leakage through penetrations at 997' 10" MSL would be beyond the capacity of the raw water pumps. During the preparation of a calculation to demonstrate the validity of this method it was determined that the grid backwash pipe for each grid and the surface sluice penetrate the east wall of the intake structure through an unsealed penetration (a total of 7 penetrations). The grid backwash line is an 18" pipe passing through a 24" sleeve. Flooding through the penetrations could have impacted the ability of the station's raw water pumps to perform their design accident mitigation functions. This eight-hour notification is being made pursuant to 10 CFR 50.72 (b)(3)(v). The penetration is at an elevation of 997'10" MSL. The design flood for the station is at 1014' MSL. The raw water pumps would not be affected until a river level of 1007'6" MSL was reached. The river level is currently approximately 993.5' MSL and has been less than 995'MSL since prior to December 1, 2010. The raw water pumps are currently operable. The National Weather Service Weather Forecast Office is predicting a rise in river level of 2 feet over the next 5 days. Actions are in progress to seal the penetration. The licensee has instituted a temporary plug contingency plan dependant on river level. The licensee will notify the NRC Resident Inspector. | ||
| ENS 46689 | 22 March 2011 15:58:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Containment Coolers Declared Inoperable | At 10:58 CDT, today during the performance of IC-ST-IA-3010B, I&C found NG-HCV-400A-A3, CCW INLET VALVE HCV-400A NITROGEN SUPPLY ISOLATION VALVE, closed which is required to remain open for VA-3A to remain operable. This valve supplies backup nitrogen to VA-3A CCW cooler isolation valve HCV-400A on loss of instrument air to maintain cooling flow to the ventilation during an accident condition. While the nitrogen valve NG-HCV-400A-A3 was closed, performance of IC-ST-IA-3010B on VA-3B, CONTAINMENT AIR RECIR FAN, placed the containment cooler in an inoperable status. This led to Technical Specification 2.0.1 entry due to both trains of cooling being inoperable. The cause for the mispositioning of NG-HCV-400A-A3 is unknown at this time. The inoperability of VA-3A along with VA-3B rendered the containment cooling trains unavailable to perform their safety function during an accident condition. This condition is being reported pursuant to 10 CFR 50.72(b)(3)(V)(D) for mitigating the consequences of an accident. FCS entered into Technical Specification at 10:58 CDT and exited Technical Specification at 11:14 CDT. The licensee notified the NRC Resident Inspector. | ||
| ENS 46674 | 15 March 2011 20:56:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Flood Barrier Penetration Not Sealed | During investigations of flood barrier penetrations, a 4 inch conduit has been identified that is not sealed. This conduit penetrates the South wall of the auxiliary building near the transformers into room 19. Flooding through the penetrations could have impacted the ability of the station's auxiliary feedwater (AFW) pumps to perform their design accident mitigation functions. This eight-hour notification is being made pursuant to 10 CFR 50.72 (b)(3)(v). The penetration is at an elevation of 1007'-8". The river level has been less than 995 feet Mean Sea Level (MSL) since prior to December 1, 2010. The AFW pumps are operable. There are not any indications of conditions that might result in a flood. Actions are in progress to plug the penetration. The licensee has notified the NRC Resident Inspector.
Further investigation has determined that the penetration is adequately sealed inside of the affected structure. Therefore this notification is being retracted. The licensee will notify the NRC Resident Inspector. Notified R4DO (Walker). | Auxiliary Feedwater | |
| ENS 46590 | 27 January 2011 22:23:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Unsealed Penetrations Discovered in the Intake Structure | During a walkdown of the Intake Structure conducted on January 27, 2011, to identify any penetrations in the exterior envelope of the building, four unsealed conduit penetrations (each penetration was four inches in diameter) were identified. These penetrations are concealed within a junction box on the northwest corner of the building. The penetrations are at an elevation of approximately 1006 ft. - 1007 ft. mean sea level (MSL). Flooding through the penetrations could have impacted the ability of all the station raw water pumps to perform their design accident mitigation functions. This eight-hour notification is being made pursuant to 10CFR50.72(b)(3)(v). This report should have been made on January 27, 2011, and is late. Subsequent review of the issue determined this reportability. The river level has been less than 990 ft MSL since January 27, 2011. There have not been any indications of conditions that might result in a flood. The penetrations have been temporarily plugged. A permanent modification is in progress. The penetrations were plugged on February 2, 2011. The licensee notified the NRC Resident Inspector. | ||
| ENS 46368 | 27 October 2010 17:22:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown | Unit Commenced Shutdown After Declaring Containment Spray Inoperable | During pressure drop testing of the backup nitrogen supply for HCV-345 (Containment Spray Header isolation valve) the accumulator failed its test. This renders HCV-345 inoperable. HCV-344 the opposite header isolation valve also has an air leak that appears to be of similar magnitude to the leak on HCV-345. Fort Calhoun Station is conservatively considering both valves inoperable and has entered technical specification 2.0.1 which requires shutting the plant down to hot standby within 6 hours. The plant shutdown began at 1513 CDT. Repair efforts are underway on HCV-345 and HCV-344. The leakage on both valves was identified by systems engineering during testing. The licensee informed the NRC Resident Inspector.
