 The 12 finger ones are more reactive and only used for shutdown, while the 4 finger CEAs are used to control reactivity smoothly during operation.The System 80+ in 1993 was considered by members of the American Nuclear Society as the "premier" burner of weapons grade plutonium, as the reactor design can handle a full inventory of MOX plutonium.After the Cold War ended, 100 tons of surplus weapons grade plutonium existed and the System 80+ was assessed to be the best available way to "denature" it beyond use in typical bomb designs, the "burning"/fissioning process would produce reactor grade plutonium, which while still a security concern, it is considerably diminished.