scholarly journals Development of a Secondary SCRAM System for Fast Reactors and ADS Systems

2012 ◽  
Vol 2012 ◽  
pp. 1-9
Author(s):  
Simon Vanmaercke ◽  
Gert Van den Eynde ◽  
Engelbert Tijskens ◽  
Yann Bartosiewicz
Keyword(s):  
Liquid Metal ◽  
Core Region ◽  
Multiplication Factor ◽  
Negative Reactivity ◽  
Active Core ◽  
Loss Of Coolant ◽  
Gen Iv ◽  
Reactivity Insertion ◽  
Scram System ◽  
Carbide Particles

One important safety aspect of any reactor is the ability to shutdown the reactor. A shutdown in an ADS can be done by stopping the accelerator or by lowering the multiplication factor of the reactor and thus by inserting negative reactivity. In current designs of liquid-metal-cooled GEN IV and ADS reactors reactivity insertion is based on absorber rods. Although these rod-based systems are duplicated to provide redundancy, they all have a common failure mode as a consequence of their identical operating mechanism, possible causes being a largely deformed core or blockage of the rod guidance channel. In this paper an overview of existing solutions for a complementary shut down system is given and a new concept is proposed. A tube is divided into two sections by means of aluminum seal. In the upper region, above the active core, spherical neutron-absorbing boron carbide particles are placed. In case of overpower and loss of coolant transients, the seal will melt. The absorber balls are then no longer supported and fall down into the active core region inserting a large negative reactivity. This system, which is not rod based, is under investigation, and its feasibility is verified both by experiments and simulations.

Geometry Survey on the Convex Shaped Core for Recriticality Prevention Against CDA in Sodium-Cooled Fast Reactor

2018 ◽  
Author(s):  
Keiko Chitose ◽  
Yoshiaki Tachi ◽  
Toshio Wakabayashi ◽  
Naoyuki Takaki
Keyword(s):  
Molten Pool ◽  
Large Scale ◽  
Inner Core ◽  
Outer Core ◽  
Core Region ◽  
Energy Agency ◽  
The Core ◽  
Negative Reactivity ◽  
Core Height ◽  
Reactivity Insertion

In sodium-cooled fast reactors, the core is not arranged in its most reactive configuration. In this case, when the fuel melts to form a molten pool, the recriticality may occur by positive reactivity insertion due to core compaction. To prevent such recriticality, special devices of the fuel subassembly structure for discharging the molten fuel from the core region, have been investigated by the Japan Atomic Energy Agency (JAEA). On the other hand, the inherent feature of core geometry and the neutron characteristics may provide the similar effect to prevent such recriticality. The purpose of this study is to design the core specification its deformation in CDA causes negative feedback to subcritical condition, without any fuel discharge device. The convex shaped core has the longer fuel length in the inner-core region and the shorter fuel in the outer-core region. Therefore, the core geometry as intact status has a lower neutron leakage effect. When the fuel melts in CDA, the core height is compacted and negative reactivity insertion is expected during molten pool formation. The convex shaped core is based on the large-scale cylindrical homogeneous core (3,600 MWth, 4.95m in core diameter, and 0.75m in core height). The calculation showed that the compaction of cylindrical core leads to a reactivity gain, whereas the convex shaped core results in negative reactivity effect. In this geometry, both inner-core and outer-core are divided into two regions. Furthermore, we introduced the smaller diameter pin for inner-core and keep uniform Pu enrichment for all regions. The smaller diameter pins in high importance region are effective for flat-distribution. Through pin diameter survey, we confirmed the advantages of smaller diameter pin, such as reducing pressure loss of core coolant and decreasing the height of molten pool.

scholarly journals CADOR “Core with Adding DOppleR effect” concept application to sodium fast reactors

2019 ◽  
Vol 5 ◽  
pp. 1
Author(s):  
Alain Zaetta ◽  
Bruno Fontaine ◽  
Pierre Sciora ◽  
Romain Lavastre ◽  
Robert Jacqmin ◽  
...  
Keyword(s):  
Mechanical Energy ◽  
Core Size ◽  
Fuel Temperature ◽  
Fast Reactors ◽  
The Core ◽  
Loss Of Coolant ◽  
Neutron Moderator ◽  
Concept Application ◽  
Sodium Fast Reactors ◽  
Reactivity Insertion

Generation-IV sodium fast reactors (SFR) will only become acceptable and accepted if they can safely prevent or accommodate reactivity insertion accidents that could lead to the release of large quantities of mechanical energy, in excess of the reactor containment's capacity. The CADOR approach based on reinforced Doppler reactivity feedback is shown to be an attractive means of effectively preventing such reactivity insertion accidents. The accrued Doppler feedback is achieved by combining two effects: (i) introducing a neutron moderator material in the core so as to soften the neutron spectrum; and (ii) lowering the fuel temperature in nominal conditions so as to increase the margin to fuel melting. This study shows that, by applying this CADOR approach to a Generation-IV oxide-fuelled SFR, the resulting core can be made inherently resistant to reactivity insertion accidents, while also having increased resistance to loss-of-coolant accidents. These preliminary results have to be confirmed and completed to meet multiple safety objectives. In particular, some margin gains have to be found to guarantee against the risk of sodium boiling during unprotected loss of supply power accidents. The main drawback of the CADOR concept is a drastically reduced core power density compared to conventional designs. This has a large impact on core size and other parameters.

