I just finished watching The Heavy Water War, a highly entertaining Norwegian/Danish/English miniseries about the subterfuge and sabotage of the Vemork Hydroelectric Plant. While entertaining and (as far as I can tell) generally historically accurate, I had a lingering question about heavy water production and the Nazi nuclear program.
Within the series, it is shown that the nuclear program run by Heisenberg is reliant on a constant stream of heavy water, which the Nazis solely acquire from the Vemork Hydroelectric Plant in Norway, where it is a byproduct of the plant's fertilizer production. After the heavy water electrolysis chamber is destroyed by Norwegian commandos the Nazis dedicate a great deal of resources to the plants reconstruction and are able to get it operating again in a matter of months. Finally, after an Allied air raid, the Nazis make a desperation attempt to move heavy water production to the south of Germany, only to have the boat with the mechanical components and remaining stock sunk.
If all of the above is true, why didn't the Nazis move heavy water production to Germany sooner in the war? Or, better yet, simply construct additional plants with heavy water production capabilities earlier? The Vemork Plant's management is under constant pressure to increase their maximum heavy water outcome, and the Nazis seem willing to invest resources into its production, so why not construct additional plants instead? And weren't the Nazis concerned from the outset that having part of their large nuclear program rely on heavy water coming solely from a single plant would be a liability? The Nazis also believe that the plants workers and management could be actively working against their interests, so why would they not shift production to another location with a lesser risk of sabotage?
Shedding light on any of the above questions would be greatly appreciated.
It was not apparent to them that Vemork was endangered until it was fairly late in the war — 1943 or so. At that point, they did look into developing two domestic plants, which they had already scouted out as potential pilot operations — IG Farben's Ammonia Werk at Leuna and Linde Eismachinen Fabrik in Höllriegelskreuth, near Munich.
The problem was that they were very expensive (on the order of millions of Reichsmarks) and consumed huge amounts (for wartime Germany) of resources (e.g. tens of tons of coal per hour). This at a time when Germany's favors were not going so well, and the ability to justify the plants as necessary somewhat on the wane.
The Farben method required the feed material to be slightly enriched to begin with; once Vemork was destroyed and feed water from an Italian plant deemed inadequate, the plan was called into jeopardy. This was in the spring of 1944. In late July 1944, the Farben works got bombed.
I don't know exactly what happened to the Linde plant but it seems poorly thought-out as well, requiring near-pure hydrogen gas to operate.
All of their methods seem marred by the same sorts of things that plagued their overall project: poor coordination between scientists and industry, lack of cohesion about the scientific methods to be attempted, lack of willingness to commit huge sums and raw materials to risky outcomes, and the difficulties caused by being active targets of external attack (e.g. bombing, sabotage).
For more details, see Per Dahl, Heavy Water and the Wartime Race for Nuclear Energy (CRC Press, 1999).
I have not seen the show in question, but the preview I saw made it look like the Germans were actually trying to build a bomb. They were not. By 1942 they had decided they were going to pursue a very modest reactor pilot program. They were not willing to expend the resources on the project that would be necessary to get such things up and running immediately, the way the Americans were with the Manhattan Project, where three new heavy water plants were constructed within a couple of years, at the cost of some $27 million USD, equivalent to about 11 million Reichsmarks. For the Americans this expenditure represented an almost trivial amount in their total spending (and they didn't end up using heavy water for their plutonium production reactors in the end, anyway — they were just a back-up plan!). The total German state physics research expenditures in 1943 totaled some 3 million Reichsmarks by comparison — the US spent several times that per month in the same year. The German project was not being run like a real production project; it was being run like it was a group of interesting science projects being run by a few different universities. The Manhattan Project, which itself barely developed bombs ready for use in the war, was an entirely different magnitude of a beast, with top-down coordination by very dedicated people, given near-unlimited material and human resources, and had a preponderance of geniuses working at every level of execution.