Technical Brief

MCNP Simulation of In-Core Dose Rates for an Offline CANDU® Reactor

[+] Author and Article Information
Jordan G. Gilbert

Arcadis Canada Inc.,
Richmond Hill, ON L4B 3N4, Canada
e-mail: jordan.gilbert@arcadis.com

Scott Nokleby

Faculty of Engineering and Applied Science,
University of Ontario Institute of Technology,
Oshawa, ON L1H 7K4, Canada
e-mail: scott.nokleby@uoit.ca

Ed Waller

Faculty of Energy Systems and Nuclear Science,
University of Ontario Institute of Technology,
Oshawa, ON L1H 7K4, Canada
e-mail: ed.waller@uoit.ca

Manuscript received November 8, 2016; final manuscript received February 15, 2017; published online May 25, 2017. Assoc. Editor: Michal Kostal.

ASME J of Nuclear Rad Sci 3(3), 034502 (May 25, 2017) (6 pages) Paper No: NERS-16-1155; doi: 10.1115/1.4036354 History: Received November 08, 2016; Revised February 15, 2017

Inspections of pressure tubes in CANDU® reactors are a key part of maintaining safe operating conditions. The current inspection system, the channel inspection and gauging apparatus for reactors (CIGAR), performs the job well but is limited by the fact that it can only inspect one channel at a time. A multidisciplinary team is currently developing a novel robotic inspection system. As part of this work, a Monte Carlo N-particle (MCNP) model has been developed in order to predict the dose rates that the improved inspection system will be exposed to and, from this, predict the component lifetime. This MCNP model will be capable of predicting in-core dose rates at any location within the reactor, and as such could be used for other situations where the in-core dose rate needs to be known. Based on estimates from this model, it is expected that at 7 days after shutdown, the improved inspection system could survive in core for approximately 7 h, providing it uses a tungsten shield 2.5 cm in thickness around the integrated circuit components. This is expected to be sufficient to perform a single inspection.

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Fig. 1

The CIGAR inspection head

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Fig. 2

Three-dimensional rendering of the modified closure plug

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Fig. 3

Improved inspection system prototype

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Fig. 7

End view of the full reactor model

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Fig. 6

Three-dimensional rendering of the shield plug

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Fig. 5

Fuel channel section view

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Fig. 4

Three-dimensional rendering of the CANDU® fuel bundle

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Fig. 8

Axial dose distribution in channel M13

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Fig. 9

Dose rate in channel M13 and fuel activity versus time

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Fig. 10

Dose rate in channel M17 with various shields (note: DU represents depleted uranium)




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