A debate over a provision tucked deep in the Iran nuclear deal effectively stalled an energy and water spending bill in the Senate this week.
An amendment to the bill from Sen. Tom Cotton (R-Ark.) looks to block the U.S. from purchasing Iran’s heavy water, a component of nuclear reactors. The U.S. announced it would buy heavy water from the country for the first time last week.

What is heavy water and what’s it used for?
Heavy water is simply form of water, made of up different, heavier molecules than normal H2O, said James Acton, the co-director of the Nuclear Policy Program at the Carnegie Endowment for International Peace. 
Heavy water is naturally occurring, and it has a handful of practical applications. The most troubling of those — especially when it comes to Iran — is its potential for combining with uranium to produce weapons-grade plutonium.
“Iran’s reactor was a particular concern because it was clearly optimized to build weapons-grade plutonium,” Acton said. “That combination of natural uranium and heavy water in a reactor is pretty suspicious from a weapons point of view.”
There are civilian uses for heavy water, as well. Though it’s a component of only a few electricity-generating power plants worldwide — none in the United States — heavy water can fuel the powerful reactors used in nuclear research or to produce the radioactive materials used to treat certain kinds of cancer, for example.

What does the Iran nuclear deal say about heavy water?
Under the deal negotiated between Iran, the United States and a team of other nations, Iran had already agreed to remove the core of its heavy water nuclear reactor and fill it with concrete, rendering it incapable of producing a weapon.
But as an extra safeguard, the United States and others insisted Iran would reduce its stores of heavy water as well. Iranian nuclear facilities can still use heavy water, but the country’s excess stock will be drawn down to no more than 130 metric tons to prevent any secret weapon development activities.
To advance that goal, U.S. officials announced last week that it would purchase 32 metric tons of heavy water from Iran for a reported $8.6 million.
In a statement, the Department of Energy said it intends to “resell the purchased heavy water to domestic commercial and research buyers,” including the Oak Ridge National Laboratory in Tennessee.

How does Congress feel about this?
Republican lawmakers slammed the Obama administration’s purchase this week, saying the United States shouldn’t be “subsidizing” Iran’s nuclear program even if it means drawing down the country’s heavy water supply.
“Iran has an obligation to reduce its heavy water stocks,” Cotton said Thursday.
“The United States has no obligation to help them. We certainly have no obligation to buy their heavy water, and I don’t think the United States taxpayers should subsidize their nuclear program.”
Rep. Mike Pompeo (R-Kan.) introduced a similar bill in the House on Thursday.
Sen. Bob Corker (R-Tenn.), chairman of the Foreign Relations Committee, said on Thursday he “had some knowledge that developments were occurring” between the U.S. and Iran, but that he’s skeptical of any purchase agreement between the two countries.
“Should the United States government be a known end-user for Iran’s heavy water? I don’t know, probably not,” he said. “I don’t think we ought to be the built-in end user of their product.”
Cotton introduced an amendment to the Senate’s energy and water spending bill on Monday preventing the U.S. from buying heavy water in 2017.

Source: The Hill, 2 May 2016