Re: Sellafield

[GlennACarlson@aol.com]

Malformed pellets will also affect the heat transfer characteristics of the 
fuel rod.  Hot (or cool) spots could be created.  Dominant impact would 
probably be unanticipated thermal stresses in and decreased structural 
strength of clad (in addition to possible mechanical stresses from fuel 
pellet swelling) and, possibly, in pellet itself.  When operated at power, 
heat transfer effects would become apparent sooner than pellet swelling 
effects.

Assuming no change in flow channel geometry (e.g., no bulging of weakened 
clad at location of malformed pellet), thermal-hydraulic impact would 
probably be small.

Glenn A. Carlson, P.E.
St. Peters, MO
glennacarlson@aol.com

In a message dated 3/7/2000 10:10:29 AM Central Standard Time, 
edward.w.bradley@prodigy.net writes:

<< Subj:     Re: Sellafield
 Date:  3/7/2000 10:10:29 AM Central Standard Time
 From:  edward.w.bradley@prodigy.net (Ed Bradley)
 
 Fuel pellets are generally cylindrical with concave ends.  This allows for
 expansion without undue stress on the fuel cladding/tube.  An uneven shape
 will put uneven stresses on the fuel tube and possibly lead to a tube
 failure and leakage of fission products.
 
 Ed Bradley, CHP
 >
 >   Dear Radsafers,
 >
 >             As you will all be aware, BNFL is going through the mill in
 > the UK media at present at its apparent short-circuiting of quality
 > control tests on MOX fuel pellets. The information gleaned from the more
 > responsible newspapers quite often highlights safety issues associated
 > with fuel pellets that were of variable sizes. Can any of you nuclear
 > power people out there tell me what the possible safety implications are
 > to a power plant using such malformed pellets. From what I gather each
 > pellet is only 13 mm long and should be cylindical in profile, but
 > according to the Independent today, many were flower-pot in profile. How
 > serious is this? Is it a potential safety issue or will it be more of a
 > problem in energy efficiency gain in the whole plant?
 >
 >  **************************************
 >  * David J. Hornsey, Radiation Safety.*
 >  * South Building,                    *
 >  * University of Bath                 *
 
  >>
************************************************************************
The RADSAFE Frequently Asked Questions list, archives and subscription
information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html