Environmental Engineering Reference
In-Depth Information
Analyses related to operational limits and conditions
Reviews of the Final Safety Analyses Report and reconstruction of design
bases, which have been performed at the Paks NPP, resulted in a recognition
of the need for justifi cation of operational limits and conditions related to
certain ageing phenomena via adequate thermo-hydraulic, stress and frac-
ture mechanics analyses. These analyses have been included in the scope
of TLAAs required for the justifi cation of LTO of the Paks NPP. The task
also includes the justifi cation for modifi cation of the limits and conditions
in accordance with operational needs allowing rapid temperature changes
in certain cases. The temperature measurements and the temperature rate
control methodology have also been reviewed and amended.
The calculation methodology was based on an adaptation of ASME
BPVC. For the calculation of temperature transients in the primary system,
the RELAP5/mod3.3 code was used. A thermo-hydraulic model was devel-
oped for accident simulation. This model consists of a detailed model of the
primary system, the heat removal system and the automatic control system
and it takes into account operator actions during the heat-up and cool-down
processes. The thermo-hydraulic model and the calculation method have
been verifi ed via comparison of the calculated transient time histories with
the measured ones.
Containment, civil structures and structural components
Taking into account the specifi c features of the VVER-440/213 design of civil
structures and also the lack of/missing analyses performed by the designer,
eight analysis tasks were identifi ed as necessary for the justifi cation of LTO
of the Paks NPP. The need to perform stress calculations for the valida-
tion of the rather sparse information available for containment and other
safety-classifi ed structures was also recognized. Considering their content,
these calculations are not typical TLAAs, however, without suffi cient infor-
mation on the design of civil structures the newly performed TLAAs would
not have the design basis. The scope of TLAAs for Paks NPP includes the
generic tasks, like:
Analysis of buildings classifi ed into safety category for the verifi cation
of the design.
Fatigue analysis for the containment penetrations.
Fatigue analysis for the hermetic liner of the containment (welding, tran-
sition welding, area of anchors).
Fatigue analysis for the liner of the spent fuel pool (welding, transition
welding, area of anchors).
Stress and fatigue analysis for the safety-classifi ed crane in the reactor
hall with capacity of 250/32/2 tons.
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