At VC Summer we only trip with a single dropped rod if we are in startup physics testing. This is defined as entry into the Tech Spec Special Test Exceptions. The Exceptions allow relaxing the minimum temperature for criticality and the rod insertion limits. The reason for tripping with a dropped rod is that you could potentially have control rods in a strange configuration (especially during rod swap testing, etc.) which is not specifically analyzed in the safety analysis (especially shutdown margin). I agree with the concern about going subcritical, but our procedures address that by requiring a shutdown (not necessarily a trip) if you go on the source range nuclear instruments inadvertently.
Damon Bryson (803) 345-4814 dbryson@scana.com
-----Original Message----- From: pwrrm@retaqs.com [mailto:pwrrm@retaqs.com] On Behalf Of Rob.McAndrew@dom.com Sent: Tuesday, November 04, 2008 11:55 AM To: PWR Reactivity Management Subject: Re: [Pwrrm] Definition of When Startup is Complete
North Anna's AP will have the operator trip the reactor with more than one rod dropped. There is no guidance on tripping or not tripping the reactor depending on what power level the reactor is at or whether a startup is in progress. It does make sense to me though that tripping the reactor with a dropped rod during startup is the right thing to do. If I were going to define"startup" in the context of a dropped rod recovery, I would include the approach to critical and operation below the POAH. Maybe up to 5%. My concern is that the dropped rod could take the reactor subcritical and pulling it could be an approach to critical outside of a procedure. Due to temperature feedback, this would not be as likely in the power range. Our reactor is quite stable at 7% on the steam dumps so that would be where I might call the end of startup. Rob McAndrew 540-894-2859
"WILLETT, JOSEPH
E"
<jwillett@oppd.co To m> pwrrm@retaqs.com
Sent by: cc pwrrm@retaqs.com
Subject [Pwrrm] Definition of When Startup 11/04/2008 09:02 is Complete
AM
Please respond to
PWR Reactivity
Management
<pwrrm@retaqs.com
>
FCS has two requirements regarding a dropped rod. First, if we drop more than one rod at power, we trip the reactor. Second, if we drop a single rod during startup, we trip the reactor. What we don't have is a definition of when startup is considered complete, with regards to a dropped rod.
Do other plants have similar requirements and do you have a definition of when startup is complete with regards to a dropped rod?
J. E. Willett
----------------------------------------------------
Joseph E. Willett, P.E.
Principal Reactor Engineer-Fuel
Nuclear Operations Division
E-mail: jwillett@oppd.com
Omaha Public Power District Phone: (402) 533-7213
Fort Calhoun Station Pager: (402) 561-3899
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