With NASA set to embark on some sort of nuclear propulsion work to
get ready for an eventual Mars mission, I see the nuclear protesters
using the Columbia disaster as a vivid example of what could happen
if an explosion occurred on a vehicle with a nuclear cargo.

Painting a portrait of a huge debris field littered with nuclear
fallout.

I fear the public will buy into this scare tactic more readily
because of the Columbia disaster and this will spell doom for any
prospect of nuclear propulsion research.

Anyone care to reassure me otherwise.

TangoMan

Tangoman,

On the contrary, if we can't get better than a 99% launch success rate,
then we're still going to have to deal with exactly the situation you
describe after 100 launches. Is this not a valid reason for concern?

I'm not arguing one way or the other, but I think the safety question is a
valid one. I am interested to hear why you or others believe that a
nuclear-powered device breaking up on launch would not be a health risk.
(And if not, have we just found a better solution to dealing with our
nuclear waste than burying it under Yucca Mountain for a few million
years?)

But I don't want you to have to go back over discussions you may have
already had, so if you have already had this discussion on the list please
just tell me to go throttle myself and I'll go pore through the
archives for the details. :-)

Cheers,
--Justin

> I'm not arguing one way or the other, but I think the safety
question is a
> valid one. I am interested to hear why you or others believe that
a
> nuclear-powered device breaking up on launch would not be a health
risk.
> (And if not, have we just found a better solution to dealing with
our
> nuclear waste than burying it under Yucca Mountain for a few
million
> years?)

For a nuclear powered deep space vessel, which would never see
atmospheric operation, I would imagine that the fissile material
that is launched would not be "hot." The reactor components are
assembled in orbit and then the U-235/U-238 etc is launched in a
special casing that can survive explosion and ground impact.

The key is that they're not launching a functioning reactor, which
has many radioactive parts that can contaminate the environment.

The engineering challenge is thus reduced to designing a casing that
can survive disaster. Even if you have to dedicate a whole shuttle
cargo bay to lifting a casing whose mass or volume exceeds its cargo
by orders of magnitude. You can have multiply layers which collapse
as they absorb shock, compression, impact and other disaster related
stresses.

That said, I believe this type of operation is completely different
from launching used radioactive material into orbit.

An expert's opinion would be helpful on this question: is there less
radioactivity in fissile material that hasn't gone opertional yet? I
recall reading that this was true but am not certain of my
recollection.

TangoMan

Plutonium 239, the most efficient fissile material, is an alpha
emitter, which can be shielded by a couple of sheets of paper.
Enriched Uranium (98%+ U-235) fuel, used in nuclear submarine cores,
can be handled by hand prior to first going critical, because of the
shielding provided by the fuel cladding. Spent fuel will kill you
in minutes.

Ice Pilot

--- In ssi_list@... "victoriatangoman
> > I'm not arguing one way or the other, but I think the safety
> question is a
> > valid one. I am interested to hear why you or others believe
that
> a
> > nuclear-powered device breaking up on launch would not be a
health
> risk.
> > (And if not, have we just found a better solution to dealing
with
> our
> > nuclear waste than burying it under Yucca Mountain for a few
> million
> > years?)
>
> For a nuclear powered deep space vessel, which would never see
> atmospheric operation, I would imagine that the fissile material
> that is launched would not be "hot." The reactor components are
> assembled in orbit and then the U-235/U-238 etc is launched in a
> special casing that can survive explosion and ground impact.
>
> The key is that they're not launching a functioning reactor, which
> has many radioactive parts that can contaminate the environment.
>
> The engineering challenge is thus reduced to designing a casing
that
> can survive disaster. Even if you have to dedicate a whole shuttle
> cargo bay to lifting a casing whose mass or volume exceeds its
cargo
> by orders of magnitude. You can have multiply layers which
collapse
> as they absorb shock, compression, impact and other disaster
related
> stresses.
>
> That said, I believe this type of operation is completely
different
> from launching used radioactive material into orbit.
>
> An expert's opinion would be helpful on this question: is there
less
> radioactivity in fissile material that hasn't gone opertional yet?
I

--- "victoriatangoman victoriatangoman@...
> --- In ssi_list@... Justin
> > I'm not arguing one way or the other, but I think
> the safety
> question is a
> > valid one. I am interested to hear why you or
> others believe that
> a
> > nuclear-powered device breaking up on launch would
> not be a health
> risk.
> > (And if not, have we just found a better solution
> to dealing with
> our
> > nuclear waste than burying it under Yucca Mountain
> for a few
> million
> > years?)
>
> For a nuclear powered deep space vessel, which would
> never see
> atmospheric operation, I would imagine that the
> fissile material
> that is launched would not be "hot." The reactor
> components are
> assembled in orbit and then the U-235/U-238 etc is
> launched in a
> special casing that can survive explosion and ground
> impact.
>
> The key is that they're not launching a functioning
> reactor, which
> has many radioactive parts that can contaminate the
> environment.
>
> The engineering challenge is thus reduced to
> designing a casing that
> can survive disaster. Even if you have to dedicate a
> whole shuttle
> cargo bay to lifting a casing whose mass or volume
> exceeds its cargo
> by orders of magnitude. You can have multiply layers
> which collapse
> as they absorb shock, compression, impact and other
> disaster related
> stresses.
>
> That said, I believe this type of operation is
> completely different
> from launching used radioactive material into orbit.
>
> An expert's opinion would be helpful on this
> question: is there less
> radioactivity in fissile material that hasn't gone
> opertional yet? I
> recall reading that this was true but am not certain
> of my
> recollection.
>
> TangoMan
>
> We don't usually use U235 for such devices. It's not
as fissile as Plutonium ( meaning PU 239 produces more
free neutrons per nucleon). Unfortunately, PU 239 will
also combust spontaneously on exposure to Oxygen,
making it tricky to handle. But the 20 kg or so of
fissle material needed to make the reactor work only
occupies a volume of about the size of a softball. Of
course, in a propulsive device, the geometry of the
fuel isn't a nice round sphere but total volume is
small. However, protection from the radiation it
produces( gamma, free neutrons, etc.) requires a LOT
of shielding. That in itself would probably protect it
from most impacts/explosions. Nukes in jet planes are
carried quite confidently all over the place and are
designed to survive a plane crash loaded with other
explosives without the containment rupturing. That's
SOP.,,,and yes, after the reactor has been
operational, everything in the radiative vacinity of
the fuel is radiated with free neutrons and all kinds
of radioactive byproducts are formed, though none are
quite as bad as the PU itself.Does that answer your
question???

Gary 7