Roles of nuclear fuel cycle technologies ongeological disposal:

Resilience in management of spent nuclear fuel by developmentof technology and social agreement
Joonhong Ahn
Professor and Vice Chair
Department of Nuclear Engineering
University of California, Berkeley
November 28, 2013
International Symposium on Nuclear Back-end Issues and the Role of Nuclear
Transmutation Technology after the Accident of TEPCO’s Fukushima Daiichi Nuclear
Power Stations
The Shiran Hall, Kyoto University

Contents• Final disposal, difficult to realize• Couplings observed in waste management• Multifaceted performance assessment• Relation between technology development
and social discussions• Closing thoughts

Nuc. Eng., UC Berkeley© Joonhong Ahn 20132

Final disposal, difficult to realize• Canada 1998 (Failure in getting public approval for concept)– M.V. Ramana, Energy Policy, 61(2013) 196–206• USA 2009 (Political decision-making)– J. Ahn, ATOMOZ, November 2011.
– C. Singer, Energy Policy, 61(2013) 1521–1528• Japan 2012 (Science Council’s recommendation)– J. Ahn, Kagaku (Science), Iwanami, October, 2013
• South Korea 2013 (Deadlocked in US-ROK 123 agreement
negotiation)– J. Ahn, To be publishedNuc. Eng., UC Berkeley© Joonhong Ahn 2013

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Why?
• Lack of reversibility in siting process = DecideAnnounce-Defend (DAD) approach– Reversibility results from:• Adaptive, staged approach• Feedback loop between social discussions andtechnology development• Dilemma between convergence andsustainable use of nuclear power– “Footprint” issue
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For ROK, once-through scheme did notwork, because …
• The only parameters that affect the attribute of
the materials to be disposed of are time andlocation.
– to wait for decay and cooling– to site facilities• This absence of flexibility made the public
agreement difficult.

– only a limited number of stakeholders would agreewith the prefixed option.
– room for adjusting the system to meet the public’s
wide range of desire and preference is very small.

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“Footprint” issue

Dilemma between Convergence and Sustainability• Spent fuel continues to accumulate as long as nuclear
power is utilized.

– Radioactivity will not reach a steady state as long as
nuclear power is generated, and will last much longer thanthe use of nuclear energy.

• Therefore, repository footprint expands accordingly.

– (perception issue) The public would not consider this as asolution, but rather consider that the problem continues togrow bigger.
– (substantive safety issue) With an increasing radioactivity
inventory and footprint of a geological repository,
potential risk of the geological disposal also increases.

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US has many (too many?) options.
Large territory
Wide variety in geological conditions
Wide variety in technological options
No international constraints as the largest and firstweapons country• Active interactions among law makers, policy makers,regulators, and academia• BUT,••••– Interactions have been confrontational, sometimes hostile,– Because of its own nonproliferation policy, direct disposal has
been the only option, and– Local residents were not properly involved in decision-making
process for YMR siting.

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BRC Recommendations (2012)
1.
2.
3.
4.
5.
6.
7.
8.

A new, consent-based approach to siting future nuclear waste
management facilities.
A new organization dedicated solely to implementing the waste
management program and empowered with the authority andresources to succeed.
Access to the funds nuclear utility ratepayers are providing for the
purpose of nuclear waste management.
Prompt efforts to develop one or more geologic disposal facilities.
Prompt efforts to develop one or more consolidated storage facilities.
Prompt efforts to prepare for the eventual large-scale transport of spent
nuclear fuel and high-level waste to consolidated storage and disposal
facilities when such facilities become available.
Support for continued U.S. innovation in nuclear energy technology andfor workforce development.
Active U.S. leadership in international efforts to address safety, waste
management, non-proliferation, and security concerns.

Nuc. Eng., UC Berkeley© Joonhong Ahn 20138• Final disposal, difficult to realize• Couplings observed in waste management• Multifaceted performance assessment• Relation between technology development
and social discussions• Closing thoughts

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Couplings observed in spent fuelmanagement• Short term (fuel cycle) vs. Long term (disposal)– Short term  Long term

• Overall long-term performance is dependent on short-term options.

– Long term  Short term

• Without a plan for repository siting, implementation of short-term
options is difficult due to lack of public trust and confidence.

• Domestic vs. International– Domestic  International• Failure in consuming recovered fissile materials may causeinternational skepticism.

– International  Domestic• International and bilateral treaties define framework for fuel-cycle
options.
– E.g., US-Japan 123 agreement negotiation by 2018

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Effects of Fuel Cycle on Disposal• Effects of Storage• Effects of Separation• Effects of Sequestration (Waste form)• Effects of Transmutation

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Effects of storage• Cooling  Improvement of repository safety– Reduction of repository footprint– Retardation of Engineered-Barrier degradation– Reduction of uncertainty in repository performance• Reduction of radioactivity and radiotoxicity (i.e.,source terms)– Reduction of adverse consequences in severe
accidents• Increase of proliferation potential
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Protection by radiation

Dose for 8 hours at 1 m location from the spent fuel package for the Yucca Mountain Repository
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Effects of separation• High heat radionuclides (HHR) (Sr-90 and Cs-137)– with short half-lives (about 30 years) and– small masses (approximately 4 kg/metric ton of initialheavy metal (MTIHM)).

