The Research On Human Reliability Analysis Technique In Probabilistic Safety Assessment

Human errors/human-caused accidents are the major cause for the accidents in large-scale man-machine system, so human reliability analysis (HRA) has become an important part of probabilistic safety assessment (PSA). Due to the complexity of HRA object and the variety and immaturity of its techniques the HRA result possesses great uncertainty which has a great influence and impact upon the credibility and quality of PSA. The problem has received high attention from International Atomic Energy Association (IAEA) and safety management area but remains unresolved.A cognitive behavior model of large-scale complicated man-machine systems is established through the analysis upon their operational control characteristics. The classification and formation mechanism of human errors in them are analyzed on the basis of the above study and the main factors causing human errors of large-scale complicated man-machine systems are obtained. Therefore, a human error structure model and a human error formation model are brought forward to settle a theoretical foundation for HRA technique.The paper finds that only an available, usable and reliable HRA method can play complete part in PSA through an analysis of the fundamental demand of PSA upon HRA. Availability includes perfectiveness, integrality, accuracy and sensitiveness. Usability involves easy-to-use, a ready procedure, applicability and widely acceptable data. Reliability concerns a consistent result, credible data, a probative model and hypothesis and a comparable result, which has been further proved through research by making comparisons on present 12 major HRA techniques.This paper builds a HRA guiding standard on the basic framework of availability, usability and reliability. According to the standard a standardized HRA technique is established in PSA. This technique is composed of three parts: standardized model, standardized procedure and standardized basic data. The model adopted is a THERP+HCR Mode which is made up of models of THERP and HCR. The diagnosis actions closely related to time are analyzed by HCR while the actions of observation and operation which are not closely related to time by THERP. These two are mutually complementary while time function is used to be a joint to construct an organic whole.The procedure includes those of pre-accident HRA, initiating events HRA and post-accident HRA which cover the whole course of an accident. Basic data include data collection basic guide and data management system. The standardized HRA technique can eliminate the defects of HRA/PSA to the greatest extent under nowadays conditions . A HRA case is used to make an illustration in the paper.An operator reliability experiment was firstly conducted in a real nuclear power plant full-size simulator in China. Three cognitive patterns of skill-based, rule-based and knowledge-based involving 23 abnormal events (55 human system interactions) which are closely related to the plant safety were included in the experiment. 38 operators' response conditions and times were kinescoped and recorded and 764 data points were collected. All these data were processed and analyzed to acquire the HRA/HCR Model basic parameters adaptable to Qinshan Nuclear Power Plant system and personnel.The standardized HRA technique and human reliability data acquired in simulator experiment have been reviewed by IAEA and adopted by Qinshan Nuclear Power Plant HRA/PSA project and can be widely used in other areas.