Securing the proliferation of wireless networks in 6G requires security-based signaling as a native component. This paper analyzes Physical Layer Security (PLS) applied to 6G Radio Access Networks (RAN) to enhance Layer-1 security. The description defines a PLS air interface and system model with AI/ML-based intelligent codebook generation and detection schemes. The paper also proposes an operational overview of AI/ML integrated PLS with shared key-agreement protocol in an O-RAN architecture for 6G security. Results include codebook generation details, the impact of MIMO antenna array size, and the key-Bit Error rate (BER) of 6G-PLS detection in the presence of eavesdroppers and Rayleigh fading plus noise.