Otso Cronvall - Academia.edu (original) (raw)

Papers by Otso Cronvall

Susceptibility of boiling water reactor pressure vessel and its internals to degradation

Risk and lifetime analysis methods for structural systems and components of power plants

Worldwide Increasing demand for sustainable energy calls for flexible solutions depending on the ... more Worldwide Increasing demand for sustainable energy calls for flexible solutions depending on the local conditions. Even wind power and solar energy capacity are expanding all over the world high efficient fossil fuel power plant will continue to be the basic concept in development countries where the need for new energy is large and coal is cheap. The potentials for improved coal fired plants are revealed. In the western countries especially Europe the massive increase in renewable energy is challenging the future energy system and high degree of flexibility may only be establish in the long run using gas turbines as back up for the intermitting out put from wind and solar generation.

Kaksipaarretasoisten teräksisten avaruusristikoiden palotekninen mitoitus

Tämän työn tavoitteena on kehittää palotekninen mitoitusmenetelmä kaksipaarretasoisille teräksisi... more Tämän työn tavoitteena on kehittää palotekninen mitoitusmenetelmä kaksipaarretasoisille teräksisille avaruusristikoille sekä tutkia suomalaisten ja eurooppalaisten normien mukaisten materiaalimallien ja eräiden muiden ominaisuuksien vaikutuksia avaruusristikoiden käyttäytymiseen palorasitustilanteessa. Aluksi työssä on lyhyt esitys kaksipaarretasoisten avaruusristikoiden yleisistä ominasuuksista, kuormista, rakenteellisesta toiminnasta, kestävyydestä ja varmuudesta. Tässä työssä lähemmin tarkastellun Sirius -ristikkotyypin ominaisuudet on esitetty seikkaperäisemmin. Palomallinnusmenetelmistä esitetään standardipalomalli, huonepalomalli, eräitä korrelaatioita, vyöhykemallit ja kenttämallit. Myös pohditaan näiden mallinnusmenetelmien soveltuvuutta suurissa tiloissa tapahtuvien palojen mallintamiseen. Teräsrakenteen käyttäytymisen mallintaminen esitetään lyhyesti. Rakenteellisen teräksen materiaaliominaisuudet esitetään sekä yleisesti että tarkasteltavien normien mukaisessa muodossa. N...

Pipe break analysis:An updated state-of-the-art review of LBB procedures with computational examples

Numerical modelling of low-cycle fatigue behaviour of austenitic stainless piping steels

Avaruusristikoiden palotekninen mitoitus

Teräsrakenteiden tutkimus- ja kehityspäivät 2002, 2002

Treatment and numerical simulation of fatigue data of austenitic stainless piping steels

VTT Technical Research Centre of Finland, 2005

Corrosion issues in relation to copper canisters for disposal of spent nuclear fuel Timo Saario F... more Corrosion issues in relation to copper canisters for disposal of spent nuclear fuel Timo Saario Flaw detection trial using virtual ultrasonic testing Matti Sarkimo Ultrasonic inspection of nodular cast iron insert edge distance using curved linear PA-probe

The simulation and analysis of data for enhancing low cycle fatigue test proce-dures is discussed... more The simulation and analysis of data for enhancing low cycle fatigue test proce-dures is discussed in this report. The analysed materials are an austenitic stainless piping steel and an austenitic weld material. This project continues the work performed in 2003 and 2004. The fatigue test data treatment application developed within the project in 2004 for the preparation of the fatigue data has been developed further. Also, more fatigue test data has been analysed with the application than in 2004. In addition to this numerical fatigue simulations were performed with FEM code ABAQUS. With the fatigue test data treatment applica-tion one can e.g. both calculate cyclically certain relevant characteristic values, e.g. elastic range, and form a set of certain cyclical parameter values needed as a part of ABAQUS analysis input files. The hardening properties of metals were modelled with both isotropic and kinematic hardening models. The further development of the application included trimm...

