PERSISTENT SURVEILLANCE FORPIPELINE PROTECTION AND THREAT INTERDICTION

Dust and the ITER Issue CardsPresented byPhil West with Charles Skinner

Presented atDSOL ITPAToronto

November, 2006

Dust is observed in all MFE devices

• Dust samples from tokamaks comprise a wide range of sizes (10-8 to 10-3 m), shapes, and materials

• A variety of sources/causes are implicated: disruptions, ELMs, redeposition film cracking and peeling, in vessel maintenance activity

• A nuisance in today’s machines => a big issue for ITER safety, licensing– Increased accumulation due to large impulsive

heat loads, high duty cycle– Dust has a high specific surface area, --explosive – Tritiated dust readily levitated--health risk

ITPA, both DSOL and Diagnostics, should include dust as an issue to be dealt with Issue Cards

– Diagnostics [PID 4.22.2.9.8 "Dust Monitor (Provisional)]• Detection of build up behind plasma facing components in multiple

locations• Detection of build up on plasma facing surfaces• Detection of production and flight (transport)

– DSOL• First wall change out capability.• Should be a consideration in the choice of first wall materials. • Mitigation [PID 3.1.3.2.3 Control of chemical energy]

Remote removal (needs to be in PID) or destruction In-situ passivation

• Research required – Strong interaction between health safety scientists, engineers,

and research scientists– Theory and experiments on production, destruction, transport– How are these activities funded? (Is ITER credit available?)

• Who is responsible?

Project Integration Document recognizes the dust problem but does not seriously address it• PID 4.22.2.9.8 "Dust Monitor (Provisional)

– Provision is made in the space and cabling allocation for some type of dust monitor to measure at the level of the machine floor between the cassette gaps. The requirements for dust measurements are still under development and so it is not possible, at this stage, to define the measurement system."

• PID 3.1.3.2.3 Control of chemical energy– (To avoid possible hydrogen/dust explosions a special

prevention system is currently being designed and evaluated (DCR-52). This system would inject neutral gas inside the VV, in case of air and water ingress, to reduce the hydrogen and oxygen concentration at which deflagration of hydrogen can occur.  If this system is implemented in the design it may be possible to relax the requirements related to hydrogen and dust in the following three paragraphs.)