Hi Brian,
Thanks for your analysis !
Of course I agree with what you say.
The trouble is that for naval reactors, rated power and actual average operating power are different -- often drastically so (due to the load-following feature).
I think that "a run of a few days at high power" would be very unusual for a submarine.
"A run of a few HOURS at high power" seems more likely (with mid- to low-power runs the rest of the time for "hunter-killers" and near-zero for the "boomers").
Also, smaller reactors in general have a larger surface-to-volume ratio, which aids in heat dissipation (this, for example, is what limits the size of "inherently safe" modular designs like the PBMR and GT-MHR...).
Jaro
-----Original Message-----
From: Brian_Gaulke@hc-sc.gc.ca [mailto:Brian_Gaulke@hc-sc.gc.ca]
Sent: Tuesday April 23, 2002 10:46 AM
To: Franta, Jaroslav
Cc: Radsafe (E-mail)
Subject: RE: nuke navy - HMS Tireless
Jaroslav Franta wrote:
Maybe someone can provide more precise figures, but I seriously doubt the
whole premise that a submarine reactor can "melt down" -- simply because its
operating power is typically fairly low (compared to power plants), and
therefore the decay heating is low also.
Franta:
The power density in a naval nuclear power plant core should be comparable to
that of a commercial power reactor, i.e., around 100 MWth per cubic metre at
100% rated power. Assuming similar construction and the need to constrain H/U
atom ratio for maximum core life, the important differences are the mix and
activity concentration of fission products. In a core with low average power
level, the long lived fission products will be present in greater relative
amounts, but short lived fission products can be comparable after a run of a few
days at high power. Assuming comparable heat capacity and thermal conductivity
values for core materials, this could lead to similar temperature rises for
similar fission product activities.
Brian R. Gaulke, CHP
brian_gaulke@hc-sc.gc.ca