Nuclear

How an Ejector works

Terminology: Ejectors can also be referred to as Eductors, Injectors, Jet Pumps or Jet Syphons.

Depending on the application, different fluids can be used to provide the motive energy.

Normally Ejectors are pipeline mounted, but for some applications they are submerged within the process fluid (for example nuclear waste slurry tanks).

Connections are flanged or butt welded as standard.

Why use Ejectors for nuclear applications?

Butt welded Nuclear Ejector
complete with ceramic internals

• Environmentally friendly - zero emissions
• No maintenance
• No moving parts
• Proven reliability
• Easy to install
• Simple to control
• Low cost & weight
• Low noise levels
• Safe to operate
• Can be installed in tight spaces
• Handles solids, two phase flow and liquid slugs without damage

Test Facilities

Nuclear Ejector during testing

Transvac has a new state-of-the-art Research & Development facility adjacent to its manufacturing workshops in Alfreton, Derbyshire.

Transvac Ejectors for the nuclear industry are all tested prior to despatch.

Recent projects include developing and performance testing various Jet Pump designs for nuclear waste projects.

The test facility includes a number of water and slurry flow loops, a solids separation system, automated valves and data acquisition for both pipeline and in-tank mounted Jet Pump testing.

Transvac can fully performance test Ejectors using water and slurry simulants, including duty and off-design operating points.

Transvac research & test programmes are supported by CFD studies and fundamental University research.

Completed Ejectors for handling radioactive slurry

Transvac has recently supplied Sellafield Sites Limited (via Doosan Babcock) a set of Ejectors (see right) for pumping radioactive slurry as part of the SPP1 project.

Transvac carried out preliminary trials using sacrificial test units followed by full Ejector performance testing (see right top) of the finalised designs prior to despatch.

Completed units included special grade ceramic internal parts to resist abrasion during operation.

Slurry Handling

Direct Pumping of Nuclear Waste

Typically motivated by pressurised water, Liquid Jet Solids Pumps can be used to entrain and transfer radioactive waste from settlement tanks / ponds. Liquid is often used to transport radioactive slurries in order to maintain velocity within long discharge pipelines and thereby prevent solids settlement. When pumping abrasive slurries, materials are typically stainless steel complete with ceramic internals.

Buffer Storage Application

Following on from the Direct Lift Ejector, the Transvac Air Jet Ejector (AJE) again uses compressed air as the motive to draw air from the system. As is shown in the diagram on the right..

Slurry Lift Application

For this application Transvac Liquid Jet Solids Pumps are installed above the radioactive slurry. In operation 'Pulse Jets' submerged in the slurry agitate an area around the suction 'leg' of the Liquid Jet Solids Pump allowing it to transfer slurry to reception tanks elsewhere on site. As the tank slurry is removed liquor is added to the tank to maintain a constant head. The Jet Pumps include Transvac ceramic internals to resist wear.

Submerged Application

For this application Transvac Liquid Jet Solids Pumps complete with a special fluidising jet systems are to be submerged in the radioactive slurry. In operation the fluidising jets agitate an area around the suction ports of the Jet Pump allowing it to transfer slurry to reception tanks elsewhere on the site. As the tank empties the Jet Pump and fluidising jets are gradually lowered. The Jet Pumps include Transvac ceramic internals to resist wear.

Indirect Transfer Storage Application

Transvac Air Jet Syphons are used to decant (directly transfer) radioactive liquor from cell sumps into the BSV tank as shown in the diagram. Using compressed air as the motive fluid enables the transportation of radioactive liquor without adding any extra fluid to the quantity handled. Gas is not an effective medium for directly entraining and pumping liquids. It can only be used as the motive fluid for Air or Gas Jet Syphons when entraining and pumping small quantities of liquids / slurries over short distances. Steam is a very effective medium to motivate Ejectors when directly pumping radioactive slurries over short distances.

One advantage of using steam is that it is easy to provide and adds very little additional liquid to the radioactive slurry being pumped, which can be major benefit for downstream processes. Typically discharge pressures would be >2 barg.

Indirect Pumping of Nuclear Waste

Steam, Air or Nitrogen can be used to motivate an Ejector to create a vacuum within a transfer vessel to draw in liquids / slurries. Steam, Air or Nitrogen is not in direct contact with the fluid being pumped. Once the volume of liquid reaches a preset level in the transfer vessel the Ejector is switched off. The vessel contents can then be simply drained by gravity to the discharge point. This systems is usually used for transferring small quantities of suction fluids.

Tank Mixing

Jet Mixers for Tank Mixing

Tank Jet Mixers provide a simple method of mixing and agitating tanks with no in-tank moving parts and no maintenance. Performance is controllable by adjusting the motive fluid flow provided by an external pump. Each Tank Jet Mixer is designed to suit the process mixing requirement and single Mixers or a number of mixers mounted on an in-tank manifold are available.

Transvac can offer the basic mixers or a complete system including pipework, pumps and valves. Materials of construction can offered in most materials including ceramics.

Advantages of Jet Mixers

• No moving parts
• No splashing or aerosol created
• Operates at variable depths
• No bridges or bearings used
• No in-tank maintenance needed
• Evenly distributes mixing
• Controllable mixing
• Simple, reliable and robust

Tank Jet Mixers for mixing nuclear waste

Each Tank Jet Mixer is designed to suit the process mixing requirement and single Mixers or a number of mixers mounted on an intank manifold are available. Transvac can offer the basic mixers or a complete system including pipework, pumps and valves.

Materials of construction are chosen to suit the process conditions, common materials include stainless steel, carbon steel, Polypropylene, PVCu, PTFE, and GRP and ceramic.