Re: Nuclear reactors

[Ludwik Kowalski <kowalskiL@MAIL.MONTCLAIR.EDU>]

Larry Woolf wrote:

> Some relevant information about inherently safe nuclear reactors.
>
> http://www.ga.com/triga/frtyears.html

Thanks for sharing. To distinguish my comments and questions
from what is quoted I will use upper cases.

1) "TRIGA, the most widely used research reactor in the world"

RESEARCH REACTORS ARE DIFFERENT FROM POWER
REACTORS. WHEN THEY REFER TO A 22,000 MW REACTROR
THEY PROBABLY MEAN THE POWER DURING A SHORT
PULSE, NOT THE AVERAGE POWER OVER MANY DAYS
OR WEEKS. CAN A 1000 MW POWER REACTOR BE MADE
"INHERENTLY SAFE" USING THE TRIGA APPROACH?

I HAVE TROUBLE WITH WHAT FOLLOWS BELOW.

2) "In meeting this challenge [of extreme safety], the idea of the
"warm neutron principle" was introduced as a first step towards
the design of an inherently safe reactor. In a water-cooled reactor,
the general result from suddenly removing the control rods is a
catastrophic accident, leading to a melting of the fuel."
SO FAR ALL IS CLEAR

"This is because the neutrons from the fission reaction remain
"cold" from interacting with the cold water around the fuel and
maintain their ability to cause further fissioning of uranium
atoms in the fuel."

WHY IS THE SUDDEN REMOVAL OF CONTROL RODS
CAUSING NEUTRONS TO "REMAIN COLD?" IT WOULD
BE BETTER TO SAY THAT NEUTRONS WHICH WOULD
BE ABSORBED IN CONTROL RODS ARE NOW ABLE TO
CAUSE FISSION? BUT THAT IS ONLY A SIDE COMMENT.

" This in turn results in the temperature of the fuel continuing
to increase rapidly until it finally melts." OK SO FAR.

" However TRIGA is no ordinary light water reactor because
much of its "moderation" of neutrons is due to the hydrogen
that is mixed in with the fuel itself. Therefore, as the fuel
temperature increases when the control rods are suddenly
removed, the neutrons inside the hydrogen-containing fuel rod
become warmer than the neutrons outside in the cold water."

FISSION NEUTRONS DO NOT ":BECOME" WARMER,
THEIR ENERGIES CAN ONLY GO DOWN AFTER
COLLIDING WITH HYDROGEN ATOMS. THE "BECOME
WARMER BECAUSE" MAKES NO SENSE TO ME.

"These warmer neutrons inside the fuel cause less fissioning in
the fuel and escape into the surrounding water."

LESS THAN WHAT? IS IT NOT TRUE THAT NEUTRONS
IN THE RODS WOULD HAVE HIGHER ENERGIES IF
HYDROGEN WAS NOT PRESET? NEUTRONS OF HIGHER
ENERGIES ARE LESS ABLE TO CAUSE FISSION (ON THE
AVERAGE) THAN WHEN HYDROGEN IS PRESENT. IN
OTHER WORDS, CONTRARY TO WHAT THEY SAY,
PRESENCE OF HYDROGEN MAKES NEUTRONS MORE
FISSIONING, NOT LESS FISSIONING.

" The end result is that the reactor automatically reduces power
within a few thousandths of a second, faster than any engineered
device can operate. In other words, the fuel rods themselves act
as an automatic power regulator, shutting the reactor down
without engineered devices."

I BELIEVE THEM BUT I DO NOT UNDERSTAND THEIR
EXPLANATION. AM I THE ONLY ONE TO WHOM THIS
TEXT SEEMS TO BE AN EMPTY TALK BY A PUBLIC
RELATION PERSON WHO IS NOT A PHYSICIST?
Ludwik Kowalski