As the safety and reliability requirements for Nuclear Power Plants continue to intensify, the communication infrastructure of Safety Distributed Control Systems (Safety-DCS) has become a critical technical challenge. The increasing number of network nodes and the growing volume of transmitted data complicate the network architecture of Safety-DCS systems. Consequently, there is an urgent need to reduce system complexity while enhancing the security of communication transmissions. This paper introduces an innovative communication architecture based on orthogonal coding, which simplifies system design by enabling multiple nodes to share a common transmission medium, thus alleviating the complexity associated with allocating dedicated communication channels to each node. In addition, the proposed coding scheme incorporates inherent physical-layer security, thereby significantly improving data transmission security and ensuring the protection of sensitive operational data from potential threats. The study demonstrates the considerable potential of orthogonal coding to enhance both the communication efficiency and security of Safety-DCS, providing a novel framework for the design references of next-generation communication infrastructures in Nuclear Power Plants.