Seismic Analysis - Rolls-Royce

SERVICE OFFERING
Seismic Analysis
SAFETY, LICENCING AND ENVIRONMENTAL ENGINEERING
Establishing structural integrity against
extreme earthquakes
Seismic phenomena
Earthquakes are one of nature’s most violently destructive forces, with
the ability to cause catastrophic damage with little or no advanced
warning. Earthquakes are generated when sudden movements occur at
faults in the earth’s crust to relieve high levels of geological stress. These
unpredictable events release massive amounts of energy.
This energy radiates away from the initiating fault in all directions in
the form of seismic waves travelling at high speeds and covering great
distances. When we experience an earthquake at the Earth’s surface we
are feeling the local effects of these radiating seismic waves.
Seismic risk and the nuclear sector
Despite popular belief to the contrary, the UK lies in a moderately active
seismic region and experiences many minor tremors every year. Such
frequently occurring events are of relatively small intensity and don’t
present a significant risk to public safety. As a consequence, these minor
tremors are rarely noticed.
Against this background of low intensity seismic activity, a quantifiable
risk exists for the UK to experience much larger and considerably more
damaging earthquakes with the capability to compromise the integrity of
otherwise robust engineering structures.
To protect against the risks of potential radiological consequences, all
safety cases for nuclear licenced facilities are required to consider extreme
environmental hazards, including large earthquakes, and to demonstrate that
risk levels to the public are maintained below regulated limits of acceptability.
To meet this objective, nuclear safety-related buildings and plant are
designed to withstand earthquake hazards of varying magnitude. At the
most extreme hazard level, it is typical for the seismic integrity of those
structures, systems and components (SSC) that are essential for the safe
shutdown of nuclear facilities to be substantiated against earthquakes
with a 1 in 10,000 year return frequency.
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NUCLEAR INNOVATION & TECHNOLOGY

Analytical expertise
As the designated design authority for generations of nuclear steam
raising plant (NSRP) powering the Royal Navy fleet of nuclear submarines,
Rolls-Royce has an excellent understanding of Pressurised Water Reactors
(PWR) and related equipment and systems, their operational and safety
functions and their behaviour under dynamic loading conditions.
In support of nuclear site safety cases, Rolls-Royce has developed extensive
knowledge and experience in the seismic analysis and integrity assessment
of safety-related structures and components in
the NSRP, associated fuel-handling and
maintenance equipment and civil
engineering structures.
Reactor access house
Example applications
Where practicable, alternative seismic assessment techniques are adopted
which can introduce significant timescale and cost benefits. One such
approach is the seismic walkdown screening method employing the
generic implementation procedures (GIP) for equipment qualification, as
developed by the seismic qualification utilities group (SQUG).
Innovation
Rolls-Royce has earned a reputation for being an industry innovator with
a track record based on the successful implementation of cutting edge
solutions to a broad range of engineering challenges. However, not all
innovations depend on increasing analytical complexity. A recent example
is the development of a simplified procedure for seismic assessment and
qualification of small bore piping.
The method is based on first principle pipe bending calculations and
permits assessment of complex piping layouts by breaking them down
into a series of conservatively simplified piping spans.
Dynamic structural loads and stresses resulting from seismic events are
obtained by employing a range of industry standard analysis techniques,
including:
The first two approaches are ideally suited to determining the seismic
response of linear dynamic structures, while the third technique can
be applied to solve problems that involve both linear and non-linear
behaviour.
Rolls-Royce has considerable experience in the interpretation, analysis
and manipulation of dynamic signal data. In-structure transient solutions
derived using either of the two time history analysis methods are
commonly subject to numerical processing to create secondary response
spectra. In turn, these are used to define localised seismic loading for
design and assessment of components or sub-systems. Synthetic time
histories are also generated to match with design spectra, as and when
required.
Astute class small bore
piping finite element models
Applying this approach has delivered dramatic cost savings and major
reductions to the lengthy timescales previously associated with such
large-volume analysis tasks.
7406/SO.27/Nov10
Rolls-Royce Power Engineering plc
PO Box 2000, Derby DE21 7BD, England
Tel: +44 (0)1332 632688
Fax: +44 (0)1332 622936
Email: nuclearsolutions@rolls-royce.com
www.rolls-royce.com
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