Resource Requirements and Proliferation Risks ...

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Average Reactor. Capacities (MW). Source: IAEA. 2011. Nuclear Power Reactors in the World: 2011 Edition. Vienna: International Atomic Energy Agency.
Resource Requirements and Proliferation Risks Associated with Small Modular Reactors M.V. Ramana Nuclear Futures Laboratory Princeton University, U.S.A. Opportunities and Challenges for Nuclear Small Modular Reactors AAAS Annual Meeting Chicago, February 15, 2014 This work has been done in collaboration with Laura Berzak Hopkins and Alexander Glaser 1

Overview Size of SMRs and its Implications Modeling Reactors to Calculate Resource Requirements & Waste Generation Proliferation Risk Assessment

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Average Reactor Capacities (MW) Operating

Under Construction

PWR

924

972

BWR

913

1312

PHWR

496

538

Source: IAEA. 2011. Nuclear Power Reactors in the World: 2011 Edition.Vienna: International Atomic Energy Agency. 3

Categories Capacity Small

< 300 MWe

Medium

300 - 700 MWe

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Modularity Assembled from factoryfabricated modules Each module represents a portion of finished plant Current large nuclear plants require substantial amount of field work 5

Size and Scale Economic Viability of SMRs => large numbers (hundreds, perhaps thousands) needed to compensate for small size Important to understand the implications of such significant deployment on quantities of concern: uranium availability (including enrichment), waste generation, risk of proliferation 6

Proliferation Risk: Does the large-scale deployment of SMRs pose a risk of more countries obtaining nuclear weapons? 7

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Nuclear energy production involves use and production of enriched uranium and plutonium; could be diverted surreptitiously or openly (breakout) A country embarking on setting up nuclear power plants also acquires know-how on a variety of areas related to making nuclear weapons

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Tough question: “States that develop civilian nuclear power facilities are more capable of developing nuclear weapons; but are they more likely to do so?” - Scott Sagan Answer will depend on case and vary with time Approach here is to evaluate different kinds of nuclear reactors (SMRs, LWRs) in terms of their potential to provide greater capability Implicit assumption: state intent on proliferating 10

Calculating Resource Requirements by Modeling Reactors

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Multiple reactor designs

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integral pressurizedwater reactor designs

Two Broad Categories of SMRs that we modelled

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Long-lived Core reactor designs: do not require refueling for two or more decades; typically fast spectrum reactors

“Open Source” SMR-1 iPWR - 200 MWe (600 MWt; 33% efficiency) Standard PWR assemblies (full or reduced height) Core has 37 to 69 fuel assemblies All in/out core

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“Open Source” SMR-II Long-lived core operated in once-through mode 200 MWe, 500 MWt, 40 % efficiency Fast-spectrum reactor Central core zone with enriched starter fuel (12%); surrounded by blankets

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System for Neutronics Calculations MCNP determines power distribution and spectrum-averaged cross sections for up to 100 burnup zones in the core; depletion calculations with ORIGEN for each zone

Mathematica MO 3

MCODE

MCNP

Release 1.0 (MIT NED)

Release 5 (Los Alamos)

ORIGEN Release 2.2 (Oak Ridge)

A. Glaser, Neutronics Calculations Relevant to the Conversion of Research Reactors to Low-Enriched Fuel Ph.D. Thesis, Department of Physics, Darmstadt University of Technology, April 2005 17

keff versus core average burnup for the notional iPWR. The reactivity drop is steeper than in a gigawatt-scale reactor due to the higher neutron leakage from the core and the all-in all-out core management scheme.

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Uranium-235 depletion and plutonium buildup in the core of a notional 200 MWe SMR with a long-lived core. End of lifetime core plutonium inventory ∼ 2.8 tons (average plutonium-239 content ∼ 80%)

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Resource and fuel cycle requirements 1000 MWe for 30 years (300 days per year; 9,000 effective full power days) Standard LWR

iPWR

LLC SMR

(50 MWd/kg)

(30 MWd/kg)

(fast spectrum, once-through)

540 tons

900 tons

102 tons*

(5%-enriched fuel)

(5%-enriched fuel)

(12%-enriched starter fuel)

Uranium requirements

6200 tons

10320 tons

2910 tons

(to make fuel)

(reference)

