Marin Kostov - Academia.edu (original) (raw)

Papers by Marin Kostov

... of assess-ment and enhancement of seismic capacity of existing nuclear power plants of theWER... more ... of assess-ment and enhancement of seismic capacity of existing nuclear power plants of theWER type. ... the Assessment and Improvement of Seismic Capacity CONSTRAINTS (BUDGET, SCHEDULE) OVERALL OBJECTIVE: SEISMIC QUALIFICATION OF WWER TYPE NPP's ...

Nuclear Engineering and Design, Apr 1, 2014

There are continuous attempts to describe the damaging potential of the seismic (or vibratory) mo... more There are continuous attempts to describe the damaging potential of the seismic (or vibratory) motion by a single parameter or a set of damage indicating parameters (DIP). Recently CAV and I JMA JMI are becoming two very promising parameters. Originally CAV was introduced as a parameter alongside spectral characteristics of ground motion for assessment of the operational state of a nuclear power plant after a seismic event. The aim is to shorten the time for evaluation of OBE exceedance and to provide guidance for the quick restart of a seismically affected plant. Meanwhile, there has been a growing experience and confidence that the DIP could be used not only as global indicator, i.e. assessment of the severity of excitation on the plant site but also as damage descriptor at equipment level, i.e. at each equipment location. The procedure proposed is similar to that for floor response spectra generation and safety evaluation against seismically induced forces. The current paper is presenting basic relations between damage parameters and structural damage derived from the European strong motion data base. The seismic experience data base is utilized to assess the capacity/damage of equipment. A formalized approach is considered for evaluation of critical facilities subjected to dynamic vibratory loading. The following sequence of evaluation steps is discussed: Step One: For the safety equipment the standard in-structure CAV is calculated and compared with a threshold to screen-out the equipment for further considerations. An additional and optional threshold could be the in-structure I JMA intensity estimate. Step Two: For all locations where standard CAV of in-structure vibrations is higher than the threshold, the floor response spectra are evaluated. They have to be compared with the equipment capacity spectra. The latter are represented by design floor response spectra multiplied by a safety factor or seismic ruggedness spectra. Step Three: Alternatively or simultaneously with the ultimate capacity assessment (force driven design) a displacement based evaluation of the ultimate drift capacity of the respective equipment can be performed. It has to be stressed that under high frequency excitation the displacement (drift) estimated capacity is by far more realistic than the force based estimates. If none of the above checks is positively answered detailed conventional analysis can follow; however, a much smaller amount of equipment would remain for assessment.

Proceedings of the International Astronomical Union, Dec 1, 2019

The increase in the amount of scientific information in heliophysics is related to both quantitat... more The increase in the amount of scientific information in heliophysics is related to both quantitative – increasing the number of high-power telescopes and the size of light receivers coupled to them, and qualitative reasons – new modes of observation, large-scale and multiple studies of the solar corona in different ranges, large-scale numerical experiments to simulate the evolution of various processes and formations, etc. The paper discusses the role and importance of methods for processing images of the solar corona, the store of obtained “raw” data and the need to access high-performance computing systems in order to obtain scientific results from the observational experiments, the need of international collaboration and access to the data in the era of increase in the amount of scientific information in heliophysics.

In this paper the floor response spectra generation methodology for Kozloduy NPP, Unit 1-2 of VVE... more In this paper the floor response spectra generation methodology for Kozloduy NPP, Unit 1-2 of VVER 440-230 is presented. The 2D coupled soU-structure interaction models are used combined with a simplified correction of the final results for accounting of torsional effects. Both time history and direct approach for in-structure spectra generation are used and discussion of results is made.

Assessment of the effects of a large aircraft impact on a NPP reactor building are the basic topi... more Assessment of the effects of a large aircraft impact on a NPP reactor building are the basic topics of the present work. The focus is on the dynamic response of the internal sub-structures, by means of floor response spectra. The factors influencing the floor response spectra, as the nonlinearities of the impact area, load time function shape and the impact velocity are pointed out and subsequent conclusions are made. Alternative motion parameters for assessment of the damage potential and procedure for indirect assessment of the equipment capacity are also discussed.

