Hitler's Sunken Secret
will use a viewing guide while watching a program about Nazi Germany's
production of heavy water during World War II, and discuss answers to their
questions after watching.
Students will be able to:
- copy of the "Heavy Water Goes Down" student handout
1940, the Germans captured Norway and took possession of the Norsk Hydro plant
in Vemork. The Germans were interested in the plant because it could be used to
manufacture heavy water. Although chemically like H2O, the hydrogen
atoms in heavy water are made of the heavy isotope deuterium (heavy water is
also known as deuterium oxide, D2O). The nuclei in each heavy water
molecule contain a neutron in addition to the proton normally found in
hydrogen. At Vemork, heavy water was produced through electrolysis, a process
in which an electric current is conducted through an ion-containing
Allied forces feared that the heavy water, which can help moderate a nuclear
reaction, was a part of Germany's atomic weapons program. Norwegian Resistance
workers at the Hydro factory provided the Allies with information about the
plant. The Allies joined with members of the Norwegian Resistance to plan and
execute three attacks on the plant prior to bombing the ferry believed to be
transporting barrels of heavy water.
At the time of the Hydro's sinking, the sabotage was considered a
success. However, some evidence suggests that the Germans may have planted
barrels on the ferry that did not contain heavy water, and that the actual
barrels with heavy water were shipped out of Norway to Germany at a later date.
Organize students into five teams. Assign each team a set of four questions.
The questions generally follow the sequence of the film. You can assign the
questions in their current sequence, allocate them by themes, or choose a mix
of simple and more complicated questions for each team.
Distribute a copy of the student handout to each team before viewing.
Discuss appropriate background information with students.
Show the program and have students individually take notes on the questions
their team has been assigned.
After watching the program, have students meet in their teams to discuss
their notes. Beginning with the first question assigned, ask teams to come to
consensus on an answer. The team response should be written down as the answer
to each question. Continue until all questions are answered.
Have teams share the questions and answers that came out of their team work.
(See Activity Answer for possible answers. Accept all reasonable
answers.) Ask students in the rest of the class if they agree with what the
team has presented. If students don't agree, ask them to explain why and
provide evidence from the program that will support their opinions. When
possible, expand upon a question or provide additional historical background
To conclude, discuss with students how the decisions were made to halt
Germany's production of heavy water. What evidence was each decision based
upon? How did time play a factor in the decisions? Do students think the Allied
forces and Resistance fighters did or did not have enough information to base
their decision on? Have students support the positions they choose.
As an extension, have students generate questions they have about World War
II. Group together students who have related questions. Have teams research and
answer their own questions and present their findings to the class.
answers to the questions listed on the student handout:
Why were the Germans interested in heavy water? they wanted to build a
nuclear bomb and heavy water is a key ingredient
What was the name of the ferry used to transport passengers and
(purportedly) heavy water? the Hydro How many people died when
the ferry went down, and who were they? 14 civilians, and 4 German
Why were historians interested in finding out what was on the Hydro?
to discover whether heavy water was actually onboard the ferry
Why was the Norsk Hydro plant built in the remote sRjukan
Valley? the plant was situated near a large waterfall that could provide
What was originally made at the Vemork factory? fertilizer How was it
made? hydrogen was extracted from water by electrolysis and then reacted
with nitrogen in the air to make ammonia.
What by-product was created at the plant? heavy water
What did physicists come to realize about heavy water? that it could play
an important role in the creation of a nuclear bomb
How much water does it take to make 1 kilogram of heavy water? 50
Once the Allies understood how heavy water could be used, what action did
they take? they teamed up with members of the Norwegian Resistance to try to
destroy the Norsk plant.
How did the Allies attempt to destroy the plant? What were the results of
their efforts? the first attempt failed when weather prevented sending in 30
men by gliders; the second attempt was partially successful in bombing the
heavy water production facility; and the third attempt succeeded in bombing the
factory but not the heavy water plant.
What did the Germans do to make even more heavy water? they used
high-concentration cells and doubled the production apparatus
What did the Allies and Resistance learn about the shipment of heavy water?
barrels of heavy water were to be transported to Germany by train and then
by ferry; rail cars would board a ferry named Hydro.
What was the ethical dilemma related to sinking the Hydro?
civilians would be at risk.
Describe the operation that sank the Hydro. a team of saboteurs
placed a bomb at the bottom of the ferry; 10 minutes after schedule, the ferry
left the dock; 30 to 40 minutes later the bomb exploded and sank the
Why was it important to locate the Hydro and examine the contents of
the heavy water barrels? some historians did not believe the operation
achieved its main objective, destroying German's supply of heavy water
How would the investigators be able to tell if the barrel had lake water or
heavy water in it? they would check the pH of the water—heavy water
has a much higher pH (about 14.0) than lake water (about 9.0)
Why did the investigators have to slowly maneuver the barrel as they lifted
it from the water? the barrel could have exploded and released caustic
potassium hydroxide-laden heavy water
How did investigators know what percentage of heavy water the barrel was
supposed to contain? the manifest showed that the barrel they were testing
was 1.5 percent enriched
What were the results of the testing? the pH of the barrel water was
more than 14.0
How did one of the saboteurs feel about the bombing when asked about it 60
years later? he said he didn't react to the bombing, but just swallowed what
he had done; he noted he slept just as well at night as he had before the
NOVA—Hitler's Sunken Secret
Read a book excerpt about the Norsk Hydro plant bombing raid, learn how near
the Nazis were to developing a nuclear weapon, examine spy messages regarding
the Hydro ferry bombing, and discover how heavy water can be used to turn
relatively common uranium into weapons-grade plutonium.
Physics 2000: Isotopes
Offers a tutorial on atoms and isotopes.
Sinking Hitler's Bomb
Retells the story of the sinking of the Hydro.
Assault in Norway: Sabotaging the Nazi Nuclear Bomb
by Thomas M. Gallagher. Harcourt Brace Jovanovich, 1975.
Recounts operations that destroyed a heavy water plant in Norway and a
large shipment of heavy water on the way to Germany.
Heavy Water and the Wartime Race for Nuclear Energy
by Per F. Dahl. The Institute of Physics, 1999.
Reviews the scientific role that heavy water played in the wartime
efforts and chronicles the air attacks on the Norwegian plant making heavy
The "Heavy Water Goes Down" activity aligns with the following National
Science Education Standards (see books.nap.edu/html/nses).
Science Standard F
Science in Personal and Social Perspectives
Science and technology in society
Science Standard F
Science in Personal and Social Perspectives
Science and technology in local, national, and global challenges
Classroom Activity Author
Developed by WGBH Educational Outreach staff.