Adapting CANDU Small Modular Reactor to Northern Service (G. Harvel and D. Meneley)

ADAPTING SMR-CANDU TO NORTHERN SERVICE

by G. Harvel and D. Meneley University of Ontario Institute of Technology, Oshawa, Ontario, Canada Glenn.Harvel@uoit.ca, Dan.Meneley@uoit.ca

3rd International Technical Meeting on Small Reactors 2014 November 5-7 The Ottawa Marriott Hotel, Ottawa, Ontario, CANADA

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THE SMALL MEDIUM-OR-MODULAR REACTOR 

Small may be beautiful, but big is cheap (Comm. Ed.) 

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e.g. Niche market or strange financing conditions  

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Small local demand and/or remote, off-grid location Aberrant rules for charging project costs into the rate base

Large units often carry obsolescent reference designs  

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Given the same project requirements, this is always true Changing the rules can make the statement false

Too big for the market?

Too many frills – a touch of Byzantium?

Small units may enable factory assembly 2

WHAT IS A MODULAR REACTOR – AN SMR? 

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Define: A reactor whose primary heat generation and transport systems consist of self-contained interchangeable units.

The CANDU fuel channel is a module by this definition, as is each reactor core of the NuScale modular system CANDU modules must be tightly coupled to reduce neutron leakage, while most modular designs feature neutronically separated cores.

Modularity usually produces higher costs, but always results in greater flexibility in cash flow & schedule 3

BASIC DESIGN THE CANDU MODULECONCEPT (CANDU 6)

9 pressure tube 10 calandria tube 11 calandria tubesheet 12 inboard bearings 1 channel closure 2 closure seal insert 13 shield plug 14 end shield shielding 3 feeder coupling balls 4 Liner tube 5 End fitting body 15 end shield lattice tube 6 outboard bearings 16 fuelling tubesheet 7 annulus spacer 17 channel annulus bellows 8 fuel bundle 18 positioning assembly 4

THE CANDU SMALL (OR LARGE) MODULAR DESIGN 

“If you want a smaller fire, just use fewer logs” -- John Foster, former president of AECL

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In the beginning, there was NPD 

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Converted from a vessel design to a channel design, in anticipation of larger commercial unit power requirements This prototype plant operated well for 25 years

Back to the future? 

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We thought we needed a small power reactor for remote sites NPD produced 22 Mwe (gross) 

Could be produced from about 15 channels – (minimum grouping?)

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DYNAMICS OF REACTOR DEVELOPMENT The customer always controls the process  The customer sets ideal project objectives: 

a

brand new design with a perfect operating record  a design that solves old operating problem but opens no new licensing questions  accepted as safe by a majority of people  privately owned, but government funded  much cheaper than designs that came before 

Customer may be confused by competing claims 6

WHAT DRIVES THE SMR FASHION SHOW? Cheaper  Faster  Better 

not satisfied with today’s designs  Research is more fun than project engineering  Big plants are old stuff -- can’t we do better? 

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IN THIS STUDY, THE NEEDS ARE DIFFERENT  

Postulate: Major mining opportunity in Ontario Consequence: Medium-scale power is needed 

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400-600 Mwe, with high reliability

Can CANDU fill this need?  

Of course -- we have CANDU 6E – too big?

A 200 Mwe plant – just about right 

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Douglas Point? – too old

Who can do this job right now? – a very short list  

Import the plant from India Design & build our own 8

PLANT & SITE CHARACTERISTICS INFLUENCE DESIGN 

Remote, off-grid site was chosen by the customer  Harsh

local climate – extremes, winter & summer  Fuelling and fuel management  Site security and safeguards  Operating staff complement  Operating License 

Immediate need for electric power and heat  Large

commercial mining operations planned  Community needs, locally and in surrounding district 9

GOING BIG? – QINSHAN–3 PLANT IN CHINA Two CANDU6 units in parallel Paired unit arrangement is good Total capacity is 3 times too large Cash flow too high in early days

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SECOND OPTION – 200 MWe CANDU-TYPE

Douglas Point Generating Station 200 Mwe prototype, at Bruce A and B Nuclear power Development Location: India. Many improvements in performance and safety design.

Has been in operation for 14+ years.

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THE CANDU 80 CONCEPT – R. HART, 1996 100 Mwe net output  True SMR concept – for remote sites, oil sands  Applicable for countries new to nuclear energy  Low power density, large operating margins  Proven technology throughout  Low specific capital cost, low operating cost  Short project cycle 

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COMPROMISE CHOICE OF DESIGN CONCEPT 

CANDU 80 – 100 Mwe (net)  Good

match for adapting Darlington plant concept ✔  Multiple units match SMR idea & provide redundancy  High

reliability suits a remote site  Low cash flow in early years of project  Adequate growth potential in long term 

The CANDU 80 design incorporates mostly proven components and systems  It

is easily adapted further – e.g. multi-unit layout ✔ 13

CANDU 80 – ORIGINAL & MODIFIED Now further modified for two fuelling machines & figure of eight PHT loop

Reactivity mechanism deck

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DARLINGTON VACUUM CONTAINMENT

