The Challenge
To remove all sodium residues from the reactor vessel within PFR. Ensuring minimal sodium is left within the vessel on completion of bulk draining, a camera/pump draining system has been devised to ensure as much bulk material is removed prior to the progression of Water Vapour Nitrogen treatment of the vessel. The points below detail the project background and the proving trials to be undertaken at the facility in the near future.

On completion of bulk sodium removal, it is anticipated a heel of sodium will be left in the dished end of the PFR reactor vessel. Quantity anticipated at about 2Te but this may be less/more dependant on when the Primary Sodium Extraction Pump loses suction.
Equipment to be utilised for heel pool removal, camera/lighting system with integral pumping system, is remotely deployed and the systems are connected via an umbilical of hoses/control cabling. The system is integrated to the reactor vessel at the Reactor Transfer Port (RTP) by the means of a small glovebox.
The RTP currently has the primary sodium extraction heater (PSEH) fitted, which will be removed prior to insertion of the camera system. Trials will be undertaken at T3|UK for the PSEH removal. The removal process involves ‘bagging out’ the upper half of the heater and ‘flasking out’ the lower half on account of anticipated higher radiation levels.

Trials Set Up
To replicate the conditions in which the equipment will be deployed in PFR

• A lower assembly was manufactured which effectively mimics the Rotor/Shock absorber assembly within the reactor vessel.
• Lower assembly was trace heated to provide ambient temperatures in excess of 200°C to simulate reactor vessel temperature. The assembly has been subsequently lagged to retain the generated heat.
• The lower assembly has a tank incorporated to allow it to be filled with a sodium replica medium for pumping trials and commissioning of the system. Water is the intended test medium (similar properties to molten sodium.)
• The lower assembly is to be submerged into the pit at a depth equivalent to the depth of the reactor vessel in PFR.
• An upper assembly was manufactured that incorporates a mock up of the RTP within PFR.
• The upper assembly will be positioned over the pit and the two sections connected via a tube liner between both sections. At this stage, a complete mock up of the reactor conditions will have been achieved.

Trials process
On assembly of the heel pool camera/pump equipment, trials will be undertaken to allow the following to be verified:

• Fitment and deployment of the equipment.
• Effectiveness and integrity of the camera in hazardous environment (hot).
• Effectiveness and integrity of the pumps in the environment and position of the heel pool i.e. the ability to pump sodium up and out of the reactor.
• Prove working documents are fit for purpose.
• Commission the plant and establish pumping cycles.
• Test safety/emergency shutdown procedures and equipment are functional.
• Train operatives in the use of the plant and give familiarisation with operating procedures.
• Allow for final close out of any outstanding design/safety case issues prior to plant implementation.

Benefits
Throughout the trials, testing and training process, improvements will be identified as well as any problems with the current system. On completion of works at T3|UK, a proven, fit-for-purpose and safe solution to a difficult problem will be delivered to site for use in the PFR. Not only does this give assurances to the facility that operator and plant safety will not be compromised but it also gives the regulators assurances that every effort has been made to mitigate against un-foreseen problems than can occur during the design/manufacturing stages of a project.