Study and Methodology Development for Cyclic Loading Application to Fatigue Analyses

Pipe break analysis: An updated state-of-the-art review of LBB procedures with computational examples

(b) Let the parameter of interest be timedependent, and fit this trend model over the entire data... more (b) Let the parameter of interest be timedependent, and fit this trend model over the entire data period. 5. Estimate the unknown constants in the chosen model. Also, quantify the uncertainties in the unknown constants, and obtain a Bayesian uncertainty distribution for the parameter of interest. This distribution can be used in a PSA. 6. Perform checks on the validity of the model, such as goodness of fit checks. Perform checks on the sensitivity of the results to the choice of the model. If the model survives this validation process, use the results found in Step 5. Otherwise, go back to an earlier step and reconsider the decisions made. The above six steps are discussed below in Sections 2.1.1 through 2.1.6. 2.1.1. Identify parameter of interest Typically, the concern is that an active component fails to operate when demanded. There are two common ways to model failure on demand. • The standbyfailure model. Pr(failure on demand) = λt, where t is the time since the last repair or successful demand. • The failureondemand model. Pr(failure on demand) = p, a number that does not depend on the time since the last demand. These two models are discussed and compared in Section 2.3 of the Handbook of Parameter Estimation for Probabilistic Risk Assessment (Atwood et al. 2003), denoted HOPE in this document. The main point of the discussion below is that the random number of failures in an extended period can be treated as approximately Poisson, whichever of the above two models is used. Consider the first bullet above, in which a component that is normally in successful state occasionally fails. In principle a failure occurs at some random time, then it is discovered, and the component is repaired and returned to service. When it after a time fails again, this process is repeated. Under some simple assumptions given in the above reference, this is a homogeneous Poisson process (HPP). (See HOPE or Cox and Isham 1980 for more information.) The random number of failures in some fixed time s is Poisson(λs). If the component is only known to be failed when a demand occurs, then failures are not discovered immediately. However, if demands are frequent (in practice, if there are many more demands than failures), then the random number of failures in time s can be treated as approximately Poisson(λs). The time s is called the exposure time, i.e. the elapsed time when failures could occur. The parameter λ is called the failure rate or the Poisson intensity. Now suppose that the failure rate λ is a function of component age, λ(t), where t denotes component age. Then, under simple assumptions given in Section 7.2.2.1 of HOPE or in Thompson (1981), the model is a nonhomogeneous Poisson process (NHPP), and the random number of failures between ages a and b is Poisson with mean: ò b a dt t λ) (. (1) If λ is constant and b − a = s, this integral reduces to λs, and the NHPP is an HPP. Consider now the second bullet above, the failureondemand model, with p constant. The random number of failures in n demands is binomial(n, p). However, European Commission EUR 22483 EN-DG JRC-Institute for Energy Models and data used for assessing the ageing of systems, structures and components (European Network on Use of Probabilistic Safety Assessment (PSA) for Evaluation of Ageing Effects to the Safety of Energy Facilities)

On applications concerning OECD pipe failure database OPDE

Development and application of risk informed in-service inspection analysis procedures

Characteristics and development of risk informed in-service inspection (RI-ISI) methodology for n... more Characteristics and development of risk informed in-service inspection (RI-ISI) methodology for nuclear piping systems are examined in this report. This involves applying the combination of probabilistic fracture mechanics (PFM) and Markov system analyses, and by refining an existing and commonly applied risk analysis procedure. The applicability of the developed risk matrix approach was examined as a pilot study performed to a piping system in an existing Finnish nuclear power plant (NPP).

Assessment of piping failure potential, Screening criteria and load application methods for proba... more Assessment of piping failure potential, Screening criteria and load application methods for probabilistic piping degradation analyses, RI-ISI methodologies, and International co-operation. This presentation describes the main results achieved in the RAIPSYS project, more detailed results are documented in written scientific journal articles, conference articles, VTT research reports and international research publications.

This report summarises the results of a research project on risk-informed in-service inspection (... more This report summarises the results of a research project on risk-informed in-service inspection (RI-ISI) methodology conducted in the Finnish national nuclear energy research programme SAFIR (2003–2006). The purpose of this work was to increase the accuracy of risk estimates used in RI-ISI analyses of nuclear power plant (NPP) piping systems, and to quantitatively evaluate the effects of different piping inspection strategies on risk. Piping failure occurrences were sampled by using probabilistic fracture mechanics (PFM) analyses. The PFM results for crack growth were used to construct transition matrices for a discrete-time Markov process model, which in turn was applied to examine the effects of various inspection strategies on the failure probabilities and risks. The applicability of the developed quantitative risk matrix approach was examined as a pilot study performed to the Shut-down cooling piping system 321 in NPP unit OL1 of Teollisuuden Voima Oy (TVO). The analysed degrada...

