Hybrid Energy Systems

David Shropshire

Planning and Economic Studies Section Head

Division of Planning, Information and Knowledge Management

Department of Nuclear Energy

IAEA Workshop on Small Modular Reactor Safety and Licensing,

held in Hammamet, Tunisia 12 – 15 December 2017

Talk Outline

• Energy policy drivers

• Applications of SMRs

• Load following requirements

• Power management options for load following

• Challenges with reactor power maneouvering

• Hybrid system

• Case-study courtesy of NuScale Power

Energy Policy

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Energy Security – Fuel Supply

Independence

Energy Security – Meeting the

Generation Gap

Climate Change – Meeting CO2

Reduction targets

Economics and Affordability

Applications

SMRs have been designed for the following

applications:

• Electricity Generation

• Portable Water Production

• District Heating

• Hydrogen Production

• Process Heat Application

Designed for flexibility including load following

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Load Following

• Large reactors lack flexibility to change output over short timescales and role has been to provide base-load electricity

• Technical and safety issues make it difficult to load following unless adapted to do so with complicated procedures and thermally tolerant components

• Gas powered plants are very flexible and can vary outputs in order to meet shortcomings in electricity demands coming from renewables

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Need for Load-following

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EPRI User Requirements

Rev. 13 (SMR) Description

• 24 hour load cycle: 100%>20%>100%

• Ramp rate of 40% per hour

• Capable of automatic frequency response

• Step change of 20% in 10 minutes

• Frequency variation tolerance

Regulatory Requirements

• Many reactors were designed for load-following and have automatic grid control features

• In the US some load-shape

• In France large reactors load follow because they produce 75% of electricity

• SMRs are designed to load follow but then so are many larger reactors

• So what do the vendors need to do to satisfy the safety regulator and operator?

• What would be the requirements that an SMR would have to meet to operate as part of a hybrid energy system?

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Challenges with Reactor

Power Manoeuvring

• Fuel design - resilient to frequent thermal cycling

• Capacity factor – thermal and operational cycling accelerate component degradation

• Reactivity control – continued low power requires boron adjustment

• Waste heat rejection – turbine by-pass requires additional cooling tower capacity

• Refueling schedule – affected by low power

• Staffing – routine power manoeuvring affects workload

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Light water nuclear/renewable

hybrid system

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Load-following requirements

• Predictability hourly, daily and weekly is important to make it economic

• Long term predictions can be planned for by supplying to other utilities or for cogeneration

• Short term shortages require excess capacity or the ability to divert electricity from other customers

• Smart grid and control is essential

• Operating an SMR close to 100% is key

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Case Study courtesy of

NuScale Power

• Integrating NuScale Power SMR (50MWe per

module) with Horse Butte Wind Farm (<60MWe)

• Deployment of clean base-load electrical power

to replace coal fired generation

• Use for Cogeneration

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Horse Butte Wind Farm

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12-module NuScale plant

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Power Management Options for

Load Following Operations

• Take one or more modules off-line

• Manoeuvring reactor power for hourly changes in

demand

• By-passing module’s steam generator directly to

condenser for rapid responses

• Allow power changes by control rod movement

down to 40% power

• Beginning of life modules offer greater flexibility

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NuScale load-following

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Load-following Options

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Economic Perspective

• Not reduce power output or dump steam

• Sell excess electricity to other utilities through Excess Imbalance Market

• Require Automatic Generation Control

• Use electricity or heat for other purposes such as desalination, chemical production (cogeneration)

• Hybrid Energy System can be optimised to meet grid demand and other valued products without varying nuclear plant output

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Decision to Load-follow

• Economics – large capital investment so plant

needs to operate 100%

• Regulatory requirements – these have yet to be

defined but will need to be informed by research

on the behaviour of the plant and components

• Policy mandates – strategic approach to operation

so that it integrates with renewables and also has

a range of products so as not to waste heat

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Thank you!

For inquiries on SMR, please contact:

IAEA Nuclear Power Technology Development Section