In-pile critical heat flux and post-dryout heat transfer measurements – A historical perspective

• Published in: Nuclear engineering and design Vol. 317; pp. 44 - 50
• Main Author: Groeneveld, D.C.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.06.2017; Elsevier BV
• Subjects: Blowdown; Bundles; Bundling; Calcium carbonate; Chalk; Fluid dynamics; Heat flux; Heat transfer; NRX reactors; Nuclear fuels; Reactors; Rivers; Thermocouples
• ISSN: 0029-5493; 1872-759X
• DOI: 10.1016/j.nucengdes.2017.03.029

In the 1960s’ and 1970s’ Canada was a world leader in performing in-reactor heat transfer experiments on fuel bundles instrumented with miniature sheath thermocouples. Several Critical Heat Flux (CHF) and Post-CHF experiments were performed in Chalk River’s NRU and NRX reactors on water-cooled 3-, 18-, 19-, 21-, and 36-element fuel bundles. Most experiments were obtained at steady-state conditions, where the power was raised gradually from single-phase conditions up to the CHF and beyond. Occasionally, post-dryout temperatures up to 600°C were maintained for several hours. In some tests, the fuel behaviour during loss-of-flow and blowdown transients was investigated – during these transients sheath temperatures could exceed 2000°C. Because of the increasingly more stringent licensing requirements for in-pile heat transfer tests on instrumented fuel bundles, no in-pile CHF and post-dryout tests on fuel bundles have been performed anywhere in the world for the past 40years. This paper provides details of these unique in-pile experiments and describes some of their heat transfer results.