Conference Proceedings Paper
Calandria and Shield Tank Assembly Replacement
9th International Conference on CANDU® Maintenance - 2011 December 04-06
Ron Mottram (Bruce Power)
Joshua Guin (MEC Nuclear Safety Solutions Limited)
Bruce Power is planning for the refurbishment of Bruce A Units 3 and 4, and has developed an innovative and alternative solution to the current Bruce A Units 1 and 2 in-situ replacement of calandria tubes, pressure tubes and end fitting assemblies for its continued refurbishment of the Bruce A power generation station reactors. The proposed refurbishment concept involves modular replacement of the Calandria and Shield Tank Assembly (CSTA) with the goal of reducing the risk, cost and schedule over current means of replacement of the 480 fuel channel assemblies in the original reactor. Effectively this would install a completely new reactor.
The paper will identify the origins of the approach and discuss the range of topics that required to be resolved to produce a feasible solution. The organizational structure chosen to undertake the work will be briefly discussed.
The issues that required resolution included:
- Interference handling
- Removal and replacement of containment concrete and liner
- Heavy lifting and structural integrity
- Dose estimation and contamination control
- Radiation shielding during handling and storage
- Waste storage
- Interaction with the regulator
- Safety and licensing issues
- Environmental assessment
- Design of the replacement CSTA
- Fabrication cost and schedule
- Constructability and cost estimation
- Risk evaluation
The work was completed in two main phases with increasing levels of detail considered at each stage. The phases were:
- Establishing if there was a feasible solution to safely remove and replace an irradiated assembly weighing over 3000 tons.
- Defining constraints and identifying major work areas
- Producing a high level business case.
- Refining the outcomes from Phase1 and assessing if there was a cost beneficial handling method that would allow the CSTA to be removed and reinstalled complete with end fittings.
- Developing the conceptual engineering and producing a cost and schedule for comparison with the traditional refurbishment approach.
- Carrying out safety analysis to demonstrate that the design of the new CSTA provides safety improvements over the original design.
- Preparation of the CSTA design to a point at which it can be submitted to the TSSA for preliminary registration.
The paper should interest a wide spectrum of nuclear personnel due to the range of topics that needed to be fully understood and for which solutions were required.
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