Long-term exposure of materials in a repository may
result in significant alterations in material structures.
The activated decommissioning wastes including the
reactor pressure vessel and its internals made of
stainless steel, as well as, spent fuel claddings and
reactor graphite contain nitrogen as impurity. 14C is
generated as a result of nuclear reactions involving
nitrogen (14N) or 13C atoms in these materials. 14C is
one of the most important radionuclides when considering
safe disposal of nuclear waste due to its long half-life.
Both organic and inorganic carbons have been identified
in leaching experiments with carbon containing steel,
although clearly higher proportion is released as small
organic molecules. The origin of these compounds and
their reaction mechanisms is not fully understood. The
specific iron-water experiments suggest that both the
carbide carbon and the reduction of aqueous CO2 could be
the sources of hydrocarbons in solution.
Carbon analyses are highly sensitive to filtration which
may cause incorrect results by either releasing or
sorbing organic compounds. The filters should be cleaned
by soaking in double distilled water (DDW) before use or
at least to discard the initial filtration volumes. The
best materials for DOC analysis are hydrophilic
polyethersulphone and hydrophilic polypropylene membrane
filters which induced least interference.
In this literature research, it has become clear that
there is very little conclusive knowledge and evidence on
the form and fate of 14C in irradiated steel materials. A
need for careful assessment of the different routes of
14C production in neutron-activated materials and its
chemical form and transport is required.
|Place of Publication||Espoo|
|Publisher||VTT Technical Research Centre of Finland|
|Number of pages||42|
|Publication status||Published - 2014|
|MoE publication type||Not Eligible|
- carbon speciation
- decommissioning waste