If you go back to your Top View, you'll see that everything now is perfectly aligned to the centre of the world (Fig.32).
Fair enough? Let's move on.
At this point, you could call the reactor done, but just to show you a few more tricks, I'll keep going. Remember, even though we set out to do a reactor, I now have some other ideas of things we could try and see what kind of results we might come up with.
1. With our Group still selected, and back in the Perspective view, go up to Group > Open. By opening the group we can have access to all of the group members. Copy up the second cylinder we made so that you can achieve the following image (Fig.33)
When you're done, select on the Pink borders and Close the group.
2. Now add a Symmetry modifier to the group and set the Mirror Axis to Z. It should look like this (Fig.34).
Now let's make some more changes.
3. Open the Symmetry modifier to get to its sub-object mode and select on Mirror (Fig.35).
4. Now move the Mirror axis down until you get this (Fig.36).
When you're done, get out of sub-object mode by simply clicking on Mirror (which is yellow if you're in sub-object mode).
5. Add a second Symmetry modifier but this time set the Mirror Axis to Z but also check Flip. And then go into its sub-object mode and move the axis up until you get something like this (Fig.37).
I hope that you see the power of the Symmetry modifier.
6. Now add a Bend modifier to the whole object (remember to get out of sub-object mode first). And set the Angle to 180 (Fig.38).
7. Apply another Symmetry modifier: check Flip and move the mirror axis over until you get this (Fig.39).
8. Now I will rotate the whole group onto its side (turn Angle Snap Toggle back on) and make 3 more copies like we have done before (Fig.40).
I hope you get the picture here; by using just one primitive, look at what we have created! It is just getting to know your tools and what you can do with them.
I've taken this a little further to give you something to try out on your own. I haven't done anything you don't know how to do at this point I've just played with settings you already know about.
See if you can make this (Fig.41).