Chapter 05_Small Nuclear Power Reactors

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mallNuclearPowerReactors

Already operating in a remote corner of Siberia are four small units at the Bilibinoco-generation plant. These four 62 MWt (thermal) units are an unusual graphite-moderated boiling water design with water/steam channels through themoderator. They produce steam for district heating and 11 MWe (net), electricityeach. They have performed well since 1976, much more cheaply than fossil fuel

alternatives in the Arctic region; and Also in the small reactor category are the Indian 220 MWe pressurized heavy water

reactors (PHWR) based on Canadian technology, and the Chinese 300-325 MWePWR such as built at Qinshan Phase I and at Chashma in Pakistan, and now calledCNP-300. The Nuclear Power Corporation of India (NPCIL) is now focusing on540 MWe and 700 MWe versions of its PHWR, and is offering both 220 and 540MWe versions internationally. These, small established designs are relevant tosituations requiring small to medium units, though they are not state of the arttechnology.

Small nuclear power reactors are, classified into the following six categories as per theWorld Nuclear Association (Updated 12 October 2010):

1. LIGHT WATER REACTORS (LWR):

US experience of small light water reactors (LWR) has been of very small military powerplants, such as the 11 MWt, 1.5 MWe (net) PM-3A, reactor, which operated at McMurdo


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Sound in Antarctica 1962-72, generating 78 million kWh. There was also an Armyprogram for small reactor development, and some successful small reactors from themain national program commenced in the 1950s. One was the Big Rock Point BWR of 67MWe, which operated for 35 years to 1997.

The following designs, the KLT and VBER have conventional pressure vessels plusexternal steam generators (PV/loop design):

1. KLT-40S:Russia's KLT-40S from OKBM Afrikantov is a reactor well proven in icebreakersand now proposed for wider use in desalination and, on barges, for remote areapower supply. Here a 150 MWt unit produces 35 MWe (gross) as well as up to 35MW of heat for desalination or district heating (or 38.5 MWe gross if power only).These are, designed to run 3-4 years between refueling with on-board refuelingcapability and used fuel storage. At the end of a 12-year operating cycle, the wholeplant is, taken to a central facility for overhaul and storage of used fuel. Two units

will be, mounted on a 20,000 tonne barge to allow for outages (70% capacityfactor). Although the reactor core is normally, cooled by forced circulation, thedesign relies on convection for emergency cooling. Fuel is uranium aluminumsilicide with enrichment levels of up to 20%, giving up to four-year refuelingintervals.

The first floating nuclear power plant, theAkademik Lomonosov, commencedconstruction in 2007 and is, planned to be located near to Vilyuchinsk. The plant isdue to be, completed in 2011;

2. VBER-150:A larger Russian factory-built and barge-mounted unit (requiring a 12,000 tonne

vessel) is the VBER-150, of 350 MWt, 110 MWe. It has modular construction and is,derived by OKBM from naval designs, with two steam generators. Uranium oxidefuel enriched to 4.7% has burnable poison; it has low burn-up (31 GWd/t average,41.6 GWd/t maximum) and eight-year refueling interval; and

3. VBER-300OKBM Afrikantov's larger VBER-300 PWR is a 295 MWe unit, the first of which isplanned to be, built, in Kazakhstan. It was, originally envisaged, in pairs as afloating nuclear power plant, displacing 49,000 tonnes. As a cogeneration plant, itis, rated at 200 MWe and 1900 GJ/hr. The reactor is, designed for 60-year life and90% capacity factor. It has four steam generators and a cassette core with 85 fuel

assemblies enriched to 5% and 48 GWd/tU burn-up. Versions with three and twosteam generators are, also envisaged, of 230 and 150 MWe respectively. Inaddition, with more sophisticated and higher-enriched (18%) fuel in the core, therefueling interval can be pushed from two years out to 15 years with burn-up to 125GWd/tU. A 2006 joint venture between Atomstroyexport and Kazatomprom setsthis up for development as a basic power source in Kazakhstan, then for export.


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The following thirteen nuclear power reactor designs under this category, have, the steamsupply system inside the reactor pressure vessel ('integral' PWR design). All nuclearpower reactor designs have, enhanced safety features relative to current LWR.

