atw - International Journal for Nuclear Power | 04.2023

atw Vol. 68 (2023) | Ausgabe 4 ı Juni
| Fig. 6a
Overview of the areas and faculties to be assessed (plain image no dispersion clouds).
ENVIRONMENT AND SAFETY 67
of AMRs / Small Modular Reactors (SMR) which are
deployed in a co generation arrangement where the
heat energy is used for numerous activities, such as;
production of hydrogen, manufacture of additional
products like ammonia and Sustainable Aviation
Fuel (SAF), electricity generation, industrial process
heat, district heating, etc.
The illustrations provided (Figure 6a to 6e) show
the results which UDM is capable of producing. They
provide highly illustrative dispersion plumes which
can be layered over satellite imagery to make a clear
indication of the dispersion of materials based on expected
or typical environmental parameters for the
area being studied. The illustrations show the typical
outputs that would be expected for assessments for
radiological and chemical hazard dispersions.
In the images a hypothetical location for an ammonia
plant at Tees Valley has been selected. Following the
current work UDM will be able to make assessment of
both radiological and chemotoxic consequences and
the results presented in a highly graphical manner
to allow clear indication of the extent of potential
hazard zones. Understanding the implications of siting
certain potential major accident hazard facilities
together in a co generation arrangement will provide
support to justification of siting and overall decision
making.
Advantages of UDM
Over the last two decades UDM has seen substantial
development and improvements to model a wider
range of source terms and material effects. This includes
the following key enhancements:
p Long Range Dispersion and Elevated Sources,
p First Order Buoyant Puff Model,
p First and Second order Evaporation,
p Dense Gas modelling,
p Biological and Radiological Decay,
p Radiological Cloudshine.
By considering a wider range of input factors than
traditional ‘Expanding Cube’ models, UDM can
model the effects of a wider range of environmental
parameters to provide higher fidelity output. Obstacles
such as buildings and surface roughness are
considered in UDM, as well as more detailed wind
profiles and different combinations of releases. This
leads to the following potential benefits:
p Tighter Margins on Safety Cases: Models
which do not take into account the surroundings
of a release need to use increased safety
margins to allow for the greater variations
between the simulated and real worlds. This
potentially results in unnecessarily large areas
predicted to be affected. For incident response,
this means larger cordons with more people
displaced and disrupted. Furthermore, effects
such as urban channelling may result in the
plume going outside the area predicted by a
more approximate model.
p Rapid Setup and Simulation: There are a
number of modelling approaches available that
can provide greater fidelity than UDM, such as
Environment and Safety
Dynamic Dispersion Modelling to Enable Informed Decision Making in a Modern Nuclear Safety Case ı Howard Chapman, Stephen Lawton, Joseph Hargreaves, Robert Gordon, Tim Culmer