At Catawba Nuclear Station, we also trip the reactor if more than 1 rod drops.
For beginning of cycle reactor startup including low power physics testing and for mid-cycle reactor startups, our requirement is to reinsert rod banks if a single rod drop occurs. For BOC, requirement applies as long as we are in the test procedure for low power physics testing. For other reactor startups, we have a test procedure for approach to criticality (in addition to the normal operating procedure). The requirement to reinsert rod banks if a single rod drop occurs is applicable while we are in the test procedure for reactor startup.
In both cases once we are out of the test procedure for reactor startup and back into the normal operating procedure for unit startup, there is no shutdown requirement for a single dropped rod. Effectively, our definition of startup for the purposes of response to single dropped rod is "while in test procedure for reactor startup/physics testing"
The transition from test procedure to operating procedure occurs at approximately 10-8 amps on intermediate range, about a decade below point of adding heat.
Other potential definitions of reactor startup with respect to single dropped rod could be:
1. Mode 2, k-eff < 1 2. Mode 2, below point of adding heat 3. Mode 2
Except for physics testing, the time spent in mode 2 during reactor startup is usually so small that it doesn't make much difference which definition you use. I do not think it is necessary to extend definition of reactor startup into mode 1.
Dan Wellbaum Reactor Engineering Catawba Nuclear Station
________________________________ From: pwrrm@retaqs.com To: pwrrm@retaqs.com Sent: Tue Nov 04 09:02:17 2008 Subject: [Pwrrm] Definition of When Startup is Complete
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
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Joseph E. Willett, P.E.
Principal Reactor Engineer-Fuel
Nuclear Operations Division
E-mail: jwillett@oppd.commailto:jwillett@oppd.com%20
Omaha Public Power District Phone: (402) 533-7213
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