Lives are threatened whenever there is an act of theft or destruction against a nuclear and radiological facility thus, physical protection systems are effectively employed to prevent or mitigate loss of valuable assets. Health facilities that provide radiotherapy services have in their facility a temporary storage unit where disused radioactive sources 60Co, 137Cs and 192Ir are kept and this raises concerns for effective physical protection. An integrated physical protection System was considered to consolidate of all sub systems, sensors and elements related to protection system for an effectively secured environment at a radiological facility. Sequence adversary diagram (ASD) was developed to depict the paths that enemies can take to achieve sabotage or stealing objectives and analyze flews in the paths. The approach to this security system effectiveness focuses on using probabilistic statistical methods for risk evaluation considering detection, delays and response. This paper considers the basic and effective elements required for physical protection system for a radiological center and makes risk evaluation as an approach of security system effectiveness which can serve as fundamental guiding principle for decision makers in the establishment of an effective physical protection for a radiological center.