No Reactor Hyperlink to Description

1 RITM-200 OKBM Afrikantov is developing a new icebreaker reactor

2 VK-300 Another larger Russian reactor is the VK-300 boiling water reactor3 VKT-12 A smaller Russian BWR design is the 12 MWe, transportable VKT-12

4 ABV A smaller Russian OKBM Afrikantov PWR unit under development is 5 CAREM The CAREM reactor being developed byINVAP in Argentina, under 6 SMART On a larger scale, South Korea's SMART (System-integrated Modular 7 MRX The Japan Atomic Energy Research Institute (JAERI) designed the8 NP-300 Technicatome (Areva TA) in France has developed the NP-300 PWR9 NHR-200 The Chinese NHR-200 (Nuclear Heating Reactor) developed by10 IRIS Westinghouse's IRIS (International Reactor Innovative & Secure) is

11 mPower In mid-2009, Babcock & Wilcox (B&W) announced its B&W12 NuScale A smaller unit is the NuScale multi-application small PWR, a 16013 TRIGA The TRIGA Power System is a PWR concept based on GeneralAtomics'

2. HIGH TEMPERATURE GAS-COOLED REACTORS (HTR):

Building on the experience of several innovative reactors built in the 1960s and 1970s, newhigh-temperature gas-cooled reactors (HTR), being developed. These reactors will be
http://www.aimamc.com/apc/ritm_200.pdfhttp://www.aimamc.com/apc/vk_300.pdfhttp://www.aimamc.com/apc/vk_300.pdfhttp://www.aimamc.com/apc/vk_300.pdfhttp://www.aimamc.com/apc/vkt_12.pdfhttp://www.aimamc.com/apc/vkt_12.pdfhttp://www.aimamc.com/apc/vkt_12.pdfhttp://www.aimamc.com/apc/abv.pdfhttp://www.aimamc.com/apc/abv.pdfhttp://www.aimamc.com/apc/carem.pdfhttp://www.aimamc.com/apc/carem.pdfhttp://www.aimamc.com/apc/carem.pdfhttp://www.aimamc.com/apc/smart.pdfhttp://www.aimamc.com/apc/smart.pdfhttp://www.aimamc.com/apc/smart.pdfhttp://www.aimamc.com/apc/mrx.pdfhttp://www.aimamc.com/apc/mrx.pdfhttp://www.aimamc.com/apc/mrx.pdfhttp://www.aimamc.com/apc/np_300.pdfhttp://www.aimamc.com/apc/np_300.pdfhttp://www.aimamc.com/apc/np_300.pdfhttp://www.aimamc.com/apc/nhr_200.pdfhttp://www.aimamc.com/apc/nhr_200.pdfhttp://www.aimamc.com/apc/nhr_200.pdfhttp://www.aimamc.com/apc/iris.pdfhttp://www.aimamc.com/apc/iris.pdfhttp://www.aimamc.com/apc/mpower.pdfhttp://www.aimamc.com/apc/mpower.pdfhttp://www.aimamc.com/apc/mpower.pdfhttp://www.aimamc.com/apc/nuscale.pdfhttp://www.aimamc.com/apc/nuscale.pdfhttp://www.aimamc.com/apc/nuscale.pdfhttp://www.aimamc.com/apc/triga.pdfhttp://www.aimamc.com/apc/triga.pdfhttp://www.aimamc.com/apc/triga.pdfhttp://www.aimamc.com/apc/triga.pdfhttp://www.aimamc.com/apc/nuscale.pdfhttp://www.aimamc.com/apc/mpower.pdfhttp://www.aimamc.com/apc/iris.pdfhttp://www.aimamc.com/apc/nhr_200.pdfhttp://www.aimamc.com/apc/np_300.pdfhttp://www.aimamc.com/apc/mrx.pdfhttp://www.aimamc.com/apc/smart.pdfhttp://www.aimamc.com/apc/carem.pdfhttp://www.aimamc.com/apc/abv.pdfhttp://www.aimamc.com/apc/vkt_12.pdfhttp://www.aimamc.com/apc/vk_300.pdfhttp://www.aimamc.com/apc/ritm_200.pdf


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capable of delivering high temperature (up to about 1000C) helium either for industrialapplication via a heat exchanger, or to make steam conventionally via a steam generator,or directly to drive a Brayton cycle gas turbine for electricity with almost 50 percentthermal efficiency possible (efficiency increases around 1.5 percent with each 50Cincrement). Improved metallurgy and technology developed in the last decade makes

HTR more practical than in the past, though the direct cycle means that there must behigh integrity of fuel and reactor components.

