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Tritium Extraction Facility HVAC Lessons Learned

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Tritium Extraction Facility HVAC Lessons Learned

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    1. Tritium Extraction Facility “HVAC Lessons Learned”

    2. Overview Facility Background Heating Ventilation Air Conditioning (HVAC) System Overview Programmable Logic Controller (PLC) Upgrade HVAC Event Analysis of Event Lessons Learned

    3. Facility Background $500 million dollar line item project. Finished ahead of schedule in 2006. Restored Nation’s capability to produce Tritium. No new Tritium produced since 1988.

    4. Facility Background

    5. HVAC System Production support system. Maintain minimum average exhaust airflows to maintain required pressure differentials. Maintain Life Safety and NFPA codes.

    6. HVAC System

    7. HVAC Challenge 2 Separate buildings (TPB and RHB) 1 Supply system Challenge: Maintain correct building differential pressures to 2 separate buildings off 1 supply system Solution: Automated control system

    8. PLC Network

    9. PLC Upgrade May of 2007, upgraded the PLC from the Quantum to Unity model. This upgrade provided a larger memory size for hot standby capability. No software changes were made. Software was determined to be compatible from post installation testing. No operational issues were encountered with the new Unity PLC until late August 2007.

    10. HVAC EVENT August 29, 2007 Work was completed on Preheat/Reheat coils for HVAC system. Building ventilation had been in a reduced mode and could now be brought back to a normal mode. Upon startup, both cask decon fans faulted causing ventilation to shutdown. Further attempts to start ventilation were unsuccessful. Due to problems acquiring troubleshooting equipment, diagnosis of cask decon fault was hampered. September 10, 2007 Cask Decon fault was attributed to PLC induced equipment chattering. Equipment chattering would begin whenever the standby PLC (Unity) went offline. Standby PLC went to an offline state when new software was loaded as part of the preheat/reheat work. It was discovered that even though the Standby PLC indicated it was “Offline” when the software modification was made, it was indeed “Online”. Temporary fix was to shutdown the Standby PLC.

    11. What Occurred

    12. HVAC EVENT October 1, 2007 Vendor technical support was finally able to attribute the root cause to the Constant-Read/Constant-Write function used in the software. Bottom Line: Constant-Read/Constant-Write function did not work in the Unity PLC as it had with the Quantum PLC. Vendor suggested replacing the Constant-Read/Constant-Write functions with an Input/Output Table instead. This fixed the problem.

    13. Lessons Learned Thoroughly test software AND equipment prior to installation, even if it is a “like-for-like” install. Design control systems that allows for timely transition from auto to manual mode. Have in place diagnostic software and equipment.

    14. Questions

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