Reactor Engineering

NE – 4 (Lecture - 22) AHWR

S. Dayal ACE KM

AHWR

• Developed to use Thorium for generation of commercial nuclear power

• 300 MWe• Pressure Tube type reactor: vertical PT• Boiling Light Water: BLW• Passive Safety Features

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Safety Features AHWR

• negative void coefficient of reactivity. • Passive safety systems• Heat sink in the form of Gravity Driven Water

Pool GDWP• Removal of core heat by natural circulation. • ECCS injection directly inside the fuel. . • Two independent shutdown systems.

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+ Features of AHWR

• No Hi Pressure D2O as coolant, no leakage loss / recovery systems

• Recovery of heat generated in Moderator System for feed-water heating

• Shop assembled coolant channels, quick replacement of pressure-tube

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+ Features of AHWR

• Steam Drums in place of steam-generators• Higher Steam pressure than in PHWR• Production of 500 m3/day of DM Water in

Desalination Plant, by using steam from LP Turbine

• Design Life : 100 Years• No exclusion Zone, due to advanced safety

features

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Specifications of AHWR

• Power: 920 MWth, 300 MWe• Core: Vertical, Pr. Tube; ID: 120 mm• Coolant: Boiling Light Water• No. of Coolant Channels: 452• Fuel Pins: 54 = 24 (Th+Pu) + 30 (Th+U233)• Fuel Length: 3.5 m• Core Flow Rate: 2230 kg/s

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Specifications of AHWR

• Coolant Inlet: 259 Deg. Cel.; Outlet: 130 Deg. Cel.

• Steam Quality: 18.6 %• Steam Generation Rate: 414.4 kg.• Steam Pressure: 70 bar• PSS: 40 Shutoff Rods (Boron Carbide)• SSS: Liquid Poison Injection in Moderator• Control Rods: 1309/10/12 RE-4, Le-22 7

Specifications of AHWR

• Lattice Pitch: 245 mm• Discharge Burnup: 24000 MWd/t

• -- up-to 40,000

• Dysprosium is used as burnable poison Dy2O3 in ZrO2

• Natural Dysprosium has 5 isotopes 160 – 164

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Fuel

• 54 pins– Innermost Ring: 12 Pins (Th233 U)O2, U233 enrichment

3.0 %

– Middle Ring: 18 Pins (Th233 U)O2, U233 enrichment 3.75 %

– Outermost Ring: 24 Pins (Th Pu)O2, Pu enrichment 2.5% in upper-half & 4.0% in lower-half

– Central Rod has burnable poison Dy2O3

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Fuel Cluster

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Cross Section of Fuel Cluster

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PHW Reactor Components

• Inlet header• Feeders• Coolant Channel• Outlet feeders called “tail-pipes”– End-Shield– Feeder Vault– Calandria Vault

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Reactor Structure

• Cylindrical Aluminum Tank: 330cm ID & 500 cm high

• Tank is adequately sized to provide 40 cm D2O radial reflector around the core

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Calandria Vault

• Concrete block, for shielding• Two movable shield trolleys, at the top • Water Filled Reactor Vault Tank, open at top

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General arrangement

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Moderator System

• D2O will be used• Cover Gas– Helium

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Instrument & Control

• Neutron (flux) Power measurement– For reactor regulation and Control– Detectors are located in Graphite fillers below

Reactor– In-Core: flux mapping system

• 25 LEU based, fission counters

– Source range monitors: pulse channels

• Conventional Instrumentation– Flow, Pressure, Temperature & Level– To generate: ALARM (Hi, V-Hi), TRIP

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Range overlap of channelsSource Range: Pulse ChannelInter. & Power Range: Six DC Channels (Multi Range DC Channel: MRDC)

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Shutdown Devices

• Shut-Off rods – Six: Cadmium (encased in Al) Rods– 68 mk –ive reactivity addition

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AHWRAHWR

4

15

5

6

10

911

13

1214

16

17

8

3

2

7

1

2 Primary Containment1 Secondary Containment

3 Gravity Driven Water Pool4 Isolation Condenser

5 Passive Containment Isolation Duct6 Vent Pipe7 Tail Pipe Tower8 Steam Drum9 100 M Floor

10 Fuelling Machine

11 Deck Plate

13 Header 14 Pile Supports

15 Advanced Accumulator

17 Passive Containment Cooler

16 Pre - Stressing Gallery

12 Calandria with End Shield

Status

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• Structured peer review completed• Pre-licensing design safety appraisal by AERB

in progress

AHWR: a quick, safe, secure and proliferation resistant solution

AHWR is a 300 MWe vertical pressure tube type, boiling light water cooled and D2O moderated reactor (A configuration to provide low risk nuclear energy using available technologies)

AHWR can be configured to accept a range of fuel types including LEU, U-Pu , Th-Pu , LEU-Th and 233U-Th in full core

AHWR Fuel assembly

Bottom Tie Plate

Top Tie Plate

Water

Tube

Displacer

Rod

Fuel Pin

Major design objectives

Significant fraction of Energy from Thorium

Several passive features 3 days grace period No radiological impact

Passive shutdown system to address insider threat scenarios.

Design life of 100 years.

Easily replaceable coolant channels.

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PSA Level 3 calculations for AHWR indicate low probability of impact in public domain

Plant familiarization & identification of design aspects important to severe accident

Plant familiarization & identification of design aspects important to severe accident

PSA level-1 Identification of significant events with large contribution to Core Damage Frequency

PSA level-1 Identification of significant events with large contribution to Core Damage Frequency

Level-2 : Source Term (within Containment) Evaluation through Analysis

Level-2 : Source Term (within Containment) Evaluation through Analysis

Release from Containment Release from Containment

Level-3 Atmospheric Dispersion With Consequence Analysis

Level-3 Atmospheric Dispersion With Consequence Analysis

Level-1, 2 & 3 PSA activity block diagram

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SWS: Service Water System (63 %)

APWS: Active Process Water System

ECCS HDRBRK: ECCS Header Break

SLOCA: 15 %

LLOCA: Large Break LOCA

MSLBOB: Main Steam Line Break Outside Containment

Contribution to CDF

AHWR 300-LEU is a 300 MWe system fuelled with LEU-Thorium fuel, has passive safety features, high degree of operator

forgiving characteristics, no adverse impact in public domain, high proliferation resistance and inherent security strength.

Peak clad temp. hardly rises even in the complete station blackout and failure of primary and secondary systems.

Reactor Block components

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Shut Off Rod drive mechanism, Typical Rod-drop profile

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Main HT System

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Emergency Core Cooling System

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ECCS

• Passive mode during first 15 minutes, from accumulators– 4 Accumulators, 240 m3, Nitrogen at 5.0 MPa

• From Gravity driven water pool for next three-days (low pressure injection)– Passivity is obtained by “Fluidic Flow Control

Device”– 6000 m3 of water– 4 loops. HX, pump, filter, IX & chemical addition

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Gravity Driven water Pool [GDWP]

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AHWR: Design evaluation by INPRO method

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• IAEA initiated project on, International Project on Innovative Nuclear Reactors & Fuel Cycles

• Evaluation criteria in six areas– Economics -- Environment & Sustainability– Safety -- Waste Management– Proliferation -- Cross cutting issues

• Reports have been sent to IARA for AHWR

End of RE – 4 Lecture – 22

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