Fuel for these reactors is in the form of TRISO (tristructural-isotropic) particles less thana millimetre in diameter. Each has a kernel (ca. 0.5 mm) of uranium oxycarbide (oruranium dioxide), with the uranium enriched up to 20% U-235, though normally less.This is surrounded by, layers of carbon and silicon carbide, giving a containment forfission products which is stable to over 1600C.

There are two ways, in which these particles are, arranged: in blockshexagonal 'prisms'of graphite, or in billiard ball-sized pebbles of graphite encased in silicon carbide, eachwith about 15,000 fuel particles and 9g uranium. There is a greater amount of used fuelthan from the same capacity in a light water reactor. The moderator is graphite.

HTR can potentially use thorium-based fuels, such as highly enriched or low-enricheduranium with Th, U-233 with Th, and Pu with Th. Most of the experience with thoriumfuels has been in HTR. With negative temperature coefficient of reactivity (the fissionreaction slows as temperature increases) and passive decay heat removal, the reactors areinherently safe. HTR therefore do not require any containment building for safety. Theyare sufficiently small to allow factory fabrication, and will usually be, installed belowground level.

Here are some major designs, which are, covered under this category:No Reactor Hyperlink to Description

1 HTTR,GHTR Japan Atomic Energy Research Institute's (JAERI's), High

2 HTR-10 China's HTR-10, a 10 MWt high-temperature gas-cooled3 HTR-PM Construction of a larger version of the HTR-10, China's HTR

4 PBMR South Africa's pebble bed modular reactor (PBMR) draws on5 GT-MHR A larger US design, the Gas Turbine - Modular Helium Reactor

6 EM2 In February 2010, General Atomics announced a modified version of

7 Antares Another full-size HTR design is the Antares reactor being put

8 Adams Engine A small HTR concept is the Adams Atomic Engines' 10 MWe direct

9 MTSPNR A small Russian HTR which was being developed by the N.A

3. LIQUID METAL-COOLED FAST NEUTRON REACTORS (LMFNR):Fast neutron reactors have no moderator, a higher neutron flux and are normally, cooledby liquid metal such as sodium, lead, or lead-bismuth, with high conductivity and boilingpoint. They operate at or near atmospheric pressure and have passive safety features,
http://www.aimamc.com/apc/httr.pdfhttp://www.aimamc.com/apc/htr_10.pdfhttp://www.aimamc.com/apc/htr_pm.pdfhttp://www.aimamc.com/apc/pbmr.pdfhttp://www.aimamc.com/apc/gt_mhr.pdfhttp://www.aimamc.com/apc/em2.pdfhttp://www.aimamc.com/apc/antares.pdfhttp://www.aimamc.com/apc/adam_engine.pdfhttp://www.aimamc.com/apc/adam_engine.pdfhttp://www.aimamc.com/apc/mtspnr.pdfhttp://www.aimamc.com/apc/mtspnr.pdfhttp://www.aimamc.com/apc/adam_engine.pdfhttp://www.aimamc.com/apc/antares.pdfhttp://www.aimamc.com/apc/em2.pdfhttp://www.aimamc.com/apc/gt_mhr.pdfhttp://www.aimamc.com/apc/pbmr.pdfhttp://www.aimamc.com/apc/htr_pm.pdfhttp://www.aimamc.com/apc/htr_10.pdfhttp://www.aimamc.com/apc/httr.pdf


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(most have convection circulating the primary coolant). Automatic load following is,achieved due to the reactivity feedbackconstrained coolant flow leads to higher coretemperature, which slows the reaction. Primary coolant flow is by convection. Theytypically use boron carbide control rods.

