What value is there in a Mock-up to support Decommissioning? Part 3

 The first mock ups 

In the past, when facilities became outdated, unusable for various reasons, or rendered redundant due to an accident, the common practice for many years and even decades was to ‘make safe’ and place them under a care and maintenance regime.

This approach was often chosen because decommissioning was deemed too challenging or expensive, or because of significant radiation concerns. Additionally, some facilities were situated within  vital production areas, making decommissioning  too disruptive. There are many examples of facilities entering this care and maintenance state ranging from early research reactors and cell lines, to a production facility in a famous healthcare company, which was simply encased in concrete. Notably it was recently reported that a large facility at Dounreay was entered for the first time in several decades.  

This care and maintenance practice was widespread until the early 1990’s. However, the increasing costs associated with ageing facilities, prolonged dormancy, deteriorating ventilation systems, and the need to repurpose the building or land prompted a revaluation. 

These factors led the Government to establish the forerunner of the NDA (Nuclear Decommissioning Authority) around 1990, called the Liabilities Management Unit (LMU). Before consolidating all liabilities and estimating the total decommissioning cost across the entire UK, the LMU had to develop protocols for estimating and planning decommissioning.

For the start of this process they picked a conveniently located facility on the AERE Harwell site, not far from London, known as B540.2. The facility had two important elements, a large structure with many industrial hazards (a Variable Energy Cyclotron) and a ‘hot-cell’ facility contaminated with plutonium.

This project effectively developed the first use (in nuclear) of a Work Breakdown Structure (WBS) to determine a protocol for estimating decommissioning projects. The ‘hot cells’ could not be decommissioned manually and required remote dismantling using a hydraulically powered articulated arm. There was much debate about constructing a practical mock-up to test a variety of aspects of the arm’s operation, which added both cost and time to the programme. However this effort  ultimately served to establish several universal benefits; 

• To verify that the system, including the arm, its coverage, movement and basic operations of the remote device, functioned as required.
• To facilitate operator training ensuring that both the basic controls and visibility aspects (such as the use of windows and/or cameras) were suitable for the intended operations.
• To support operator training in terms of developing techniques for interacting with the facility and becoming more efficient, thus enhancing safety and speed in using the systems for operations.
• To demonstrate the capability to  recover from an accident state – a critical safety case requirement.
• To provide reassurance to the client, and in many cases the regulators and safety approval committee’s that the proposed solution will work.
• To allow for adjustments to the arm’s design while in a ‘clean’ state, before entering the contaminated area, which is typically a more cost-effective approach.  

The mock-up used a simple structure to simulate the cells and cutting operations and incorporated a new system for packing waste into cans. Additionally, it successfully demonstrated the ability to recover from an accident, specifically a scenario involving the loss of hydraulic fluid. These demonstrations effectively built confidence in the overall approach, validating its feasibility and safety for the decommissioning project within the B540.2 facility.