nirex
Technical Report
Part 3
[Inspection Cell – methods of inspection]
Prepared by
Mr. Sebastian Roberts
Mr. Tim Pegg
Mr. Sam Billing
Mr. Nick Petousis
Mr. Iain Hughes
Mr. Danny Thomas
Mr. Carl Young
Mr. Kevin Yong
Directed by
Dr. Phil Purnell
AIM
Visual inspection plays an important role in both monitoring of packages and also
inspection of packages. This report looks into how visual inspection could be implemented in
the inspection cell.
INTRODUCTION
Visual inspection is one of the inspection methods being adopted in the inspection
cell and also waste monitoring in the storage vault. This report discusses the advantage and
disadvantage of visual inspection and how it could be implemented into the Phased
Geological Repository Centre (PGRC).
ADVANTAGE
 Visual inspection is reliable. Sophisticated electronic sensors rely on batteries and
circuits. A small break down or malfunction in one of these two could cause
malfunction of the whole sensor.
 Visual inspection doesn’t require much operational cost and maintenance cost is
relatively cheaper compared to other forms of inspection.
 Visual inspection only requires maintenance of shielded windows, such as cleaning
and changing oil film.
 Visual inspection could also be done in a ‘real-time’ basis. Instead of some inspection
methods which require time for computer or experiments to be finished, visual
inspection provides a direct output to the viewer. Hence, it could be done relatively
quickly.
DISADVANTAGE
 Visual inspection is somehow difficult to be implemented.
 Visual inspection could only be conducted with shielded windows approximately
1.2m thick, or by mounting cameras on robotic crawlers.
 Visual inspection is often obstructed by blind spots or inaccessible of crawlers.
 Visual inspection is arguably not reliable for it is subjective and difficult to compare
results.
 Often permissible crack widths are often difficult to be observed by the eye.
 Shielded windows are also expensive and maintenance work is relatively difficult to
be conducted.
BEST PRACTICE
 Visual inspection should be done with adequate lighting. Hence adequate lighting
within the inspection cell should be made.
 It is also advisable that robotic crawlers to be equipped with lightings to allow visual
inspection to be conducted easily.
 CCTV should also be radioactive resistant and be able to zoom, pan and tilt. This is to
increase flexibility of cameras.
 Blind spots should be minimised through outlay of the inspection cell. Waste
monitoring within the vault however should allow access for robotic crawlers.
 It is best practice to be able to view the process of inspecting packages and
repackaging them via a shielded window. This could assure that all processes are
carried out smoothly.
3D MAPPING
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As each package enters the PGRC for the first time, it will be mapped en route to the
storage vault. This will take place in the Inspection Cell of the target vault. This will
provide a ‘reference map’ of the package.
After emplacement in the storage vault, each package will be taken to the Inspection
Cell at regular intervals during the 300 year monitoring period to be mapped again.
(e.g. approximately every 17 years if 1 package* from each vault is inspected each
day).
Subsequent maps will be compared to the reference map to note changes to the
envelope dimensions of a package over time.
* In the reference case, 1 package = 4x 500L drums/ 1x3m3 box/ 1x3m3 drum
HOW IT WORKS
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a 2D pattern of light stripes is projected onto the object.
The light stripes will reflect off the object and reach the camera lens at different
angles due to the non-flat surface of the object.
The pattern is imaged by means of a camera which is placed at an angle relative to the
light projector.
ACCURACY
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can detect change in envelope dimensions of the package to approximately 1mm.
crack detection is possible in that small areas of the drum can be zoomed in on and
mapped.(e.g. an area of 0.1x0.1m would detect changes in dimensions of 0.001mm)
What is the upper limit for the max allowable crack size before reworking is needed?
Figure 1 – Specifications of 3D Mapping system1
Figure 2 – Example of comparison of a subsequent map and a reference map.1
Yellow is zero deviation, while red corresponds to +1mm and blue corresponds to -1mm
deviation.
Figure 3 – Schematic of 3D Mapping system1
THREE POSITIONS OF 3D MAPPING.
a)To map the sides of a package, the 3D mapping equipment will be located as in Figure
4. The package will be rotated such that four sides are mapped.
Figure 4 – 3D mapping of the sides of a package
b)To map the top of the package, the 3D mapping equipment will move to the top of the
window.
Figure 5 – 3D mapping of the top of a package
c)To map the base of the package, the 3D mapping equipment will move to the base of
the window and the package will be lifted.
Figure 6 – 3D mapping of the base of a package
REFERENCES
[1]
(March 2006). “Optical shape measurement with structured
light”. [Online]. Viewed 2007 February 16. Available:
http://www.sintef.no/upload/IKT/OpticalMeasurementSystems/Fact%20sheets
/Structured_Light_Factsheet.pdf
Skothei,. Øystein.
BIBLIOGRAPHY
Sintef (2005). “3D shape measurement”. [Online]. Viewed 2007 February 16.
Available: http://www.sintef.no/content/page1____6799.aspx