PSAM 16 - Session W12 Overview

PSAM 16 Conference Session W12 Overview

Session Chair: Enrique Meléndez-Asensio (ema@csn.es)

Paper 1 SH141

Lead Author: Hyun Gook Kang Co-author(s): Junyung Kim, kimj42@rpi.edu Asad Ullah Amin Shah, shaha11@rpi.edu

Concept Design, Application and Risk Assessment of New Forced Safety Injection Tank for Station Blackout Accident Scenario
In the current fleet of nuclear power plants, engineered safety systems are designed to perform fundamental safety functions. These fundamental safety functions are crucial, and failure of any one of these may lead to devastating accidents like the Fukushima Daiichi accident. The lesson learned from the Fukushima accident led to the development of advanced passive safety systems for all the new reactor designs and additional safety enhancement to the current nuclear fleet, such as accident tolerant fuel and diverse and flexible coping strategies (FLEX). Safety injection tanks (SIT) are designed to refill the core in the event of medium-large or large break LOCA accidents, and are an essential part in the engineered safety features. The amount of coolant inventory inside the SITs can also provide extended time to core damage if utilized in other accidents such as Station Blackout. This research presents the conceptual design of the new forced safety injection tank (FSIT). FSIT is designed by introducing a piston-assemblies on the top of the existing SITs. The principle of operation is that when the FSIT is actuated, the pressure of the FSIT is increased above the discharge pressure using the backpressure from the pressurizer or steam generator (SG) to drive inventory into the system to gain additional time to core damage. This time can be imperative in deploying FLEX to recover the lost safety system. The basic Pascal's principles are applied in the conceptual design of FSIT. A FSIT piston-assembly has two pistons with different pressing areas; the piston with a larger area is designed to be in a low-pressure region and the other in the FSIT region. For example, when the FSIT system is actuated from back pressure from SG, the back pressure from SG is augmented by a piston area ratio. It drives the piston against the FSIT pressure up to the system pressure to inject the coolant by force. The model for FSIT was developed using ordinary differential equations (ODE) and solving them using a semi-implicit finite difference scheme. It is expected that FSIT can reduce the risk for several accident scenarios such as small break LOCA, medium break LOCA, steam generator tube rupture, station blackout (SBO), etc. In this research, we focused on its applicability to SBO for demonstration purpose. Turbine-driven auxiliary feedwater (TDAFW) pumps are critical components in the event of SBO. Early failure of these TDAFW pumps will likely lead to core damage. In such scenarios, the series operation of FSITs can extend the core damage timings to a point where the injection from the FLEX becomes available to extend the core damage timings further up to 72 hrs. of operation. The probabilistic risk assessment is performed to quantify the risk contribution of FSIT to the SBO accident scenario. Keywords: PRA, FLEX, RELAP5, Station Blackout (SBO), Forced Safety Injection Tank.

Concept Design, Application and Risk Assessment of New Forced Safety Injection Tank for Station Blackout Accident Scenario

In the current fleet of nuclear power plants, engineered safety systems are designed to perform fundamental safety functions. These fundamental safety functions are crucial, and failure of any one of these may lead to devastating accidents like the Fukushima Daiichi accident. The lesson learned from the Fukushima accident led to the development of advanced passive safety systems for all the new reactor designs and additional safety enhancement to the current nuclear fleet, such as accident tolerant fuel and diverse and flexible coping strategies (FLEX). Safety injection tanks (SIT) are designed to refill the core in the event of medium-large or large break LOCA accidents, and are an essential part in the engineered safety features. The amount of coolant inventory inside the SITs can also provide extended time to core damage if utilized in other accidents such as Station Blackout. This research presents the conceptual design of the new forced safety injection tank (FSIT). FSIT is designed by introducing a piston-assemblies on the top of the existing SITs. The principle of operation is that when the FSIT is actuated, the pressure of the FSIT is increased above the discharge pressure using the backpressure from the pressurizer or steam generator (SG) to drive inventory into the system to gain additional time to core damage. This time can be imperative in deploying FLEX to recover the lost safety system. The basic Pascal's principles are applied in the conceptual design of FSIT. A FSIT piston-assembly has two pistons with different pressing areas; the piston with a larger area is designed to be in a low-pressure region and the other in the FSIT region. For example, when the FSIT system is actuated from back pressure from SG, the back pressure from SG is augmented by a piston area ratio. It drives the piston against the FSIT pressure up to the system pressure to inject the coolant by force. The model for FSIT was developed using ordinary differential equations (ODE) and solving them using a semi-implicit finite difference scheme. It is expected that FSIT can reduce the risk for several accident scenarios such as small break LOCA, medium break LOCA, steam generator tube rupture, station blackout (SBO), etc. In this research, we focused on its applicability to SBO for demonstration purpose. Turbine-driven auxiliary feedwater (TDAFW) pumps are critical components in the event of SBO. Early failure of these TDAFW pumps will likely lead to core damage. In such scenarios, the series operation of FSITs can extend the core damage timings to a point where the injection from the FLEX becomes available to extend the core damage timings further up to 72 hrs. of operation. The probabilistic risk assessment is performed to quantify the risk contribution of FSIT to the SBO accident scenario. Keywords: PRA, FLEX, RELAP5, Station Blackout (SBO), Forced Safety Injection Tank.

