WVP Contamination Reduction

The Challenge

The Waste Vitrification Plants (WVP) are the Sellafield fuel reprocessing bottleneck and are under Regulatory pressure to reduce Highly Active Liquor stocks. Unacceptably high levels of contamination on vitrified product containers caused multiple swabbing of containers within the Control Cell. On average some 52 swabs were required to reduce this contamination to within specification levels taking significant operational time compared to the process design intent of 10 swabs.

The task set for the Container Contamination Reduction Team (a multi-disciplinary team involving personnel from MSS Operations and the OR Team) was to reduce the number of swabs per container to a maximum of 25 swabs. The OR role within this team was to provide statistical analysis expertise and ensure that a robust data-driven approach was employed throughout.

The Solution

The entire process from Container Introduction to the Swabbing Robot was evaluated using a team-based problem solving approach. Hypotheses were generated and tested using a variety of statistical methods to identify and then eliminate the root causes of process variation. The solutions that have been successfully implemented in conjunction with WVP operations include: 

• The monitoring and control of the differential pressures within the Vitrification and Pour Cells to target root cause of neck contamination. 
• Introduction of a door closure regime to control the environment of the product containers. 
• The Just in Time (JIT) introduction of product containers.

Fig 1: The Number of Swabs used During the Study

The Benefit 

• Root causes of container contamination identified and eliminated. 
• Average swabs reduced from 52 to 25. 
• Process variation reduced. 
• Ability to respond more rapidly to changes in process performance. 
• The model predicted potential cost savings/increased revenue of £17m per annum for the next 5 years. 
• This data-driven problem solving process can be appropriately applied across other plants.