Posted by Morris Dovey on January 1, 2012, 10:08 pm
On 1/1/12 2:37 PM, Han wrote:
I have two batches of powder, a half-kilogram jar from a reagent supply
company and a one-pound ZipLoc bag from an eBay vendor. Neither was
particularly well-sealed and I haven't seen any problems. The safety
sheet for powdered nickel warns against inhaling, ingesting, or
absorbing powder through skin/eyes. I'm being careful.
The plan is to load the Ni into the reactor chamber/containment vessel,
then seal and evacuate the chamber to remove the oxygen before
introducing hydrogen. At this stage of the planning process, I'm a lot
more concerned with H2 safety than I am with Ni problems.
The control software design is centered about finding any deviation from
"tame" behavior, and automatically shutting the reactor down if any such
deviation is found. It appears that a full ("cold") automatic shutdown
can be completed within about a tenth of a second - which should make it
much safer than the big fission reactors.
Posted by Han on January 2, 2012, 1:15 am
I don't know the properties of your Ni powder, Morris. I was afraid that
you'd have to rigorously exclude oxygen and water, but to my surprise for
reduction reactions with H2 and Raney-nickel that doesn't seem necessary,
based on at least one example here:
I got to this from:
http://en.wikipedia.org/wiki/Nitrile_reduction , which I got from googling
for "reduction reaction with hydrogen and raney nickel"
email address is invalid
Posted by vaughn on January 2, 2012, 1:25 am
It all depends on how you define "shutdown". In the naval reactor I used to
operate, I could have the rods sitting at the bottom in about a second, but the
reactor was subcritical after the first few inches of rod travel. However the
recent debacle in Japan taught us that there can be many definitions and many
levels of "shut down".
Posted by Morris Dovey on January 2, 2012, 2:54 am
On 1/1/12 7:25 PM, vaughn wrote:
The reaction here appears entirely dependent on temperature and gas
pressure in the reaction chamber. I'm inserting a first solenoid valve
in the hydrogen supply line between the regulator and a T-fitting to
kill the gas flow, and a second solenoid valve in the line between the
T-fitting and an evacuated tank. The third leg of the T-fitting connects
to the reactor gas port.
Shutdown consists of removing power (if still on) from the pre-ignition
heater, closing the first valve to stop the flow of H2 and to protect
the pressure regulator, and then opening the second valve to evacuate
the reaction chamber. As the chamber is evacuated the pressure will drop
precipitously and that will cause a corresponding temperature drop.
After the first valve has been closed and the second has been opened,
the pressure regulator will be closed.
The fusion reaction should stop long before the pressure drops even to
atmospheric, and the (coincidental) temperature drop should provide a
double measure of safety, although residual heat in the reaction chamber
won't much matter because the necessary H2 component won't be present.
If this sounds simplistic and crude, it's because it is - but it should
suffice to determine with reasonable safety whether or not a fusion
reaction can be induced at all. If it can, then the next phase will
investigate the effects of post-ignition modulation of the gas pressure
to attain/maintain a given target temperature.
Posted by Jim Wilkins on January 2, 2012, 11:38 am
Can you find a normally-closed valve for that, so the power fail
configuration is safe?