- Nuclear Science and Engineering.
- Presley, Mary R
- George E. Apostolakis. Massachusetts Institute of Technology. Dept. of Nuclear Science and Engineering. Massachusetts Institute of Technology. Dept. of
Nuclear Science and Engineering.
- 115 p.
- Massachusetts Institute of Technology
- M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See
provided URL for inquiries about permission.
- Quantification of human error probabilities (HEPs)
for the purpose of human reliability assessment (HRA) is very
complex. Because of this complexity, the state of the art includes
a variety of HRA models, each with its own objectives, scope and
quantification method. In addition to varying methods of
quantification, each model is replete with its own terminology and
categorizations, therefore making comparison across models
exceedingly difficult. This paper demonstrates the capabilities and
limitations of two prominent HRA models: the Electric Power
Research Institute (EPRI) HRA Calculator (using the HRC/ORE and
Cause Based Decision Tree methods), used widely in industry, and A
Technique for Human Error Analysis (ATHEANA), developed by the US
Nuclear Regulatory Commission. This demonstration includes a brief
description of the two models, a comparison of what they
incorporate in HEP quantification, a "translation" of
terminologies, and examples of their capabilities via the Halden
Task Complexity experiments. Possible ways to incorporate learning
from simulator experiments, such as those at Halden, to improve the
quantification methods are also addressed. The primary difference
between ATHEANA and the EPRI HRA Calculator is in their objectives.
EPRI's objective is to provide a method that is not overly resource
intensive and can be used by a PRA analyst without significant HRA
experience. Consequently, EPRI quantifies HEPs using time
reliability curves (TRCs) and cause based decision trees (CBDT).
ATHEANA attempts to find contexts where operators are likely to
fail without recovery and quantify the associated HEP. This
includes finding how operators can further degrade the plant
condition while still believing their actions are correct. ATHEANA
quantifies HEPs through an expert judgment elicitation
- (cont.) ATHEANA and the EPRI Calculator are very
similar in the contexts they consider in HEP calculation: both
factor in the accident sequence context, performance shaping
factors (PSFs), and cognitive factors into HEP calculation.
However, stemming from the difference in objectives, there is a
difference in how deeply into a human action each model probes.
ATHEANA employs a HRA team (including a HRA expert, operations
personnel and a thermo-hydraulics expert) to examine a broad set of
PSFs and contexts. It also expands the accident sequences to
include the consequences of a misdiagnosis beyond simple failures
in implementing the procedures (what will the operator likely do
next given a specific misdiagnosis?) To limit the resource burden,
the EPRI Calculator is prescriptive and limits the PSFs and
cognitive factors for consideration thus enhancing consistency
among analysts and reducing needed resources. However, CBDT and
ATHEANA have the same approach to evaluating the cognitive context.
The Halden Task Complexity experiments looked at different factors
that would increase the probability of human failures such as the
effects of time pressure/information load and masked events. EPRI
and ATHEANA could use the design of the Halden experiments as a
model for future simulations because they produced results that
showed important differences in crew performance under certain
conditions. Both models can also use the Halden experiments and
results to sensitize the experts and analysts to the real effects
of an error forcing context.
- by Mary R. Presley.
- Thesis (S.M. and S.B.)--Massachusetts Institute of
Technology, Dept. of Nuclear Science and Engineering,
- Includes bibliographical references (p.
- M.I.T. theses are protected by copyright. They may be
viewed from this source for any purpose, but reproduction or
distribution in any format is prohibited without written
permission. See provided URL for inquiries about
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