Department of Energy National Security Act for Fiscal Year 2008

(Sec. 3112) Prohibits any FY2008 fissile materials disposition program funds from being obligated or expended until the Secretary of Energy (Secretary) submits to the defense and appropriations committees a plan for the expenditure of such funds that remain available as of October 1, 2007. Prohibits the aggregate amount that may be obligated for such program within FY2008 program funds from exceeding the amount that the Secretary certifies to such committees will be obligated for that program in fiscal years 2008 and 2009. Provides conditions for the availability of unutilized funds: (1) absent the latter certification; and (2) under certification of partial use.

(Sec. 3113) Amends the John Warner National Defense Authorization Act for Fiscal Year 2007 relating to the availability of funds for the Waste Treatment and Immobilization plant to: (1) remove the requirement that the Defense Contract Management Agency review and recommend for implementation the earned value management system to be used by the construction contractor at the plant; and (2) instead require an independent entity to conduct such review.

Subtitle C: Other Matters - (Sec. 3121) Amends the: (1) National Defense Authorization Act for Fiscal Year 2004 to repeal certain requirements with respect to the nuclear test readiness posture; and (2) Atomic Energy Defense Act to require the Secretary to report to the defense and appropriations committees on U.S. nuclear test readiness. (Under current law, the Secretary is required to report to Congress on costs and programmatic and other issues associated with the conduct of nuclear tests within specified time frames.)

(Sec. 3122) Expresses the sense of Congress that, among other things: (1) the United States should reaffirm its commitment to the Nuclear Non-Proliferation Treaty (Treaty) and initiate talks with Russia to reduce its number of strategic and non-strategic nuclear weapons; (2) the United States and other Treaty parties should work to reduce the total number of nuclear weapons in their respective stockpiles; (3) the United States, Russia, and other states should work to negotiate and ratify a treaty for the cessation of production of fissile material; (4) the Senate should ratify the Comprehensive Nuclear-Test-Ban Treaty; (5) the United States should commit to dismantle as soon as possible all retired warheads; and (6) the United States and other Treaty parties should work to decrease the reliance on, and importance of, nuclear weapons.

(Sec. 3123) Directs the: (1) Secretary to report to the defense and appropriations committees and the Comptroller General (CG) on the status of environmental initiatives undertaken to accelerate the reduction of environmental risks and challenges posed by the legacy of the Cold War; and (2) CG to review the report and report results to such committees.

(Sec. 3124) Requires a report from the CG to the defense committees on the management of the protective forces of DOE.

Title XXXII: Defense Nuclear Facilities Safety Board - (Sec. 3201) Authorizes appropriations for FY2008 for the Defense Nuclear Facilities Safety Board.