atw - International Journal for Nuclear Power | 10.2020

atw Vol. 65 (2020) | Issue 10 ı October
2 Planning and
preparation of the study
The preparation for the ISV started
in 2015 with the definition of relevant
aspects to be analysed. The choice
of these aspects was based on human
factors requirements which in turn
have been derived by considering
the relevant standards and regulations
within the domain of controls
rooms in general and more specifically
nuclear power plant control rooms.
The standards considered include
among others the IEC 1771 [1] and
IEC 60964 [2]. The Finnish regulation
YVL 5.5 [3] has to be considered for
the main control room and manmachine
interfaces in the control
room and their validation. Furthermore
NUREG 0711 [4] provides
additional guidance.
Based on the literature, a total
of six aspects were identified that
were to be investigated in the ISV.
These aspects are: task performance,
human errors, situation awareness,
com munication, coordination and
mental workload.
2.1 Scenarios
The six aspects should be examined in
different operating conditions. For this
purpose, four scenarios were defined
which varied in content, difficulty and
complexity and which cover a wide
range of conceivable operating conditions,
from normal operation to
emergency operations. For each of the
four scenarios, a target path with an
expected sequence of specified control
tasks or switching actions was defined.
using the ‘strategy flow charts’ (SFC)
of the operating manual. In the OL3
operating manual, strategies for different
states of the plant (e.g. normal
operation, start up, abnormal operations
etc.) are described in the
SFC, whereas tasks are described in
‘ detailed instruction modules’ (DIM).
For different states of the plant spe cific
SFCs describes the sequence of tasks
(DIMs) and necessary actions in the
form of flowcharts. The target path for
a scenario thus contained a sequence
of DIMs in one or more SFCs which
had to be processed (see Figure 2 for
an example of a SFC with target path).
Each scenario was planned to be
carried out three times within the ISV,
using a different shift crew each time.
The individual run of one scenario by
one crew is called ‘trial’. This resulted
in a balanced test plan of 12 trials
(4 scenarios x 3 trials). One trial was
carried out per day.
The scenarios covered normal
operation (scenario A), abnormal
operation (scenario B) and emer gency
operation (scenarios C and D). A plant
start-up (from reactor critical up to
25 % nuclear power) with a periodic
test of the criticality behaviour of the
core (which was supported by a
reactor physicist), was included in
scenario A.
Otherwise, the four scenarios A to
D included numerous unexpected
disturbances and additional tasks,
e.g.:
1. unavailability of components,
problems with components (e.g.
vibration of the turbine, vibration
of a reactor coolant pump), fire
alarm in a diesel building, smoke in
the main control room which
caused the crew to move to the
remote shutdown station.
2. Problems with digital controls:
Failure of workstations, failure of
the electronic OM, complete loss of
the PICS, and combinations of
these problems.
3. The daily load of the shift crews:
short-term requests from the network
operator to reduce power,
communication requirements such
as repeated telephone calls from
the management, asking for the
status of certain activities, a
shift takeover, and communication
requirements with regulatory body
and plant management during
incidents etc.
With the exception of the start-up
scenario A, all scenarios started with a
short phase of normal operation
(about 20 min). The scenarios were
planned with a length of three to six
hours. However, during the execution
it turned out that especially the
start-up scenario A took much longer
(up to nine hours).
2.2 Aspects investigated
Six aspects were identified which
should be investigated in the ISV: task
performance, human error, situation
awareness, communication, coordination
and operator mental workload.
These aspects were operationalized
using one or more testing instruments
and one or more variables each.
Pass/fail criteria were defined in
advance for each variable. If these
criteria were not met, the trial was
considered failed. In order to increase
the reliability of the measurement of
the variables, subjective assessments
and the collection of qualitative data
(e.g. collection of the subjective
assessments of the crew members)
were avoided as far as possible and an
attempt was made to develop clear
criteria for the measurement of all
variables. The operationalization of
the aspects is precisely described in
section 3.
2.3 Equipment
The scenarios were executed in the
full scope simulator (FSS) of OL3. In
the FSS the main control room (MCR)
and the remote shutdown station
(RSS) are simulated. Both rooms can
be observed from an observation
room through a one-way mirrored
window. All information displayed
on the screens in the MCR and RSS
are also available on screens in the
observation room.
A special paper-based “observation
tool” (see section 4) was developed
for the observation and data collection
within the ISV. Questionnaires to
assess situation awareness, coordination
and workload were prepared on
mobile tablet computers.
Audio and video recordings were
used as backup for the data acquisition
with the observation tool.
For the video recordings of the crews’
actions, the four cameras permanently
installed in the FSS were used
(three cameras in the MCR, one in the
RSS). In addition, the SICS panel and
the screens of the operators were
recorded with three mobile video
cameras.
2.4 Participants
The scenarios were carried out with
shift crews from OL3. A total of six
trained and licensed crews was available
for the ISV. Each crew participated
in two different trials.
The crews were not aware of the
test plan. They didn’t know the total
number of scenarios in the test plan,
nor did they know which scenario
they would be working on. All test
participants had to declare in writing
that they would not pass on any information
about the courses of the test or
details of the scenarios.
Three Human Factors Experts from
the HFC/MTO Safety consortium
served as observers for the ISV. Three
simulator trainers with thorough
knowledge of the OL3 procedures and
operational manual were asked to
observe and evaluate task performance
and human error. Each simulator
trainer was assigned to one
of the operators as an observer. An
additional expert from TVO was
responsible to simulate the external
communication of the operators via
telephone. He answered operators’
phone calls to the plant management,
network operator, maintenance department
etc.
ENVIRONMENT AND SAFETY 499
Environment and Safety
Are They Ready for Operation? How to Assess the Control Room System of a New NPP ı Rainer Miller, Rodney Leitner, Sina Gierig and Harald Kolrep