Assessment of the probability of failure due to crack growth constitutes one part of the risk inf... more Assessment of the probability of failure due to crack growth constitutes one part of the risk informed in-service inspection methodology. In Nuclear Power Plant (NPP) piping systems, failure of a component due to crack growth generally occurs when the crack has penetrated through the pipe wall. Most of the factors contributing to the crack growth are not strictly deterministic. It can only be estimated how probable it is that these factors will have certain values. As a result, we cannot usually say (without inspections) that there is a crack on some particular weld and that this crack will propagate through the pipe wall in some given time, for example exactly in 4 years. What we can try to estimate, however, is the probability that there exists a crack in some particular weld and the probability that this crack will propagate through the pipe wall in some given time, for example within the following 4 years. Computation of these probabilities requires usually numerous deterministic crack growth analyses with different sets of input values assigned for the parameters which govern the crack growth. The process of assigning input value sets for the parameters is called sampling. The main aim in sampling is to obtain adequate balance between accuracy of the estimates for the probabilities and the number of the different input value sets. How successfully this aim is achieved, depends on the sampling method chosen. Confidentiality

Risk-informed Inspections of Piping (PURISTA). PURISTA summary report

SAFIR2010. The Finnish Research Programme on Safety 2007-2010. Final Report. Puska, Eija Karita &... more SAFIR2010. The Finnish Research Programme on Safety 2007-2010. Final Report. Puska, Eija Karita & Suolanen, Vesa. VTT Research Notes 2571, 357 - 367 The overall objective of the PURISTA project was to support the implementation of risk-informed in-service inspection (RI-ISI) at Finnish nuclear power plants by studying relevant issues related to RI-ISI. Main objectives were the development of structural reliability methods for quantification of piping leak and break probabilities, the development of methods for evaluating inspection capability and the link between inspection qualification, detection probability and RI-ISI, and studying issues related to risk-ranking, selection of inspection sites and acceptance criteria of a RI-ISI programme. The project has contributed to several international activities, including the participation in the work of the Task Group on Risk (TGR) of the European Network for inspection and Qualification (ENIQ). The overall objective of the PURISTA projec...

Susceptibility of boiling water reactor pressure vessel and its internals to degradation

Risk and lifetime analysis methods for structural systems and components of power plants

Worldwide Increasing demand for sustainable energy calls for flexible solutions depending on the ... more Worldwide Increasing demand for sustainable energy calls for flexible solutions depending on the local conditions. Even wind power and solar energy capacity are expanding all over the world high efficient fossil fuel power plant will continue to be the basic concept in development countries where the need for new energy is large and coal is cheap. The potentials for improved coal fired plants are revealed. In the western countries especially Europe the massive increase in renewable energy is challenging the future energy system and high degree of flexibility may only be establish in the long run using gas turbines as back up for the intermitting out put from wind and solar generation.

Kaksipaarretasoisten teräksisten avaruusristikoiden palotekninen mitoitus

Tämän työn tavoitteena on kehittää palotekninen mitoitusmenetelmä kaksipaarretasoisille teräksisi... more Tämän työn tavoitteena on kehittää palotekninen mitoitusmenetelmä kaksipaarretasoisille teräksisille avaruusristikoille sekä tutkia suomalaisten ja eurooppalaisten normien mukaisten materiaalimallien ja eräiden muiden ominaisuuksien vaikutuksia avaruusristikoiden käyttäytymiseen palorasitustilanteessa. Aluksi työssä on lyhyt esitys kaksipaarretasoisten avaruusristikoiden yleisistä ominasuuksista, kuormista, rakenteellisesta toiminnasta, kestävyydestä ja varmuudesta. Tässä työssä lähemmin tarkastellun Sirius -ristikkotyypin ominaisuudet on esitetty seikkaperäisemmin. Palomallinnusmenetelmistä esitetään standardipalomalli, huonepalomalli, eräitä korrelaatioita, vyöhykemallit ja kenttämallit. Myös pohditaan näiden mallinnusmenetelmien soveltuvuutta suurissa tiloissa tapahtuvien palojen mallintamiseen. Teräsrakenteen käyttäytymisen mallintaminen esitetään lyhyesti. Rakenteellisen teräksen materiaaliominaisuudet esitetään sekä yleisesti että tarkasteltavien normien mukaisessa muodossa. N...

