Physics Design of 600 MWth HTRPhysics Design of 600 MWth HTR&&

5 MWth Nuclear Power Pack5 MWth Nuclear Power Pack

Brahmananda ChakrabortyBhabha Atomic Research Centre, India

Indian High Temperature

Reactors Programme

Compact High Temperature Reactor (CHTR)A technology demonstration facility

Nuclear Power Pack (NPP)To supply electricity in remote areas not connected to grid

High Temperature Reactor (HTR)For hydrogen generation

500 600 700 800 900 10000

10

20

30

40

50

60

Goals

Max. temp

Cu-Cl Ca-Br2

I-S

Ove

rall

H2 C

onv.

Eff.

, %

Temperature, oC

Ref: High Efficiency Generation of HydrogenFuels Using Nuclear Power, G.E. Besenbruch, L.C. Brown, J.F. Funk, S.K.

Showalter, Report GA–A23510 and ANL reports

I-S Process Reaction Scheme

HH22SOSO44HH22O + SOO + SO22 + ½ O+ ½ O22

2HI2HI II22

HH22SOSO44 HH22O + SOO + SO22 + ½ O+ ½ O22850850ooCC

HEAT

2HI2HI HH22 + I+ I22450oC

HEAT

2HI + H2HI + H22SOSO44 II22 + SO+ SO22 + 2H+ 2H22OO120120ooCC

WATERWATEROO22

H2

HEATHH22SOSO44HH22O + SOO + SO22 + ½ O+ ½ O22

2HI2HI II22

HH22SOSO44 HH22O + SOO + SO22 + ½ O+ ½ O22850850ooCC

HEAT

HH22SOSO44 HH22O + SOO + SO22 + ½ O+ ½ O22850850ooCC

HH22SOSO44 HH22O + SOO + SO22 + ½ O+ ½ O22850850ooCC

HEATHEAT

2HI2HI HH22 + I+ I22450oC

HEAT

2HI2HI HH22 + I+ I22450oC

2HI2HI HH22 + I+ I22450oC

HEATHEAT

2HI + H2HI + H22SOSO44 II22 + SO+ SO22 + 2H+ 2H22OO120120ooCC

WATERWATEROO22

H2

HEAT

600 MW(Th) HTR

ObjectiveTo provide high temperature heat required for thermo-chemical processes for hydrogen productionPebble bed reactorIt is a Pebble Bed Reactor moderated and reflected by graphite & loaded with randomly packed spherical fuel elements called Pebble and cooled by molten Pb/Bi.

Key featuresUse of triso particlesIts an advanced design with a higher level of safety and efficiency

HEAT EXCHANGERS

CHUTE FOR FUELING

CORE BARREL

REACTORVESSEL

COOLANT INLET

COOLANT OUTLET

Core configuration for pebble bed design

Cross-sectional

view of triso particle and

pebble

Triso Particle

(U+Th)O2 Kernel (250 μm)

Pyrolitic Graphite (90 μm)

Inner Dense Carbon (30 μm)

Silicon Carbide (30 μm)

Outer Dense Carbon (50 μm)

Advantages of Pebbles

On line refuelingHomogeneous core (less power peaking)Simple fuel managementOne way of control by replacing dummy pebbles

High efficiency thermo-chemical processesHydrogen production

Intermediate heat exchangers for heat transfer for hydrogen production + High efficiency turbo-machinery based electricity generating system + Water desalination system for potable water

Energy transfer systems

233UO2 & ThO2 based high burn-up TRISO coated particle fuel

FuelNatural circulation of coolantMode of coolingGraphiteReflectorMolten leadCoolantGraphiteModerator

1000°C / 600°CCoolant outlet/inlet temperature

600 MWth for following deliverables (Optimized for hydrogen Production)1.Hydrogen: 80,000 m3/hr2.Electricity: 18 MWe • Drinking water: 375 m3/hr

Reactor power

Proposed Broad Specifications

Pebble Configuration

Pebble diameter (fuelled portion): 90 mm

Outer pebble diameter: 100 mm

Number of pebbles: 150000

Packing density (Volume %) ≈59%

Challenges in the design

To design optimum pebble and core configuration to get maximum energy per gm inventory of fissile isotopes.

Control initial excess reactivity

Computational Technique

Multi-group Integral Transport theory code “ITRAN” & Diffusion theory code “ Tri-htr” used for simulations.

