Chemical Engineering 412

Introductory Nuclear Engineering

Lecture 21Nuclear Power Plants III

Nuclear Power Plants: Advanced Reactors

Spiritual Thought2

Fast Reactors - Advantages

• Most transuranics act as fuel– Reduces waste toxicity – Reduces waste lifetime (dramatically)

• Expand potential fuel –– Thermal is primarily odd-numbered actinides (235U)– Fast is all actinides, including 238U, Th, etc.

• In waste• Depleted uranium• Actinides generated in the fuel

• When operated in breeder (as opposed to burner) mode, creates more fissionable fuel than it consumes, extending total available fuel.

Fast Reactors – Disadvantages

• Low response time– complicates control!– control rods less effective, other means must be used:

• Fuel thermal expansion• Doppler broadening• Absorbers• Reflectors

• Small cross sections – large critical mass– Leads to either large cores or high enrichment.

• Sodium and sodium/potassium highly reactive!– Lead, salts and gases avoid this problem, but more absorption

• Liquid metals and salts can become radioactive – (n, 𝜸𝜸) reactions – 4He avoids this problem (absorption cross section near zero).

• Potential positive void coefficient of liquids – not He.

Waste

0.001

0.01

0.1

1

10

100

1000

10 100 1,000 10,000 100,000 1,000,000

Years

Rel

ativ

e R

adio

logi

cal T

oxic

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Transuranic Elements (TRUs)

MOXSingle Pass

TRUs

TRUs with No Pu

Fission Products(same for all cases)

Natural UraniumOre

Westinghouse Approach

300 years

Traditional Fuel Cycle Approaches

© 2013 Westinghouse Electric Company LLC. All Rights Reserved.

Conversion Ratio

• Ratio of Created fuel to burned fuel– Breeder reactors 1.01 up to ~1.21– Burner reactors ~0.1-0.2

• Example:• In a critical reactor fueled with natural uranium, it is

observed that, for every neutron absorbed in 235U, 0.254 neutrons are absorbed in resonances of 238U and 0.640 neutrons are absorbed by 238U at thermal energies. There is essentially no leakage of neutrons from the reactor.

– What is the conversion ratio?– How much 239Pu in kg is produced when 1 kg of 235U is

consumed?

6

Small Modular Reactors

• Small – < 300 MWe (IAEA definition) – Right size for remote grids– Insurance cutoff

• Modular – systems can be almost entirely fabricated in shops– 7, 3, 1 – factory, site, hole– Advantages

• Large reduction in capital cost!• Reduction of financial risk• construction at a single location• ability to add incremental power.

• Disadvantages– Loss of economies of scale.– Lower Power density.

• Include III, III+, and IV or other designs

B&W iPWR SMR Design

Source: Integral Pressurized Water Reactor, Patent US 20130301776 A1 Nov 14, 2013

6,8 – upper and lower pressure vessels30 – reactor core

40,42 – control rod insertion and guide

24 – steam generator26 – pressurizer

32-38 – optional reactor coolants pumps and

associated drive, impeller, etc.

B&W/Bechtel mPower Reactor

• 530 MWth developed by joint venture of Babcock & Wilcox and Bechtel, 155 to 180 MWe output on air or water cooling, respectively

• 13 ft diameter, 83 ft tall• $226 M in DOE cost-shared funding• TVA Clinch River potential host site• 5% enriched fuel for 4-yr core life• Construction permit target date 2015• 825 psi (56 bar) steam w/ 50 °F (28 °C)

superheat

Toshiba 4S

• Super-safe, small and simple (4S) design.

• Na-cooled fast reactor using U-Zr or U-Pu-Zrfuel, allowing operation for up to 30 years without refueling

• Uses a movable neutron reflector to adjust neutron population.

• Electro-magnetic (EM) pumps, with natural circulation used in emergencies

Small Modular Reactors

• Strengths:– Grid Stability

• Compact and modular– Economics

• Smaller up-front investment– Safety

• No-large bore piping• Improved passive safety (no operator action)

• Weaknesses:– Economics

• Unproven, new licensing process ($1B needed)• Small technology improvement for $1B

– Safety• Still only 7 days of passive cooling in some

scenarios– Waste

• No improvement on current methods© 2013 Westinghouse Electric Company LLC. All Rights Reserved.

Small Modular ReactorsName Power Technology ProducerVK-300 300 MWe BWR Atomstroyexport, RussiaS-PRISM 311 MWe FBR GE Hitachi Nuclear Energy4S 10–50 MWe FNR Toshiba - JapanGT-MHR 285 MWe HTGR General Atomics (USA), Minatom (Russia) et al.PBMR 165 MWe HTGR Eskom, South Africa, et al.BREST[2] 300 MWe LFR RDIPE (Russia)Hyperion Power Module[1] 25 MWe LFR Hyperion Pwr Gen - Santa Fe, NM USASVBR[3] 10–100 MWe LFR OKB Gidropress (Russia)MASLWR 45 MWe LWR NuScale Power LLC, USAFuji MSR 100–200 MWe MSR ITHMSO, Japan-Russia-USAWAMSR 200 MW MSR Transatomic Power, USACAREM 27 MWe PWR CNEA & INVAP, ArgentinaFlexblue 50–250 MWe PWR Areva TA / DCNS group, FranceIRIS-100 100 MWe PWR Westinghouse-led, internationalKLT-40 35 MWe PWR OKBM, RussiamPower 180 MWE PWR Babcock & Wilcox, USAMRX 30–100 MWe PWR JAERI, JapanNP-300 100–300 MWe PWR Areva TA, FranceSMART 100 MWe PWR KAERI, S. KoreaSMR-160 140 MWE PWR Holtec International, USAWestinghouse SMR 225 MWe PWR Westinghouse Electric Company, USA TerraPower 10 MWe TWR Intellectual Ventures - Bellevue, WA USA