Here are the major designs under this category:No Reactor Hyperlink to Description

1 Hyperion PowerModule

The Hyperion Power Module is a 70 MWt/25 MWe

2 ENHS The Encapsulated Nuclear Heat-Source is a liquid metal-cooled3 STAR_LM,

STAR-H2,SSTAR:

The Secure Transportable Autonomous Reactor

4 ARC-100 Advanced Reactor Concepts LLC (ARC) is commercializing

5 LSPR A lead-bismuth-eutectic (LBE) cooled fast reactor of 1506 Rapid-L A small-scale design developed by Toshiba Corporation in

7 PRISM GE with the US national laboratories had been developing

8 BREST Russia has experimented with several lead-cooled reactor

9 TWR An old design has resurfaced as the Travelling Wave Reactor

10 Korean FastReactor Designs

In South Korea, the Korea Atomic Energy Research
http://www.aimamc.com/apc/hyperion_power_module.pdfhttp://www.aimamc.com/apc/enhs.pdfhttp://www.aimamc.com/apc/star_lm.pdfhttp://www.aimamc.com/apc/arc_100.pdfhttp://www.aimamc.com/apc/lspr.pdfhttp://www.aimamc.com/apc/rapid_l.pdfhttp://www.aimamc.com/apc/prism.pdfhttp://www.aimamc.com/apc/brest.pdfhttp://www.aimamc.com/apc/twr.pdfhttp://www.aimamc.com/apc/korean.pdfhttp://www.aimamc.com/apc/korean.pdfhttp://www.aimamc.com/apc/twr.pdfhttp://www.aimamc.com/apc/brest.pdfhttp://www.aimamc.com/apc/prism.pdfhttp://www.aimamc.com/apc/rapid_l.pdfhttp://www.aimamc.com/apc/lspr.pdfhttp://www.aimamc.com/apc/arc_100.pdfhttp://www.aimamc.com/apc/star_lm.pdfhttp://www.aimamc.com/apc/enhs.pdfhttp://www.aimamc.com/apc/hyperion_power_module.pdf


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4. MOLTON SALT REACTORS (MSR):During the 1960s, the USA developed the molten salt breeder reactor concept as theprimary back- up option for the fast breeder, reactor (cooled by liquid metal) and a smallprototype 8 MWt Molten Salt Reactor Experiment (MSRE) operated at Oak Ridge overfour years. U-235 fluoride was in molten sodium and zirconium fluorides at 860C that

flowed through a graphite moderator. There is now renewed interest in the concept inJapan, Russia, France and the USA, and one of the six Generation IV designs selected forfurther development is the molten salt reactor (MSR).

In the MSR, the fuel is a molten mixture of lithium and beryllium fluoride salts withdissolved enriched uranium, thorium or U-233 fluorides. The core consists of uncladgraphite moderator arranged to allow the flow of salt at some 700C and at low pressure.

Heat is, transferred to a secondary salt circuit and thence to steam. It is not a fastneutron reactor, but with some moderation by the graphite is epithermal (intermediateneutron speed). The fission products dissolve in the salt and are removed continuously inan on-line reprocessing loop and replaced with Th-232 or U-238. Actinides remain in thereactor until they fission or are converted to higher actinides which do so. MSR have anegative temperature coefficient of reactivity, so will shut down as temperature increasesbeyond design limits.Here is the description for each:


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No Reactor Hyperlink to Description

1 LFTR The Liquid Fluoride Thorium Reactor (LFTR) is one kind of MSR

2 Fuji MSR The Fuji MSR is a 100 MWe design to operate as a near-breeder3 AHTR The Advanced High-Temperature Reactor (AHTR) is a larger

5. AQUEOUS HOMOGENEOUS REACTORS (AHR):Aqueous homogeneous reactors (AHR) have the fuel mixed with the moderator as aliquid.

Typically, low-enriched uranium nitrate is in aqueous solution. About 30 AHR have been,built, as research reactors and have the advantage of being self-regulating and having thefission products continuously removed from the circulating fuel. However, corrosionproblems and the propensity of water to decompose radiolytically (due to fissionfragments) releasing gas bubbles have been design problems.

