<p>Radiation protection is a critical pillar supporting the use of nuclear energy and nuclear technologies. The radiation protection system has been established with the accumulation of knowledge and experience. However, it is challenging for an individual or even a committee to master related knowledge and experience comprehensively and meticulously. An intelligent assistant that possesses extensive knowledge and experience in radiation protection is eagerly required. In this work, we propose an intelligent assistant in radiation protection based on a Large Language Model (LLM) with a knowledge base. The assistant can provide reliable answers with references from authoritative publications. The assistant was developed using open-source toolkits and open-source LLMs, and demonstrated satisfying answers to professional queries. Users can obtain reliable answers with references through the web-based user interface (UI). The assistant is designed for local deployment and utilizes private datasets, thereby addressing issues related to privacy and data security. The effectiveness of the assistant was evaluated by comparing it with LLM applications with web search. The results show that our method with a much smaller number of model parameters can deliver more precise and pertinent responses within the domain of radiation protection than web search-based systems. This work is a preliminary attempt to establish an intelligent assistant in the field of radiation protection, and it shows the potential for using LLM to increase efficiency in radiation protection-related tasks.</p>