There are continuous attempts to describe the damaging potential of the seismic (or vibratory) mo... more There are continuous attempts to describe the damaging potential of the seismic (or vibratory) motion by a single parameter or a set of damage indicating parameters (DIP). Recently CAV and IJMA (JMI) are becoming two very promising parameters. Originally CAV was introduced as a parameter alongside spectral characteristics of ground motion for assessment of the operational state of a nuclear power plant after a seismic event. The aim is to shorten the time for evaluation of OBE exceedance and to provide guidance for the quick restart of a seismically affected plant. Meanwhile, there has been a growing experience and confidence that the DIP could be used not only as global indicator, i.e. assessment of the severity of excitation on the plant site but also as damage descriptor at equipment level, i.e. at each equipment location. The procedure proposed is similar to that for floor response spectra generation and safety evaluation against seismically induced forces. The current paper is ...

In this paper the floor response spectra generation methodology for Kozloduy NPP, Unit 1-2 of VVE... more In this paper the floor response spectra generation methodology for Kozloduy NPP, Unit 1-2 of VVER 440-230 is presented. The 2D coupled soil-structure interaction models are used combined with a simplified correction of the final results for accounting of torsional effects. Both time history and direct approach for in-structure spectra generation are used and discussion of results is made.

DEVELOPMENT

... of assess-ment and enhancement of seismic capacity of existing nuclear power plants of theWER... more ... of assess-ment and enhancement of seismic capacity of existing nuclear power plants of theWER type. ... the Assessment and Improvement of Seismic Capacity CONSTRAINTS (BUDGET, SCHEDULE) OVERALL OBJECTIVE: SEISMIC QUALIFICATION OF WWER TYPE NPP's ...

8 th Pacfic …, 2007

In the recent 50 years many dams have been constructed in Bulgaria. Almost all of them are situat... more In the recent 50 years many dams have been constructed in Bulgaria. Almost all of them are situated in regions with high and moderate seismicity. The regulations and codes that have been in force during the design and construction of the structures differ considerably from the ...

Nuclear Engineering and Design, 2014

There are continuous attempts to describe the damaging potential of the seismic (or vibratory) mo... more There are continuous attempts to describe the damaging potential of the seismic (or vibratory) motion by a single parameter or a set of damage indicating parameters (DIP). Recently CAV and I JMA JMI are becoming two very promising parameters. Originally CAV was introduced as a parameter alongside spectral characteristics of ground motion for assessment of the operational state of a nuclear power plant after a seismic event. The aim is to shorten the time for evaluation of OBE exceedance and to provide guidance for the quick restart of a seismically affected plant. Meanwhile, there has been a growing experience and confidence that the DIP could be used not only as global indicator, i.e. assessment of the severity of excitation on the plant site but also as damage descriptor at equipment level, i.e. at each equipment location. The procedure proposed is similar to that for floor response spectra generation and safety evaluation against seismically induced forces. The current paper is presenting basic relations between damage parameters and structural damage derived from the European strong motion data base. The seismic experience data base is utilized to assess the capacity/damage of equipment. A formalized approach is considered for evaluation of critical facilities subjected to dynamic vibratory loading. The following sequence of evaluation steps is discussed: Step One: For the safety equipment the standard in-structure CAV is calculated and compared with a threshold to screen-out the equipment for further considerations. An additional and optional threshold could be the in-structure I JMA intensity estimate. Step Two: For all locations where standard CAV of in-structure vibrations is higher than the threshold, the floor response spectra are evaluated. They have to be compared with the equipment capacity spectra. The latter are represented by design floor response spectra multiplied by a safety factor or seismic ruggedness spectra. Step Three: Alternatively or simultaneously with the ultimate capacity assessment (force driven design) a displacement based evaluation of the ultimate drift capacity of the respective equipment can be performed. It has to be stressed that under high frequency excitation the displacement (drift) estimated capacity is by far more realistic than the force based estimates. If none of the above checks is positively answered detailed conventional analysis can follow; however, a much smaller amount of equipment would remain for assessment.

