atw - International Journal for Nuclear Power | 11/12.2019

atw Vol. 64 (2019) | Issue 11/12 ı November/December
FEATURE | ENVIRONMENT AND SAFETY 518
based on the workers’ activity, most often based on the
PSFs. This is because PSFs characterize the important
aspects of human error and provide numerical criteria for
adjusting the average HEP level [9]. Therefore, the key
step in the HRA for decommissioning activities of a nuclear
power plant is to select appropriate PSFs, develop the
classification system, and quantify their impacts on the
decommissioning activity.
3.1 Criteria for selecting PSFs
When selecting PSFs that affect the decommissioning
activities of nuclear plants, it is important to carefully
select all the important situational factors that affect the
hazard level so as to not miss any of the factors. In addition,
it should be ensured that there is no overlap in the meaning
and scope of the PSFs; furthermore, the factors should be
selected based on their actual effect on human error
analysis. Therefore, the PSFs are selected for the HRA of
the decommissioning activities of the nuclear power plant
considering the following criteria.
p The PSFs should be selected to appropriately reflect the
work characteristics. Therefore, the TA results of the
work should be fully reflected by the PSFs.
p The internal and external factors that might affect
the workers’ performance should be comprehensively
considered.
p When a worker encounters an abnormal event, the
internal factors should be included in the PSFs
appro priately to account for the reactions that occur
naturally in workers, including physical, cognitive, and
emotional factors.
p The external factors should comprehensively include
those that directly or indirectly affect the workers’
response to performance, i.e., the business organization
and work environment factors, among others.
p Based on previous research results, in our case, the
PSFs will consist of three levels (namely, Level 1, Level
2, and Level 3). Though there are direct and indirect
dependencies between the PSFs in Level 1 and Level 2,
the PSFs are selected in a manner that there is no
dependency between the Level 3 PSFs.
p In practice, the PSFs are selected based on factors
that directly affect the trends of the ongoing events.
Therefore, factors such as workers’ training and work
shifts, among others, indirectly affecting the work
performance of the workers, are excluded from the PSF
Classification Direct effect Indirect effect
Personal Factors
System factors
Task factors
| Tab. 3.
Derived PSF factor.
• Duration of mental stress
• Mental tension
• Pain or discomfort
• Hunger or thirst
• Emotional state
• Duration of physical stress
• Disruption of circadian rhythm
• Lack of sleep
• Work hours
• Shift rotation
• Suddenness of onset
• State of current practice or skill
• Motivation and attitudes
• Personality and
intelligence variables
knowledge of required
performance previous
training/experience
• Sensory deprivation
• Distractions (noise, glare,
movement, flicker. color)
• Complexity
• Movement constriction
• Workplace layout
• Threats of failure
• Lack of physical exercise
• High jeopardy risk
• Conflicts of motives
about job performance
selection because they are considered to be inherent in
the other PSFs themselves.
p The PSFs should have clear definitions so that their
meanings and roles do not overlap. Therefore, as much
as possible, the scale of the PSFs should be reduced by
grouping all the PSFs and reducing the number of tasks
involved.
3.2 Selection and definition of PSFs
Based on our review of existing literature related to the
work performances of individual workers from various
industrial fields, we observed that it is not easy to find
a consensus on the factors influencing the workers’
performance. However, considering the results of these
previous studies, it is deemed that the possibility for human
error can be determined based on the degradation of the
workers’ human error factor, i.e., their task performance.
The Institute of Nuclear Power Operations (INPO)
presents 85 error precursors that can lead to possible
human errors considering the business requirements, personal
abilities, work environments, and human nature in
terms of the operation of the nuclear power plants [10].
These precursors are considered as the risk variables for
human errors made by workers.
Therefore, it is realistic to utilize an Error Precursor,
i.e., PSF, that affects work performance. While estimating
the probability of human error, it is desirable to add
psychological factors that cannot be directly managed
after the possibility of human error for manageable
factors is reduced through safety management or accident
prevention activities. The PSFs extracted for use in the
human error assessment model in this study are listed
in Table 3 below.
3.3 Development of a classification system
for PSFs
TA was conducted to derive the PSFs for RPVI cutting,
which is one of the primary tasks involved in the
decommissioning of nuclear power plants. Because it is
difficult to select PSFs such that their meanings and roles
are clearly delineated, the PSFs are classified into three
major categories, which are defined by their task analysis
results. In other words, the human factors of the workers
themselves, the operating system factors related to the
work, and the ergonomic factors linking the worker and
the dismantling activities were suitably classified.
In particular, an important aspect of the TA is “Human,”
i.e., a worker who performs the task of decommissioning
the RPV and can cause human errors. It is noteworthy
that human factors are important to consider not only
in the field of nuclear power generation, but also, in
other industrial fields, such as the railways and aviation
[11-16].
p Supervisors and workers might be affected psychologically
while performing the tasks described above.
Because the cutting process takes considerable time, it
is important to consider the various stresses and
emotional conditions that supervisors and workers
might experience.
p In particular, the work environment and conditions for
the cutting task in normal or abnormal situations affect
the workers’ physical and physiological factors. Thus, to
perform the RPVI cutting tasks, wearing the appropriate,
protective work clothes and protective cap
and having good physical and health conditions to
carry or handle the equipment are considered important.
Furthermore, while performing the tasks, the
Feature
Development of Performance Shaping Factors for Human Error Reduction during Reactor Decommissioning Activities through the Task Analysis Method ı Byung-Sik Lee, Hyun-Jae Yoo and Chang-Su Nam