Environmental Engineering Reference
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Microstructure features such as grain size and shape, amount of CW, and
perhaps others.
Texture.
The radial hydrides can be present in a wide variety of sizes and distribu-
tions as well as fractions of the total hydrides present and each type of struc-
ture can have a different effect on mechanical properties. This emphasizes
the importance of characterizing the structures when they are related to the
mechanical properties measured.
5.5 Inspection methods
There are several reasons why poolside and/or hot cell examinations are
undertaken on fuel assembly (FA) components (Rudling & Patterson,
2009 ). These are:
1
Root cause investigations of failed FA components
(a) A 'failed' FA component has a wider meaning in this respect. It not
only means that the component has physically failed but it could
also mean that the component does not behave satisfactorily, for
example FA bowing that is so large that control rods cannot be
inserted.
2
Maintaining good fuel reliability by:
(a) Providing baseline data before a change in operational environ-
ment of the fuel.
(b)
Getting early warnings of potential issues.
3
Fuel vendor design and licensing data such as:
(a) Providing data to material models and fuel performance codes
(b) Verifi cation of the good performance of a new fuel design
(c) Assessment of the effects of changes in the operating environment;
for example, water chemistry improvements or higher exposures
The in-pool examinations are usually non-destructive, but can also involve
destructive operations such as breaking a fl ow tab off a spacer or cutting
coupons from a channel for measurement of hydrogen concentration. Hot
cell examinations normally start with non-destructive followed by destruc-
tive examinations. The costs for hot cell examinations are much more expen-
sive than those carried out in pool. However, certain material characteristics
can only be assessed in a hot cell. In the following subsections examples of
different examination techniques and results obtained are discussed. The
interested reader is referred to Rudling & Patterson (2009).
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