In 2008, the IAEA summarized: "The use of solution reactors for the production of medical isotopes is potentially

advantageous because of their low cost, small critical mass, inherent passivesafety, and simplified fuel handling, processing and purification characteristics.These advantages stem partly from the fluid nature of the fuel and partly from the
http://www.aimamc.com/apc/lftr.pdfhttp://www.aimamc.com/apc/fuji_msr.pdfhttp://www.aimamc.com/apc/ahtr.pdfhttp://www.aimamc.com/apc/ahtr.pdfhttp://www.aimamc.com/apc/fuji_msr.pdfhttp://www.aimamc.com/apc/lftr.pdf


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homogeneous mixture of the fuel and moderator in that an aqueous homogeneousreactor combines the attributes of liquid fuel homogeneous reactors with those ofwater moderated heterogeneous reactors. If practical methods for handling aradioactive aqueous fuel system are implemented, the inherent simplicity of thistype of reactor should result in considerable economic gains in the production of

medical isotopes."

Thermal power can be 50-300 MW at low temperature and pressure, and low enricheduranium fuel used. However, recovering desired isotopes on a continuous productionbasis remains to be, demonstrated. As well as those in solution, a number of volatileradioisotopes used in nuclear medicine can be, recovered from the off-gas arising fromradiolytic boiling. For isotopes such a Sr-89, this is very much more efficient thanalternative production methods.

At the end of 2007, Babcock & Wilcox (B&W) notified the US Nuclear Regulatory

Commission that it intended to apply for a license to construct and operate a MedicalIsotope Production System (MIPS) an AHR system with low-enriched uranium in small100-200 kW units for Mo-99 production. A single production facility could have foursuch reactors. B&W expects a five-year lead-time to first production. The fuel is, broughtto criticality in a 200-litre vessel. As fission proceeds, the solution is circulated through anextraction facility to remove the Mo-99 and then back into the reactor vessel, which is atlow temperature and pressure. In January 2009, B&W Technical Services Group signed anagreement with radiopharmaceutical and medical device supplier Covidien to developtechnology for the MIPS.

6. MODULAR CONSTITUTION USING SMALL REACTOR UNITS:The IRIS developers have outlined the economic case for modular construction of theirdesign (about 330 MWe), and the argument applies similarly to other smaller units.

They point out that IRIS with its size and simple design is ideally suited for modularconstruction in the sense of progressively building a large power plant with multiplesmall operating units. The economy of scale is, replaced here with the economy of serialproduction of many small and simple components and prefabricated sections. Theyexpect that construction of the first IRIS unit will be, completed in three years, withsubsequent reduction to only two years.

Site layouts have been developed with multiple single units or multiple twin units. Ineach case, units will be, constructed so that there is physical separation sufficient to allowconstruction of the next unit while the previous one is operating and generating revenue.In spite of this separation, the plant footprint can be very compact so that a site withthree IRIS single modules providing 1000 MWe capacity is similar or smaller than onewith a comparable total power single unit.


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Eventually IRIS is, expected to have a capital cost and production cost comparable withlarger plants. However, any small unit such as this will potentially have a funding profileand flexibility otherwise impossible with larger plants. As one module is finished andstarts producing electricity, it will generate positive cash flow for the next module to be,built.

Westinghouse estimates that 1000 MWe delivered by three IRIS units built at three-yearintervals financed at 10 percent for ten years require a maximum negative cash flow lessthan $700 million (compared with about three times that for a single 1000 MWe unit).For developed countries small modular units offer the opportunity of building asnecessary; for developing countries it may be the only option, because their electric gridscannot take 1000+ MWe single units.

This chapter was published on Inuitech Intuitech Technologies for Sustainability onJanuary 18, 2011:http://intuitech.biz/?p=7840

Resources:1. World Nuclear Association Small Nuclear Power Reactors:http://www.world-

nuclear.org/info/default.aspx?id=534&terms=Small%20Reactors
http://intuitech.biz/?p=7840http://intuitech.biz/?p=7840http://intuitech.biz/?p=7840http://www.world-nuclear.org/info/default.aspx?id=534&terms=Small%20Reactorshttp://www.world-nuclear.org/info/default.aspx?id=534&terms=Small%20Reactorshttp://www.world-nuclear.org/info/default.aspx?id=534&terms=Small%20Reactorshttp://www.world-nuclear.org/info/default.aspx?id=534&terms=Small%20Reactorshttp://www.world-nuclear.org/info/default.aspx?id=534&terms=Small%20Reactorshttp://www.world-nuclear.org/info/default.aspx?id=534&terms=Small%20Reactorshttp://intuitech.biz/?p=7840

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Chapter 05_Small Nuclear Power Reactors