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DOE Scales Back High-Temp Next-Gen Nuclear Amid Major Concerns
Energy Washington Week, Vol. 5, No. 37, 10 September 2008
The Energy Department -- responding to significant concerns -- has scaled back the extremely high temperatures at which it had proposed to develop the "next generation nuclear plant" (NGNP) but is moving forward in the expectation that the "new concept for nuclear utilization" still will produce a wide variety of energy-related benefits besides nuclear electricity, according to Shane Johnson, the DOE Principal Deputy Assistant Secretary and Chief Operating Officer for the Office of Nuclear Energy.
Even though the operating temperatures have been scaled back, Johnson asserts the new technology will still produce process heat that will allow petrochemical companies to reduce their natural gas use -- thereby making it available for home heating and other uses -- as well as the production of hydrogen that many envision as the cornerstone of clean transportation energy.
While potentially far-reaching for a number of energy benefits, the NGNP has also drawn significant controversy. The Union of Concerned Scientists (UCS), a major non-government organization in nuclear policy, believes the extremely high temperatures envisioned for the NGNP raise technical hurdles that warrant a different schedule for developing the technology than the 2021 deadline set forth in the Energy Policy Act of 2005. Sufficient time will be needed to develop and test ultra-high temperature materials, to develop and validate models for analyzing reactor performance, and to develop and qualify the fuel, a UCS source says.
In an interview with EnergyWashington Week, Johnson says that DOE shares the concerns raised by USC and others about the earlier proposal to run the NGNP -- a "very-high-temperature gas-cooled reactor" (VHTR) -- at temperatures up to 950 or 1,000 degrees Centigrade. Seeing the higher temperatures as "too big a stretch" because the department "has little experience outside the labs with such temperatures," DOE has scaled back to 850 degrees C, which is "within the experience base" DOE has with high-temperature reactors, Johnson says. DOE will nevertheless continue to research higher temperature systems because they offer higher efficiency than conventional light water reactors now widely used.
With light water reactors, which have a 33-34 percent efficiency, only a third of the thermal energy becomes electricity. But with the 950-1,000 degree temperatures, a 45 percent efficiency can be achieved. In backing off to 850 degrees, DOE is settling with 40 percent efficiency. An Aug. 15 report to Congress delineating the joint DOE and Nuclear Regulatory Commission (NRC) plan for developing and licensing the NGNP describes the VHTR as "a new and unproven reactor design" that can provide high-temperature process heat up to 950 degrees.
The reactors are also smaller -- ranging from 10 to 300 MW -- instead of the current 1100 MW-1700 MW unit size, according to an industry source.
Johnson explains that the VHTR was selected after DOE in 2001 initiated "a technology road map for next generation reactors on an international basis." Some 100 scientists and engineers from 14 countries participated in proposing and examining a range of options. The VHTR (and a sodium fast reactor) was selected because of its range of benefits besides electricity.
The UCS source believes the NGNP was forced on DOE by Congress at the behest of Sen. Larry Craig (R-ID), who criticized the department's Global Nuclear Energy Partnership during hearings and pushed the NGNP, which is to be built in Idaho. The report to Congress "makes it abundantly clear that the congressionally mandated timetable for developing, licensing and constructing the NGNP by 2021 is completely unrealistic," the source says.
Johnson acknowledges Craig has been a strong advocate of the VHTR and wants to see the DOE Idaho National Lab play a significant role in developing the technology. In addition, DOE was provided more appropriations than it asked for to promote the VHTR. But Craig did not force the technology on DOE, Johnson says, noting that DOE was "headed down this path before [EPACT 2005]" required it.
Although DOE "has tinkered with gas-cooled reactors" since the 1970s, the UCS source says the VHTR requires higher temperatures than the department has experience with, because of the interest in producing hydrogen with the heat. "They don't have materials suitable for nuclear use," the source says, explaining that materials must have greater reliability when nuclear energy is involved than when materials are used in high-temperature industrial processes. With gas-cooled reactors, the hundreds of thousands of small pellets used in the fuel must be symmetrical, with "no variation in the micro-spheres," and the source adds that they are "sensitive to manufacture defects."
"There's a certain rejection rate in every man-made process," Johnson says, so with the millions of fuel "kernels" that will be used in the VHTR "you'll see some defects." In response to this concern, DOE is developing inspection tools to identify and reject out-of-spec kernels. During the NRC licensing review fuel performance will be a key issue so a lot of effort is being focused on the issue, and the scientific community will be involved in peer review to assure quality, Johnson says.
A senior director with the Nuclear Energy Institute (NEI), an industry organization, also stresses that with VHTR designs the fuel quality must be higher than in other types of reactors "so there will be more emphasis on quality" because there are more manufactured kernels, raising the possibility for defects. Companies are planning to irradiate defective kernels in test facilities to assess what happens.
The NEI source says one or two companies are "pushing hard" to move the technology along and are "on the verge of full-scale testing" of materials under high temperatures, and developing the fuel. While 850 degrees is the more realistic temperature for now, companies are targeting 950 degrees "to eventually get there," the source says.
On the issue of highly reinforced cement and steel containment used for current nuclear facilities -- something the UCS source says must be a requirement -- Johnson says DOE has made no decision. Such containment is justified for the many light water reactors that subject water to 2,200 pounds per square inch (psi) pressure to keep it from boiling; containment structures are designed to be protective in the event that a cooling pipe rupture occurs, creating a "high energy" event as the water is released and flashes to steam. With VHTR, which is cooled by helium gas, the pressure is 800 psi. That lower pressure may mean less containment structure is needed, Johnson says, adding that the issue is being analyzed because heavy-duty containment would add significantly to the cost of VHTR and affect the technology's long-term economic viability.
DOE is developing a request for proposals to be published by the end of 2008 that will ask companies to estimate the cost of developing VHTR prototype facilities.
.....wonder how they can justify US participation in the ITER project, with its 100,000,000 degree plasma temperature on one side, and a huge pool of cryogenic liquid on the other ? .....are they getting the materials from aliens or what ??

Anyhow, you know what this means for LFTR development : At best, an MSRE replay could be attempted, with this sort of attitude.....