[ RadSafe ] FW: Off list reply: Re: BWR SCRAM sequence

[Doug Aitken]

I received this reply from a colleague that clearly sets to rest the
question and I thought it would be good to share it.

Many thanks!

Regards

Doug

 

Doug,

No. The boron and other neutron absorbers in the control rods already
inserted into the core(s) coupled with the very low enrichment of the fuel
and the burnable neutron absorbers used therein will not at all allow a
re-criticality. A similar analysis applies to the fuel in the spent fuel
pools. Things are going to be very hot for a while, and we want them to keep
water on whatever the geometry is of the core(s)/spent fuel to keep the hot
fission products from vaporizing/volatizing  and escaping into the
atmosphere. Fortunately, a re-criticality is not an issue in any of this
tragedy. 

Doug Aitken wrote: 

As a person with only a basic understanding of the workings of these
reactors, any detail will be very welcome.
One question I keep getting is what happens if the rods melt and pool in the
base of the containment. Will the mass of material go critical? 
 
Regards
Doug
 
Doug Aitken
QHSE Advisor, Schlumberger D&M Operations Support
Cell Phone: 713-562-8585
(alternate e-mail: doug.aitken at slb.com )
Mail: c/o Therese Wigzell,
Schlumberger,
Drilling & Measurements HQ,
300 Schlumberger Drive, MD15,
Sugar Land, Texas 77478
 
 
 
-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu
[mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of James Barnes
Sent: Thursday, March 17, 2011 8:30 AM
To: radsafe at health.phys.iit.edu
Subject: [ RadSafe ] BWR SCRAM sequence
 
Dear all;
 
Being primarily a PWR HP, I was hoping some of you BWR types might help me
with something.
 
During a normal SCRAM on a BWR, am I correct in assuming that the steam
generated by the reactor is shunted directly to the turbine condenser so it
can be used as a heat sink?
 
Can somebody walk me thorugh the sequence of SCRAM to cold shutdown as to
how the various systems are activated and approximately what conditions
trigger those systems?
 
This is during a "routine" SCRAM (sudden rod insertion) resulting in the
system being taken to cold shutdown.  Not a LOCA or some other type
of outlier event.
 
Thanks,
 
James Barnes
_______________________________________________
You are currently subscribed to the RadSafe mailing list
 
Before posting a message to RadSafe be sure to have read and understood the
RadSafe rules. These can be found at:
http://health.phys.iit.edu/radsaferules.html
 
For information on how to subscribe or unsubscribe and other settings visit:
http://health.phys.iit.edu
 
_______________________________________________
You are currently subscribed to the RadSafe mailing list
 
Before posting a message to RadSafe be sure to have read and understood the
RadSafe rules. These can be found at:
http://health.phys.iit.edu/radsaferules.html
 
For information on how to subscribe or unsubscribe and other settings visit:
http://health.phys.iit.edu