ORION and its application to fuel cycle assessment in the UK

Robert Gregg & Kevin Hesketh

Aims

Overview of ORION fuel cycle modelling

computer code

With illustration of fast reactor scenarios

in the UK

ORION development started 15 years

ago following BNFL’s need to have a

‘holistic’ view of the fuel cycle

Requirements:

Easy to use

Robust and accurate physics methods

General enough to model virtually any

fuel cycle (steady state or at

equilibrium)

(image: Areva)

ORION - the main GUI

A model can contain any number of objects connected in any way:

Buffer

Fabrication plant

Reactor

Active process plant (e.g. reprocessing plant)

Passive process plant (e.g. cooling pond)

External feed

Variable time step (1 month up to 1 year)

Up to 10 feeds can be defined for each object

For fuel with a varying fissile quality, reactivity equivalence coefficients can be used to

estimate the fissile fraction required

Performs decay and transmutation calculations, tracking 2552 nuclides:

Dynamic control of reactor deployment

ORION – the basics

A closed UK fuel cycle

DECC studies

UK Government: 80% CO2 emission cuts by 2050

Recognised potential contribution from nuclear power as well as other low CO2 energy

sources

NNL is in the process of formulating a UK funded nuclear R&D

programme to support national strategic goals:

CO2 reduction

energy security

long term sustainability

Fuel cycle assessments performed to help highlight benefits of a

particular reactor or fuel and to help guide and justify a future R&D

programme:

Legacy plutonium reuse in new build or purpose-procured reactors?

Future reprocessing?

Thorium fuel cycle and MSR use?

Future fast reactors?

Only sodium cooled fast reactor fuel cycles considered in this

presentation

Purpose of these calculations were to:

Gauge how difficult it will be for the UK to transition to a MOX fuelled SFR

closed fuel cycle

The impact fast reactor spent fuel cooling time will have on VHLW waste

volumes

The impact of recycling Am (and Np) will have on a future UK repository

The impact a single or multiple generation of fast reactors would have on

the repository

Scope

Closed fuel cycle

Reprocessing

Throughput

Geological

Disposal (100 yr interim

storage)

MAGNOX+AGR+SxB New build LWR Newer built fast reactor fleet (target)

Different capacities

modelled – 70 Gwy(e)

is an ’ambitious’

maximum

?

MAGNOX

THORP

Future LWR (separating Pu + U)

SFR (separating Pu + U (+ Np and Am)

Pu availability for an SFR fleet

Max SFR fleet 10%-20% lower

than preceding LWR fleet size

Assuming all PWR used fuel reprocessed

5 years cooled (+2 yrs for rep/fab)

No MOX use in LWR fleet

Pu availability for an SFR fleet

Impact of cooling time on spent fuel handling and reprocessing ..

Inventories will eventually be used to help develop reprocessing flowsheets

2 year

5 year

.. Impact on VHLW volumes and interim storage requirements

SFR Results PWR Results Legacy

2 y

ears

2 y

ears

, N

p+

Am

recycle

5 y

ears

5yr, N

pAm

2.5kW/canister

Impact on repository footprint

Over short time scales, thermicity (decay heat) of the nuclear waste is

limiting

Repository footprint will depend on total decay heat

Thermal limits ensure surrounding bentonite clay remains < 90oC

Decay heat of material entering repository integrated up to 2450 (roughly

200-300 years in repository) – relative sizes of the HLW portion of the

repository can be estimated

Thermicity from a finite fuel cycle

1 generation of PWRs followed by

1 generation of SFRs recycling Pu and Am

1.0

0.56

0.41

Finite vs. equilibrium

Rep. size (HLW) halved

if Pu is recycled through

a fast reactor fuel cycle Significant amount of Am in

fast reactor spent fuel once

the SFR fleet is retired

Np/Am recycle results in a

factor of 6-7 drop in decay

energy deposited in repository,

assuming indefinite operation

Conclusions

Maximum fast reactor fleet size 10-20% smaller than

preceding LWR fleet

Small preceding LWR fleet = small fast reactor fleet

Reducing cooling time from 5 to 2 years results in no drop in SFR fleet

size …

However, VHLW waste volumes increase by a factor of 2-3 and

reprocessing becomes more challenging

Fast reactor closed fuel cycle (single generation) reduces

thermicity of spent fuel by a factor of 2:

Recycling Np+Am reduces thermicity by a further 10%.

Thermicity dominated by final SFR cores

More noticeable if fuel cycle operates indefinitely (6 – 7x improvement)

Current day and future nuclear in the UK

• Sizewell

• Bradwell

• Dungeness Hinkley Point •

Berkeley and Oldbury •

Wylfa •

Trawsfynydd •

Heysham •

Calder Hall/Sellafield •

Chapel Cross •

Hunterston •

• Torness

• Hartlepool

MAGNOX

AGR

PWR (Sizewell B)

NEW BUILD

CURRENT DAY UK NUCLEAR INDUSTRY

MAGNOX stations– all spent fuel reprocessed (11)

AGR stations- some spent fuel reprocessed (6)

PWR station (Sizewell B) (1) – spent fuel stored on site (wet, and soon dry)

FUTURE POSSIBLITIES

UK has a commitment to radically cutting green house gas emissions by 2050

Possible new build sites (7 sites)?

Sizewell (2 x EPR?)

Hinkley Point (2 x EPR - definite)

Oldbury (2 x ABWR?)

Wylfa (2/3 x ABWR?)

Cumbria (Sellafield) (AP1000s?)

Bradwell, Hartlepool, Heysham (?)

Eventually >125tHM separated Pu (Sellafield)

Pu-use in new build/purpose-procured reactors?

RepU-reuse in Sizewell B and new build fleets ?

Future reprocessing of PWR spent fuel in 2050?

Replacement closed fast reactor fleet from 2050?

Separated Pu

These policies requires fuel cycle scenario assessments to estimate their impact – the UK Nuclear Fission Roadmap