Current status of MELCOR 2.2 for fusion safety analyses

MELCOR is an integral code developed by Sandia National Laboratories (SNL) for the US Nuclear Regulatory Commission (USNRC) to perform severe accident analyses of Light Water Reactors (LWR). More recently, MELCOR capabilities are being extended also to analyze non-LWR fission technologies. Within the European MELCOR User Group (EMUG), organized in the framework of USNRC Cooperative Severe Accident Research Program (CSARP), an activity on the evaluation of the applicability of MELCOR 2.2 for fusion safety analyses has been launched and it has been coordinated by ENEA. The aim of the activity was to identify the physical models to be possibly implemented in MELCOR 2.2 necessary for fusion safety analyses, and to check if those models are already available in MELCOR 1.8.6 for fusion version, developed by Idaho National Laboratory (INL). From this activity, a list of modeling needs emerged from the safety analyses of fusion-related installations have been identified and described. Then, the importance of the various needs, intended as the priority for model implementation in the MELCOR 2.2 code, has been evaluated according to the technical expert judgement of the authors. In the present paper, the identified modeling needs are discussed. The ultimate goal would be to propose to have a single integrated MELCOR 2.2 code release capable to cover both fission and fusion applications

Current status of Melcor 2.2 for fusion safety analyses

MELCOR is an integral code developed by Sandia National Laboratories (SNL) for the US Nuclear Regulatory Commission (USNRC) to perform severe accident analyses of Light Water Reactors (LWR). More recently, MELCOR capabilities are being extended also to analyze non-LWR fission technologies. Within the European MELCOR User Group (EMUG), organized in the framework of the USNRC Cooperative Severe Accident Research Program (CSARP), an activity on the evaluation of the applicability of MELCOR 2.2 for fusion safety analyses has been launched and it has been coordinated by ENEA. The aim of the activity was to identify the physical models to be possibly implemented in MELCOR 2.2 necessary for fusion safety analyses, and to check if those models are already available in MELCOR 1.8.6 fusion version, developed by Idaho National Laboratory (INL). From this activity, a list of modeling needs that emerged from the safety analyses of fusion-related installations has been identified and described. Then, the importance of the various needs, intended as the priority for model implementation in the MELCOR 2.2 code, has been evaluated according to the technical expert judgment of the authors. In the present paper, the identified modeling needs are discussed. The ultimate goal would be to propose to have a single integrated MELCOR 2.2 code release capable to cover both fission and fusion applications

Combining regenerative medicine strategies to provide durable reconstructive options: auricular cartilage tissue engineering

Recent advances in regenerative medicine place us in a unique position to improve the quality of engineered tissue. We use auricular cartilage as an exemplar to illustrate how the use of tissue-specific adult stem cells, assembly through additive manufacturing and improved understanding of postnatal tissue maturation will allow us to more accurately replicate native tissue anisotropy. This review highlights the limitations of autologous auricular reconstruction, including donor site morbidity, technical considerations and long-term complications. Current tissue-engineered auricular constructs implanted into immune-competent animal models have been observed to undergo inflammation, fibrosis, foreign body reaction, calcification and degradation. Combining biomimetic regenerative medicine strategies will allow us to improve tissue-engineered auricular cartilage with respect to biochemical composition and functionality, as well as microstructural organization and overall shape. Creating functional and durable tissue has the potential to shift the paradigm in reconstructive surgery by obviating the need for donor sites

A comprehensive overview of radioguided surgery using gamma detection probe technology

The concept of radioguided surgery, which was first developed some 60 years ago, involves the use of a radiation detection probe system for the intraoperative detection of radionuclides. The use of gamma detection probe technology in radioguided surgery has tremendously expanded and has evolved into what is now considered an established discipline within the practice of surgery, revolutionizing the surgical management of many malignancies, including breast cancer, melanoma, and colorectal cancer, as well as the surgical management of parathyroid disease. The impact of radioguided surgery on the surgical management of cancer patients includes providing vital and real-time information to the surgeon regarding the location and extent of disease, as well as regarding the assessment of surgical resection margins. Additionally, it has allowed the surgeon to minimize the surgical invasiveness of many diagnostic and therapeutic procedures, while still maintaining maximum benefit to the cancer patient. In the current review, we have attempted to comprehensively evaluate the history, technical aspects, and clinical applications of radioguided surgery using gamma detection probe technology

Application of MELCOR 1.8.2 (fusion version) and MELCOR 2.1 on the DEMO Helium Cooled Pebble Bed blanket concept

Several incidental/accidental conditions can hamper the safety of a fusion reactor, and the Loss of Coolant Accident (LOCA) of the blanket Primary Heat Transfer System (PHTS) is one of the most challenging [1]. To date, one of the main codes employed for incidental conditions analyses in fusion installations is MELCOR 1.8.x. Although, this version is quite old, and newer version were released (MELCOR 2.1.6342). A code-to-code comparison between M 1.8.2 and M 2.1 has been performed to check the differences, and to highlight positive and negative aspects of both codes

LOCA Accident for the DEMO Helium Cooled Blanket

The exploitation of Fusion as energy source requires also the demonstration of a limited impact in term of risk to the sta, to the public, and to the environment, well below the limits established by international committees and national safety authorities. Therefore, a systematic safety analysis has to follow the design development to demonstrate that the safety objectives are met for each solution proposed. This analysis points out the dominant accident sequences as well as outlines the possible prevention, protection and mitigation actions and relevant systems. One of the most challenging accidents is a large break of the primary cooling system, due to the possible consequences in terms of radiological releases to the environment. However, thanks to the relative small radiological inventory and to the lower decay heat density, the risk associated with a break of the primary cooling loop in a fusion reactor is lower than the risk of the same event in a fission reactor. However, this event should be detected as soon as possible to limit the consequences: e.g. limiting radioactive inventory from the primary confinement, impairment of secondary confinement due to the enthalpy of the helium mass released. Therefore, the Primary Heat Transfer System (PHTS) of the DEMO helium cooled Blanket requires system performances far dierent to that one of the fission reactors cooled by pressurized water. For this purpose a numerical assessment of PHTS has been carried out, considering two possible layout solutions. This analysis has been performed employing MELCOR 1.8.2 and aims to support the design of the Blanket and its PHTS with some safety-related consideration

Analysis of the Ingress of Coolant Event tests performed in the upgraded ICE facility aimed at the ECART code validation

The activities on the validation of the ECART code against the eight Ingress of Coolant Event (ICE) tests performed in the upgraded ICE facility are discussed. These analyses have been carried out to extend the ECART validation to incidental sequences related to future fusion plants, specifically - in the case of ICE - versus Loss Of Coolant Accident (LOCA) in volumes with near vacuum conditions. The upgraded ICE facility consists of a boiler, injecting water at high pressure inside a low-pressure tank simulating the Plasma Chamber (PC). This PC is in turn connected to the Vacuum Vessel (VV) through the divertor, and to the pressure Suppression (ST) by means of several relief pipes. Finally, the VV is connected with the Drain Tank (DT). Eight tests were performed investigating different numbers of relief pipes, different initial PC and VV temperatures, and different injected water mass flow rates, pressures and temperatures. The ECART results show an overall good agreement with the experimental data, confirming that ECART is also a valuable tool for the safety analysis in future fusion plants, as already pointed out in previous work