ML13014A100
| 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 19 BL 17 BL 15 BL 13 BL 11 BL 9 BL 7 BL 5 BL 3 BL 2 BL 1 BL 4 BL 16 BL 14 BL 18 BL 20 BL 22 BL 6 BL 8 BL 10 BL 12 BL 29 BL 31 BL 33 BL 30 BL 32 BL 34 BL 24 BL 26 BL 28 BL 21 BL 23 BL 25 BL 27 BL 35 Main Header
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).
- Substance Found
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
- 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?