PSAM 203 Topical Conference in Tokyo OS-VIII : Human Factors and (#08) Human Reliability Analysis of Ultimate Response Guideline in a Compound Disaster Kang-Hung Liu, Sheue-Ling Hwang, Tsu-Mu Kao and Hui-Wen Huang Institute of Nuclear Energy Research (INER), Taiwan National Tsing-Hua University (NTHU), Taiwan Hyatt Regency Tokyo, Japan April 6, 203
Before the Fukushima nuclear accident, when an accident or a severe accident occurred, operators in nuclear power plant should follow emergency operating procedures (EOPs) or severe accident management guidance (SAMG). EOP and SAMG are symptom-basis procedures to cope with severe transient and accident, and also real-time operational parameters dependency. However, during a station blackout (SBO), EOP and SAMG may not be able to be successfully performed because most of plant parameters are not available to be monitored. To ensure safety of reactor and spent fuel pool, the ultimate response guideline () was developed to manage accidents caused by the compound disaster beyond design basis. Page 2
The core concept of is treats accidents beyond design basis as off-normal or abnormal events Ultimate Response Guideline () Page 3
Launch -Process Page 4
Simplified Plant Analysis Risk Human Reliability Assessment (SPAR-H), a method, was developed to assess human error probabilities (HEPs) in NPPs The important aspect of the SPAR-H method is that human activity is assigned to one of two general task categories, action and diagnosis. The analysis method is based on eight performance shaping factors (PSF) that encapsulate the majority of the contributors to human error SPAR-H Page
PSFs PSF Levels Multiplier for Multiplier for Available Time Inadequate time Diagnosis Action P(failure) =.0 P(failure) =.0 Barely adequate time ( 2/3 x nominal) 0 Nominal time When less than three negative multiple PSFs are presented Extra time(between and 2x nominal & >30 min) 0. 0. to 0.0 Expansive time > 2x nominal & >30 min Stress/ Stressors Complexity Experience/ Training When three or more than three negative multiple PSFs are presented Procedures Ergonomics/ HMI Fitness for Duty SPAR-H Wore Process 0 0. 0.0 Extreme High Normal Highly complex Moderately complex Nominal Obvious diagnosis Low Normal High Not available Incomplete Available, but poor Normal Diagnostic/ symptom oriented Missing/Misleading Poor Normal Good Unfit 2 2 2 2 0. 0 3 0. 0. 0 0 20 20 0. 0 0 0 0 0. 0. P(failure) =.0 P(failure) =.0 Degraded Fitness Normal Poor Normal Good 2 0.8 0. Page 6
The summary of each PSF in Fukushima Daiichi accident PSFs Available Time Stress/ Stressors Conditions In most cases, there is extra time. Such severe accident could endanger social safety. Facing the dilemma of social safety or loss of assets. Complexity - Experience/ Training - Procedures Ergonomics/ HMI - Fitness for Duty - Work Processes - Many variables such as disaster situations, social responsibility, assets of company, and external assistance, are involved with concurrent diagnoses. OSP (off-site power) restoration was not available due to damage. SAMG countermeasures in late 990s and has been use in Japan. Following SAMG and EOP. Unable to control in extended SBO condition from MCR. Only a few plant parameters available to monitor. Damage made it very difficult to access systems and components, which delayed actions. The fitness for duty of the crew is plant and crew specific. This analysis was determined from a generic model and therefore nominal is an appropriate choice. The work processes are plant and crew specific. This analysis was determined from a generic model and therefore nominal is an appropriate choice. in Severe Accident Management Page 7
event tree with severe accident for NPP Reactor water level keeps dropping or Station blackout Diagnosis Operator diagnoses event Unpurified water Continuous venting Available Service freshtime water 0. Extra time > 30 min injection permission Depressurize reactor of containment injection Stress/ Such severe accident could authorized Stressors Complexity Experience/ Training Procedures Ergonomics/ HMIS F Fitness for Duty 0.844 0. S(Sucess) S F Work Processes Action Reservoir gravity injection endanger social safety. Normal. 0. Extensive training and experience. Fire engine with creek Normal. or seawater Such severe injection # STATE accident could endanger social safety. Normal. 3 No training for SBO OK Normal. Normal. OK 2 Only a few plant parameters available to Unable to control in extended SBO(Station 0 0 S monitor. Blackout) condition from MCR. OK 3 F S The fitness for duty of the crew is plant The fitness for duty of the crew is plant and S and crew specific. This analysis was crew specific. This analysis was determined F 4 thereforex nominal determined from a generic model and from a generic model and F therefore nominal is an appropriate choice. is an appropriate choice. S X The work processes are plant and crew The work processes areplant and crew F specific. This analysis was determined specific. This analysis was determined from from a generic model and therefore a generic model and therefore nominal is an X 6 nominal is an appropriate choice. appropriate choice. F(Failure) HEP 0.02 7 X 8 X 0.30 in Severe Accident Management Page 8
in Severe Accident Management Page 9
00.00% 9.00% Human reliability 89.69% 90.00% 86.87% 8.00% 88.42% 8.07% Vice president Plant manager 80.00% 77.4% 7.00% 74.2% 70.00% Low Nominal Training level High The human reliability of with different training levels of staffs and different decision maker Page 0
With a new concept of severe accident management, provides a generic and safety procedures to follow when severe accident happened. With current conditions, the training level of staffs and the decision maker in NPP, the human reliability of procedures analysed by SPAR-H is about 8%~86%. It s a feasible alternative to manage severe accident beyond design basis. However, forming a complete set is needed to reduce the HEP. To upgrade training level of staffs or to help plant manager make decision of executing will enhance the human reliability of procedures. Page
Page 2