Systems, methods and apparatus including an electrical penetration assembly for coupling a plurality of photo-multiplier tubes (PMTs) inside of a tub enclosure of a nuclear detector with an acquisition electronics system (AES) outside of the tub enclosure. The electrical penetration assembly may include at least one flex circuit, a plurality of flex circuit-PMT connectors, at least one flex circuit-AES connector, a flex circuit guide, a tub-penetration mechanical support, a support-to-tub retention mechanism, and a light seal.