CAD MODELLING OF RADIOACTIVE PLANT: THE ROLE OF DIGITAL PHOTOGRAMMETRY IN 
HAZARDOUS NUCLEAR ENVIRONMENTS 
David Chapman, Andrew Deacon, Asad Hamid 
Department of Photogrammetry and Surveying 
University College London 
United Kingdom 
Rudiger Kotowski 
K? Photogrammetry, Software,Consulting 
Stuttgart 
West Germany 
Commission V 
Abstract 
The maintenance, refurbishment and ultimate decommisioning of nuclear installations increasingly depend upon remote 
operations employing a variety of robotic tools. 
Planning, simulation and execution of robotic entries demand accurate ‘as-built’ CAD models of the plant geometry. 
These are usually derived from existing general arrangement drawings which are supplemented by ad-hoc surveys and 
imagery gathered during routine inspections. 
This paper describes a number of strategies which have been developed to allow the remote measurement of active 
plant, emphasising the potential role of digital photogrammetry. In particular the paper will describe the component 
parts of a remote measuring system for hazardous environments (HAZMAP) which links a robotic measurement unit 
to a digital photogrammetric workstation allowing real-time image measurement and off-line CAD modelling via 
linkages between 3D plant design packages and a photogrammetric toolkit. 
Keywords: CAD/CAM, Industrial, Photogrammetry 
  
1.0 INTRODUCTION 
Techniques for the construction of as-built models of 
plant items include traditional surveying measurements 
(by theodolite, tape and level), theodolite intersection 
(e.g. Leica ECDS system), close range 
photogrammetry, holography and laser ranging or 
triangulation (ASPRS 1989). 
Of these techniques both photogrammetry and 
holography offer the potential of rapid acquisition of an 
image archive suitable for subsequent analysis. Access 
to such an archive is of considerable benefit in planning 
and execution of robotic operations since it enables the 
construction of as-built models of the plant which 
include both precise geometrical details of plant 
locations and details of clutter or debris which may not 
exist in design records. 
Whilst as-built photogrammetric surveys of nuclear 
installations prior to commissioning are becoming 
increasingly common (e.g. Legac, 1991) many were 
designed prior to the advent of CAD modelling tools. In 
these situations the creation of accurate plant models is 
likely to demand the integration of engineering drawings 
with measurements from remote measurement systems. 
Unfortunately the deployment of such measurement 
systems is adversely affected by the ionising radiation in 
active plant cells. The nature and magnitude of 
    
acceptable radiation exposure varies between the systems 
but can be crudely represented by the Figure 1 which 
shows the effective limits for deployment of systems in 
terms of the integrated radiation dose (measured in 
Rads). Since varying dose rates (measured in Rads/hr) 
will be encountered in differing parts of the plant the 
time available for deployment and acquisition of remote 
measurements may vary from a few minutes to many 
hours. 
  
Dose (R) 
  
1E+00 + 
  
Limit for Limit for CCD Successful use Limit for 
photographic based devices of holographic Vidicon 
imaging techniques imaging 
systems 
Figure 1. Radiation tolerance of inspection systems 
  
  
  
The first section of this paper explores the potential for 
the use of such systems in radioactive environments and 
comments on documented experience of the techniques 
in the construction of CAD models of active plant. 
Next the advantages of a hybrid prototype measurement 
system are described in the light of trials which are