(67% increase)

(53% reduction)

Enrichment

3.90 million SWU

6.48 million SWU

2.19 million SWU

(reference)

(67% increase)

(44% reduction)

Plutonium inventory in spent fuel

6.5 tons

9.0 tons

14.0 tons

(12 kg per ton of fuel)

(10 kg per ton of fuel)

(69 kg per ton of fuel)

540 tons

900 tons

204 tons

(reference)

(67% increase)

(38% reduction)

Fuel demand

Waste volume

one standard LWR, 1000MWe five iPWRs, 200MWe five LLC SMRs, 200 MWe

*Does not include 20 additional tons of depleted uranium for blankets

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iPWR: 67% increase in uranium, enrichment, and fuel demands; cumulative plutonium about 40% higher than for a standard PWR; concentration slightly lower LLC SMR: uranium and enrichment requirements are 53% and 44% below those of a standard LWR; 110% more plutonium; concentration 6 times higher (i.e., significant “temptation” to reprocess) 21

Proliferation risk assessment

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Technical and non-technical factors Characteristics of the proliferator (goals, resources, and technical capabilities) Fuel cycle choices Extrinsic measures Intrinsic features of the nuclear system

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Scenario based approach

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Models contain sets of discrete nodes (states) with specified nuclear material at each state and transitions between nodes treated as timedependent random processes characterized by physically meaningful time parameters

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PRCALC - Graphical User Interface (GUI) to make choices 26

Steps Define system’s states (nodes and transitions with associated time and material parameters) Identify proliferators’ potential targets Choose target material and proliferation rate PRCALC calculates probability of proliferation success, average time for doing so, etc.

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Scenario assumptions Host country has no declared enrichment or reprocessing facilities, but clandestine reprocessing facility Fresh fuel assemblies delivered from outside Transported from there to the reactor(s) Spent fuel assemblies transported to a centralized spent fuel repository Transported back to the country of origin 28

Reference Markov model for a plutonium diversion scenario. The model takes into account intrinsic and extrinsic features safeguards! and assumes existence of clandestine system elements, in this case, a clandestine reprocessing plant. The stage times shown in the nodes correspond to the average residence time for a fuel assembly in that stage; the in-core residence time is 4.5 years for the PWR, 3 years for the iPWR, and 30 years for the LLC SMR. Diversion of spent fuel is not equivalent to successful proliferation. Proliferators may still fail to separate out 1 SQ of material due to technical difficulties in the reprocessing of the diverted material.

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Markov Model Results

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LLC-SMR

iPWR

GW-PWR

To first order, the probability scales with the number of fuel assemblies and their plutonium content. These calculations assume that the types of applied safeguards and their effectiveness are identical for all systems. The scenario does not take into account the potential impact of geographical distribution of reactors, which is likely to be different for SMRs and gigawatt-scale reactors 31

GW-PWR

iPWR

LLC-SMR

Under equilibrium conditions, the proliferation time decreases with the number of fuel assemblies and approaches an asymptotic value of 24 weeks, the assumed time that it takes to reprocess the diverted spent fuel and obtain enough separated plutonium for one weapon. The calculated times are valid for an equilibrium or steady-state situation that corresponds to case with a very large number of reactors operating. 32

Both measures of proliferation risk change in the expected way – success probability increases and time decreases – with increasing flow of material iPWRs: more uranium and plutonium flow implies higher proliferation success probability LLC SMRs: higher concentration of plutonium implies higher proliferation success probability Overall probabilities small - but many reactors! 33

Future Questions

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Effect of geographical separation

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Effect of new types of safeguards Ongoing “Safeguards and Security by Design” activities that aim to evaluate reactor and other nuclear facility designs for proliferation vulnerabilities at an early stage Some technical characteristics of SMRs do increase some diversion risks while reducing others. One SMR design, the use of a “common refueling area for multiple modules” was found to reduce the effectiveness of safeguards 36

Conclusions Analyzed two broad kinds of SMRs iPWRs -higher requirements for uranium ore and enrichment services, and produce a larger volume of nuclear waste compared to GW-scale reactors SMRs with long-lived cores, uranium and uranium enrichment requirements as well as waste generation rate are reduced Increased plutonium production per unit of electrical energy generated translates into an increased proliferation risk 37