Environmental Engineering Reference
In-Depth Information
of failures of elements and subsystems), highlighting the most characteristic
and presumably the most dangerous of ad-hoc situations.
- Analysis of ad-hoc situations, constructing a 'tree' of events,
determining the levels and probability distributions of impacts on critical
elements of nuclear facilities, separation and quantitative description of the
limited (necessary and sufficient) list of options for the anomalous effects
on the critical elements of nuclear facilities;
- Analysis of the possible reactions of nuclear facilities (the critical
elements of nuclear facilities) to the anomalous effects and failures, the
definition of the probability of catastrophic outcomes from nuclear facilities
in case of certain types of failures and abnormal influences.
4. Determination of types and levels of damaging factors from the
nuclear facility in catastrophic outcomes. Evaluation of the aggravation or
reduction of the damaging effects of the nuclear facility on the natural and
social environment, technosphere, the actions of staff.
5. Estimation of probabilities
p
i
of the death of individuals in the event
of catastrophic outcomes in each of the selected fragments of the life cycle
of the nuclear facility
6. Description of the types of damage
U
to the public in the event of a
catastrophic outcome of the nuclear facility. Definition of indicators and a
single measure of damage
U
.
7. Estimation of damages
U
i
of different kind to the public in the event
of catastrophic outcomes from nuclear facilities at each of the selected
fragments of the life cycle of the nuclear facility.
8. Hazard assessment and risk
R
of
the nuclear facility for social
projects, including various types of risk at different stages of their life cycle,
in accordance with the generalised and integral indexes of the probability
p
and damage
U
.
In the statistical and probabilistic risk analysis of nuclear power plant
it is fundamentally important to estimate the probability of failures. The
characteristic data obtained in at the end of 20th century include the data on
the total number
N
of disruptions of operation of nuclear power plants and
the coefficients of variation of the number of disruptions from year to year.
In this case, the recorded data include the total number of failures
of systems (components), the number of failures in safety systems, the
number of human errors, the number of deficiencies in the organisation of
operations, the number of activation of emergency protection systems, and
the number of independent and dependent 'overlapping' of failures.
The detected defects develop by the mechanism of intergranular stress
corrosion cracking of metal. Most of the welds with unacceptable defects
are repaired. Decisions on suitability for service are taken for welded joints
with unacceptable defects and special measures are proposed for other
welded joints with defects of the unacceptable size.
The formation of cracks in welded joints of pipelines increases the
probability
p
of failures with depressurisation of the preliminary circulation
Search WWH ::
Custom Search