Analyses of loss-of-coolant accidents involving release of insulation material under consideration of the measures taken for PWR from expert's point of view

Kerntechnik ◽  
2011 ◽  
Vol 76 (1) ◽  
pp. 58-65
Author(s):  
J. Huber ◽  
M. Becker ◽  
J. Unterrainer ◽  
T. Thiele ◽  
C. Reichel ◽  
...  
Keyword(s):  
Point Of View ◽  
Insulation Material ◽  
Loss Of Coolant

On Determination of Acceptable Safety Class in Design of Pipe-In-Pipe (PIP) Systems

2014 ◽  
Author(s):  
Soheil Manouchehri ◽  
Guillaume Hardouin ◽  
David Kaye ◽  
Jason Potter
Keyword(s):  
Failure Modes ◽  
Structural Integrity ◽  
Oil And Gas ◽  
Gas Production ◽  
Point Of View ◽  
Insulation Material ◽  
Limit States ◽  
Oil And Gas Production ◽  
Operational Conditions ◽  
Outer Pipe

Pipe-In-Pipe (PIP) systems are increasingly used in subsea oil and gas production where a low Overall Heat Transfer Coefficient (OHTC) is required. A PIP system is primarily composed of an insulated inner pipe which carries the production fluid and an outer pipe that protects the insulation material from the seawater environment. This provides a dry environment within the annulus and therefore allows the use of high quality dry insulation system. In addition, from a safety point of view, it provides additional structural integrity and a protective barrier which safeguards the pipeline from loss of containment to the environment. Genesis has designed a number of PIP systems in accordance with the recognized subsea pipeline design codes including DNV-OS-F101 [1]. In section 13 F100 of the 2013 revision, a short section has been included in which PIP systems are discussed and overall design requirements for such systems are provided. It has also been stated that the inner and outer pipes need to have the same Safety Class (SC) unless it can be documented otherwise. This paper looks at the selection of appropriate SC for the outer pipe in a design of PIP systems based on an assessment of different limit states, associated failure modes and consequences. Firstly, the fundamentals of selecting an acceptable SC for a PIP system are discussed. Then, different limit states and most probable failure modes that might occur under operational conditions are examined (in accordance with the requirements of [1]) and conclusions are presented and discussed. It is concluded that the SC of the outer pipe of a PIP system may be lower than that of the inner pipe, depending on the failure mode and approach adopted by the designer.

Test and Evaluation of a Filtering System for Retention of Fibres in a Coolant Flow After Loss-of-Coolant Accident

2012 ◽  
Author(s):  
T. Gocht ◽  
W. Kästner ◽  
A. Kratzsch ◽  
M. Strasser
Keyword(s):  
Cooling System ◽  
Reactor Core ◽  
Heat Removal ◽  
Test Facility ◽  
Experimental Investigations ◽  
Time Interval ◽  
Insulation Material ◽  
Loss Of Coolant Accident ◽  
Loss Of Coolant ◽  
Core Cooling

In case of an accident the safe heat removal from the reactor core with the installed emergency core cooling system (ECCS) is one of the main features in reactor safety. During a loss-of-coolant accident (LOCA) the release of insulation material fragments in the reactor containment can lead to malfunctions of ECCS. Therefore, the retention of particles by strainers or filtering systems in the ECCS is one of the major tasks. The aim of the presented experimental investigations was the evaluation of a filtering system for the retention of fiber-shaped particles in a fluid flow. The filtering system consists of a filter case with a special lamellar filter unit. The tests were carried out at a test facility with filtering units of different mesh sizes. Insulation material (mineral rock wool) was fragmented to fiber-shaped particles. To simulate the distribution of particle concentration at real plants with large volumes the material was divided into single portions and introduced into the loop with a defined time interval. Material was transported to the filter by the fluid and agglomerated there. The assessment of functionality of the filtering system was made by differential pressure between inlet and outlet of the filtering system and by mass of penetrated particles. It can be concluded that for the tested filtering system no penetration of insulation particles occurred.

