ML13014A100

Sprinkler Clogging LaSalle Exelon - Presentation During September 2011 NEI Fire Protection Information Forum

ML13014A100
Person / Time
Site:	LaSalle
Issue date:	09/12/2011
From:	Keller W Exelon Generation Co, Nuclear Energy Institute
To:	Office of Nuclear Reactor Regulation
References
Download: ML13014A100 (13)

Text

Chemistry Lab Pre-action System Clogging Wes Keller September 12, 2011

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Background===

• Chemistry Lab

• Drop Ceiling

• Lab Below Ceiling

• Cables Over Ceiling (Crowded)

• Ionization Smoke Detection Above Ceiling

• Pre-action Spray System (Tray Dedicated)

• Pressurized with Air (Standby)

• 18 Month Surveillance for Flow Testing

 Tested through a single, very accessible nozzle

 No specification as to which nozzle(s) to flow test through

 35 Branch Lines

 283 Spray Nozzles (250º F Nozzles)

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Background===

• After Test Completion

• The nozzle is reinstalled

• System is re-pressurized with compressed air. This causes an oxygen-dense environment.

• The piping in the Overlab System is galvanized, but the high-oxygen atmosphere combined with trapped water is a potentially corrosive environment.

System Layout FP Water from Deluge Valve BL 13 BL 9 BL 5 BL 3 BL 1 BL 15 BL 11 BL 7 BL 35 BL 33 BL 31 BL 29 BL 27 BL 25 BL 23 BL 21 BL 17 BL 19 Main Header BL 4 BL 2 BL 20 BL 10 BL 8 BL 6 BL 22 BL 18 BL 12 BL 16 BL 14 BL 34 BL 32 BL 30 BL 28 BL 26 BL 24

Issue Description

• On October 1st, 2010 at approximately 00:55

• Preaction Spray System Function Test in the Chemistry Overlab

• A Mud like substance blocked all flow through the 1/2 ball valve attached to the hose that routes water to the floor drain during the test

• System was declared inoperable and associated time clocks and compensatory measures were established. A comprehensive investigation was performed for above the lab area and all 35 Branch Lines (BLs) were flushed.

• BLs 2 and 5 were found to have blockage. A mud like substance was found in BL 2 and a rag was found in BL 5.

• As an extent of condition Unit 1 and Unit 2 Cable Spreading Rooms and Unit 1 and Unit 2 D/G Corridors were immediately tested in accordance with procedure since they have similar pre-action spray system. No similar issues were found.

• Equipment Apparent Cause Evaluation (EACE) Performed

Issue Description Issue Description Issue Description Sample of Mud-Like Substance

• A sample of the sediment was collected and sent to Powerlabs in Wilmington, IL for elemental analysis.

• Powerlabs stated that elemental analysis can be used to determine if the sediment is internal to the piping system (corrosion) or external to the piping system (sediment/silt/soil).

Sample of Mud-Like Substance

• Substance Found

• Nearly a 50/50 split of Zinc Oxide and Iron Oxide

Immediate Corrective Actions

• Procedural & PM Changes

• Engineering: Provide necessary guidance for system flush plan on a periodic basis to operations department to revise the procedure

• Provided a method of performing an entire system flush IAW NFPA 13A Section 5-4.2

• Method includes flushing the most remote locations in each of the 35 Branch Lines on a periodicity that essentially flushes the entire system

• Operations: Revise the procedure as appropriate following guidance given from Engineering

• Revision in progress. It is to be implemented prior to the next performance

Future Actions

• System Modifications

• Low Point Drains

• Pressurize the Overlab System with Nitrogen instead of air

• Compressed air causes a higher Oxygen content to exist in the pipe, leading to accelerated corrosion in the presence of raw water

• Guidance from Nexus Engineering suggests that going to Nitrogen will eliminate the need for low point drains and potentially eliminate the need for extensive flushing as prescribed by the EACE Corrective Actions

Overlab Flushing Questions?