1500 cubic meters
Did you really pick the figure from the RBMK reactor type?
For PWRs, 250 m³ of LILW per GW annum is 28.5 m³ of LILW per TWh.
2.5 million turkeys in a 2.4 kW oven for 3.5 hours uses 0.021 TWh.
So 2.5 million turkeys and 0.6 m³ total low and intermediate wastes generated. Most of this can be released after ~300 years with negligible activity over natural background. That is a long time but not "basically forever".
They're over by a factor of 6 which would add up to 21 hours, not 24. I don't know what they've done to get 2.5 million, it should be 417 thousand with those numbers.
Edit: Oh dear. They said each oven could completely cook 6 turkeys in a day so they rounded to that number. At least it no longer reads GW/day.The source