BWR - boiling water reactorFBR - fast breeder reactorFNR - fast neutron reactor

HTGR - high-temperature gas reactor

LFR - lead-cooled fast reactorMSR - molten salt reactor

PWR - pressurized water reactorTWR - traveling wave reactor

Traveling Wave Reactor

• Fast reactor core with fission igniter buried for entire 60 year or so lifetime.

• Reaction front propagates through core in wave fashion.• Core also is long-term containment, simplifying

decommissioning and waste storage.• Designed at both modular and utility scales

Pebble Bed Reactor

• Inherently safe (strong Doppler effect decreases fuel reactivity with increasing temperature)

• VHTGR cannot have steam explosion.

Hybrid Designs

• Hybrid of HTGR and MSR• Developed by both Chinese and US

– MIT, UW, UCB + Westinghouse and INL – US DOE NEUP IRP 2011

• Strengths: – Safety

• High thermal inertia• Atmospheric pressure• No air-ingress• Melt down-proof fuel

– Grid• Modular, small, low investment

• Weaknesses:– Economics

• Licensing, e.g. pebble locations• No data, high development costs

– Safety• Fuel handling challenges

– Waste• How to reprocess pebbles??

Integral, Inherently Safe Light Water Reactor (I2S-LWR)

• 4 Loop PWR, rated at ~1000 MWe

• Designed to capture benefits of SMR concepts– Integral PWR; primary

components in RPV– Elimination of large bore piping– Modular construction– Economically competitive

• Enhanced passive safety systems

Primary System

• Core• Flow channels• Reactor vessel internals (RVI)• Pressurizer• Reactor coolant pumps (RCP)• Primary heat exchangers

(PHX)• Decay heat removal – heat

exchangers (DHR-HX)• Flow assisting devices• Reactor pressure vessel

Core

• 10.11ft Diameter• 12 ft active fuel height

• 121 Fuel Assemblies– 19 x 19 fuel grid

• Based on Westinghouse17x17 RFA

– U3Si2 pellets with SS clad– 336 rods per assembly

• Internal CRDMS with RCCA– 33 RCCAs– 24 rodlets per RCCA

• HM Loading of 72.9 MT

Reflectors and Core plates

• Support plate below fuel assemblies– 10 cm thick– Core barrel supports plate via

Chamfered edge• Reflector consists of stainless

steel rings– 10 rings– Stacked vertically around core– Flow holes to facilitate cooling

• Upper Alignment plate – 10 cm thick– Rests on uppermost reflector– Fits snugly within vessel

Flow Channels

• No primary piping• Hot leg upper core

barrel• Pressurizer

integral• Pump under

pressurizer, within the RPV itself

• PWR SG PHX, in annular region

• Cold leg annular

Reactor Vessel Internals (RVI)

• Inside Upper Core Barrel Region

• Internal CRDMs• RCC guide tubes• I&C

– Cabling– Instruments

• Penetrations• Sampling systems

Pressurizer

• Integral Pressurizer• Same functions as

standard PWR Pressurizer

• Based on IRIS pressurizer

• Adapted based on Westinghouse SMR learning– Individual standard

electric heaters

Reactor Coolant Pumps

• Horizontally mounted, radially at top of RPV

• Hydraulics located in annular region below pressurizer

• Sealless, canned motor or wet winding pumps

• Circulating primary fluid cools pump internals

Primary Heat Exchangers

• Dozens of 1 mm flow channels on a 2m thick flat plate– No zig-zags,

turbulent flow, not laminar flow

– Parametric studies to find ideal arrangements

• Micro-channel heat exchangers (mC-HX)

Decay Heat Removal Heat Exchangers (DHR-HX)

• Decay heat removal heat exchangers (DHR-HX)

• Natural circulation driven

• Helical Coil Exchanger– 115 tubes– 12 rows of coils– Low thermal expansion

stresses– Low flow resistance

Flow Assisting Devices

• Designed to mitigate minor flow losses

• Verified by CFD, experiment, historical use– Rounded flow holes

below pressurizer– Flow skirt for uniform

core inlet flow– Beveled edges– Gradual flow

expansions

Reactor Pressure Vessel

• Inner diameter of vessel of 15.4 ft

• Nominal thickness of 11 in

• Based on IRIS design• Radial support flange

between secondary flow nozzels for vessel support

• Preliminary design/functions

Challenges

• Volume requirements within RPV– Water makeup

volume– Additional

components/cabling– Maintenance and

personnel access– Shielding– Heat transfer in both

SS and transients• Primary and