Analyses for Design and Modification of NPP

Design of NPP is routinely modified during its life-cycle due to the operational experience, increased requirements on safety, lifetime and efficiency, new technologies and knowledge, regulator’s requirements or recommendations resulting from PSR (Periodic Safety Review).

In the area of design and modification of NPP we offer following services:

• Consulting assistance within preparation of project
• Assistance with proper definition of particular DSA
• Development of models of systems/components and their validation
• Optimization of system/component design
• Assessment of newly designed system/component within scenarios of AOO, DBA and DEC conditions
• Recommendations on application/operation of newly designed system/component
• Independent assessment of third party DSA
• Assessment of newly designed system/component on operational and accident documentation
• Performance of DSA for SAR (Safety Analysis Report) update

LTO – Long Term Operation

Typical lifetime of NPPs is usually several tens of years, some of them reach up to 60 years. Currently ongoing process of LTO (Long Term Operation) at Dukovany and Temelin NPP has the target of reaching 60 years as well. Due to aging and wearing of some components, the design of NPP is continuously modified and renewed to maintain currently required safety level and targeted lifetime of the plant.

NPP Power Uprating

Another common reason for changes in design is the implementation of NPP power uprating, which is usually related to introduction of new fuel design and extension of cycle length.

Nuclear Safety

Accidents at Chernobyl and Fukushima raised the pressure for increasing the safety of nuclear power plants worldwide. Based on the assessment of stress tests results, a number of recommendations for design amendment and extension has been formulated in order to increase design robustness and strengthen its DiD (Defense in Depth). Consequently, new regulatory requirements has been issued to cover of extreme external conditions (earthquake, extreme temperatures and rain/snow, etc.) and newly defined DEC (Design Extension Conditions) area, which consider even very unlikely combination of events or consequences. These requirements has been also integrated into the new Czech Atomic law (263/2016 Coll.) and related regulations.



Changes and amendments of NPP design from above-mentioned reason are usually to such an extent new and extensive, that they couldn’t be verified at real plant. This is a moment when deterministic safety analyses must be employed. TES’ experts significantly contribute to such calculational assessment.

Our experience, together with application of certified computational codes, methodologies and thoroughly validated models under conditions of AOO (Anticipated Operational Occurrence), DBA (Design Basis Accident) and DEC guarantees high quality results of DSA calculations for NPP design and modifications.