TY - BOOK
T1 - Modelling of DIgital I&C, MODIG
T2 - Interim report 2015
AU - Authén, Stefan
AU - Bäckström, Ola
AU - Holmberg, Jan-Erik
AU - Porthin, Markus
AU - Tyrväinen, Tero
N1 - Project code: 108550
PY - 2016
Y1 - 2016
N2 - The NKS-project MODIG (MODelling of DIGital I&C) aims to
get a consensus approach for a reliability analysis of a
plant design with digital I&C, improved integration of
probabilistic and deterministic approaches in the
licensing of digital I&C, improved failure data
collection including software failure probability
quantification, and a practical application of
probabilistic safety assessment (PSA). A survey of the
defence-in-depth (DiD) framework and PSA's role in it has
been made. The assessment of DiD and diversity is in
principle straightforward for PSA, e.g., risk metrics can
be used to evaluate DiD levels 3, 4 and 5. A PSA model
always includes uncertainties, which needs to be
accounted for especially when comparing with
deterministic assessment. Regarding digital I&C, the
focus of the assessment is on the DiD levels 1, 2 and 3.
In addition the logic model of PSA can be used in the
assessment of deterministic failure criteria. Spurious
actuation is a functional failure mode when a component
performs a function without a real demand. Spurious
actuations are of special interest for I&C due to complex
effects via system dependences and due to a huge number
of possible failure locations. There is a need to develop
a reasonable but comprehensive approach both for
deterministic and probabilistic analyses. Analysis
requirements have been compiled, and a generic failure
modes taxonomy and an analysis approach have been
outlined. The software reliability task has been working
on the confidence building in the method to estimate
application software failure probability. The impact of
pooling data from high and low demand systems is
discussed. The principle of the probability estimation
has been adjusted from the approach developed in the
DIGREL project. A solution for the software complexity
assessment has been prepared. I&C failure data is one of
the information sources needed for the assessment of I&C
reliability. Vendors have data sources as they typically
have access to experience data from many plants, have
needed insight on the software development processes and
are capable to analyse the causes of the detected
failures. International collaboration and discussions are
still needed in order to forward the use of I&C failure
data in PSA.
AB - The NKS-project MODIG (MODelling of DIGital I&C) aims to
get a consensus approach for a reliability analysis of a
plant design with digital I&C, improved integration of
probabilistic and deterministic approaches in the
licensing of digital I&C, improved failure data
collection including software failure probability
quantification, and a practical application of
probabilistic safety assessment (PSA). A survey of the
defence-in-depth (DiD) framework and PSA's role in it has
been made. The assessment of DiD and diversity is in
principle straightforward for PSA, e.g., risk metrics can
be used to evaluate DiD levels 3, 4 and 5. A PSA model
always includes uncertainties, which needs to be
accounted for especially when comparing with
deterministic assessment. Regarding digital I&C, the
focus of the assessment is on the DiD levels 1, 2 and 3.
In addition the logic model of PSA can be used in the
assessment of deterministic failure criteria. Spurious
actuation is a functional failure mode when a component
performs a function without a real demand. Spurious
actuations are of special interest for I&C due to complex
effects via system dependences and due to a huge number
of possible failure locations. There is a need to develop
a reasonable but comprehensive approach both for
deterministic and probabilistic analyses. Analysis
requirements have been compiled, and a generic failure
modes taxonomy and an analysis approach have been
outlined. The software reliability task has been working
on the confidence building in the method to estimate
application software failure probability. The impact of
pooling data from high and low demand systems is
discussed. The principle of the probability estimation
has been adjusted from the approach developed in the
DIGREL project. A solution for the software complexity
assessment has been prepared. I&C failure data is one of
the information sources needed for the assessment of I&C
reliability. Vendors have data sources as they typically
have access to experience data from many plants, have
needed insight on the software development processes and
are capable to analyse the causes of the detected
failures. International collaboration and discussions are
still needed in order to forward the use of I&C failure
data in PSA.
KW - Digital I&C system
KW - probabilistic safety assessment
KW - reliability
KW - nuclear power plant safety
M3 - Report
SN - 978-87-7893-445-1
T3 - NKS Reports
BT - Modelling of DIgital I&C, MODIG
PB - Nordic Nuclear Safety Research NKS
ER -