Most U.S. Government spending on nuclear weapons-related programs is unclassified. But it is functionally secret since such spending is widely dispersed across many programs in several agencies and it is not formally tracked or reported.

A new study prepared for the Carnegie Endowment for International Peace estimated that the cost of U.S. nuclear weapons and weapons-related programs exceeded $52 billion last year.

“That’s a floor, not a ceiling,” said Stephen I. Schwartz, who led the study with Deepti Choubey. The estimate does not include the costs of classified nuclear weapons programs or nuclear-related intelligence programs, among other limiting factors.

The $52 billion figure far exceeds the total annual budget for international diplomacy and foreign assistance ($39.5 billion) and comprises roughly 10% of all national defense spending.

Because nuclear weapons costs are not officially tracked, it has been difficult or impossible to perform “cost-benefit” analyses of nuclear policies or to debate priorities among competing nuclear weapons programs. Yet such priorities naturally emerge, undebated.

Thus, the majority of nuclear weapons spending (55.5%) is allocated towards upgrading, operating and sustaining the U.S. nuclear arsenal. A much smaller fraction (10%) is devoted to controlling the spread of nuclear weapons and technology, the study found.

“The disparity suggests that preserving and enhancing nuclear forces is far more important than preventing nuclear proliferation,” said Mr. Schwartz.

The authors urge that a formal accounting of nuclear weapons spending be conducted by the government and reported to Congress and the public in order to provide greater clarity. And they recommend that an increased fraction of nuclear security spending be directed towards preventing nuclear proliferation.

The full report and the underlying data are available from the Carnegie Endowment. See “Nuclear Security Spending: Assessing Costs, Examining Priorities,” by Stephen I. Schwartz with Deepti Choubey, January 2009.