Closed Model for Calculation of Differential Pressure After a Loss of Coolant Accident in Boiling Water Reactors

2009 ◽  
Author(s):  
Alexander Kratzsch ◽  
Wolfgang Ka¨stner ◽  
Rainer Hampel
Keyword(s):  
Differential Pressure ◽  
Boiling Water ◽  
Boiling Water Reactors ◽  
Insulation Material ◽  
Closed Model ◽  
Loss Of Coolant Accident ◽  
Safety Research ◽  
Loss Of Coolant ◽  
Water Reactors ◽  
Residual Heat

The paper deals with the calculation of differential pressure on sieves after a loss of coolant accident (LOCA) in boiling water reactors. One of the main features in reactor safety research is the safe heat dissipation from the reactor core and the reactor containment of light-water reactors. In the case of loss of coolant accident the possibility of the entry of insulation material into the reactor containment and the building sump of the reactor containment and into the associated systems to the residual heat exhaust is a serious problem. This can lead to a handicap of the system functions. To ensure the residual heat exhaust it is necessary the emergency cooling systems to put in operation which transport the water from the sump to the condensation chamber and directly to the reactor pressure vessel. A high allocation of the sieves with fractionated insulation material, in the sump can lead to a blockage of the sieves, inadmissibly increase of differential pressure, build-up at the sieves and to malfunctioning pumps. Hence, the scaling and retention of fractionated insulation material in the building sump of the reactor containment must be estimated. This allows the potential plant status in case of incidents to be assessed. The differential pressure is the essential parameter for the assessment of allocation of the sieves.

scholarly journals A Comparative Study of Traditional and Contemporary Building Envelope Construction Techniques in terms of Thermal Comfort and Energy Efficiency in Hot and Humid Climates

2019 ◽  
Vol 11 (13) ◽  
pp. 3582 ◽  
Author(s):  
Lotfabadi ◽  
Hançer
Keyword(s):  
Thermal Comfort ◽  
Vernacular Architecture ◽  
Building Design ◽  
Building Envelope ◽  
Point Of View ◽  
Thermal Calculation ◽  
Insulation Material ◽  
Energy Usage ◽  
Construction Techniques ◽  
Hot And Humid Climates

Expectations of traditional and contemporary buildings are different in terms of thermal comfort. Traditional buildings mostly achieve comfort through passive means, without HVAC support, but old levels of thermal satisfaction do not meet today’s expectations, although their passive thermal performances are notable for contemporary building designs. In this regard, the current study tries to investigate the possibility of comparing traditional and contemporary buildings’ construction techniques to achieve thermal comfort from an architectural point of view. In other words, is it possible to achieve passive building design by considering vernacular architecture principals as a reference? Likewise, how well can architects define insulation layers in contemporary construction surfaces in hot and humid climates? To this end, a dynamic, numerical, thermal calculation case study has been modeled in Famagusta, Northern Cyprus, to answer the above-mentioned questions. A mixed-use mode benefitting free-run periods is proposed and compared with a mode providing 24 hours of air-conditioning in different scenarios using the same initial settings. Thus, different floor-to-ceiling heights, insulation placements and indoor conditions have been tested separately in both winter and summer periods. The results show that thermal comfort can be achieved in free-run periods only during a limited percentage of the year. Furthermore, although increasing building heights may lead to a rise in the free-run periods, in contemporary buildings it increases the total energy usage of the buildings between 6% and 9% in the mixed mode. Therefore, vernacular architecture strategies are proper in their own context. However, this energy usage can still be controlled and optimized by such considerations as insulation material placement. In this regard, the best envelope properties for different building functions are proposed for application in hot and humid climates.

