Complex sentence: On 12 December 1942 CP-1's power output was increased to 200 W, enough to power a light bulb; but lacking shielding of any kind, it was a radiation hazard for everyone in the vicinity.
Split into simpler sentences: On 12 December 1942 CP-1's power output was increased to 200 W, enough to power a light bulb. Lacking shielding of any kind, it was a radiation hazard for everyone in the vicinity.