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DARLINGTON FUEL TRANSFER TO & FROM TROLLEY Attach one fuelling machine to each end of a sigle fuel channel Add & Remove fuel at the reactor face Lower fuelling machines into trolley Move trolley to fuel bay location & attach Unload used fuel, load fresh fuel, return to next unit for fuel & defuel operation

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CANDU SMR CONTAINMENT & CONTROL

4 units – 1 control room

Used fuel storage

Vacuum Building (If Required)

Project Phase 2 (If Required)

Reactor Vaults

Fuelling Machine Room

Fuelling Duct

4 units – 1 control room

Used fuel storage

Total Output -- 800 Mwe 17

SCALE FACTORS 

Different parts of small vs large plants follow different scale requirements:  e.g.

unit output is proportional to core volume:

(30 x 30 x 12 x 50 x n1)/(30 x 30 x 10 x 50 x n2) = 881/100 n2 = 100/880 x 480 x 12/10 = 65.5  65 channels 

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e.g. space between units varies with core length plus fuelling machine length

Vacuum building may or may not be required 

Suppression spray in fuelling duct instead?

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CANDU-SMR CONCEPT & ADAPTIVE FEATURES – 1 

Basic design principles  

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Major operational features     

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Evolution of reference design from earlier designs Primary objective is electricity and process heat production On-power refueling ✔ Fuel is useless for diversion for weaponry ✔ Remote fuelling from new fuel storage to used storage bay ✔ Extensive capability for load levelling ✔ Total independence from external grid ✔

Operating concept  

Day to day (limited) intervention by local trained staff ✔ Remote monitoring and periodic visits by expert staff ✔

CANDU-SMR CONCEPT & ADAPTIVE FEATURES - 2 Design concept reference ---Darlington NGS A ✔  Stepwise installation ✔ 

 one

unit at a time, plus common systems as needed  Final planned configuration: eight (8) identical units  Two-track fuelling machine trolley, one spent fuel bay at each end of station. 

Build in same sequence as Darlington (2-1-3-4) ✔  Take

account of lessons learned on that project 20

MAJOR SYSTEM PERFORMANCE SPECS     

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Cost-competitive with petroleum for heating and electricity Licensable in Canada, under small-reactor licensing guidelines 100% plant availability (including backup) “No-freeze” protective design of all systems Portable in segments, both new and as a used facility Full range load following –seconds to days, with energy storage Computer controlled operation plus remote safety intervention Daily fuel changing at power Infrequent fuel restocking – minimum one-year at full power Used fuel transport to most convenient location for short and medium term storage.

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FUEL SUPPLY AND MANAGEMENT 

Small, cheap, natural uranium fuel assemblies  Easily

transported, both as new and when used  Useless for unauthorized diversion to weaponry 

Automated fuel movement  Today’s

design is already semi-automatic  Automate the fuelling from fresh storage rack to used fuel bay  On-site staff only to monitor plant and carry out routine operations. Central facility operators to carry out more complex operations.

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UNIT POWER OUTPUT VARIATION 

This plant will have, especially early in its life, few customers. It follows that its output must be continuously variable over quite a large range.  It

may be necessary to choose a “normal operating power” setpoint significantly lower than the full power capability of the design.  This

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will influence rated power installed at a particular time

Frequency control is included in this plant’s role

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MORE GENERATION DEMAND FACTORS Diurnal fluctuations  Weekly/monthly industrial demand fluctuations  Annual weather fluctuations  Cumulative variations – domestic, industrial  Service area increases and decreases 

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WINTER-SUMMER VARIABILITY – AN OPPORTUNITY? High energy demand in winter– use full system capacity (warming of homes & barns)  Low energy demand in summer – use excess capacity for growing crops, warming fishponds?  Greenhouse agriculture  Extend the local summer season 

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SYNTHETIC OIL PRODUCTION – A WAY OUT? 

See Charles Forsberg – “Nuclear Beyond Baseload Electricity: Variable Electricity and Liquid Fuels” http://canes.mit.edu/sites/default/files/pdf/NES-115.pdf

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Consider oil and gas economics vs costs and benefits of local synthetic oil production.

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ENERGY STORAGE – ANOTHER WAY OUT? Desirable due to highly variable load profile  Site loads include large thermal requirement  Molten salt storage tank – heated by excess electricity 

 Possibly

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use on-site wind and/or diesel-electric

Water storage tank – excess thermal output of SMR plant  Possibly

include back-pressure turbine 27

ON-SITE TANK STORAGE CONCEPTS Wind farm (or other) electricity source

Molten Salt Tank Backup steam generation Methane production

Diesel backup

Excess electricity

CANDU-SMR Power Plant Reject heat

“Natural” gas storage

Local Electric Loads

Reject Heat

F/W heating

Hot Water Tank

Local heat loads

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NEXT STEPS -- CANDU SMR 

Major tasks  Find

at least one customer  Get the cost down – simplify & refine the concept  Minimize operator intervention tasks at local level  Initiate communication/discussion with CNSC  Conduct preliminary and detailed design  Build/maintain a computer-based design package  Refine the cost estimate 29

SUMMARY Many productive options are available  Energy supply in the High Arctic is a challenge 

 Social

acceptance is a major factor  There are additional technical challenges  Commercial competition will be fierce  First-of-a-kind risks may be large  Licensing is a big question – as always

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