F. J. Blom

Fatigue is an important ageing mechanism for long-term operation (LTO) of nuclear power plants. The effect of the reactor coolant environment on fatigue is one of the factors to take into account. Application of environmental fatigue codes, generally, leads to large margins for actual fatigue failure of components. In combination with longer operat...

A pressurized thermal shock (PTS) in a reactor pressure vessel (RPV) wall of a Pressurized Water Reactor (PWR) could eventually lead to reduced integrity of the RPV. A PTS scenario may be initiated by a Loss-of-Coolant Accident (LOCA) in which the Emergency Core Cooling (ECC) injection causes a thermal shock in the vessel wall while the RPV is stil...

Turbulent mixing of hot and cold flows can lead to thermal fatigue of piping systems. Especially in primary pipework of nuclear power plants this is an important, safety related issue. Because the frequencies of the involved temperature fluctuations are generally too high to be detected well by common plant instrumentation, accurate numerical simul...

A pressurized thermal shock (PTS) in a reactor pressure vessel (RPV) wall of a pressurized water reactor (PWR) could eventually lead to reduced integrity of the vessel. A severe PTS scenario is a Loss-of-Coolant Accident (LOCA) in which the Emergency Core Cooling (ECC) injection causes a thermal shock in the vessel wall. The traditional one-dimensi...

The Pressurized Thermal Shock (PTS) is one of the transients of concern in a nuclear reactor. The phenomenon takes place when the down-comer and internal Reactor Pressure Vessel (RPV) surfaces are rapidly cooled down while the system is still under pressure. This event is considered life limiting for the safety case where cracks are postulated and...

In this study a probabilistic Leak-Before-Break (LBB) analysis was carried out based on the R6 FAD Option 1 assessment method. The method uses the material fracture toughness and yield stress in order to determine, deterministically, a Critical Crack Length (CCL) and a Leakage Rate (LR) through a crack. In order to define the fracture toughness of...

Deterministic assessment codes can contain large safety factors that give very conservative results. By applying probabilistic analysis to these deterministic assessments, an implicitly accepted probability of failure can be determined. The probability of failure is implicit because it is calculated with the parameter values resulting in a state th...

For many nuclear power plants worldwide the operation period will be extended from 40 to 60 years. As the operation period increases the knowledge of ageing mechanisms like fatigue becomes more important. Knowledge of the influence of the environment is crucial, since environmental fatigue results in a modification of the existing fatigue assessmen...

Fatigue is an important ageing effect to manage for long term operation (LTO) of nuclear power plants (NPPs). One of the steps in the process of LTO assessment is the revalidation of TLAAs (time limited ageing analyses). The safety margins of NPP Borssele with respect to fatigue were demonstrated by projecting the fatigue analyses to the end of the...

This paper describes the effect of variability of fracture toughness of nuclear pressure vessels during a PTS event. The model used in this paper is based on the NESC-1 experiment. To determine the behavior of the surface breaking defect NRG performed three dimensional finite element calculations and subsequently extended these calculations to the...

For many nuclear power plants worldwide the operation period will be extended from 40 to 60 years in the coming years. As the operation period increases the importance of knowledge of ageing mechanisms like fatigue increases. Knowledge of the influence of the environment is crucial, since environmental fatigue is a relatively new development which...

Long Term Operation (LTO) of nuclear power plants (NPPs) requires an ageing management review and a revalidation of Time Limited Ageing Analyses (TLAAs) of structures and components important for nuclear safety. An important ageing effect to manage is fatigue. Generally, the basis for this is formed by the fatigue analyses of the safety relevant co...

Irradiation Assisted Stress Corrosion Cracking (IASCC) is considered a primary ageing issue for the Reactor Pressure Vessel (RPV) internals of Pressurized Water Reactors (PWR). In particular, this complex phenomenon which develops in an environment featuring thermal and mechanical stresses, interaction with corrosive compounds and irradiation, is a...

For many nuclear power plants worldwide the operation period will be extended from 40 to 60 years in the coming years. As the operation period increases the importance of knowledge of ageing mechanisms like fatigue increases. Knowlegde of the influence of the environment is crucial, since environmental fatigue is a relatively new development which...

Turbulent mixing of hot and cold flows is one of the possible causes of thermal fatigue in piping systems. Especially in primary pipework of nuclear power plants this is an important, safety related issue. Since the frequencies of the involved temperature fluctuations are generally too high to be detected well by common plant instrumentation, accur...

NPP Borssele is in operation since 1973. In the framework of the long term operation (LTO) of the NPP Borssele until 2034, the integrity of the safety relevant systems, structures and components in terms of physical ageing will have to be demonstrated during the years beyond 2013. Most of the fatigue analyses in the current safety report are based...

Fluctuating stresses imposed on a piping system are potential causes of thermal fatigue failures in energy cooling systems of nuclear power plants (4). These stresses are generated due to temperature fluctuations in regions where cold and hot flows are intensively mixed together. A typical situation for such mixing appears in turbulent flow through...