Nonproliferation role of 231Pa and 232U from a fusion breeder for the

Ralph Moir Vallecitos Molten Salt Research 607 E. Vallecitos Rd., Livermore, CA 94550 USA [email protected] www.ralphmoir.com/ Thorium Energy Alliance 2014 Conference (TEAC6) May 29, 2014, Chicago Incentives for molten salt reactors are so great that one asks why the reactor has not already been developed?

5/13/14 Abstract

Initial and makeup 233U fuel for a thorium molten salt reactor can be produced in a fusion breeder with 2.4% 232U that will make this fuel “self-protected” by its strong gamma radiation according to IAEA standards. 232U significantly contributes towards nonproliferation of nuclear weapons use. Fusion technology even early in its development towards a commercial power plant nevertheless can produce 233U by neutron capture in 232Th and simultaneously produce both 231Pa and 232U in a neutron reaction having a 6 MeV threshold making fusion’s 14 MeV neutrons uniquely well suited for this purpose. The 231Pa can make 232U by neutron capture in the fusion breeder in large enough quantity to make the simultaneously produced 233U self protected with 2.4% 232U. Excess 231Pa can be extracted and exported to fission reactors where by neutron capture 232U is made in situ for nonproliferation purposes. When the fission reactor’s conversion ratio of fertile to fissile approaches unity (breeding or isobreeding) its fissile 233U is produced internally with too little 232U nonproliferant made to satisfy the 2.4% rule because fission’s neutrons are below the 6 MeV threshold. In this case, as the conversion ratio approaches unity, 231Pa is supplied so that the production of 232U by neutron capture in 231Pa keeps 232U/233U=2.4%. In the long term, producing 233U by fusion breeding avoids the need for isotope enrichment facilities to be greatly expanded thus contributing to nonproliferation. In the short term, before fusion bred 231Pa, 232U and 233U become available, the required fissile material can come from enriched 235U with enough 238U to be denatured for nonproliferation or can come from from spent fuel. Key words: molten salt reactor, thorium, fusion breeder, 231Pa, 232U, 233U nonproliferation

5/13/14 2 Nonproliferation strategy #1

§ The Denatured Molten Salt Reactor (DMSR) dilutes 233U and 235U with enough 238U to be below weapons grade. § 233U/U<13% § 235U/U<20% § Also safeguards and emphasize openness and transparency Recommendation to MSR developers: Initially go for DMSR

5/13/14 3 With denaturing 238U builds up and Th drops off. With 233U from fusion 232Th would not drop off and 238U would not build up.

120,000 232 100,000 Th Th inventory 80,000 235U 20% 233U U238inventory DMSR 60,000 Inventory, kg Inventory, U238 inventory makeup Fusion makeup 40,000 Th inventory

20,000 238U

0 0 5 10 15 20 25 30 t, years DMSR=ORNL/TM-7207 4 5/13/14 With denaturing 233U and 235U reach steady values in about 3 y.

DMSR-235U startup & makeup 4,000

U235inventory U233inventory 3,000 Pu239inventory 233 2,000 U

1,000 235 Fissile inventory, kg inventory, Fissile U 239Pu 0 0 5 10 15 20 25 30 Time, y

5/13/14 5 Nonproliferation strategy #2 2nd Gen MSR § Spike the fissile 233U with fusion produced 2.4% 232U, a strong gamma and heat generator making the material undesirable for weapons. § Employ safeguards and emphasize openness and transparency Recommendation to MSR developers: Generate a market for 233U, 232U and 231Pa

Recommendation to fusion developers: Design a fusion breeder for 233U, 232U and 231Pa

5/13/14 6 The reaction paths that lead to 232U with % for each route for the (Li/MS, Be/MS) blankets

•(0.3%, 0.1%) •(0.03%, 0.01%)

•(16%, •(84%,98%) 2%)

233U is produced in the following reaction ! 232 233 233 " 233 " 5/13/14 n+ Th! Th! Pa + e ! U + e 7

231Pa and 232U are produced in the following reactions

232 233 233 •1 n+ Th! Th! Pa + e" n+ 233Pa ! 2n + 232Pa!232U + e" Fast

n 232Th 233Th 233Pa e" 233U e" •2 + ! ! + ! + n+ 233U ! 2n+ 232U Fast

232 231 231 " •3 n+ Th ! 2n+ Th! Pa + e Fast

231 232 232 " n+ Pa! Pa! U + e

5/13/14 8 Fusion is unique for producing 231Pa & 232U

Threshold cross-sections Fusion for producing 232U 100% neutrons > 6 MeV)

N(E) fission spectra N(E) fusion spectra/5 0.4 2.5 Th232 n,2n Fission Pa233 n,2n 2.0 0.3 U233 n,2n 1.5 3% neutrons > 6 MeV). 0.2 1.0 0.1 0.5 barns section, cross (n,2n) 0 0.0 spectra neutron fusion and Fission 0 5 10 15 20 Neutron energy, MeV

