Annual Report

function. Success criteria for safety systems are
determined by a range of methods including experimental
validation and phenomenological
modelling, which often include some estimation
of the associated uncertainties. However,
current PSA methods use strictly conservative
estimates, based on the supporting analysis,
and this is reflected in single deterministicstyle
fault trees.
Measuring Crack Initiation and Growth in the
Presence of Large Strains using the Potential
Drop Technique
Researcher: Keith Tarnowski
Supervisor: Dr Catrin Davies
Sponsor: EdF Energy
Accurate laboratory measurements of crack initiation
and growth are of vital importance for
characterising material behaviour for use in
the residual life assessment of structural components.
The Potential Drop (PD) technique
is one of the most common methods of performing
these measurements, but such measurements
are also sensitive to large inelastic
strains which are often erroneously interpreted
as crack growth. Despite the maturity of the PD
technique, the extent of these errors is not fully
understood and the most appropriate method
of suppressing them is unknown.
I have developed a sequentially coupled structural-electrical
FE based tool capable of predicting
the influence of strain on PD measurements.
Using this tool in conjunction with experimental
measurements, performed using a novel low
frequency alternating current potential drop
system, I have demonstrated that errors due to
the presence of inelastic strains when measuring
crack extension can be extremely large. The
standard approaches of measuring crack initiation
and growth during fracture toughness and
creep crack growth testing of ductile materials
are not fit‐for‐purpose. Alternative methods of
interpreting the test data have been proposed
which greatly improve the accuracy of these
laboratory measurements.
A Coupled Systems Code – CMHD Solver for
Fusion Blanket Design
Researcher: Michael Wolfendale
Supervisors: Dr Mike Bluck and Dr Ben Chuilon
Sponsors: Culham Centre for Fusion Energy and AMEC
Fusion blankets are required to operate in a
harsh environment under the influence of a
number of interdependent and synergistic
physical phenomena, working across several
length scales. For magnetic confinement reactor
designs using a conducting fluid as coolant/
breeder, the difficulties in flow modelling are
challenging due to interactions with the large
magnetic field. Blankets comprise a number of
common features such as ducts, manifolds and
connections. As such, blankets are an ideal
candidate for the application of a code coupling
methodology, with a thermal hydraulic
systems code modelling portions of the blanket
such as the ducts, amenable to 1D analysis,
and CFD providing detail where necessary. It is
the aim of this study to develop such a modelling
approach, enabling extensive thermal
hydraulic simulation of the blanket and associated
systems and accounting for MHD effects in
a computationally efficient manner that lends
itself to the design process.
Improvements in Ultrasonic Inspection
Techniques for High-Density Polyethylene Pipe
Joints
Researcher: Jack Egerton
Supervisors: Prof Mike Lowe, Dr Peter Huthwaite, Dr
Tariq Dawood and Dr Harshad Halai
Sponsors: EDF Energy
This project aims to improve ultrasonic nondestructive
evaluation (NDE) of welds in high-
Centre for Nuclear Engineering Annual Report 2014-2016 46