In order to assist with operation and design of higher-mark nuclear reactors, I propose the creation of a "coolant pump" block that, when placed next to either a nuclear reactor or reactor chamber block, can provide an additional 2 H/t of cooling to the reactor hull, consuming 5 EU/t to do so. Redstone current can be applied to shut down the pump, with operation resuming as soon as the current is removed. The block CANNOT be placed in such a way that it would border more than one reactor chamber or nuclear reactor, as a pump can only support a single reactor (one reactor can have multiple pumps, however).
The advantage of this would be to allow higher-efficiency reactors or breeder reactors to operate, as well as ease the design process by allowing the user to trade electrical output for thermal output, and/or maintain the reactor at a preferable temperature without completely starting or stopping the reaction process, something that is highly beneficial to efficient breeder reactor design.
Another option for the pump is to allow the pump to remove either 1, 2, 3, or 4 H/t at the cost of 2.5EU/t each, rounded up to the nearest integer amount, configured either via GUI switch or by placing redstone dust in 1, 2, 3, or 4 slots.