5/13/14 9 231Pa and 232U are produced in a fusion blanket of Li followed by a Li Th molten thorium molten salt. salt

kg PR = 4.318 F ! Pfusion (MW ) MWfusion ! y

231 § Fn,2n = 0.0246 Pa 32,800 y half-life 233 233 § Fn, g = 0.515 Pa 27.0 d half-life, decays to U

5/13/14 10 Revenues from 231Pa and 232U at assumed value per gram

231 kg Pa $82, 000 231 PR = 0.1062 Pfusion (MW ) " Pnuclear (MW ) for $1000 / g of Pa MWfusion ! y MWnuclear ! y

233 kg Pa $130, 000 233 = 2.224 Pfusion (MW ) " Pfusion (MW ) for $60 / g of U MWfusion ! y MWfusion ! y

233 kg Pa $103, 000 233 = 1.72 Pnuclear (MW ) " Pnuclear (MW ) for $60 / g of U MWnuclear ! y MWnuclear ! y

1 GWe; Pnuclear/Pfusion=1.3

5/13/14 11 Revenues from electricity and isotopes 0.48 Q 4.8 48 0.2 0.2 50 $/MWeh Breeding revenues 0.1 DC=0,BDC=0.5 0.1 Ÿ Electrical DC=BDC=0.5 0.1 $/Wnuc y revenues 0 Breeding revenues 0 $/Wnuclear-year M=2.1 no DC

Annual revenues/ revenues/nuclear Annual -0.1 -0.1 1 10 100 MQ

Q=fusion power/input power= Gain

5/13/14 12 Cost for isotopes depends on electricity sales/purchases (Q)

1000 50 $/MWeh

etadc=0.0 100 sales Pa

231 1.25 $/Wnuclear

10 1.5 $/Wnuclear

U, $/g no U, 2.0 $/Wnuclear 233 1 0.1 1 10 100 Q Q=fusion power/input power= Gain 5/13/14 13 The value of 233U can be corrected for the 231Pa sales.

150 233U=150 $/g without 231Pa sales

100 U, $/g U,

233 100 $/g

50 Value of Value 50 $/g

0 0 1000 2000 3000 Value of 231Pa, $/g

5/13/14 14 Supply 233U + 2.4% 232U to MSR for startup and makeup fissile For conversion ratio (CR)>0.75 232U/233U falls below 2.4% 0.1

0.08

U 0.06 233

U/ 0.04 232 IAEA "self protected" 0.02 by 2.6 MeV gamma rays

0 0 0.2 0.4 0.6 0.8 1 Conversion ratio, CR

5/13/14 15 For CR>0.75 supply 231Pa to MSR as well as 233U.

Then 232U/233U ≥ 2.4% for any CR.

0.1 7 6 0.08 5 231Pa 0.06 4 232U/233U kg/y 0.04 3 232U/233U 2 0.02 231Pa/y 1 0 0 0 0.5 1 Conversion ratio, CR 1 GWe

5/13/14 16 For startup on 239Pu (or 235U), 239Pu is replaced~2 y with 233U without 232U

1500 233U

inventory, inventory, 1000 233U, CR=0.75

Pu 0.9 kg

239 1 500 239Pu Pu239 U and and U 0 233 0 1 2 3 Time, y

Assume 1500 kg/1 GWe

5/13/14 17 For startup on 239Pu or 235U an initial supply of 232U and 231Pa is needed. 232U/233U builds up to 2.4% 15 years starting with 231Pa=25.5 kg. 0.04 232U 40 232U, kg 0.03 232U/233U 30

0.02 20 CR=0.75 232U/233U 0.9 0.01 1 10 self-protection U232, CR=0.8 0 0 0 5 10 15 20 Time, y 35 kg 232U initially would keep 232U/233U ≥ 2.4% Otherwise we have a problem.

5/13/14 18 6840 kg/y 233U is extracted by fluorination and 150 kg/y 231Pa by reductive extraction

3000 MW fusion

5/13/14 19 Conclusions Nonproliferation strategy #1

First generation MSR should use denatured (235U/U<0.2) Also safeguards and emphasize openness and transparency

5/13/14 20 Nonproliferation strategy #2 2nd gen MSR when fusion is available § Spike the fissile 233U with fusion produced 2.4% 232U, a strong gamma and heat generator making the material undesirable for weapons. § Employ safeguards and emphasize openness and transparency Recommendation to MSR developers: Generate a market for 233U, 232U and 231Pa

Recommendation to fusion developers: design a fusion breeder for 233U, 232U and 231Pa

See my website for details 5/13/14 21