• Low-heat radionuclides (LHR)– with long half lives and– significant masses

Forsberg CW. Rethinking high-level waste disposal: separate disposal of high-heat
Nuc. Eng., UC Berkeley© Joonhong Ahn 2013
radionuclides (90Sr and 137Cs). Nuclear Technology. 2000 Aug; 131(2): 252-268.

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Size of nuclear-reactor fleet in a country (Gwyr)

Country’s nuclear utilization

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Convergence of HHR

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LHR
• Uranium:– occupies majority (~ 95%) of the mass;– is hardly soluble and immobile in a reducing environment
in groundwater.

• Plutonium, and minor actinides (TRU):– are fissionable materials, for which stringent control for
safeguard and safety are required;– are highly radiotoxic due to alpha emission;– are hardly soluble particularly in a reducing environment;• Long-lived fission products, such as I-129, Se-79, andTc-99, and Cs-135:– are relatively mobile in geological formations, i.e., highsolubility and weak sorption retardation with rock duringhydrological transport by groundwater

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Effects of waste forms/canisters• Radionuclide loadings in waste form Determines the number of canisters and footprint– Heat emission– Proliferation resistance– Radionuclide release rates• Dissolution rates of waste form

– Radionuclide release rates– Alteration of near-field environment• Choice of backfill/buffer materials
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Effects of Transmutation

中山、安、放射性廃棄物研究 (1996) ２（１＆２） 27 - 34
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With solubility limited mechanism, repository
performance is controlled by S/V ratio.

With no heat emission, abig sphere gives the best
performance.

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Comparison
1.E+00

Direct - Severe

Total release rate, mol/year

1.E-01
1.E-02
1.E-03

P&T - Severe

1.E-04

Direct - Normal

1.E-05

P&T - Normal

1.E-06
1.E-07
1.E-081.E+03

1.E+04

1.E+05

1.E+06

1.E+07

1.E+08

Time, year
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• Final disposal, difficult to realize• Couplings observed in waste management• Multifaceted performance assessment– Taking Japanese case as an example• Relation between technology development
and social discussions• Closing thoughts
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Conventional vs. Multifaceted
performance assessment• Conventional PA is done to confirm that acertain system comprises with regulatory
guidelines.
• Multifaceted PA is done to compare
performance of multiple options frommultiple viewpoints.

Nuc. Eng., UC Berkeley© Joonhong Ahn 201323

Multifaceted PA• In the first round, “cost” comparison should not
be the primary viewpoint.
– Remember Muskie Act 1970.
– How to frame the problem?

• Once the public understands and shares what thesociety would like to achieve, cost will become
the primary issue, but can be solved bytechnological development and breakthrough.
– Cf. Discussion after Fukushima Daiichi accident inJapan is misaddressed because cost comparison
seems to be the most decisive factor.

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Issues that Japan faces-- Short and Mid-term ranges -• National wealth is draining out.
– Import of fossil fuels• Additional 4 trillion yen/year• Additional 175 million ton CO2 emission /year– Huge investment could become irrecoverable.
• Nuclear power plants,• Rokkasho reprocessing plant• International competitiveness and influence arebeing lost.
• Pu stockpile can complicate US-Japan bilateralrelation.
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Issues that Japan faces-- Long-term range -• Risk to be imposed on future generations isheavily dependent on options taken in shortand mid-term ranges.
– Amount and contents to be disposed of become
substantially different.
– Technologies available in future will be different,or maybe decreased.

• Options for mitigating global warming issues
will be limited.
Nuc. Eng., UC Berkeley© Joonhong Ahn 2013

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Options• Option（0）：Full-fledged fuel cycle• Option（IV）：Phase out
immediately（０）（I）
Fleet capacity– Maintain the same fleet capacity (e.g.,
50 LWRs equivalent; includes FBRs)– PUREX (U, Pu recovered)– Recovery of TRU for transmutation– Disposal: HLW vitrified waste （legacy+ future）– Disposal：HLW vitrified waste（legacy）, Pu stockpile, Spent fuelincluding MOX, Recovered U

Nuc. Eng., UC Berkeley© Joonhong Ahn 2013

（II）（IV） （III）

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• Option（I）

Options• Option（II）– Fleet capacity that can beaccommodated by Rokkasho
capacity– No LWR replacement; HTGR
– PUREX (U, Pu recovered)– TRISO– Disposal：HLW vitrified waste（legacy）, TRISO, Recovered U
Nuc. Eng., UC Berkeley（I）

Fleet capacity– Fleet capacity that can beaccommodated by Rokkasho
capacity– Old reactors replaced as needed– PUREX (U, Pu recovered)– MOX– Disposal：HLW vitrified waste（legacy + future）, MOX SF,
Recovered U

（０）

（II）

（IV） （III）• Option（III）© Joonhong Ahn 2013

– No replacement of reactors– No reprocessing– Legacy Pu is made into MOX andused in remaining LWRs
– Disposal：HLW vitrified waste（legacy）, MOX SF, Spent fuel,Recovered U
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Long term
Radiological performanceof repository

Proliferation resistance ofa geological repository

Radiological performanceof fuel cycle

International
competitiveness andinfluence

Domestic
Recovery of investment;
National wealthNuc. Eng., UC Berkeley

International
Bilateral relations withUS (and others)

Short term

© Joonhong Ahn 201329

Performance Viewpoints (Domestic)• Radiological performance of repository– difficulty for meeting regulatory requirements;– radiological risk resulting from a severe accident.