Pipe break analysis:An updated state-of-the-art review of LBB procedures with computational examples

Numerical modelling of low-cycle fatigue behaviour of austenitic stainless piping steels

Avaruusristikoiden palotekninen mitoitus

Teräsrakenteiden tutkimus- ja kehityspäivät 2002, 2002

Treatment and numerical simulation of fatigue data of austenitic stainless piping steels

VTT Technical Research Centre of Finland, 2005

Corrosion issues in relation to copper canisters for disposal of spent nuclear fuel Timo Saario F... more Corrosion issues in relation to copper canisters for disposal of spent nuclear fuel Timo Saario Flaw detection trial using virtual ultrasonic testing Matti Sarkimo Ultrasonic inspection of nodular cast iron insert edge distance using curved linear PA-probe

The simulation and analysis of data for enhancing low cycle fatigue test proce-dures is discussed... more The simulation and analysis of data for enhancing low cycle fatigue test proce-dures is discussed in this report. The analysed materials are an austenitic stainless piping steel and an austenitic weld material. This project continues the work performed in 2003 and 2004. The fatigue test data treatment application developed within the project in 2004 for the preparation of the fatigue data has been developed further. Also, more fatigue test data has been analysed with the application than in 2004. In addition to this numerical fatigue simulations were performed with FEM code ABAQUS. With the fatigue test data treatment applica-tion one can e.g. both calculate cyclically certain relevant characteristic values, e.g. elastic range, and form a set of certain cyclical parameter values needed as a part of ABAQUS analysis input files. The hardening properties of metals were modelled with both isotropic and kinematic hardening models. The further development of the application included trimm...

Study and Methodology Development for Cyclic Loading Application to Fatigue Analyses

Pipe break analysis: An updated state-of-the-art review of LBB procedures with computational examples

(b) Let the parameter of interest be timedependent, and fit this trend model over the entire data... more (b) Let the parameter of interest be timedependent, and fit this trend model over the entire data period. 5. Estimate the unknown constants in the chosen model. Also, quantify the uncertainties in the unknown constants, and obtain a Bayesian uncertainty distribution for the parameter of interest. This distribution can be used in a PSA. 6. Perform checks on the validity of the model, such as goodness of fit checks. Perform checks on the sensitivity of the results to the choice of the model. If the model survives this validation process, use the results found in Step 5. Otherwise, go back to an earlier step and reconsider the decisions made. The above six steps are discussed below in Sections 2.1.1 through 2.1.6. 2.1.1. Identify parameter of interest Typically, the concern is that an active component fails to operate when demanded. There are two common ways to model failure on demand. • The standbyfailure model. Pr(failure on demand) = λt, where t is the time since the last repair or successful demand. • The failureondemand model. Pr(failure on demand) = p, a number that does not depend on the time since the last demand. These two models are discussed and compared in Section 2.3 of the Handbook of Parameter Estimation for Probabilistic Risk Assessment (Atwood et al. 2003), denoted HOPE in this document. The main point of the discussion below is that the random number of failures in an extended period can be treated as approximately Poisson, whichever of the above two models is used. Consider the first bullet above, in which a component that is normally in successful state occasionally fails. In principle a failure occurs at some random time, then it is discovered, and the component is repaired and returned to service. When it after a time fails again, this process is repeated. Under some simple assumptions given in the above reference, this is a homogeneous Poisson process (HPP). (See HOPE or Cox and Isham 1980 for more information.) The random number of failures in some fixed time s is Poisson(λs). If the component is only known to be failed when a demand occurs, then failures are not discovered immediately. However, if demands are frequent (in practice, if there are many more demands than failures), then the random number of failures in time s can be treated as approximately Poisson(λs). The time s is called the exposure time, i.e. the elapsed time when failures could occur. The parameter λ is called the failure rate or the Poisson intensity. Now suppose that the failure rate λ is a function of component age, λ(t), where t denotes component age. Then, under simple assumptions given in Section 7.2.2.1 of HOPE or in Thompson (1981), the model is a nonhomogeneous Poisson process (NHPP), and the random number of failures between ages a and b is Poisson with mean: ò b a dt t λ) (. (1) If λ is constant and b − a = s, this integral reduces to λs, and the NHPP is an HPP. Consider now the second bullet above, the failureondemand model, with p constant. The random number of failures in n demands is binomial(n, p). However, European Commission EUR 22483 EN-DG JRC-Institute for Energy Models and data used for assessing the ageing of systems, structures and components (European Network on Use of Probabilistic Safety Assessment (PSA) for Evaluation of Ageing Effects to the Safety of Energy Facilities)