At 1647 CDT, the licensee exited technical specification 2.0.1 after declaring HCV-344 operable. The Unit is currently at 74% power. The licensee will stabilize power at 70% and then commence power escalation. The licensee informed the NRC Resident Inspector. Notified R4DO (Proulx).
Following the original notification, the Fort Calhoun Station reviewed and reanalyzed the acceptance criteria for the subject valve air accumulators. The analysis determined that the valves had been and were operable during the event. Therefore, the report under 10CFR50.72(b)(3)(v)(D) is being retracted. The licensee has notified the NRC Resident Inspector. Notified R4D0 (Howell). | Containment Spray | |
| ENS 46594 | 9 September 2009 14:02:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Unsealed Penetrations Discovered in the Intake Structure | On September 9, 2009, the NRC Component Design Basis Inspection (CDBI) Team identified Fire Protection penetrations on the west side of the Intake Structure were not sealed and it has been determined that the penetrations were below the USAR (Updated Safety Analysis Report) credited flood level. Flooding through the penetrations could have impacted the ability of all the station Raw Water Pumps to perform their design accident mitigation functions. Reference Fort Calhoun Station Condition Report 2009-4166. This eight-hour notification is being made pursuant to 10 CFR 50.72 (b)(3)(v). This report should have been made on September 9, 2009, and is late. Subsequent review of the issue determined this reportability. The penetrations have since been sealed. The licensee notified the NRC Resident Inspector. See EN #46590 dated 2/3/2011 for a similar event at Fort Calhoun. | ||
| ENS 44138 | 14 April 2008 17:45:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | High Energy Line Break Analysis Revealed Potential Accident Mitigation Deficiency | During review of a High Energy Line Break (HELB) analysis a condition was discovered where a break in the auxiliary steam system could result in a loss of all the containment fans and coolers, which are required to be maintained operable due to procedural restrictions to mitigate a design basis accident. The plant entered Technical Specification (T.S.) 2.0.1 at 1245 CDT. This specification requires a plant shutdown within 6 hours. Operations personnel isolated auxiliary steam to the affected areas of the Auxiliary Building at 1305 CDT. With auxiliary steam isolated to the Auxiliary Building, containment fans and associated coolers were restored to an operable status. Plant exited T.S. 2.0.1 at 1305 CDT. The licensee notified the NRC Resident Inspector.
An exhaustive review of the high energy line break licensing and design basis for the auxiliary steam system as it impacts the safety functions or the containment coolers has determined that the required safety functions are met for the licensed and designed basis of the plant. Therefore the previous notification (EN 44138) of April 14 is being withdrawn. The licensee notified the NRC Resident Inspector. R4DO (Pick) notified. | ||
| ENS 42512 | 19 April 2006 14:45:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Postulated Scenario Where Containment Spray System May Be Unable to Fulfill Design Safety Function | During a review of the operation of the plants emergency cooling system for the containment an unanalyzed single failure was discovered. The identified single failure scenario could result in the containment spray system being unable to fulfill its design safety functions. In the event of loss of offsite power occurring after the initiation of an accident signal, the 480V undervoltage relays serve to trip open containment spray pump breakers (as well as other ESF breakers) in order to prepare the breakers for resequencing after the diesel generator output breakers have closed onto their associated buses. The undervoltage trip bypass function performed by the sequencer timer relay contacts serves to prevent tripping ESF breakers due to inadvertent actuation of the undervoltage trip circuits and allows ESF breakers to trip only when sequencers have been reset by a loss of voltage at the 4160V bus level. In situations where a loss of power occurs at the 480 volt level without a coincident loss of power at the associated 4160 volt level, ESF loads supplied from the lost 480 volt bus, such as containment spray pumps, do not receive a trip signal due to the undervoltage blocking feature of the sequencing relays. For most ESF loads, this is not a problem and can be considered part of a single failure scenario affecting only one train of ESF equipment. In the case of containment spray pumps SI-3B and SI-3C, however, the failure of the associated breakers to trip during a single failure of bus 1B4B, results in the operation of a single spray pump, SI-3A with two containment spray valves open. This results in one pump operation to two containment spray headers. Operating the containment spray system in a one pump, two header configuration creates the possibility of inadequate system performance. This configuration may result in overloading the running pump (due to runout) and inadequate NPSH to the running pump. This condition was intended to be prevented by a modification which installed an interlock between spray pumps SI-3B and SI-3C and spray valve HCV-344. The modification apparently failed to consider the single failure of specific 480 Volt buses. Spray valve HCV-344 has been disabled in the closed position so that no external signals will allow the valve to be opened. Disabling this valve places the plant in a 24 hour LCO (Technical Specification 2.4.2.d) starting at 0950 CDT. The licensee notified the NRC Resident Inspector.