Paper SH141 | Download the paper file. | Download the presentation PowerPoint file.

Name: Hyun Gook Kang (kangh6@rpi.edu)

Bio: Dr. Kang is a Professor of Nuclear Engineering Program at Rensselaer Polytechnic Institute (RPI). Before joining RPI, he was an Associate Professor at the Department of Nuclear Engineering at Korea Advanced Institute of Science and Technology (KAIST) and PRA research staff of the Korea Atomic Energy Research Institute (KAERI). He also taught at Khalifa University in UAE in 2011 and 2012. After his PhD from KAIST in 1999, Dr. Kang’s research focus has been on innovations of dynamic risk assessment of safety-critical systems. The topics include risk evaluation associated with digital I&C systems, passive safety features, the intelligence of control and protection, and advanced emergency procedures. His long-term research goal is to develop an autonomous operation scheme for nuclear power plants.

Country: USA
Company: Rensselaer Polytechnic Institute
Job Title: Professor

Paper 2 RO316

Lead Author: Robby Christian Co-author(s): Vaibhav Yadav vaibhav.yadav@inl.gov Steven R. Prescott steven.prescott@inl.gov Shawn St. Germain shawn.stgermain@inl.gov

Presenter of this paper: Vaibhav Yadav (vaibhav.yadav@inl.gov)

A Dynamic Risk Framework for the Optimization of Physical Security Posture of Nuclear Power Plants
This paper describes an ongoing work within the Light Water Reactor Sustainability pathway at Idaho National Laboratory (INL) to optimize security and cost of nuclear power plants. It introduces the dynamic risk assessment tool developed at INL, Event Modeling Risk Assessment using Linked Diagrams (EMRALD). EMRALD was leveraged to optimize the security posture of a nuclear power plant by integrating force-on-force (FOF) simulations and operator mitigation actions including the dynamic and flexible coping strategies (FLEX). To illustrate the methodology, four attack scenarios were modeled in a commercially available FOF simulation tool using a hypothetical nuclear power plant facility. The simulation results provide valuable insights into possible attack outcomes, as well as the probabilistic risk of core damage event given these outcomes. Safety mitigation procedures were modeled in EMRALD dependent on the attack outcomes by considering human operator uncertainties. The results demonstrate that the number of armed responders can be optimized, while still maintaining the same protection level as the initial security posture. The proposed modeling and simulation framework of integrating FLEX equipment with FOF models enables the nuclear power plants to credit FLEX portable equipment in the plant security posture, resulting in an efficient and optimized physical security system.

A Dynamic Risk Framework for the Optimization of Physical Security Posture of Nuclear Power Plants

This paper describes an ongoing work within the Light Water Reactor Sustainability pathway at Idaho National Laboratory (INL) to optimize security and cost of nuclear power plants. It introduces the dynamic risk assessment tool developed at INL, Event Modeling Risk Assessment using Linked Diagrams (EMRALD). EMRALD was leveraged to optimize the security posture of a nuclear power plant by integrating force-on-force (FOF) simulations and operator mitigation actions including the dynamic and flexible coping strategies (FLEX). To illustrate the methodology, four attack scenarios were modeled in a commercially available FOF simulation tool using a hypothetical nuclear power plant facility. The simulation results provide valuable insights into possible attack outcomes, as well as the probabilistic risk of core damage event given these outcomes. Safety mitigation procedures were modeled in EMRALD dependent on the attack outcomes by considering human operator uncertainties. The results demonstrate that the number of armed responders can be optimized, while still maintaining the same protection level as the initial security posture. The proposed modeling and simulation framework of integrating FLEX equipment with FOF models enables the nuclear power plants to credit FLEX portable equipment in the plant security posture, resulting in an efficient and optimized physical security system.

Paper RO316 | Download the paper file. |

A PSAM Profile is not yet available for this author.
Presenter Name: Vaibhav Yadav (vaibhav.yadav@inl.gov)

Bio: Dr. Vaibhav Yadav is a senior scientist at Idaho National Laboratory where he performs and leads several research efforts in the areas of risk, reliability, safety, security and regulations of nuclear power plants. His research can be categorized into following domains namely, risk-based and risk-informed methodologies, digital twin technologies, cyber security and physical security. He has extensive experience in working with US commercial utilities to develop and implement risk-informed computational methodologies for optimizing physical security. He is currently serving as a member of the Physical and Cyber Security Subcommittee of the ANS/ASME Joint Committee on Nuclear Risk Management.

Country: United States of America
Company: Idaho National Laboratory
Job Title: Research Scientist