Re: [Phys-l] Japan situation : information, or lack thereof

[Bill Nettles <bnettles@uu.edu>]

> -----Original Message-----
> From: phys-l-bounces@carnot.physics.buffalo.edu [mailto:phys-l-
> bounces@carnot.physics.buffalo.edu] On Behalf Of Hugh Haskell
> Sent: Tuesday, May 03, 2011 9:59 PM
> To: Forum for Physics Educators
> Subject: Re: [Phys-l] Japan situation : information, or lack thereof
Snip...
> It is true that Enterprise has 8 reactors, but I have not heard that
> it ever got down to one operating reactor. I served on board
> Enterprise (albeit not in the reactor department) from 1967-69, at
> the tail end of a fuel cycle (I left the ship as is pulled into
> Norfolk for its second refueling). The reactor officer was a friend
> of mine and so I knew something about how the reactors were
> operating, since the fuel was nearing the end of its useful life he
> had to nurse the reactors with some care. If they were put under much
> stress the xenon fraction in the fuel rods would zoom up and the
> reactors could scram due to the high neutron capture x-section of
> xenon, so our maneuvering was somewhat limited, and all major power
> changes had to be scheduled in advance so as to avoid the xenon
> effect. But I do not believe that any of the reactors ever shut down
> other than intentionally while I was on board. This may have happened
> either before or after my time, but not while I was there.

[Bill Nettles] "Scram" is a technical term referring to the forced shutdown of the chain reaction by inserting the control rods.  What you are referring to is called xenon poisoning and sub-criticality.
   Snip
> I don't look
> forward to one of those ships being sunk and spilling its nuclear
> fuel all over the bottom of the ocean.
[Bill Nettles] The sites of the Thresher and Scorpion accidents have been measured for years with no signs of leakage from the reactors. The nuclear fuel itself in Naval Reactors is designed to maintain integrity with extreme shock loads, (much higher than any earthquake). Even if the reactor vessel was breached in a battle, the actual fuel would remain inside the elements (which would sink quickly). I think your statement "all over the bottom of the ocean" is hyperbole. The fuel wouldn't be dispersed. It's not "loose" like commercial fuel.

> I think the Enterprise reactors were BWR, but I'm not sure. 
[Bill Nettles] No, all Naval reactors, except the original Seawolf, have been and are PWR.

[Snip]

> I often wondered about this but didn't
> know enough about reactor technology at the time to ask the proper
> questions.

 [Bill Nettles] They wouldn't have told you depending on need to know. Actual operating parameters are classified material. But sizing factors and maintenance issues play a big role in determining what is used in those plants.