On applications concerning OECD pipe failure database OPDE

Development and application of risk informed in-service inspection analysis procedures

Characteristics and development of risk informed in-service inspection (RI-ISI) methodology for n... more Characteristics and development of risk informed in-service inspection (RI-ISI) methodology for nuclear piping systems are examined in this report. This involves applying the combination of probabilistic fracture mechanics (PFM) and Markov system analyses, and by refining an existing and commonly applied risk analysis procedure. The applicability of the developed risk matrix approach was examined as a pilot study performed to a piping system in an existing Finnish nuclear power plant (NPP).

Assessment of piping failure potential, Screening criteria and load application methods for proba... more Assessment of piping failure potential, Screening criteria and load application methods for probabilistic piping degradation analyses, RI-ISI methodologies, and International co-operation. This presentation describes the main results achieved in the RAIPSYS project, more detailed results are documented in written scientific journal articles, conference articles, VTT research reports and international research publications.

This report summarises the results of a research project on risk-informed in-service inspection (... more This report summarises the results of a research project on risk-informed in-service inspection (RI-ISI) methodology conducted in the Finnish national nuclear energy research programme SAFIR (2003–2006). The purpose of this work was to increase the accuracy of risk estimates used in RI-ISI analyses of nuclear power plant (NPP) piping systems, and to quantitatively evaluate the effects of different piping inspection strategies on risk. Piping failure occurrences were sampled by using probabilistic fracture mechanics (PFM) analyses. The PFM results for crack growth were used to construct transition matrices for a discrete-time Markov process model, which in turn was applied to examine the effects of various inspection strategies on the failure probabilities and risks. The applicability of the developed quantitative risk matrix approach was examined as a pilot study performed to the Shut-down cooling piping system 321 in NPP unit OL1 of Teollisuuden Voima Oy (TVO). The analysed degrada...

Assessment of the probability of failure due to crack growth constitutes one part of the risk inf... more Assessment of the probability of failure due to crack growth constitutes one part of the risk informed in-service inspection methodology. In Nuclear Power Plant (NPP) piping systems, failure of a component due to crack growth generally occurs when the crack has penetrated through the pipe wall. Most of the factors contributing to the crack growth are not strictly deterministic. It can only be estimated how probable it is that these factors will have certain values. As a result, we cannot usually say (without inspections) that there is a crack on some particular weld and that this crack will propagate through the pipe wall in some given time, for example exactly in 4 years. What we can try to estimate, however, is the probability that there exists a crack in some particular weld and the probability that this crack will propagate through the pipe wall in some given time, for example within the following 4 years. Computation of these probabilities requires usually numerous deterministic crack growth analyses with different sets of input values assigned for the parameters which govern the crack growth. The process of assigning input value sets for the parameters is called sampling. The main aim in sampling is to obtain adequate balance between accuracy of the estimates for the probabilities and the number of the different input value sets. How successfully this aim is achieved, depends on the sampling method chosen. Confidentiality

Risk-informed Inspections of Piping (PURISTA). PURISTA summary report

SAFIR2010. The Finnish Research Programme on Safety 2007-2010. Final Report. Puska, Eija Karita &... more SAFIR2010. The Finnish Research Programme on Safety 2007-2010. Final Report. Puska, Eija Karita & Suolanen, Vesa. VTT Research Notes 2571, 357 - 367 The overall objective of the PURISTA project was to support the implementation of risk-informed in-service inspection (RI-ISI) at Finnish nuclear power plants by studying relevant issues related to RI-ISI. Main objectives were the development of structural reliability methods for quantification of piping leak and break probabilities, the development of methods for evaluating inspection capability and the link between inspection qualification, detection probability and RI-ISI, and studying issues related to risk-ranking, selection of inspection sites and acceptance criteria of a RI-ISI programme. The project has contributed to several international activities, including the participation in the work of the Task Group on Risk (TGR) of the European Network for inspection and Qualification (ENIQ). The overall objective of the PURISTA projec...