scholarly journals SIMULATION OF BREED AND BURN FUEL CYCLE OPERATION OF MOLTEN SALT REACTOR IN BATCH-WISE REFUELING MODE

2021 ◽  
Vol 247 ◽  
pp. 13003
Author(s):  
Valeria Raffuzzi ◽  
Jiri Krepel
Keyword(s):  
Molten Salt ◽  
Fuel Cycle ◽  
Fission Products ◽  
Molten Salt Reactor ◽  
Core Size ◽  
Spent Fuel ◽  
Fluid Core ◽  
Active Core ◽  
Breed And Burn ◽  
Gen Iv

The Molten Salt Reactor (MSR) is one of the most revolutionary Gen-IV reactors and it can be operated, especially with chloride salts, in the so-called breed and burn fuel cycle. In this type of fuel cycle the fissile isotopes from spent fuel do not need to be reprocessed, because the excess bred fuel covers the losses. The liquid phase of the MSR fuel assures its instant homogenization, and the reactor can be operated with batch-wise refueling thus reaching an equilibrium state. At the same time, the active core of the chloride fast MSR needs to be bulky to limit neutron leakage. In this study, the code Serpent 2 was coupled to the Python script BBP to simulate batch-wise operation of the breed and burn MSR fuel cycle. The script, previously developed for solid assemblies shuffling, was modified to simulate fuel homogenization after fertile material addition. Several fuel salts and fission products removal strategies were simulated and their impact was analyzed. Similarly, the influence of blanket volume was assessed in a two-fluid core layout. The results showed that the reactivity initially grows during the irradiation period and later decreases. The blanket has a large impact on the performance and it can be used to further increase the fuel burnup or to shrink the active core size. The breed and burn fuel cycle in MSR can reach high fuel utilization without fuel reprocessing and a multi-fluid layout can help to decrease the core size.

Oxygen Monitoring in the Natural Convection Loop Colonri I

2013 ◽  
Author(s):  
Fosca Di Gabriele ◽  
Lukas Kosek
Keyword(s):  
Liquid Metal ◽  
Oxygen Content ◽  
Electrochemical Sensors ◽  
Liquid Metals ◽  
Construction Materials ◽  
Liquid Lead ◽  
Protective Oxide ◽  
Key Issues ◽  
Oxygen Monitoring ◽  
Gen Iv

Oxygen has a fundamental role for the safe operation of GEN IV reactors cooled by Heavy Liquid Metals, HLM. The use of oxygen sensors and dosing the gas in the environment are key issues for the chemistry control of HLMs, in particular when corrosion of structural materials is of concern. In fact, the oxygen concentration must be high enough to grow a protective oxide scale on the surface of the construction materials (steels) in order to prevent their dissolution in the liquid metal. On the other hand, a certain threshold must not be exceeded to prevent precipitation of oxides within the flow paths of the plant. For measuring and controlling the concentration of dissolved oxygen in liquid lead alloys, electrochemical sensors were developed and have been studied for several years. This study focuses on the work carried out in the CVR, in the convection loop COLONRI I, containing liquid Lead-Bismuth Eutectic, LBE. This vertical loop has several locations where sensors can be placed for monitoring of the local oxygen content. A research study was initiated on the aim of assessing the response and reliability of the sensors in various locations, when different gases were dosed in the liquid metal. For over 1000 hours the sensors were monitored as variables, such as oxygen content and temperature, were changed. Their response as a function of their position was qualitatively evaluated and discussed.

Additional Improvements to Appendix G of ASME Section XI Code for Nozzles

2011 ◽  
Author(s):  
Hardayal S. Mehta ◽  
Timothy J. Griesbach ◽  
Daniel V. Sommerville ◽  
Gary L. Stevens
Keyword(s):  
Thermal Gradient ◽  
Research Council ◽  
Core Region ◽  
Prior Work ◽  
The Past ◽  
Active Core ◽  
Asme Code ◽  
Corner Solutions ◽  
Reactor Pressure ◽  
Calculation Procedures

This paper is the second in a continuing series of papers to highlight additional bases and recommended improvements to Appendix G. In 2008, the authors prepared a paper that reviewed some of the original basis documents for Appendix G for calculating pressure-temperature (P-T) limits and identified recommended areas for improvement. The 2008 paper discussed the fact that the original Appendix G in Section XI of the ASME Code was primarily based on Welding Research Council (WRC) Bulletin 175, and identified the changes that have been made to Appendix G over the past 20 years. However, the nozzle corner solutions have remained the same as those given in WRC 175. Proposed revisions to Appendix G are included in this paper regarding the stress intensity factor (K) calculation procedures for pressure and thermal gradient loading at a nozzle corner based on the various solutions described in the authors’ previous paper and on other more recent investigations. The current paper is focused on incorporating the results of additional studies that have been completed associated with nozzle corner solutions. This additional work has become more important because plants must address the effects of nozzles in the reactor pressure vessel (RPV) as a part of pressure-temperature (P-T) curve development, especially if the nozzles are located sufficiently close to the active core region such that they accumulate significant fluence. In addition, the treatment of operating stresses exceeding the material yield stress is discussed and the basis for the limit of material yield strength to 90 ksi in G-2110(b) is provided. Finally, this paper identifies other areas for future improvements in Appendix G, including those areas remaining to be addressed from prior work.

scholarly journals Reactor behavior comparisons for two liquid metal-cooled fast reactors during an event of loss of coolant

2019 ◽  
Vol 16 ◽  
pp. 100556 ◽  
Author(s):  
Alejandría-D. Pérez-Valseca ◽  
Sergio Quezada-García ◽  
Armando-M. Gómez-Torres ◽  
Alejandro Vázquez-Rodríguez ◽  
Gilberto Espinosa-Paredes
Keyword(s):  
Liquid Metal ◽  
Fast Reactors ◽  
Loss Of Coolant
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