Loading...

Probabilistic safety assessment of a UF 6 production process

Ebrahimi, B ; Sharif University of Technology | 2012

1985 Viewed
  1. Type of Document: Article
  2. Publisher: 2012
  3. Abstract:
  4. Application of Probabilistic Safety Assessment (PSA) to a Uranium hexafluoride (UF 6) production process is presented in this paper. The process is constituted from three main units: UF 4 conversion to UF 6, condensation of produced UF 6 gas and tail gas treatment. Radioactive gas is present in all parts of the process and occurrence of high pressure or high temperature in the process equipments may lead to radioactive release to workplace and environment. The work is mainly based on PSA experience in nuclear power plants. Accordingly for the process, eight group of Initiating Events (IE) that lead to UF 6 gas release have been identified using HAZOP study. For each IE, based on related safety systems and functions, accident sequence analysis is performed with Event Tree Analysis (ETA). Safety systems and functions failure probability is calculated with Fault Tree Analysis (FTA). Due to greater reliance placed on operator in Non-Reactor Nuclear Facilities (NRNF) compared to NPPs, special consideration is taken into account for human Reliability Analysis (HRA). HRA is performed according to Swain and Guttman method (i.e. THERP) described in NUREG/CR-1278. Results of the study show frequency of 3.77E-04 (1/year) for radioactive gas release in the process. Considering worst possible condition for radioactive source term released in the workplace, maximum dose exposure for operator is 10 mSv. According to internationally accepted Probabilistic Safety Criteria (PSC) for Non-Reactor Nuclear Facilities (NRNF), the plant risk is acceptable. However using two importance measures namely Fussel-Vesely and Birnbaum importance, suggestions for safety improvement of plant are provided. Fussel-Vesely measure shows great contribution of human errors in plant risk which could be reduced by further training. Birnbaum measure on the other hand shows importance of CCFs which could be alleviated using diversity in equipments or changes in test and maintenance policy
  5. Keywords:
  6. Birnbaum ; Birnbaum importance ; Dose exposure ; Event tree analysis ; Failure Probability ; Gas release ; High pressure ; High temperature ; Human errors ; Human reliability analysis ; Importance measure ; Initiating events ; Maintenance policy ; Nuclear facilities ; Probabilistic safety ; Probabilistic safety assessment ; Process equipments ; Production process ; Radioactive gas ; Radioactive release ; Radioactive sources ; Safety improvement ; Sequence analysis ; Tail gas ; Uranium hexafluorides ; Fault tree analysis ; Maintenance ; Nuclear power plants ; Production engineering ; Radioactivity ; Reliability analysis ; Risk management ; Safety engineering ; Security systems ; Uranium ; Gases
  7. Source: Advances in Safety, Reliability and Risk Management - Proceedings of the European Safety and Reliability Conference, ESREL 2011 ; 2012 , Pages 1384-1389 ; 9780415683791 (ISBN)
  8. URL: http://www.crcnetbase.com/doi/abs/10.1201/b11433-195