Destroy three power sources | Forerunner Halo 4 Guide

In this are you find three power sources. First one on the right from entrance, two more on the other side. In the room with those sources you can find also ammo.

When you destroy all targets, a portal opens between two cores opposite to the entrance. Go two levels upside. Activate an elevator at the end of bridge, which leads to source of radiation. Turn it off and go through the portal.