On April 19, 2006, Ft. Calhoun station reported that an unacceptable single failure scenario had been identified that could result in the containment spray system being unable to fulfill its design safety functions. The failure scenario required that there be a loss of power at the 480 volt AC level without a coincident loss of power at the associated 4160 volt AC level. This resulted in the potential for one pump operation to two containment spray headers. Following a review of failures that would cause this it was determined that of all the possible failure mechanisms that could impact the capability of affected 480 volt AC bus, such that both trains of containment spray pump could be adversely affected, the only failure mechanism that has unacceptable consequences is a failure of multiple phases of AC power failing in an open circuited manner without a fault occurring and, consequently, without supply breakers opening. This failure mechanism has been determined not to be credible. Therefore, it is not necessary to assume that this type of failure could occur as part of a design basis event. Therefore, no credible single failure could result in the failure of the containment spray system to perform its intended safety function. The report of April 19, 2006 is being retracted June 1, 2006. The licensee notified the NRC Resident Inspector. R4DO (Spitzberg) notified. | Containment Spray | |
| ENS 41386 | 8 February 2005 15:20:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | Steam-Driven Auxiliary Feedwater (Afw) Pump Declared Inoperable Due to Design Issue | The following information was obtained from the licensee via facsimile: At 0920 (hrs.) CST, on February 8, 2005, Fort Calhoun Station declared the steam driven auxiliary feedwater (AFW) pump (FW-10) inoperable due to discovery of a design problem with the pump turbine. The station entered the appropriate technical specification action statement at that time. The pertinent action statements for auxiliary feedwater ((T.S.) 2.5.1) read as follows: B (Action statement): With one AFW train inoperable for reasons other than condition A, restore the AFW train to OPERABLE status within 24 hours. C (Action statement: If the required action and associated completion times of condition A or B are not met, then the unit shall be placed in MODE 2 in 6 hours, in MODE 3 in the next 6 hours, and less than 300 (degrees) F without reliance on the steam generators for decay heat removal within the next 18 hours. A change to the design basis is in progress to allow the pump to be made operable within 24 hours. The design problem is due to the AFW pump drains. The manufacturer states that the drain lines must drain below the level of the AFW turbine. The current configuration is that the drains are aligned to the condenser which is approximately 18 feet above the elevation of the AFW turbine. This is not a problem during normal AFW turbine operation as the condenser would most likely be in service. However, the condenser cannot be relied upon during all accident conditions that require AFW actuation. The licensee has notified the NRC Resident Inspector.
The licensee faxed the following retraction: Fort Calhoun Station (FCS) has conducted a thorough engineering evaluation of the effects on water in the turbine exhaust housing of the steam driven feedwater pump (FW-10). It was concluded that FW-10 was able to perform its design function based on the results of the evaluation. FW-10 was determined to be operable as required during past plant operation whether or not condenser vacuum was available. The conclusion was based on four points: 1. The preparer's experience with a multi-stage turbine that was started with water up to the centerline of the rotor and sustained no damage. 2. OPPD's strong evidence that FW-10 has been operated multiple times with some water in the casing. 3. A simple conservative analysis of the forces on a turbine blade when operated in a water submerged condition. The blade stresses were determined to be well below allowables for the loading condition presented with the blade moving through the static water volume during a startup event. 4. In addition, inspection of the turbine in 1998 and 2005 does not show any adverse indications of stress or wear. Therefore this notification is being retracted.. The plant is presently in a scheduled refueling outage. The licensee will notify NRC Resident Inspector. | Steam Generator Feedwater Auxiliary Feedwater Decay Heat Removal |