I'm worried about your reactor design, you're only venting 1040Hu/s of total 1280Hu/s generation, meaning after a half hour that reactor will have a meltdown...
If you want some examples of better vented reactors: (use reactor planner to view the designs)
3 x QU @ 1120Hu/s 21p7erx76c8pagu0wvp132sxeu4prsllcjw4vn4o94y50sx8o2c2kbxmz0i1907c8tn8myu07dw67ls
2 x QT + 2 x QU @ 1200Hu/t a8h8kqhej60hngg3xlu1wnklhu05fkebp23awcae34xx13ksdqlh26egbdaljd1h1asa3oisw5wrtvk
4 x QU @ 1280Hu/s 21p7etbybfaf22smi0kfmp6ywg9m4gv0ap4cflyvhojhohqly79334ggxmz8n9igwvjctnestbjbnr4
4 x QU @ 1280Hu/s 21p7jtsqvapow26toarfd376b3hckhqcqzojp1gq3jch1ucu43qe7jf0p2b8zofbi1ovgp518p5y8e8
The last design reminds me most about your current setup in that the rods are in the same location, and thus has the same efficiency, but it vents all the heat generated by the rods, so no risk of meltdowns...
I have some additionally better designs if you are willing to go down the route of iridium reflectors for higher efficiency, but these are some of the best non reflected designs I've seen and used that are 100% stable. The mixed thorium and uranium reactor won't run att full blast all the time without some form of automation, but it won't ever go critical when one of the rod types get used up ahead of the others...
-edit- spelling fix.