• Radiological performance of fuel cycle– complexity of processes and activities included in
respective options, and so– amount of regulatory work necessary to maintainnormal operation• Recovery of investment; National wealth– Utilization of existing facilities

Nuc. Eng., UC Berkeley© Joonhong Ahn 201330

Performance Viewpoints(International)• Proliferation resistance of a geologicalrepository– attractiveness as weapons-usable materials.

• International competitiveness and influence– Economical, technological, political• Bilateral relations with US (and others)– Pu stockpile

Nuc. Eng., UC Berkeley© Joonhong Ahn 201331

Radiological
performance of
best
repository

Option (0)(Full Fledge)
Radiological
performance offuel cycle

Long term

2nd
3rd
worst

Domestic

International
competitivenessand influence
International

Recovery of investment;
National wealthNuc. Eng., UC Berkeley

Proliferation resistanceof a geological repository© Joonhong Ahn 2013

Short term

Bilateral relationswith US (and others)

32

Radiological
performance of
best
repository

Option (I)(LWR+PUREX+MOX)
Radiological
performance offuel cycle

Long term

2nd
3rd
worst

Domestic

International
competitivenessand influence
International

Recovery of investment;
National wealthNuc. Eng., UC Berkeley

Proliferation resistanceof a geological repository© Joonhong Ahn 2013

Short term

Bilateral relations
with US (and others)

33

Radiological
performance of
best
repository

Option (II)(LWR->HTGR+PUREX)
Radiological
performance offuel cycle

Long term

2nd
3rd
worst

Domestic

International
competitivenessand influence
International

Recovery of investment;National wealthNuc. Eng., UC Berkeley

Proliferation resistanceof a geological repository© Joonhong Ahn 2013

Short term

Bilateral relations
with US (and others)

34

Radiological
performance of
best
repository

Option (III)(LWR+NoPUREX+MOX)
Radiological
performance offuel cycle

Long term

2nd
3rd
worst

Domestic

International
competitivenessand influence
International

Recovery of investment;
National wealthNuc. Eng., UC Berkeley

Proliferation resistanceof a geological repository© Joonhong Ahn 2013

Short term

Bilateral relations
with US (and others)

35

Radiological
performance of
best
repository

Option (IV)(Immediate phase out)
Radiological
performance offuel cycle

Long term

2nd3rdworst

Domestic

International
competitivenessand influence
International

Recovery of investment;
National wealthNuc. Eng., UC Berkeley

Proliferation resistanceof a geological repository© Joonhong Ahn 2013

Short term

Bilateral relations
with US (and others)36• Final disposal, difficult to realize• Couplings observed in waste management• Multifaceted performance assessment• Relation between technology development
and social discussions• Closing thoughts

Nuc. Eng., UC Berkeley© Joonhong Ahn 201337

Aftermath of Fukushima-- Discussions for “better” systems -• More robust reactors• Capable operator• Competent and independent regulatorysystem• Energy security/independence• Accident mitigation & damage minimization– Which part of the society has actually beendamaged?
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Resilient nuclear technology• Resilience of a reactor– Advanced reactors and fuels (inherently safe reactors)– Back-fit of existing reactors• Resilience of a fleet of reactors/fuel cycles– Replacement of old reactors with new reactors– Spent fuel/high-level waste treatment and disposal• Resilience of energy portfolio– Flexibility of adjusting (increase or decrease) share of
nuclear power, depending on situations/needs• Resilience of society– Public-participatory system for decision making,– Complicated stakeholders

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Where should public participation beimplemented?
• Selection of viewpoints for multifaceted assessment– Different stakeholders would have different priorities, and thus
consider different sets of viewpoints more important or crucial.
– However, including too many viewpoints would not make assessment
useful for grasping trade-off relations embedded in the current issue.
– This leads to an idea of establishing a committee with participation ofvarious stakeholders for the purpose of selecting a relatively small
number of viewpoints for multifaceted assessment.

• Evaluation/ranking with respect to each viewpoint– While this has been done historically by judgment of technical experts,
evaluation can and should also be done by public participation.
– Multiple sets of results for different population could be obtained andcompared.

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Closing thoughts• Nuclear fuel cycle technology plays crucial roles inaugmenting technological options.
• BUT,• Technological development should be carried under theguidance of, and to serve for, public-participatory,
reversible and adaptive decision making, which is essentialfor social resilience.
• For such decision-making process, multifaceted
performance assessment for technological options plays animportant role.
– Performance metrics, based on in-depth analysis of issues thatthe society faces, and the goal that the society agrees.
– PA should be conducted not only by experts but also by laypeople.
– Metrics, goals, and assessment should be done iteratively.

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