Numerical Simulation of the Insulation Material Transport to a PWR Core Under Loss of Coolant Accident Conditions

2010 ◽  
Author(s):  
Thomas Ho¨hne ◽  
Alexander Grahn ◽  
So¨ren Kliem ◽  
Ulrich Rohde ◽  
Frank-Peter Weiss
Keyword(s):  
Liquid Velocity ◽  
Reverse Flow ◽  
Mineral Wool ◽  
Insulation Material ◽  
Material Transport ◽  
Spacer Grids ◽  
The Core ◽  
Loss Of Coolant Accident ◽  
Loss Of Coolant ◽  
Core Cooling

In 1992, strainers on the suction side of the ECCS pumps in Barseba¨ck NPP Unit 2 became partially clogged with mineral wool because after a safety valve opened the steam impinged on thermally-insulated equipment and released mineral wool. This event pointed out that strainer clogging is an issue in the course of a loss-of-coolant accident. Modifications of the insulation material, the strainer area and mesh size were carried out in most of the German NPPs. Moreover, back flushing procedures to remove the mineral wool from the strainers and differential pressure measurements were implemented to assure the performance of emergency core cooling during the containment sump recirculation mode. Nevertheless, it cannot be completely ruled out, that a limited amount of small fractions of the insulation material is transported into the RPV. During a postulated cold leg LOCA with hot leg ECC injection, the fibers enter the upper plenum and can accumulate at the fuel element spacer grids, preferably at the uppermost grid level. This effect might affect the ECC flow into the core and could result in degradation of core cooling. It was the aim of the numerical simulations presented to study where and how many mineral wool fibers are deposited at the upper spacer grid. The 3D, time dependent, multi-phase flow problem was modelled applying the CFD code ANSYS CFX. The CFD calculation does not yet include steam production in the core and also does not include re-suspension of the insulation material during reverse flow. This will certainly further improve the coolability of the core. The spacer grids were modelled as a strainer, which completely retains all the insulation material reaching the uppermost spacer level. There, the accumulation of the insulation material gives rise to the formation of a compressible fibrous cake, the permeability of which to the coolant flow is calculated in terms of the local amount of deposited material and the local value of the superficial liquid velocity. Before the switch over of the ECC injection from the flooding mode to the sump mode, the coolant circulates in an inner convection loop in the core extending from the lower plenum to the upper plenum. The CFD simulations have shown that after starting the sump mode, the ECC water injected through the hot legs flows down into the core at so-called “breakthrough channels” located at the outer core region where the downward leg of the convection roll had established. The hotter, lighter coolant rises in the centre of the core. As a consequence, the insulation material is preferably deposited at the uppermost spacer grids positioned in the breakthrough zones. This means that the fibers are not uniformly deposited over the core cross section. When the inner recirculation stops later in the transient, insulation material can also be collected in other regions of the core. Nevertheless, with a total of 2.7 kg fiber material deposited at the uppermost spacer level, the pressure drop over the fiber cake is not higher than 8 kPa and all the ECC water could still enter the core.

The Geosciences Applied to Lunar Exploration

1962 ◽  
Vol 14 ◽  
pp. 169-257 ◽  
Author(s):  
J. Green
Keyword(s):  
Lunar Surface ◽  
Probable Mechanism ◽  
Point Of View ◽  
Lunar Exploration ◽  
Geological Model ◽  
Apply Geophysics ◽  
Surface Features ◽  
The Impact

The term geo-sciences has been used here to include the disciplines geology, geophysics and geochemistry. However, in order to apply geophysics and geochemistry effectively one must begin with a geological model. Therefore, the science of geology should be used as the basis for lunar exploration. From an astronomical point of view, a lunar terrain heavily impacted with meteors appears the more reasonable; although from a geological standpoint, volcanism seems the more probable mechanism. A surface liberally marked with volcanic features has been advocated by such geologists as Bülow, Dana, Suess, von Wolff, Shaler, Spurr, and Kuno. In this paper, both the impact and volcanic hypotheses are considered in the application of the geo-sciences to manned lunar exploration. However, more emphasis is placed on the volcanic, or more correctly the defluidization, hypothesis to account for lunar surface features.

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