The government's role in advancing new nuclear power plant designs will get more expensive if the Trump administration and Congress are serious about moving the new reactors to market, the head of the nation's nuclear energy watchdog told lawmakers Wednesday.

Kristine Svinicki, the Republican chairwoman of the Nuclear Regulatory Commission, told the Senate Environment and Public Works Committee that the program among the commission, the nuclear industry, and the Department of Energy to move small reactor designs to market will get more expensive, surpassing the fiscal 2017 allocation for advanced reactors.

"I think that going forward, we get to taking that framework and applying it to specific technical issues," Svinicki said. "From a budgetary standpoint, that's where it gets more expensive because then the labs need to be doing things, we need to be doing things, weighing in on their testing plans and data plans, and say if you collect this data will it be sufficient for us to make a regulatory determination."

The new designs the agency is working on certifying, and ultimately licensing, represent the future of the industry amid growing concerns about the premature retirement of the existing nuclear fleet's reactors and the need for smaller, lower cost nuclear energy designs to replace them.

The commission's work on the new nuclear power plant designs is facing a limited budget. It is not clear if Congress has a plan to assist that process as the NRC has seen its budget shrink in recent years to bring it in line with its oversight of a smaller nuclear power fleet and a limited number of new plants being built. Most of the NRC's budget comes from fees being collected from the licensees, with a smaller amount coming from congressional appropriations.

Congress has given the agency $5 million for it to coordinate with the Energy Department, private companies, and federal laboratories on the development of the new reactor designs.

"If this 'off the fee base' funding is spent and no additional 'off fee base' funds are appropriated, the NRC would have to recover advanced reactor activity costs through fees, which would result in additional bills to licensees and applicants," a NRC spokesman said.

The NRC is focused on building its ability to evaluate the designs through a series of plans to understand how close it is to approving a new reactor design and, later, approving a construction license.

"What we don't want to have is total gaps in our expertise and regulatory capacity, where we just have to throw up our hands and say, 'We don't known anything about that type of material, so we're never going to be able to approve its use,'" Svinicki said.

Energy Secretary Rick Perry has touted a portable reactor design that the NRC is evaluating that acts more like a hot-tub-sized battery to produce electricity for years without the need for refueling. Perry said at a conference earlier this year that those type of reactors represent the innovation piece of the administration's energy agenda.

Meanwhile, the federally managed Tennessee Valley Authority submitted the first application to construct a small modular reactor. The design it is looking to operate is based on more conventional, water-cooled technologies, not the battery type designs that Perry is pushing.

TVA is looking to the new nuclear designs to replace some of its retiring coal-fired power plant fleet. The small reactors will be developed in addition to more solar and clean energy resources.

Sen. Sheldon Whitehouse, D-R.I., said Wednesday that he is working on developing bipartisan legislation to help prevent the existing fleet of nuclear power plants from closing. He said nuclear power plants produce no greenhouse gas emissions, which many scientists blame for raising the Earth's temperature. Whitehouse said the closure of the plants should be prevented to keep U.S. carbon emissions low.

He suggested that the legislation he is working on would provide incentives for nuclear generators akin to the low-carbon energy credits that some states have adopted to assist renewables and nuclear power plants.