An arrangement for protecting an integrated circuit device (11) against latch up during a nuclear event comprising a capacitance (15) and a switch (17) connected in parallel across the power supply lines (13) of the device. When the power supply lines are connected to a power supply (19) the capacitance (15) stores energy sufficient to supply necessary operating currents to the device (11) during its normal operation. The switch (17) is arranged so that, under a transient gamma pulse incident thereon during a nuclear event, its impedance is set to a low value at such a rate that the energy stored by the capacitance is discharged through the switch and the voltage applied to the device (11) via the power supply lines is pulled down to such a level and at such a rate as to prevent transient gamma pulse induced latch-up in the device (11).