On Joe Gonyeau's "The Virtual Nuclear Tourist" site http://www.nucleartourist.com/type/candu2.htm he says:
"A second [CANDU] shutdown system is via gadolinium nitrate liquid "neutron poison" injection. Both systems operate via separate and independent trip logic.
The gadolinium nitrate system function is similar to that of the PWR high pressure safety injection system or the BWR standby liquid control system."
I think the function of the PWR HPIS is to make-up losses under loss-of coolant conditions, but may contain a neutron poison to guarantee shutdown. Guaranteeing shutdown is not the same as being a fast shutdown system.
At http://www.nrc.gov/reading-rm/doc-collections/gen-comm/info-notices/1991/in91012.html there is a brief description of the BWR STANDBY LIQUID CONTROL SYSTEM which says:
"The SLCS system is required to provide liquid poison [sodium pentaborate solution] in the event that control rod insertion is inadequate to achieve and maintain a cold [xenon-free] shutdown condition."
This is a pumped system, but does not sound as if it is a fast-acting means of shutdown.
From: Simon Day [mailto:firstname.lastname@example.org]
Sent: Friday August 02, 2002 2:18 PM
To: Canadian Nuclear Discussion List
Subject: Re: [cdn-nucl-l] cdn-nucl-l: poison injection as a fast
Ben, Adam, Jeremy and others who replied off list,
Thank you for the information on the CANDU SDS-2 system. Yes, that
Darlington figure of -55 mk stands out against the others.
So, following the non-CANDU road now, the impressions are that
poison injection is not used as a fast shutdown mechanism for PWRs or
even BWRs. Is this indeed the case and if not, the remaining question I
have is whether it is possible and if so how is it done, to inject
soluble poison into a high pressure system.
Fast shutdown systems for a PWR/BWR? Rods plus .... ? ..... One
thought was depressurization of the core as that would lead to voiding.
Interesting as that is a self-limiting type system. Thoughts?
Have a nice long weekend folks,
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