The Yongbyon plant and reactor formed the centrepiece of North Korea's plutonium-based weapons programme.
While a handful of lawmakers were briefed on the allegations last year, the decision to widen the circle substantially comes as US officials ramp up efforts to persuade North Korea to provide a long overdue declaration of its nuclear programs.
On Tuesday a delegation of US nuclear experts travelled to North Korea for talks with top officials on the issue.
The leader of the delegation is expected to report back to Washington on Friday.
Tom Casey, spokesman for the US state department, said that while he hoped that latest round of meetings would make progress there was no indication "how close or how far away we are" from a breakthrough.
"This really is an issue where it's not done until everything is done," he said.
A North Korean declaration of all its nuclear activities forms a key component of a six-nation aid-for-disarmament deal, brokered by China last year, but there has been disagreement as to what constitutes a full and accurate declaration.
Once Pyongyang produces the declaration, the US is expected to ease sanctions identifying North Korea as a state sponsor of terrorism.
Spokesmen for the White House and for the office of the Director of National Intelligence have not commented on the reports.
On Tuesday a senior congressional aide said the briefing scheduled for congress is timed to coincide with the imminent lifting of sanctions on North Korea.
Michael Green, a former National Security Council official now at the CSIS think tank, told Reuters that a compromise the US and North Korea reached recently in Singapore on the declaration had run into congressional resistance.
"The administration is now being asked, in order to [win] congressional support for lifting sanctions ... to explain more details about the parts that are no longer covered [by the declaration]", Green said.
Several politicians, both Republican and Democrat, have suggested that the Bush administration is softening its stance on North Korea in its desperation to secure some kind of deal.
Last week Bush administration officials confirmed they had stepped back from their push for a detailed declaration addressing the North's alleged secret uranium enrichment programme and suspected proliferation activities, including nuclear cooperation with Syria.
Instead the US now says it wants the North to simply acknowledge Washington's concerns and then set up a system to verify that the country does not continue such activity.