... of assess-ment and enhancement of seismic capacity of existing nuclear power plants of theWER... more ... of assess-ment and enhancement of seismic capacity of existing nuclear power plants of theWER type. ... the Assessment and Improvement of Seismic Capacity CONSTRAINTS (BUDGET, SCHEDULE) OVERALL OBJECTIVE: SEISMIC QUALIFICATION OF WWER TYPE NPP's ...

Nuclear Engineering and Design, Apr 1, 2014

There are continuous attempts to describe the damaging potential of the seismic (or vibratory) mo... more There are continuous attempts to describe the damaging potential of the seismic (or vibratory) motion by a single parameter or a set of damage indicating parameters (DIP). Recently CAV and I JMA JMI are becoming two very promising parameters. Originally CAV was introduced as a parameter alongside spectral characteristics of ground motion for assessment of the operational state of a nuclear power plant after a seismic event. The aim is to shorten the time for evaluation of OBE exceedance and to provide guidance for the quick restart of a seismically affected plant. Meanwhile, there has been a growing experience and confidence that the DIP could be used not only as global indicator, i.e. assessment of the severity of excitation on the plant site but also as damage descriptor at equipment level, i.e. at each equipment location. The procedure proposed is similar to that for floor response spectra generation and safety evaluation against seismically induced forces. The current paper is presenting basic relations between damage parameters and structural damage derived from the European strong motion data base. The seismic experience data base is utilized to assess the capacity/damage of equipment. A formalized approach is considered for evaluation of critical facilities subjected to dynamic vibratory loading. The following sequence of evaluation steps is discussed: Step One: For the safety equipment the standard in-structure CAV is calculated and compared with a threshold to screen-out the equipment for further considerations. An additional and optional threshold could be the in-structure I JMA intensity estimate. Step Two: For all locations where standard CAV of in-structure vibrations is higher than the threshold, the floor response spectra are evaluated. They have to be compared with the equipment capacity spectra. The latter are represented by design floor response spectra multiplied by a safety factor or seismic ruggedness spectra. Step Three: Alternatively or simultaneously with the ultimate capacity assessment (force driven design) a displacement based evaluation of the ultimate drift capacity of the respective equipment can be performed. It has to be stressed that under high frequency excitation the displacement (drift) estimated capacity is by far more realistic than the force based estimates. If none of the above checks is positively answered detailed conventional analysis can follow; however, a much smaller amount of equipment would remain for assessment.

Proceedings of the International Astronomical Union, Dec 1, 2019

The increase in the amount of scientific information in heliophysics is related to both quantitat... more The increase in the amount of scientific information in heliophysics is related to both quantitative – increasing the number of high-power telescopes and the size of light receivers coupled to them, and qualitative reasons – new modes of observation, large-scale and multiple studies of the solar corona in different ranges, large-scale numerical experiments to simulate the evolution of various processes and formations, etc. The paper discusses the role and importance of methods for processing images of the solar corona, the store of obtained “raw” data and the need to access high-performance computing systems in order to obtain scientific results from the observational experiments, the need of international collaboration and access to the data in the era of increase in the amount of scientific information in heliophysics.

In this paper the floor response spectra generation methodology for Kozloduy NPP, Unit 1-2 of VVE... more In this paper the floor response spectra generation methodology for Kozloduy NPP, Unit 1-2 of VVER 440-230 is presented. The 2D coupled soU-structure interaction models are used combined with a simplified correction of the final results for accounting of torsional effects. Both time history and direct approach for in-structure spectra generation are used and discussion of results is made.

Assessment of the effects of a large aircraft impact on a NPP reactor building are the basic topi... more Assessment of the effects of a large aircraft impact on a NPP reactor building are the basic topics of the present work. The focus is on the dynamic response of the internal sub-structures, by means of floor response spectra. The factors influencing the floor response spectra, as the nonlinearities of the impact area, load time function shape and the impact velocity are pointed out and subsequent conclusions are made. Alternative motion parameters for assessment of the damage potential and procedure for indirect assessment of the equipment capacity are also discussed.

