Status of Qualification of High-Temperature Reactor Fuel Element Spheres

Heit, Werner; Huschka, H.; Rind, W.; Kaiser, Günter

doi:10.13182/nt85-a33594

Cited by 50 publications

(21 citation statements)

References 3 publications

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“…, and the as-manufactured properties of an earlier German fuel (Heit et al 1985 Fuel development for this fuel form has included traditional in-reactor experiments followed by safety testing and postirradiation examination, as well as operation of both pebble bed and prismatic gas reactors in the U.S. and abroad. Although many of the variables critical to obtaining acceptable particle fuel performance are known, it is not clear that all of the important phenomena have been identified and that all the fabrication attributes needed to make acceptable fuel have been established.…”

Section: A Irradiation Experiments and From Us Heatup Tests Of Indmentioning

confidence: 99%

“…The starting material is an aqueous solution of uranyl nitrate, to which polyvinyl alcohol (PVA) and other non-specified additives are added to form a broth (Mehner et al 1990, Heit et al 1985. Droplets of the broth are generated by a 600Hz vibrator (Huschka and Vygen 1977) and fall through ammonia gas, which induces gelation of the droplet surface by PVA precipitation (Wolf et al 1975).…”

Section: German Fuelmentioning

confidence: 99%

“…Droplets of the broth are generated by a 600Hz vibrator (Huschka and Vygen 1977) and fall through ammonia gas, which induces gelation of the droplet surface by PVA precipitation (Wolf et al 1975). The partially gelated droplets finally fall into a concentrated aqueous solution of ammonia for bulk gelation (Heit et al 1985, Mehner et al 1990. At this stage of the fabrication process, uranium is in the form of ammonium diuranate (Huschka and Vygen 1977).…”

Section: German Fuelmentioning

confidence: 99%

“…At this point in the process, the chemical form of uranium is UO 3 (Mehner et al 1990), which is reduced to UO 2 by a H 2 stream at 1600-1700°C (Heit et al 1985, Huschka andVygen 1977). During this step the kernel density increases to its final value ranging from 10.8 to 10.9 g/cm 3 (Mehner et al 1990, Heit et al 1985 or, assuming a UO 2 theoretical density of 10.97g/cm 3 (Todreas and Kazimi 1990), to between 98 and 99% TD. All kernels are classified by means of vibrating tables to eliminate the odd-shaped particles (Mehner 1990).…”

Section: German Fuelmentioning

confidence: 99%

“…The OPyC is also deposited from a mixture of C 2 H 2 , C 3 H 6 and Ar at 1300°C at a rate of 4-6 µm/min (Huschka and Vygen 1977). Finally, the oddshaped coated particles are eliminated by means of vibrating tables (Heit et al 1985).…”

Section: German Fuelmentioning

confidence: 99%

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Key Differences in the Fabrication, Irradiation, and Safety Testing of U.S. and German TRISO-coated Particle Fuel and Their Implications on Fuel Performance

Petti¹,

Maki²,

Buongiorno³

et al. 2002

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High temperature gas reactor technology is achieving a renaissance around the world. This technology relies on high quality production and performance of coated particle fuel. Historically, the irradiation performance of TRISO-coated gas reactor particle fuel in Germany has been superior to that in the United States. German fuel generally displayed in-pile gas release values that were three orders of magnitude lower than U.S. fuel. Thus, we have critically examined the TRISO-coated fuel fabrication processes in the U.S. and Germany and the associated irradiation database with a goal of understanding why the German fuel behaves acceptably, why the U.S. fuel has not faired as well, and what process/ production parameters impart the reliable performance to this fuel form. The postirradiation examination results are also reviewed to identify failure mechanisms that may be the cause of the poorer U.S. irradiation performance.This comparison will help determine the roles that particle fuel process/product attributes and irradiation conditions (burnup, fast neutron fluence, temperature, and degree of acceleration) have on the behavior of the fuel during irradiation and provide a more quantitative linkage between acceptable processing parameters, as-fabricated fuel properties and subsequent in-reactor performance. FabricationA review of the fabrication processes used in Germany and the U.S. to make coated particle fuel indicates that the scale of fuel fabrication and development efforts in the last 25 years were quite different. German fabrication of modern TRISO-coated fuel was industrial/production scale incorporating improvements from fuel produced for the German AVR and THTR reactors. Strict process control was used to adhere to a process specification that produced high quality fuel.Only ~ 100 defects were found in 3.3 million particles produced. By contrast, the U.S. program post Fort St. Vrain was a mixture of lab scale and larger scale fabrication with some fuel fabrication done by GA and some done by Oak Ridge National Laboratory. Furthermore, different fuel and coating types, different fabrication process parameters, and different coaters and compact fabrication techniques were used in an attempt to produce high quality fuel. The result was an initial defect level in U.S. fuel that varied greatly and was much greater than those produced in Germany. Table E-1 compares each of the steps in the fabrication of German and U.S. TRISO-coated fuel. The U.S. entries are based on the fabrication of fuel for the New Production Reactor (NPR) program in the early 1990s. It is important to note that many of the iv steps used to make this fuel were unique to the program and are not considered part of the traditional U.S. fabrication effort. Nevertheless, the NPR experience was used in this report primarily because it was the last manufacturing campaign in the U.S. and represents the most complete manufacturing pedigree and testing campaign of modern U.S. TRISO fuel, albeit HEU, aimed at commercial scale deployment. Furthermo...

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Section: A Irradiation Experiments and From Us Heatup Tests Of Indmentioning

confidence: 99%