Rods Group A I B II C III D IV E V X
[The 21 control rods are in a 5 x 5 grid where the four corners are empty. The very center rod is named X, the rods are then lettered concentricly. Up down left and right from X are A1 to A4, up-left, up-right, down-left and down-right diagonally from X are B1 to B4, up 2, down 2, left 2, and right 2 from X are C1 to C4, D and E are digagonally 2 like B. FIXME: This needs a diagram...] Group I is the preferred control group.
[This is important because the control rod drive is expecting to have to work against 1750 psig, but the system is at less than 600 psig.]
NOTE: A current curve of the operating band for the control group is kept in the Control Room by the Reactor Physicist.
The Start-Run switch shall remain in the START position at all primary system temperatures of 490F or below with the exception, as required for tests.
The startup rate (SUR) as indicated by the highest reading rate meter or level indicator is to be less than one (1.0) decade per minute.
The average rate of reactivity addition or subtraction from the reactor while at power, is dictated by the Doppler and temperature coefficients of reactivity. Measure ment to date indicate that the maximum load change (base load to full power or vice versa) amounts to about 50 cents of reactivity. Assuming that this reactivity is compensated for in one (1) minute by control rods, the maximum operating reactivity addition of subtraction rate is this 50 cents/min.
[Reactivity is like the gain of the reactor, the greater the reactivity the more likely that a particular neutron will create more neutrons (as opposed to leaving the reactor). It is measured in dollars, with a fraction of a dollar logicly being a cent. One dollar is the threshold of criticality (enough reactivity that the chain reaction sustains itself) including delayed (thermal) neutrons from later decay products. Two dollars is the threshold of prompt critical, which does not wait for the delayed neutrons. Prompt critical is too fast for a mechanical control rod to move fast enough to control, so typical reactors skate along at about a dollar, and inch above it to increase their power. Bombs are prompt critical.]
[The nuclear instrumentation has four types of detectors, no single detector has enough dynamic range to measure the entire power range of the reactor. As the reactor is started, one switches from the low power to the medium power detectors, to the high detectors. Their ranges overlap, so they are used to check each other, and that is what this is describing.]
[This is important because the cold feed water will cause thermal stress, and the temperature drop will abruptly increase the reactivity of the reactor.]
[I have also seen the numbers 70 MW and 72MW in other documents. I assume this 80MW number is definitive.]
[The reactor also has an automatic mode where the control rods will be automaticlly driven to throttle the reactor to follow the load. However other documents are very specific about informing the reactor operator before large changes to load.]