Question

[Problem 15-5, p.679 in Henry and Heinke.] Some of the important characteristics of each of the reactors at the Pickering Nuclear Generating Station are as follows:

                        Thermal output: 1744 MW

                        Number of fuel channels: 390

                        Fuel bundles per channel: 12

                        Uranium content per fuel bundle: 19.8 kg

                        Total weight of fuel bundle: 23.7 kg

                        Length of fuel bundle: 49.5 cm

                        Outside diameter of fuel bundle: 10.2 cm

                        Average burnup of fuel: 7500 MWd thermal/tonne U

Assume that each reactor achieves a capacity factor [CF] of 0.8, where CF = (Actual energy

produced) / (Perfect production). Calculate:

a)   The number of new fuel bundles per reactor required for each day of operation.

b)   The length of a rectangular container of cross-section, 2.6 m x 2.6 m, required to accommodate one year's output of spent fuel from each reactor. Assume that each bundle fits inside a rectangular box of outside dimensions 10.4 x 10.4 x 50 cm.

Answer 1

Since the thermal output of the fuel is 1744 MW, the amount of thermal energy produced per day, assuming 100% utilization of the fuel would be 1744 MWd (One MWd is the amount of energy generated when one megawatt of power is produced in the plant for an entire day.) One MWd corresponds to 24000 kWh.

It is known that 1 metric tonne (1000 kg) of uranium generates 7500 MWd of thermal energy. Hence, for 1744 MWd, the amount of uranium required is: , which is equal to 232.533 kg of Uranium. It has also been given that the actual energy produced is 0.8 or 80% of that predicted theoretically (capacity factor). This implies that the amount of uranium actually required is 125% of that theoretically calculated, i.e. 1.25 232.533 kg. This gives a daily uranium requirement of 290.66625 kg.

Since, it is given that 1 bundle of fuel has 19.8 kg of uranium, the number of bundles of fuel that will actually be required to meet the energy requirement of 1744 MW would be fuel rods, which is equal to 14.68 15. Hence, 15 fuel bundles would be required per day in order to achieve the operation desired.

Assuming the amount of spent fuel has the same volume as the fuel bundle introduced to the reactor, we can perform the calculations for the second part. Since each bundle fits in a rectangular box of dimension 10.4 10.4 50 cm³, each bundle has a volume of 5.408 10^-3 m³. Hence, the daily fuel volume would be 15 5.408 10^-3 m³ i.e. 0.08112 m³. Hence, the volume of fuel required yearly would be 29.6088 m³. This, when divided by the cross section of 2.6 2.6 m² yields 4.38 m as the length of the rectangular container to accommodate one year's spent fuel output from the plant.