Environmental Engineering Reference
In-Depth Information
6
D e fi nition of the acceptance criteria
7
Identifi cation of the corrective actions
8
Organising the administrative control
9
Organising the operational experience feedback.
In reality, the development is some kind of iterative process and steps over-
lap, as will be shown below.
Identifi cation of ageing mechanisms
The development of AMPs has to begin with the identifi cation of the ageing
mechanisms, critical locations and effect of ageing on the intended safety
function. When an AMP is developed for a complex structure or compo-
nent, like the reactor or steam generator, several mechanisms and critical
locations can be identifi ed. The material, conditions and stressors are con-
sidered at this step of the AMP development. Examples for the mechanisms
are listed in the Table 8.4.
As a matter of fact, the structuring of the AMPs together with the identifi -
cation of the commodities is not independent from the identifi cation of ageing
mechanisms. For example, a commodity group can be defi ned as follows, see
Table 8.7: Safety Class 3 + Piping and pipe elements + working in prepared
water (e.g. feed-water line) + carbon steel. From experience, the dominating
ageing mechanism of this group is fl ow-accelerated corrosion (FAC), a deg-
radation process resulting in wall thinning of piping, vessels, heat exchanger
and other equipment made of carbon and low alloy steel. This degradation
mechanism of the identifi ed commodity group should be addressed by proper
AMP, which can be developed for example via application of the COMSY
system (Zander, Nopper, Roessner, 2007) used by several VVER operators.
Preventive measures
The second step of the development of the AMPs is the identifi cation of
the means of preventing or controlling ageing. For example, the corrosion
phenomena on the internal surfaces can be slowed down via adequate water
chemistry parameters. General corrosion and soil corrosion may be reduced
by coatings and ensuring the undamaged state of the coatings. The most
effective way of avoiding boric acid corrosion is the timely detection and
effective termination of leakages onto carbon steel elements, which are the
subject of walk-down inspections.
Parameters to be controlled
Identifi cation of the parameters allowing the control of the degradation
process is an essential part of the AMP development. Some parameters
Search WWH ::
Custom Search