Abstract
A total of 16 Scandinavian LWRs, 11 BWRs, 3 PWRs and 2
WWERs, have been included in a data review where the
interaction
between the reactor coolant and the activity uptake in
the primary system oxides formed have been studied. The
data are intended to be used in the validation of an
oxide model developed within the ANTIOXI project. The
data evaluation
of activity buildup during reactor operation is performed
with a simplified model assuming an adsorption step on
outer
layer of the oxide followed by a diffusion process into
the layer. An alternate model for PWRs and WWERs has also
been
applied for certain nuclides assuming that the shutdown
activity transient in the coolant is the main contributor
to the activity
buildup.
The following main conclusions were obtained:
? The activity buildup for most activated corrosion
products, e.g. the cobalt isotopes, is occurring during
reactor operation,
i.e. with an adsorption step followed by a diffusion
process into the oxide. The diffusion process is supposed
to quite similar between different reactor environments
and the considerable differences seen in different
reactor environments are likely to be due to different
adsorption rates.
? The highest adsorption rates are seen in PWR and WWERs
environments. The analyses shows that a considerable
consumption of certain radionuclides, e.g. Co-58, occurs
in long, hot stainless steel sampling lines in such
reactors,
and reactor water activity measurements are recommended
to be performed via cold sampling lines.
? BWR plants show lower adsorption rates, likely due to
operation at lower pH than the PWRs and WWERs. The
BWR adsorption rates are affected by operation
conditions; the highest rates are seen in HWC plants
without zinc
injection, and the lowest rates in NWC plants that are
very low in feedwater iron. Zinc has a reducing effect on
adsorption
rate in all types of reactors.
? The activity build-up in PWRs and WWERs of some other
nuclides, Sb-122, Sb-124 and possibly Ag-110m, seems to
be controlled by the shutdown transient rather than
normal operation conditions. Some differences in this
type of
activity buildup between plants, as well as year-by-year
variations, are observed, e.g. the adsorption in the WWER
plants is significantly higher than in the PWR plants.
| Original language | English |
|---|---|
| Title of host publication | International Conference on Water Chemistry in Nuclear Reactor Systems |
| Number of pages | 8 |
| Publication status | Published - 2008 |
| MoE publication type | B3 Non-refereed article in conference proceedings |
| Event | International Conference on water chemistry of nuclear reactor systems - Berlin, Germany Duration: 15 Sept 2008 → 18 Sept 2008 |
Conference
| Conference | International Conference on water chemistry of nuclear reactor systems |
|---|---|
| Country/Territory | Germany |
| City | Berlin |
| Period | 15/09/08 → 18/09/08 |