HEART technique for Quantitative Human Error Assessment

The Human Error Assessment and Reduction Technique (HEART) was developed by Williams in 1986. Since that time it has been widely used within the UK and continental Europe for the purposes of assessing human reliability.

HEART is an easily-used form of human reliability assessment that has been used by a number of organisations since its development. This technique, which is derived from a wide range of findings in the ergonomics literature, has been designed to be simple and easily understood. It assumes that basic human reliability is dependent upon the generic nature of the task to be performed. and that under 'perfect' conditions this level of reliability will tend to be achieved consistently. HEART also assumes that any predicted reliability of task performance may be expected to change as a function of the extent to which identified Error Producing Conditions (EPC) might apply.

HEART identifies nine generic task types and proposes nominal human unreliability values and their suggested bounding values, together with thirty eight Error Producing Conditions. Depending on the amount by which the EPCs are judged to affect the predicted unreliability a selection of error reduction strategies are suggested to combat the most deleterious effects of any identified EPC.

Synergy Experience with HEART

HEART Applications

• Synergy has used HEART in a number of nuclear industry PSA studies. In the last two years, Synergy has applied HEART in the following installations to support PSAs:
  
• Nuclear submarine refit facilities at Devonport for DML. This included the assessment of both process control operations and the physical tasks necessary when dismantling and re-assembling reactor plant.
  
• Weapons handling in connection with UK submarines
  
• Transportation and storage of nuclear waste for NIREX UK
  
• Assessment of refuelling operations at Heysham and Hartlepool Nuclear Power Stations
  
• Manufacture of Reactor Cores at Rolls Royce, Derby
  

Assessment of human operations during various nuclear emergencies at Heysham Nuclear Power Station.

HEART Theoretical Development

Synergy has been closely involved in developments of the technique, particularly as follows:

• The integration of HEART with THERP (the other most widely used HRA Technique in nuclear-related PSAs).
  
• Taking account of dependency in HRA
  
• The assessment of cognitive tasks and predicting their reliability
  

The measurement and prediction of human violations

HEART Source Data

Synergy staff have undertaken a number of the experiments and practical studies which have been used as source data for the HEART method. This includes studies of inspection tasks, simulated process plant fault diagnosis, and the study of operators in nuclear plant simulators.
Synergy has also made influential contributions to the study and application of task analysis methods, particularly those methods which are used in the study of complex process operations. Task analysis is an important ingredient in the application of HEART.

The HEART Process