ENS 43136

From kanterella

Jump to navigation Jump to search

v t e ENS Event
00:45 Feb 1, 2007
Title	Potential for Penetration Recirculation Filtration System Overload
Event Description	Due to a procedure based line-up of the Penetration Recirculation Filtration (PRF) system, it has been discovered that the system is placed in a configuration that could prevent it from performing its safety function. The PRF System filters airborne radioactive particulates from the area of the fuel pool following a fuel handling accident or ECCS pump rooms and penetration area of the Auxiliary Building following a loss of coolant accident (LOCA). The PRF system is a standby system that upon a receipt of an actuating Engineering Safety Feature Actuation System signal or upon receipt of a high radiation signal or a low air flow signal from the normal spent fuel pool room ventilation system will start the PRF fans and discharge the ventilation air stream through the system's filters. The standard operating procedure for the PRF system directs the control room staff to place the system in a 'full recirculation' mode of operation following a design bases LOCA if the system can maintain a proper vacuum inside the PRF boundary. The 'full recirculation' mode of operation isolates the Recirculation fan discharge to the atmosphere and fully opens the Recirculation fan recirculation damper. This mode of operation is only an additional defense in depth measure and is not credited in the accident analysis. In this mode of operation, it has been discovered that a degraded PRF boundary which allows in leakage into the boundary which is less than the maximum allowable operational limits, could place the system in a configuration that might cause the Exhaust fan to trip. The trip is caused by an overload condition at the supply breaker due to the increased flow of the Exhaust fan to the atmosphere. With the Recirculation fan discharge isolated to the atmosphere and the Exhaust fan inoperable, the PRF system may not establish an adequate vacuum in the PRF boundary during a Post LOCA accident, thus not meeting its design function. This condition was discovered on Unit 1, A train PRF system. Since the systems are similar between Units 1 and 2, and the procedure guidance is exactly the same for the 'full recirculation' mode of operation, this condition has the potential to affect both units, both trains of PRF. Corrective actions have been completed to eliminate this mode of operation from the procedure guidance given to the control room staff for operation. A major contributor to the in leakage into the PRF boundary on Unit 1 has also been repaired which reduced the running load on the Exhaust fan for that train. With the procedure guidance removed, the system should not be placed in a 'full recirculation' mode of operation, thus eliminating the potential for a failure of the designed safety function of the system. The licensee notified the NRC Resident Inspector. * * UPDATE AT 1100 EST ON 2/28/07 FROM LEONARD SMITH TO S. SANDIN * * * The licensee is retracting this event based on the following: This is an Update / Retraction of EN#43136IAW NUREG-1022 paragraph 4.2.3 An eight hour report (EN#43136) per 10 CFR 50.72(b)(3)(v) was conservatively reported based on the potential of having the Penetration Room Filtration (PRF) system become inoperable during a LOCA or fuel handling event. It was believed the post accident system alignment could be relying exclusively on the PRF exhaust fan to draw negative pressure on the penetration rooms during post accident conditions. The report was generated when the FNP Unit 1 A-train PRF exhaust fan tripped while the system was being operated in the full recirculation mode, resulting in a loss of the PRF system capability to meet the intended function. It was concluded at that time the Post LOCA alignment of PRF could result in a similar condition since procedure guidance would have the operator place the PRF system in the full recirculation mode to enhance the cleanup function. Additional investigation, evaluation, and testing has allowed the staff to determine, due to Penetration Room Boundary (PRB) inleakage, the penetration room pressure would not meet the minimum negative pressure of -.5 in. WC in the Post LOCA alignment while in the full recirculation mode. In that case, the procedure would have the operator promptly realign the system to an acceptable configuration. Appropriate operator action would correct the system degraded condition to one that is acceptable for meeting the intended safety function. The PRF is not a fully automatic design system. Proper operation of the system in accident conditions relies on operation actions. In summary, the potential for loss of PRF systems necessary to fulfill the safety function of structures or systems that are needed to control the release of radioactive material or mitigate the consequences of an accident did not exist as a result of this set of conditions and the 10 CFR 50.72(b)(3)(v) report (EN#43136) is retracted. The licensee informed the NRC Resident Inspector. Notified R2DO (Deborah Seymour).

ENS 43136 +/-
Where
Farley Alabama (NRC Region 2)
Reporting

10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material
Time - Person (Reporting Time:+-0.15 h-0.00625 days <br />-8.928571e-4 weeks <br />-2.0547e-4 months <br />)
Opened:	James Hutto 00:36 Feb 1, 2007
NRC Officer:	Bill Gott
Last Updated:	Feb 28, 2007
43136 - NRC Website Loading map... {"minzoom":false,"maxzoom":false,"mappingservice":"leaflet","width":"350px","height":"250px","centre":false,"title":"","label":"","icon":"","lines":[],"polygons":[],"circles":[],"rectangles":[],"copycoords":false,"static":false,"zoom":6,"defzoom":14,"layers":["OpenStreetMap"],"image layers":[],"overlays":[],"resizable":false,"fullscreen":false,"scrollwheelzoom":true,"cluster":false,"clustermaxzoom":20,"clusterzoomonclick":true,"clustermaxradius":80,"clusterspiderfy":true,"geojson":"","clicktarget":"","imageLayers":[],"locations":[{"text":"\u003Cb\u003E\u003Cdiv class=\"mw-parser-output\"\u003E\u003Cp\u003E\u003Ca class=\"mw-selflink selflink\"\u003EENS 43136\u003C/a\u003E - \u003Ca href=\"/Farley\" title=\"Farley\"\u003EFarley\u003C/a\u003E\n\u003C/p\u003E\u003C/div\u003E\u003C/b\u003E\u003Cdiv class=\"mw-parser-output\"\u003E\u003Cp\u003EPotential for Penetration Recirculation Filtration System Overload\n\u003C/p\u003E\u003C/div\u003E","title":"ENS 43136 - Farley\n","link":"","lat":31.223047222222224,"lon":-85.11253055555555,"icon":"/w/images/1/14/Southern_Nuclear_icon.png"}],"imageoverlays":null}
v • d • e

v t e Emergency Notification System
Farley with 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material
WEEKMONTHYEAR2017-06-02T14:20:00 [Table view]
[ENS list for Farley]

Retrieved from "https://kanterella.com/w/index.php?title=ENS_43136&oldid=427033"