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Chapter 19 Risk management 599
1.24 am Two explosions occurred in quick succession.
The reactor roof was blown off and 30 fires started in the
vicinity.
1.30 am Duty firemen were called out. Other units were
summoned from Pripyat and Chernobyl.
5.00 am Exterior fires had been extinguished, but the
graphite fire in the core continued for several days.
The subsequent investigation into the disaster highlighted
a number of significant points which contributed to it:
● The test programme was poorly worked out and the
section on safety measures was inadequate. Because
the ECCS was shut off during the test period, the safety
of the reactor was in effect substantially reduced.
● The test plan was put into effect before being approved
by the design group who were responsible for the
reactor.
● The operators and the technicians who were running
the experiment had different and non-overlapping skills.
● The operators, although highly skilled, had probably been
told that getting the test completed before the shut-down
would enhance their reputation. They were proud of their
ability to handle the reactor even in unusual conditions
●
and were aware of the rapidly reducing window of
opportunity within which they had to complete the test.
They had also probably ‘lost any feeling for the hazards
involved’ in operating the reactor.
The technicians who had designed the test were electrical
engineers from Moscow. Their objective was to
solve a complex technical problem. In spite of having
designed the test procedures, they probably would not
know much about the operation of the nuclear power
station itself.
Again, in the words of James Reason: ‘Together, they
made a dangerous mixture: a group of single-minded but
non-nuclear engineers directing a team of dedicated but
over-confident operators. Each group probably assumed
that the other knew what it was doing. And both parties
had little or no understanding of the dangers they were
courting, or of the system they were abusing.’
Questions
1 What were the root causes which contributed to the
ultimate failure?
2 How could failure planning have helped prevent the
disaster?
Problems and applications
These problems and applications will help to improve your analysis of operations. You
can find more practice problems as well as worked examples and guided solutions on
MyOMLab at www.myomlab.com.
1
‘We have a test bank where we test batches of 100 of our products continuously for 7 days and nights.
This week only 3 failed, the first after 10 hours, the second after 72 hours, and the third after 1,020 hours.’
What is the failure rate in percentage terms and in time terms for this product?
2
3
4
5
An automatic testing process takes samples of ore from mining companies and subjects them to four sequential
tests. The reliability of the four different test machines that perform the tasks is different. The first test machine
has a reliability of 0.99, the second has a reliability of 0.92, the third has a reliability of 0.98, and the fourth a
reliability of 0.95. If one of the machines stops working, the total process will stop. What is the reliability of the
total process?
For the product testing example in Problem 1, what is the mean time between failures (MTBF) for the products?
Conduct a survey amongst colleagues, friends and acquaintances of how they cope with the possibility that
their computers might ‘fail’, either in terms of ceasing to operate effectively, or in losing data. Discuss how the
concept of redundancy applies in such failure.
In terms of its effectiveness at managing the learning process, how does a university detect failures? What could
it do to improve its failure detection processes?