Modelling of a once-through MSR without online fuel processing

Transcription

1 Modelling of a once-through MSR without online fuel processing Kien Trinh University of Cambridge The 4 th Annual Serpent Users Group Meetings 19 th September 2014

2 OUTLINE 1 Background & motivation 2 The Denatured Molten Salt Reactor (DMSR) 3 The Serpent model of the DMSR 4 Future work 2

3 Background & motivation Overview of the Molten Salt Reactor Fuel is in the form of molten halide salts(e.g. 233 UF 4 / 232 ThF 4 dissolved in LiF & BeF 2 (FLiBe)) Advantages include higher efficiency, higher fuel utilisation and improved safety Forsberg, C W. (2006). Molten-Salt-Reactor Technology Gaps. In 2006 International Congress on the Advances in Nuclear Power Plants (ICAPP 06). Reno, Nevada.

4 Background & motivation Proliferation & hazardous risk of online fuel reprocessing He He, Kr, Xe, noble metals Spent Fuel Salt Fluoride volatility Separation of TRUs Pa 233 & TRUs Separation of FPs FPs for storage Reactor core UF 6 Np & Pu Storage Th & salt U 233 & TRUs Chemical composition control of salt

5 OUTLINE 1 Background & motivation 2 The Denatured Molten Salt Reactor (DMSR) 3 The Serpent model of the DMSR 4 Future work 5

6 The Denatured Molten Salt Reactor The Denatured Molten Salt Reactor: The simplest MSR design Denatured uranium: (m U m u235 ) < 0.12m Utot No fuel reprocessing required beyond He bubbling and chemical redox control Engel, J.R. et al. (1980). Conceptual Design Characteristics of a Denatured Molten-Salt Reactor with Once-Through Fuelling. Technical Report, The Oak Ridge National Laboratory.

7 The Denatured Molten Salt Reactor The Denatured Molten Salt Reactor: The simplest MSR design He He, Kr, Xe, noble metals Spent Fuel Salt Fluoride volatility Separation of TRUs Pa 233 & TRUs Separation of FPs FPs for storage Reactor core UF 6 Np & Pu Storage Th & salt U 233 & TRUs Chemical composition control of salt

8 The Denatured Molten Salt Reactor The Integral Molten Salt Reactor: A small modular DMSR Small modular (80-600MWth) Completely sealed unit Removed & discarded after 7 years Terrestrial Energy (2013a). Integral Molten Salt Reactor. com/safety/. Accessed

9 OUTLINE 1 Background & motivation 2 The Denatured Molten Salt Reactor (DMSR) 3 The Serpent model of the DMSR 4 Future work 9

10 The Serpent model of the DMSR Modelling a multi-batch refueling scheme of the DMSR Isotopic composition vector N N = (1-f)*N Add the same volume of fresh fuel ( 233 U or 235 U & 238 U) k eff 1.0 Calculate neutron production & absorption No Yes Optimise volume fraction f of the fuel to be replaced with fresh fuel Run depletion step Research question: Lifetime fuel requirements? FPs & actinide evolution?

11 The Serpent model of the DMSR Validation of the SERPENT model: Replicating results from PSI Hastelloy-N reflectors Fuel salt Salt volume from 5 to 100% core volume Constant power (1.5 GWth) Core dimension adjusted to reach BR = 1 Graphite Křepel, J. et al. (2014). Fuel cycle advantages and dynamic features of liquid fueled MSR. Annals of Nuclear Energy, 64:

12 The Serpent model of the DMSR Validation of the Serpent model: Differences in simulation of refuelling SERPENT Additional artificial decay term in the Bateman equation of FPs: dn/dt = -λn Where: λ = ln2/30 for gaseous FPs and noble metals (30s characteristics removal time) λ = 1/(182.5*24*3600) for other FPs (6 months removal time) Fuel is topped up with 232 Th: dn Th232 /dt = +Σσ f,i N i ϕ ERANOS Non-soluble FPs are removed every 30s (by applying a similar artificial decay term) All soluble FPs are removed every 6 month The removed FPs mass was replaced by 232 Th Křepel, J. et al. (2014). Fuel cycle advantages and dynamic features of liquid fueled MSR. Annals of Nuclear Energy, 64:

13 The SERPENT model of the DMSR Discrepancies between Serpent and Eranos results Actinide 90% volume salt 10% volume salt Mass (t) SERPENT ERANOS %diff SERPENT ERANOS %diff Ra 6.75E E E E Ac 1.57E E E E Th 1.52E E E E Pa 6.05E E E E U 3.24E E E E Np 6.05E E E E Pu 1.18E E E E Am 2.18E E E E Cm 2.32E E E E Bk 2.79E E E E Cf 8.45E E E E Křepel, J. et al. (2014). Fuel cycle advantages and dynamic features of liquid fueled MSR. Annals of Nuclear Energy, 64:

14 The SERPENT model of the DMSR Slow conversion to equilibrium of the 30% volume salt case

15 OUTLINE 1 Background & motivation 2 The Denatured Molten Salt Reactor (DMSR) 3 The Serpent model of the DMSR 4 Future work 1

16 Future Work Validate Serpent model Quantify the effects of the multi-batch refuelling scheme: refuel volume versus frequency? Optimise start-up and top-up loads: ORNL proposed 74% LiF, 16.5% BeF 2 and 9.5% (ThF 4, 233 UF 4, 238 UF 4 ) and 20% enriched UF 4 top-up without further optimisation. Use 5% enriched uranium and 232 Th as top-up? Chloride instead of fluoride?