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Nuclear Fuel Energy and CO2 Balance Calculator - HELP

(last updated 12 Dec 2009)

Contents:

Introduction

This calculator performs calculations of the material, energy, and CO2 emission balance for the front end of the nuclear fuel chain. It is an enlarged version of the Nuclear Fuel Material Balance Calculator.

The calculator uses the following assumptions: the uranium is mined in an open pit or underground mine, and it is enriched for use in light water reactors, such as pressurized water reactors (PWR) or boiling water reactors (BWR).

The material balance is presented in a flow chart. Upon entry of one value into any of the flow chart's input fields, all other fields are calculated accordingly. So, it is possible to calculate the balance per tonne of uranium mined, as well as per Gigawatt-year (GWae - this is the typical annual production of a 1300MW reactor) of electricity produced in the power plant, for example.
In addition, energy consumption and related CO2 emission are summarized in a table.

The parameters used for the calculation can be set in the Process, Energy Consumption, and Emission Parameters tables. These parameters show reasonable initial values which can be modified as needed. There are no other hidden parameters used in the calculation.

The energy balance only covers the energy used for the operation of the plants; it does not include energy used for the construction or decommissioning of the plants, nor energy used for the production of any raw materials required.
For each step, the consumption of fossil fuel (such as Diesel, or natural gas used on site for purposes other than electricity generation) and electricity can be entered separately; the fossil fuel figures do not include the primary energy required for the production of the electricity.
"t" stands for metric tonne.

See special instructions for offline use of this calculator.

> See also the Nuclear Fuel Cost Calculator and the Nuclear Fuel Population Health Risk Calculator.

Process Parameters

Ore Deposit: Waste/Ore Ratio
At conventional uranium mines, overburden and waste rock has to be removed to get access to the uranium ore. The waste-to-ore ratio can range between 1 and 5 for underground mines and between 1 and 60 for open pit mines.

Ore Deposit: Ore Grade [wt-% U]
Weight-percent of uranium contained in the ore removed from the ore body for processing in the mill. Other units used are % U3O8, among others (see also Unit Conversion). Ore grades being processed at present cover a wide range of 0.026% U (Rössing, Namibia) over 1.1% U (Key Lake, Canada) up to 12.7% U (McArthur River, Canada).

Mill: Extraction Losses [%]
Not all of the uranium contained in the ore can be recovered in the milling process. The extraction losses are depending on the grade of the ore processed. Upon entry of an Ore Grade value, the calculator presents an estimated value for the Mill Extraction Losses. If you want to use another value for the losses, you can overwrite it.

Mill: Solids in tailings effluent [wt-%]
Weight-percent of solids contained in the tailings effluent stream of the mill.
For wet disposal, typical values are in the 20 to 50% range. For its model mill, U.S. NRC assumes 50% solids by weight in the tailings slurry sent to the tailings retention system [NUREG-0706]. For thickened paste disposal, values are in the 50 to 75% range.

Conversion: Losses [%]
Production losses during the conversion process.

Conversion: Solid waste per t U [t]
Amount of solid waste arising from refining and conversion, per tonne U produced.

Conversion: Liquid waste per t U [m3]
Amount of liquid waste arising from refining and conversion, per tonne U produced. Ranges between 3 and 10 m3 per t U.

Enrichment: Product Assay [wt-% U-235]
Weight-percent of the fissile isotope uranium-235 in the uranium contained in the product stream (enriched uranium hexafluoride) of the enrichment plant. Values for use in pressurized water reactors (PWR) range between 3.6% and 4.1%, and for use in boiling water reactors (BWR) between 3.0% and 3.2%. (Note: Natural uranium contains 0.711 wt-% of uranium-235)

Enrichment: Tails Assay [wt-% U-235]
Weight-percent of the isotope uranium-235 in the uranium contained in the waste stream (depleted uranium hexafluoride) of the enrichment plant. Typical values range between 0.25% and 0.30%. The tails assay can be selected according to economic feasibilty.
> See graphs: Cost balance of uranium enrichment · Optimal tails assay
(Note: feed cost includes uranium price plus conversion cost)
For current prices, see Current Uranium Prices

Fuel Fabrication: Losses [%]
Production losses during the fuel fabrication process.

Fuel Fabrication: Solid waste per t U [m3]
Amount of solid waste arising from fuel fabrication, per tonne U produced.

Fuel Fabrication: Liquid waste per t U [m3]
Amount of liquid waste arising from fuel fabrication, per tonne U produced.

Power Plant: Fuel Burnup [GWd/t U]
Thermal energy produced in the nuclear power plant from 1 metric tonne of enriched uranium contained in the nuclear fuel. It ranges between 40 and 43.4 GWd/t U for pressurized water reators (PWR), and 33 and 40 GWd/t U for boiling water reactors (BWR). GWd stands for Gigawatt-days, 1 GWd = 24 million kilowatt-hours.

Power Plant: Efficiency [%]
Efficiency of converting thermal energy into net electricity, ranges between 32% and 34.5%.

Energy Consumption Parameters

This table defines the specific energy consumption for the steps of the nuclear fuel chain. For each step, consumption of fossil fuel (such as Diesel, or natural gas used on site for purposes other than electricity generation) and electricity can be entered separately.
For conversion between energy units, see the Unit Converter.

Mining: Fossil Fuel [MJ per t ore]
Values vary in wide ranges, depending on ore deposit and mining technique used. Typical values are 407 MJ per t ore for open pit mines, and 57.7 MJ per t ore for underground mines in the US.

Mining: Fossil Fuel [MJ per t waste rock]
...

Mining: Electricity [kWhe per t ore]
Values vary in wide ranges, depending on ore deposit and mining technique used. Typical values are 2.68 kWhe per t ore for open pit mines, and 70.6 kWhe per t ore for underground mines in the US.

Mining: Electricity [kWhe per t waste rock]
...

Milling: Fossil Fuel [MJ per t ore]
A typical value is 483 MJ per t ore processed for a mill in the US.

Milling: Electricity [kWhe per t ore]
A typical value is 18.6 kWhe per t ore processed for a mill in the US.

Conversion: Fossil Fuel [MJ per kg U]
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Conversion: Electricity [kWhe per kg U]
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Enrichment: Fossil Fuel [MJ per SWU]
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Enrichment: Electricity [kWhe per SWU]
For gaseous diffusion enrichment plants, the specific electricity consumption is in the range of 2300 to 2500 kWh/SWU, while it is less than 50 kWh/SWU for modern centrifuge enrichment plants. SWU is the acronym for Separative Work Unit (also known as "kg SWU").

Fuel Fabrication: Fossil Fuel [MJ per kg U]
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Fuel Fabrication: Electricity [kWhe per kg U]
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Emission Parameters

Fossil Fuel: CO2 [t per TJ]
Specific carbon dioxide emission for the fossil fuel used.
Typical values are 74 t per TJ for Diesel fuel, and 55 t per TJ for natural gas.

Electricity: CO2 [t per GWhe]
Specific carbon dioxide emission from the production of the electricity used.
Typical values are 936 t per GWhe for coal-fired power plants, and 800 t per GWhe for Diesel generators.

Calculation Details

The formulae used by the calculator for the enrichment process can be found in Wikipedia .

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