An insight on deformation of pressurized heavy water reactor coolant channel at extreme temperature in an oxidizing environment

ABSTRACT

This paper explains a preliminary study on the effect of oxidizing environment on the sagging deformation of Pressurized heavy water reactor coolant channel at extreme temperature. The coolant channel consists of two concentric tubes- calandria tube (outer tube) and pressure tube (inner tube). It is difficult to perform experiments with full-length coolant channels in the laboratory. Hence, a scaled-down concept is developed for scaling the coolant channels with a 1:3 scale. The various aspects of the geometric scaling of tubes are elaborated in this paper. The calculations for hydrogen generation are also presented analytically using existing and widely used correlations. The zirconium alloy of the calandria tube has reacted violently with steam, and the temperature escalation beyond 750°C produces significant chemical heat flux. The calandria tube has completely decayed during the experiment, and the channel is disassembled and fragmented into segments. Few segments are equal to one weight simulator length. Since the calandria tube cannot resist the deformation of the pressure tube due to loss in its structural strength, the pressure tube has undergone enormous unrestricted sagging before the channel failure. A maximum of 320 mm sag is reported at the mid-length of the channel. The scanning micrograph of the channel surface shows spalled oxide layers containing 45.89 weight percentage oxygen.

KEYWORDS:

• Severe accidents
• scaled channel
• oxidizing environment
• sagging
• thermo-mechanical deformation
• elevated temperature

Acknowledgments

The authors acknowledge the support of the Bhabha Atomic Research Centre, India, for initiating this research activity at the Indian Institute of Technology Roorkee, India. The authors are also grateful to Nuclear Fuel Complex, India, for fabricating and supplying the scaled-down PTs and CTs. The authors are thankful to the Institute Instruments Center of the Indian Institute of Technology Roorkee for carrying out the SEM analysis. Due support of Excel instruments, Mumbai is acknowledged for meeting the design and fabrication challenges of the complex experimental test apparatus.

Disclosure statement

No potential conflict of interest was reported by the author(s).

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