Questions Relative to CHF Testing for New Pressurized Water Reactor Advanced Fuel Assemblies

2010 ◽  
Author(s):  
Christophe Herer
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Removal ◽  
Nucleate Boiling ◽  
Operating Conditions ◽  
Pressurized Water Reactor ◽  
Pressurized Water ◽  
Water Reactor ◽  
Fuel Assemblies ◽  
Advanced Fuel

One of the limiting conditions during operation of a Pressurized Water Reactor is cladding integrity in case of occurrence of any conditions I or II events. The decoupling criterion is the absence of Departure from Nucleate Boiling (DNB) during the full sequence of any of these transients. Heat transfer between the clad and the water is limited by the DNB phenomenon when local surface heat flux is greater than the so-called Critical Heat Flux (CHF). Heat production at the surface is higher than heat removal capacity by the coolant therefore a vapor blanket is formed around the clad; consequently the heat transfer will drastically drop resulting in a sudden significant increase of the local wall temperature and clad damage may appear if no corrective action is initiated. DNB can not be estimated with physical principles only. Experimental support is needed for evaluation. Occurrence of DNB is evaluated using the Departure from Nucleate Boiling Ratio (DNBR) which is a function of both core thermal hydraulic (T/H) parameters and design of the fuel assembly. Advanced fuel assemblies claim higher CHF values compared to previous designs. Along with increased DNB performances for advanced fuel assemblies, CHF correlation development and advanced methodologies enable to extend normal operating conditions of a nuclear plant. On the one hand, CHF performances really increased allow additional margin related to the loss of fuel cladding integrity whereas on the other hand optimized correlations and advanced methodologies reduce this margin. An accurate assessment of the CHF performance of the advanced fuel assemblies is therefore required. This paper will raise issues regarding the assessment of the CHF performance of new advanced fuel assemblies design. The issues will be focused on the reliability of the experimental assessment of the CHF values and the accuracy of the transposition of mock up geometries to plant core configuration (representativity of the experiments). The verification that the tests conditions (pressure, flowrate, quality, heat flux …) ensure a proper coverage of all core conditions encountered during any of the conditions I & II transients is closely linked to DNBR methods and will not be extensively covered in this paper. This paper suggests some thoughts about relevance of the demonstration carried out by vendors on these matters.

Sensitivity of CTF Solution to Subchannel Window Size

2018 ◽  
Author(s):  
Roman Mukin ◽  
Marcus Seidl ◽  
Ivor Clifford ◽  
Hakim Ferroukhi
Keyword(s):  
Heat Flux ◽  
Window Size ◽  
Local Heat ◽  
Nucleate Boiling ◽  
Pressurized Water Reactor ◽  
Reference Case ◽  
Pressurized Water ◽  
Local Flow ◽  
Power Maps ◽  
Fuel Assemblies

In this work, a so-called mini-core consisting of a 3 × 3 array of 17 × 17 pressurized water reactor (PWR) fuel assemblies (FA) is considered with the aim of identifying the most conservative window size for hot channel analysis of bowed fuel assemblies. Overall, five different mini-core configurations are analyzed: one is the reference case, i.e. without FA displacement and four different cases with diagonal and parallel FA displacements. Rod power maps for these mini-cores were exported from neutronic calculations with CASMO-SIMULATE codes. Subchannel modelling with COBRA-TF code of all five mini-cores allows one to identify the rod position with a minimum departure from the nucleate boiling ratio (DNBR) and to construct input decks with different rod window sizes around the previously identified rod position. Overall, eight different window sizes are considered: 3 × 3, 5 × 5, 7 × 7, 9 × 9, 11 × 11, 13 × 13, 15 × 15 and 17 × 17. Results of subchannel analysis for a mini-core and different subchannel window configurations are compared with the help of DNBR parameter, which is the ratio between the critical heat flux (CHF) and the actual local heat flux on a rod. An assessment of three different CHF models is applied in this work: Groeneveld CHF look-up table (LUT), W3 CHF correlation, and Doroschuk CHF LUT. The general conclusion of this work is that for deformed core configurations, an appropriate rod window size needs to be determined to adequately capture the local flow redistribution. For large displacements (the largest displacement considered in this work is 10 mm), the DNBR ratio can drop to one. DNBRs obtained with the W3 CHF correlation give the most conservative results.

