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Debunking the claims about generation IV nuclear waste

Generation IV nuclear waste claims debunked, Nuclear Monitor 24 Sept 18   Lindsay Krall and Allison Macfarlane have written an important article in the Bulletin of the Atomic Scientists debunking claims that certain Generation IV reactor concepts promise major advantages with respect to nuclear waste management. Krall is a post-doctoral fellow at the George Washington University. Macfarlane is a professor at the same university, a former chair of the US Nuclear Regulatory Commission from July 2012 to December 2014, and a member of the Blue Ribbon Commission on America’s Nuclear Future from 2010 to 2012.

Krall and Macfarlane focus on molten salt reactors and sodium-cooled fast reactors, and draw on the experiences of the US Experimental Breeder Reactor II and the US Molten Salt Reactor Experiment.

The article abstract notes that Generation IV developers and advocates “are receiving substantial funding on the pretense that extraordinary waste management benefits can be reaped through adoption of these technologies” yet “molten salt reactors and sodium-cooled fast reactors – due to the unusual chemical compositions of their fuels – will actually exacerbate spent fuel storage and disposal issues.”

Here is the concluding section of the article:

“The core propositions of non-traditional reactor

proponents – improved economics, proliferation resistance,

safety margins, and waste management – should be

re-evaluated. The metrics used to support the waste

management claims – i.e. reduced actinide mass and total

radiotoxicity beyond 300 years – are insufficient to critically

assess the short- and long-term safety, economics, and

proliferation resistance of the proposed fuel cycles.

“Furthermore, the promised (albeit irrelevant) actinide

reductions are only attainable given exceptional

technological requirements, including commercial-scale

spent fuel treatment, reprocessing, and conditioning

facilities. These will create low- and intermediate-level

waste streams destined for geologic disposal, in addition

to the intrinsic high-level fission product waste that will

also require conditioning and disposal.

“Before construction of non-traditional reactors begins,

the economic implications of the back end of these nontraditional

fuel cycles must be analyzed in detail; disposal

costs may be unpalatable. The reprocessing/treatment

and conditioning of the spent fuel will entail costs, as will

storage and transportation of the chemically reactive fuels.

These are in addition to the cost of managing high-activity

operational wastes, e.g. those originating from molten

salt reactor filter systems. Finally, decommissioning the

reactors and processing their chemically reactive coolants

represents a substantial undertaking and another source

of non-traditional waste. …

“Issues of spent fuel management (beyond temporary

storage in cooling pools, aka “wet storage”) fall outside

the scope of the NRC’s reactor design certification

process, which is regularly denounced by nuclear

advocates as narrowly applicable to light water reactor

technology and insufficiently responsive to new reactor

designs. Nevertheless, new reactor licensing is contingent

on broader policies, including the Nuclear Waste Policy

Act and the Continued Storage Rule. Those policies are

based on the results of radionuclide dispersion models

described in environmental impact statements. But the

fuel and barrier degradation mechanisms tested in these

models were specific to oxide-based spent fuels, which

are inert, compared to the compounds that non-traditional

reactors will discharge.

“The Continued Storage Rule explicitly excludes most

non-oxide fuels, including those from sodium-cooled fast

reactors, from the environmental impact statement. Clearly,

storage and disposal of non-oxide commercial fuels should

require updated assessments and adjudication.

“Finally, treatment of spent fuels from non-traditional

reactors, which by Energy Department precedent is

only feasible through their respective (re)processing

technologies, raises concerns over proliferation and fissile

material diversion. Pyroprocessing and fluoride volatilityreductive

extraction systems optimized for spent fuel

treatment can – through minor changes to the chemical

conditions – also extract plutonium (or uranium 233 bred

from thorium). Separation from lethal fission products

would eliminate the radiological barriers protecting the

fuel from intruders seeking to obtain and purify fissile

material. Accordingly, cost and risk assessments of

predisposal spent fuel treatments must also account for

proliferation safeguards.

“Radioactive waste cannot be “burned”; fission of

actinides, the source of nuclear heat, inevitably generates

fission products. Since some of these will be radiotoxic

for thousands of years, these high-level wastes should

be disposed of in stable waste forms and geologic

repositories. But the waste estimates propagated by

nuclear advocates account only for the bare mass of

fission products, rather than that of the conditioned waste

form and associated repository requirements.

“These estimates further assume that the efficiency

of actinide fission will surge, but this actually relies on

several rounds of recycling using immature reprocessing

technologies. The low- and intermediate-level wastes

that will be generated by these activities will also be

destined for geologic disposal but have been neglected

in the waste estimates. More important, reprocessing

remains a security liability of dubious economic benefit,

so the apparent need to adopt these technologies simply

to prepare non-traditional spent fuels for storage and

disposal is a major disadvantage relative to light water

reactors. Theoretical burnups for fast and molten salt

reactors are too low to justify the inflated back-end costs

and risks, the latter of which may include a commercial

path to proliferation.

“Reductions in spent fuel volume, longevity, and total

radiotoxicity may be realized by breeding and burning

fissile material in non-traditional reactors. But those

relatively small reductions are of little value in repository

planning, so utilization of these metrics is misleading to

policy-makers and the general public. We urge policymakers

to critically assess non-traditional fuel cycles,

including the feasibility of managing their unusual waste

streams, any loopholes that could commit the American

public to financing quasi-reprocessing operations, and

the motivation to rapidly deploy these technologies. If

decarbonization of the economy by 2050 is the end-goal,

a more pragmatic path to success involves improvements

to light water reactor technologies, adoption of Blue

Ribbon Commission recommendations on spent fuel

management, and strong incentives for commercially

mature, carbon-free energy technologies.”

Lindsay Krall and Allison Macfarlane, 2018, ‘Burning

waste or playing with fire? Waste management

considerations for non-traditional reactors’, Bulletin of the

Atomic Scientists, 74:5, pp.326-334, https://tandfonline.

com/doi/10.1080/00963402.2018.1507791

September 28, 2018 - Posted by Christina MacPherson | 2 WORLD, Reference, technology