An introduction to Spent Nuclear Fuel decay heat for Light Water Reactors: a review from the NEA WPNCS

Open Access

Table 17.

Uncertainties for operational parameters, manufacturing tolerances, and burnup-induced technological changes.

	Design and operational parameters

Parameters	Uncertainty [232]	1σ [233]	1σ [33, 234]	1σ [235]	1σ [236]	1σ [237]	1σ [238]	1σ [239]
Probability	–	Normal	Uniform	Uniform	See superscript	See superscript	Normal
Cladding thickness	± 40–50 μm	16.7 μm
Cladding diameter (PWR)	± 200 mm	67 μm	0.5%	0.8%		0.1^U%	0.1%	0.1%
Cladding diameter (BWR)	± 300 mm	100 μm
Pin x and y position shifts	–	–	0.5%
Fuel pellet density	≤ 2%	0.67%	0.5%				0.5%	1.65%
Fuel pellet diameter	± 20 μm	correlated with fuel pellet dens.
Enr. (²³⁴U wt.%)				5%
Enr. (²³⁵U wt.%)	± 0.05%	0.0167%	0.2%	1%			0.02%	0.05%
Enr. (²³⁸U wt.%)				0.2%
Enr. (²³⁹Pu wt.%) (MOX)			0.2%
SNF power	–	1.67%
Burnup depletion step			0.25%	1%
Water temp. (PWR only)	± 2 °C	2 °C	2%	2%	1.5^U%
Water density (PWR only)	± 0.005 g/cm³	0.005 g/cm³		2%
Void fraction (BWR only)	± 6%	6%
Fuel temperature	± 50 °C	50 °C	2%	2%
Boron content (PWR only)	± 10 ppm	10 ppm	2%	2%
Reactor pressure			1%		1^N%
Sample power					1.5^N%	2^N%
Pin x and y position shifts	–	–	0.5%

Burnup-induced technological changes
	1σ	1σ [240]	1σ [241]	1σ [242]	1σ [243]	1σ [244]
Probability	Uniform

Fuel pin displacement	0.2 mm/burnup steps
Moderator pin displacement	0.05 mm/burnup steps
Pin radius	150 μm	15–50 μm	70 μm	80 μm	160 μm	150 μm
	@ 53 MWd/kg	@ 28 MWd/kg	@ 50 MWd/kg	@ 30 MWd/kg	@ 61 MWd/kg	@ 60 MWd/kg

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