Triso particles homogenized

Comparison of fuel inventory

1.27014503.47.38.6

1.36863202.612.04.0

1.4684503.116.33.51.34022502.312.03.51.25761601.910.03.51.1507601.58.03.51.44564503.214.54.0

1.29022102.210.04.01.18791001.78.04.01.15592702.410.04.51.21691502.08.04.51.1559801.77.04.51.33723302.710.05.01.24151902.28.05.0

Remarks

Initial k-eff

Burn up (FPDs)

Amount of U233 in gm per pebble

EnrichmentPercentage

Packing Percentage

Optimized Pebble Configuration

Packing fraction 8.6%Enrichment 7.3% (H=800 cm, 900FPDs)

Comparison between different height

353.53284.8219.3U233+U235) out (Kg)1.951.901.85MWD/gm fissile

elements900

U233 =581Th232 = 8156

187,000

U233 =3.1Th232 = 43.5

1.235566.6

H=10 m

900900Burn up ( FPDs)

U233 =630Th232 = 9832

U233 =510Th232 = 6480

Amount of fuel In the core (Kg)

225,000150,000No. of Pebbles

U233 =2.8Th232 = 43.7

U233 =3.4Th232 = 43.2

Amount of heavy metal Per pebble

(gm)

1.205451.2701Initial K-eff6.17.3Enrichment (%)

H=12 mH=8 mParameters

0 100 200 300 400 5000.90

0.95

1.00

1.05

1.10

1.15

1.20

1.25

1.30

Variation of K-eff with Burn Up for different height

K-ef

f

Burn Up in FPDs

H-800 E-7.3 H-1000 E-6.6 H-1200 E-6.1

Estimation of Fuel Temperature Coefficient(H=1200, P=8.6%, E=6.1%)

-1.440x 10-51.20965800

-1.374 x 10-51.20745900

-1.214x 10-51.201931200

-1.268x10-51.203611100

Reference1.205451000

Fuel TemperatureCoefficient (per 0C)

Value of K-effFuel temperature (0C)

Major Problem

Initial K-eff is too high

1.276 for 8m height 7.3% Enrichment

1.205 for 12m height 6.1Enrichment

Study to reduce initial k-eff

OPTIONSReduce number of fuel balls & keep (fuel balls + dummy balls = constant)

Initial power will be reducedReduce enrichment

Available burn up will be less

Initial K-eff reduces

sufficiently

1.10860591/32/358.612

Beneficial1.1899716-All fuel

68.68Beneficial1.14407121/21/268.68

Not much improvement

1.23566651/21/27.38.68

Little improvement

1.15880081/21/26.18.612

REMARKINITIAL K-EFF

DUMMY BALL

FUEL BALL

E (%)P (%)H (M)

Comparison of different cases

CONCLUSIONS

For the same burn up fuel inventory is less for lower packing fraction. But as packing fraction decreases initial K-eff increases. Energy production in terms of MWD/gm of fissile inventory is more for 12m core height compared to 8m core height.Initial reactivity can be controlled by reducing enrichment as well using control rods. But burn up reduces.Further study to control initial reactivity by using ThO2 ball is in progress.Fuel temperature coefficient is satisfactorySystem can be controlled using control rods & burnable absorber.

Physics Design of5 MWth

Nuclear Power Pack

Salient FeaturesIt will be compact and can run for around 10 years without any refueling.

The reactor should be able to control and regulate its operation in a perfectly passive manner.

The overall reactivity change during core life should be less.

Basic Design Parameters

31:No. Of Control Locations

30:No. Of Fuel Assemblies

6000C:Core Outlet Temperature

4500C:Core Inlet Temperature

1000 mm:Core Height

Pb-Bi :Coolant

BeO and Graphite:Reflector Material

BeO:ModeratorMetallic U233 + Th232:Fuel

Around 10 years:Core Life

5 Mwth:Reactor Power

Nuclear Power PackNPP

30 Fuel beds24 (Ex) + 7 (In) control locations

Ø8

Ø8.5

Ø10

Metallic Fuel (90% (U233+Th) + 10% Zr)

Heat Tr. Medium

Clad of Zr-4

Fuel Pin

Important Parameters

Enrichment 14%

Core life 3000 FPDs

Amount of Gd 300gm in each of 12

0 500 1000 1500 2000 2500 3000 3500 40000.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

Variation of K-eff with Burn up

300 gm in Gd in 12 assemblies

K-ef

f

Burn up in FPDs

No Gd GD

Total fuel for entire core

U233 28.88 Kgs

Th232 156.78 Kgs

Estimation of Control Rods Worth at Hot Condition

(14% enrichment)

Max. Worth of a Single Control Rod = 14.19 mk

Worth of all Control Rods = 321.8 mk

0.80661All Control Rods in except one having Maximum worth

0.79748All Control Rods in

1.07280All Control Rods outValue of K-effPosition Of Control Rods

Height of Control Rods at Criticality(14% enrichment)

At criticality control rods will be 39.5 cm in the core plus 15 cm in the bottom reflector.

In this condition the worth of one control rod having maximum worth is 2.9 mk.

Estimation of Fuel Temperature Coefficient

Fuel temperature coefficient is at 7750C it is -1.6953 x 10-5 per 0C

CONCLUSION

Initial K-eff is very large necessitating the introduction of burnable poison in the core.

14.0 cm pitch is considered adequate.

This can be used as a Nuclear battery which will run around 10 years without any refueling.

ACKNOLEDGEMENT

P.D. KrishnaniI.V. Dulera

R. SrivenkatesanR. K. Sinha

THANK YOU

Indian High Temperature

Reactors Programme

Compact High Temperature Reactor (CHTR)A technology demonstration facility

Nuclear Power Pack (NPP)To supply electricity in remote areas not connected to grid

High Temperature Reactor (HTR)For hydrogen generation