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Reference, Questions and Help => Nuke Q&A => Topic started by: brettj22 on May 22, 2012, 12:57

Title: MTC for CE PWR's
Post by: brettj22 on May 22, 2012, 12:57

As part of a paper I'm writing I reviewed PWR operating licenses at the NRC's web site looking for MTC limits.  I've noticed that some tech spec plots of MTC for CE PWR's (Calvert Cliffs, Fort Calhoun, Millstone-2, St. Lucie-1) lead me to believe that a positive MTC is allowed at 100% power.  For example, the plot in the Calvert Cliffs Tech Specs appears to identify the 100% power limit as +0.15e-4.

Am I reading this correctly?

Thank you!

Title: Re: MTC for CE PWR's
Post by: Fermi2 on May 22, 2012, 06:33

It looks like it depends on whether they use digital or analog systems.

Digital at 100% cannot be positive.

Analog it looks like it depends on the COLR.

I'm basing this on STS.

Title: Re: MTC for CE PWR's
Post by: SmallTownNuke on Oct 30, 2012, 11:17

A slightly positive MTC is allowed at the very beginning of core life, however the overall temperature coefficient remains negative due to the FTC.  This is based off of Fort Calhoun.  Interestingly, the larger issue with MTC is the limit of how negative it can be at the end of life due to main steam line breaks (uncontrolled heat extraction).

Title: Re: MTC for CE PWR's
Post by: Fermi2 on Oct 31, 2012, 05:25

Quote from: SmallTownNuke on Oct 30, 2012, 11:17

A slightly positive MTC is allowed at the very beginning of core life, however the overall temperature coefficient remains negative due to the FTC.  This is based off of Fort Calhoun.  Interestingly, the larger issue with MTC is the limit of how negative it can be at the end of life due to main steam line breaks (uncontrolled heat extraction).

No uncontrolled reactivity addition due to rapid cooldown from hotstandby to the extent you are outside your ability for boron to control it. There IS a difference.