Performances Analyses of Crud of EPR Fuel Assembly

2017 ◽  
Author(s):  
Xuming Wang ◽  
Cenxi Yuan ◽  
Chen Ye
Keyword(s):  
Risk Assessment ◽  
Fuel Assembly ◽  
Low Risk ◽  
Third Generation ◽  
Pressurized Water Reactor ◽  
Worst Case ◽  
Pressurized Water ◽  
Water Reactor ◽  
Advanced Fuel ◽  
New Type

Taishan European Pressurized Water Reactor (EPR) is a third generation advanced pressurized water reactor (PWR), which adopts the third generation advanced fuel assembly (AFA-3G-LE) from AREVA for the first time. As suggested by American Electric Power Research Institute (EPRI), an EPRI level III crud risk assessment is necessary for new type of plants. Because crud induced power offset (CIPS) and crud induced local corrosion (CILC) can lead to axial offset anomaly (AOA) and fuel cladding failure, respectively. A EPRI level III CIPS/CILC risk assessment for Taishan EPR is performed with a new framework of simulation by using sub-channel code FLICA, crud code BOA, and Monte Carlo transport code Tripoli-4. Such framework enables a self-consistent calculation, including a detailed description on neutronics contributed by boron. The validation of present work is confirmed because of the good agreement with the experienced data of EPRI. The results show that AFA-3G-LE has a good performance on crud risk assessment. Even in the worst case, the boron-10 deposition (2.6 g) and the maximum thickness of crud (59 μm) are lower than the low risk threshold, 31.33 g and 75 μm, respectively. Hence, It is expected that Taishan EPR has a very low risk on CIPS and CILC.

AP1000 Plant CILC/CIPS Risk Assessment Using Advanced TH Methodology

2012 ◽  
Author(s):  
G. Wang ◽  
P. Sapienza ◽  
R. J. Fetterman ◽  
M. Y. Young ◽  
J. R. Secker ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Nucleate Boiling ◽  
Operating Conditions ◽  
Localized Corrosion ◽  
Pressurized Water ◽  
Assembly Design ◽  
Power Shift ◽  
Fuel Assemblies ◽  
Water Reactors ◽  
The Relationship

Similar to many existing Pressurized Water Reactors (PWR), the AP1000® cores will undergo sub-cooled nucleate boiling in the upper grid spans of some fuel assemblies at normal operating conditions. Sub-cooled nucleate boiling may increase crud deposits on the fuel cladding surface which may increase the risk of Crud Induced Power Shift (CIPS) and/or Crud Induced Localized Corrosion (CILC). A CIPS/CILC risk assessment has been performed to support the AP1000 fuel assembly design finalization. In this paper, the advanced thermal-hydraulic (TH) methodology used in the AP1000 plant CIPS/CILC risk assessments are summarized and discussed, and the relationship between the CIPS/CILC mechanisms, fuel reliability, and plant operating conditions is also presented. Finally, acceptable AP1000 core CIPS/CILC risk assessment results are summarized and suggestions that specifically target reducing CIPS/CILC risks for AP1000 plants are described.

An Experimental Investigation of High Level Vibration on the Residual Heat Removal Line of a Pressurized Water Reactor

2009 ◽  
Author(s):  
Jeffrey A. Brown ◽  
Robert D. Blevins ◽  
H. Joseph Fernando
Keyword(s):  
Heat Removal ◽  
Coupled System ◽  
Acoustic Resonance ◽  
Acoustic Mode ◽  
Side Branch ◽  
Pressurized Water Reactor ◽  
Pressurized Water ◽  
Water Reactor ◽  
High Level ◽  
Residual Heat

This paper presents the results of a scaled aero acoustic test that modeled a side branch resonance observed in the residual heat removal suction line of a large pressurized water reactor. Resolution of the acoustic resonance was sought by detuning the eddy shedding frequency from the fundamental side branch acoustic mode. The specific physical modifications and their ability to detune the coupled system are presented.

Fuel Cycle Economy of Accident Tolerant Fuel Assemblies

2018 ◽  
Author(s):  
Xu Duoting ◽  
Liu Tong ◽  
Huang Heng
Keyword(s):  
Fuel Assembly ◽  
Economic Performance ◽  
Fuel Cycle ◽  
Pressurized Water Reactor ◽  
Pressurized Water ◽  
Water Reactor ◽  
Cycle Economy ◽  
Fuel Assemblies

Taking the large commercial pressurized water reactor and its mature fuel assembly as reference, this paper has analyzed economic performance of two accident tolerant fuel (ATF) designs based on once-through fuel cycle. The results show that the fuel cycle costs of both AT F designs have grown due to application of BeO powder, which is expensive. In order to reach the same electric cost as that of the referred fuel assembly, burn-up of these two AT F designs should be enhanced to 51323MWd/tU and 52054MWd/tU respectively.

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