There are continuous attempts to describe the damaging potential of the seismic (or vibratory) mo... more There are continuous attempts to describe the damaging potential of the seismic (or vibratory) motion by a single parameter or a set of damage indicating parameters (DIP). Recently CAV and IJMA (JMI) are becoming two very promising parameters. Originally CAV was introduced as a parameter alongside spectral characteristics of ground motion for assessment of the operational state of a nuclear power plant after a seismic event. The aim is to shorten the time for evaluation of OBE exceedance and to provide guidance for the quick restart of a seismically affected plant. Meanwhile, there has been a growing experience and confidence that the DIP could be used not only as global indicator, i.e. assessment of the severity of excitation on the plant site but also as damage descriptor at equipment level, i.e. at each equipment location. The procedure proposed is similar to that for floor response spectra generation and safety evaluation against seismically induced forces. The current paper is ...

In this paper the floor response spectra generation methodology for Kozloduy NPP, Unit 1-2 of VVE... more In this paper the floor response spectra generation methodology for Kozloduy NPP, Unit 1-2 of VVER 440-230 is presented. The 2D coupled soil-structure interaction models are used combined with a simplified correction of the final results for accounting of torsional effects. Both time history and direct approach for in-structure spectra generation are used and discussion of results is made.

DEVELOPMENT

... of assess-ment and enhancement of seismic capacity of existing nuclear power plants of theWER... more ... of assess-ment and enhancement of seismic capacity of existing nuclear power plants of theWER type. ... the Assessment and Improvement of Seismic Capacity CONSTRAINTS (BUDGET, SCHEDULE) OVERALL OBJECTIVE: SEISMIC QUALIFICATION OF WWER TYPE NPP's ...

8 th Pacfic …, 2007

In the recent 50 years many dams have been constructed in Bulgaria. Almost all of them are situat... more In the recent 50 years many dams have been constructed in Bulgaria. Almost all of them are situated in regions with high and moderate seismicity. The regulations and codes that have been in force during the design and construction of the structures differ considerably from the ...

Nuclear Engineering and Design, 2014

There are continuous attempts to describe the damaging potential of the seismic (or vibratory) mo... more There are continuous attempts to describe the damaging potential of the seismic (or vibratory) motion by a single parameter or a set of damage indicating parameters (DIP). Recently CAV and I JMA JMI are becoming two very promising parameters. Originally CAV was introduced as a parameter alongside spectral characteristics of ground motion for assessment of the operational state of a nuclear power plant after a seismic event. The aim is to shorten the time for evaluation of OBE exceedance and to provide guidance for the quick restart of a seismically affected plant. Meanwhile, there has been a growing experience and confidence that the DIP could be used not only as global indicator, i.e. assessment of the severity of excitation on the plant site but also as damage descriptor at equipment level, i.e. at each equipment location. The procedure proposed is similar to that for floor response spectra generation and safety evaluation against seismically induced forces. The current paper is presenting basic relations between damage parameters and structural damage derived from the European strong motion data base. The seismic experience data base is utilized to assess the capacity/damage of equipment. A formalized approach is considered for evaluation of critical facilities subjected to dynamic vibratory loading. The following sequence of evaluation steps is discussed: Step One: For the safety equipment the standard in-structure CAV is calculated and compared with a threshold to screen-out the equipment for further considerations. An additional and optional threshold could be the in-structure I JMA intensity estimate. Step Two: For all locations where standard CAV of in-structure vibrations is higher than the threshold, the floor response spectra are evaluated. They have to be compared with the equipment capacity spectra. The latter are represented by design floor response spectra multiplied by a safety factor or seismic ruggedness spectra. Step Three: Alternatively or simultaneously with the ultimate capacity assessment (force driven design) a displacement based evaluation of the ultimate drift capacity of the respective equipment can be performed. It has to be stressed that under high frequency excitation the displacement (drift) estimated capacity is by far more realistic than the force based estimates. If none of the above checks is positively answered detailed conventional analysis can follow; however, a much smaller amount of equipment would remain for assessment.