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PostPosted: Apr 28, 2014 2:43 pm 
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Cyrill and DJW1 - welding of molybdenum alloys

Molybdenum and its alloys are in principle weldable. The challenges are oxygen in the weld and grain growth due to the heat that makes the weld brittle. Grain growth takes place at temperatures above the recrystallization temperature that is at 1000°C for mo, 1450°C for mo-tzm and 1550°C for TZC. That means it is necessary to work under argon or much better a vacuum to avoid oxygen. It is to have the heat applied as concentrated and short as possible to avoid grain growth. Good results were achieved with electron beam welding and a Mo-Re weld filler (Mo-Re remains ductile). Other promising welding methods are friction welding and supersonic welding.

Beside of welding brazing molybdenum alloys has a long history. In my concept it is used for example in the secondary HX to fix the pipes in the housing.

Diffusion bonding works with mo alloys. I would use it for the primary HX.

Question: Cyrill you mentioned that ASME does exclude mo-tzm for pressure vessels. Do you have a reference for it?


Last edited by HolgerNarrog on Apr 29, 2014 3:38 pm, edited 1 time in total.

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PostPosted: Apr 28, 2014 2:47 pm 
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Cyrill...the ductility of mo-tzm and tzc gets better with higher temperatures.


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PostPosted: Apr 28, 2014 2:54 pm 
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Boris, Thank you very much for the realistic overview of the Euratom initiative.

Do you or anyone saw anthing that the chinese published about their efforts??????

Best regards

Holger


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PostPosted: Apr 28, 2014 3:02 pm 
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Hi Boris,

concerning the structure material used for the MSFR there are some informations given about. It is indeed a nickel alloy similar to Hasteloy N but using Tungsten instead of mo for the reactor.

This structure material would be overchallenged with the HX and its requirements. They did not mention the material they plan to use for the HX but gave some material data as thermal conductivity. The data fits fine to mo-tzm and somehow to SIC.

Best regards

Holger


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PostPosted: May 01, 2014 8:34 am 
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Location: Switzerland
camiel wrote:
Well, that may be true for the European effort, but China is leading the way with regard to the FHR/MSR. Let's hope others will follow suit. Do you think there is a lot of institutional resistance from the established parties in the nuclear community ? I can recall one chairperson of the French Atomic Energy Commissariat in a video, dismissing the idea of a MSR out of hand.


Depends on what you call "leading the way". They still have a bit of a learning curve to climb. But they certainly have the biggest funding/manpower available.

To answer your question, I would say yes; but the reason why depends on who you ask. The case of France/CEA is special: SFRs have quite a bit of French history (Rapsodie, Phénix, Superphénix...) and are still widely considered to be the one reactor type that should make it to the market. The 'back-up' reactor of CEA is the GFR (Gas-cooled Fast Reactor). Why is still not perfectly clear to me: I'd say that it is a mix of history (the first french reactors, UNGGs (somewhat akin to Magnox reactors), were gas-cooled and designed by CEA, so they have experience in that), competitive advantage (since many other people are working on lead, it seems easier to make a name in gas) and neutronics performance. The chemistry division of CEA was involved in previous european MSR projects (before EVOL), but apparently not anymore. I guess this is due to funding cuts and re-centering of their activities on SFRs (namely, the ASTRID project).

In the rest of the nuclear community, well, it's not new. Many strong proponents of the defense-in-depth philosophy find it risky to have liquid fuel.


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PostPosted: May 01, 2014 8:51 am 
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HolgerNarrog wrote:
Boris, Thank you very much for the realistic overview of the Euratom initiative.

Do you or anyone saw anthing that the chinese published about their efforts??????

Best regards

Holger


Well, I have to say there is a lot (although it's not enough) of 'scientific' (as opposed to engineering) work done in the most important areas for MSRs: reprocessing and materials. The rest is a bit secondary, at this stage.

Concerning the chinese, I saw a flurry of articles recently:
He, Xiujie, Jinliang Song, Jie Tan, Baoliang Zhang, Huihao Xia, Zhoutong He, Xingtai Zhou, et al. 2014. “SiC Coating: An Alternative for the Protection of Nuclear Graphite from Liquid Fluoride Salt.” Journal of Nuclear Materials 448 (1–3): 1–3.

He, Zhoutong, Lina Gao, Xue Wang, Baoliang Zhang, Wei Qi, Jinliang Song, Xiujie He, et al. 2014. “Improvement of Stacking Order in Graphite by Molten Fluoride Salt Infiltration.” Carbon 72 (June): 304–11.

Liu, Kui, Li-Yong Yuan, Ya-Lan Liu, Xiu-Liang Zhao, Hui He, Guo-An Ye, Zhi-Fang Chai, and Wei-Qun Shi. 2014. “Electrochemical Reactions of the Th4+/Th Couple on the Tungsten, Aluminum and Bismuth Electrodes in Chloride Molten Salt.” Electrochimica Acta 130 (June): 650–59.

Liu, Wenguan, Han Han, Cuilan Ren, Xiujie He, Yanyan Jia, Song Wang, Wei Zhang, et al. 2014. “First-Principles Study of Intergranular Embrittlement Induced by Te in the Ni Sigma 5 Grain Boundary.” Computational Materials Science 88 (June): 22–27.

Zhu, Xingbao, Chengzhi Guan, Zhe Lü, Bo Wei, Yiqian Li, and Wenhui Su. 2014. “A Rapid Preparation of Acicular Ni Impregnated Anode with Enhanced Conductivity and Operational Stability.” Journal of Power Sources 256 (June): 424–29.

They're all from the CAS (Chinese Academy of Sciences) and most are from SINAP (Shanghai Institute of Applied Physics), home of the TMSR program.


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PostPosted: May 02, 2014 2:32 pm 
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Thanks Boris,

that are all very theoretic topics.

Is it to assume that the more practical topics are not going to become published?

Best regards

Holger


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