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Fusion Engineering and Design 87 (2012) 1009– 1013

Contents lists available at SciVerse ScienceDirect

Fusion Engineering and Design

journa l h o me page: www.elsev ier .com/ locate / fusengdes

tatus and progress of Indian LLCB test blanket systems for ITER

aritosh Chaudhuria,∗, E. Rajendra Kumara, A. Sircara, S. Ranjithkumara, V. Chaudharia, C. Danania,. Yadava, R. Bhattacharyaya, V. Mehtaa, R. Patela, K.N. Vyasb, R.K. Singhb, M. Sarkarb, R. Srivastavaa,. Mohanb, K. Bhanjab, A.K. Surib

Institute for Plasma Research, Bhat, Gandhinagar 382428, IndiaBhabha Atomic Research Center, Trombay, Mumbai 400 085, India

r t i c l e i n f o

rticle history:vailable online 27 March 2012

eywords:est blanket moduleead–lithium ceramic breeder (LLCB)hermal–hydraulicrocess integration design

a b s t r a c t

The lead–lithium ceramic breeder (LLCB) TBM and its auxiliary systems are being developed by Indiafor testing in ITER machine. The LLCB TBM consists of lithium titanate as ceramic breeder (CB) mate-rial in the form of packed pebble beds. The FW structural material is ferritic martensitic steel cooledby high-pressure helium gas and lead–lithium eutectic (Pb–Li) flowing separately around the ceramicbreeder pebble bed to extract the nuclear heat from the CB zones. Low-pressure helium is purged insidethe CB zone for in situ extraction of bred tritium. Currently the LLCB blanket design optimization isunder progress. The performance of tritium breeding and high-grade heat extraction is being evalu-

ritium ated by neutronic analysis and thermal–hydraulic calculations for different LLCB cooling configurationsand geometrical design variants. The LLCB TBM auxiliary systems such as, helium cooling system (HCS),lead–lithium cooling system (LLCS), tritium extraction system (TES) process design are under progress.Safety analysis of the LLCB test blanket system (TBS) is under progress for the contribution to preliminarysafety report of ITER-TBMs. This paper will present the status of the LLCB TBM design, process integrationdesign (PID) of the auxiliary systems and preliminary safety analysis results.

. Introduction

Indian test blanket module (TBM) program in ITER is one of theajor steps in Indian fusion reactor program towards DEMO and

ower plant vision. India is developing the lead–lithium coolederamic breeder (LLCB) as the blanket concept to be tested in ITER1]. It consists of lead–lithium (Pb–Li) eutectic, which acts as multi-lier and coolant. Lithium titanate (Li2TiO3) is used as the ceramicreeder material in the form of packed pebble beds. The FW struc-ural material is ferritic martensitic steel and is cooled by heliumas. Pb–Li, flowing separately around the ceramic breeder pebbleed to extract the volumetric heat from the ceramic breeder CBones. The Pb–Li flow velocity is moderate enough such that its selfenerated heat and the heat transferred from ceramic breeder beds extracted effectively.

The LLCB TBM auxiliary systems consist of helium cooling sys-ems (HCS), lead–lithium cooling systems (LLCS), helium purge

ystems (HPS), coolant purification system (CPS) and tritiumxtraction system (TES). The details of each system as the process

∗ Corresponding author. Tel.: +91 79 23952184; fax: +91 79 2395277.E-mail address: paritosh@ipr.res.in (P. Chaudhuri).

920-3796/$ – see front matter © 2012 Elsevier B.V. All rights reserved.oi:10.1016/j.fusengdes.2012.02.062

© 2012 Elsevier B.V. All rights reserved.

integration design (PID) of the auxiliary systems and preliminarysafety analysis results will be discussed in this paper.

2. LLCB TBM module

As discussed in our previous paper [2] about the flowing ofPb–Li in series around the CB, we have an alternate option TBMmodule with parallel flow of Pb–Li. In this present design of LLCBTBM, the module consists of parallel flow plate type arrangementwhere lead–lithium (Pb–Li) from inlet flows through these parallelchannels as shown in Fig. 1.

Neutronic calculations for the above design of LLCB TBM blan-ket have been carried out to estimate tritium production rateand radial profiles of nuclear heating in the blanket. The nuclearheat deposited in the TBM has been calculated to evaluate thethermal–hydraulic performance of the TBM. All Ceramic breedersare at uniform temperature with a maximum variation of 15 ◦Cbetween them. All the components of LLCB TBM are maintainedwithin the temperate window [3]. The full module of LLCB TBMwith all its components in an exploded view is shown in Fig. 2.

3. LLCB TBS

LLCB TBS consists of following major circuits:

1010 P. Chaudhuri et al. / Fusion Engineering

•

•

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Fig. 1. Side view of LLCB TBM module with the parallel flow directions of Pb–Li.

HCS for first wall and TBM structure with high-pressure hightemperature helium.LLCS for cooling the internal ceramic breeder cassettes andextract the volumetric heat from TBM.Lead–lithium–helium cooling system is a high-pressure hightemperature helium circuit for cooling Pb–Li.A low pressure tritium extraction circuit for extraction of gener-ated tritium in both ceramic and liquid metal breeder.

.1. Helium cooling system (HCS)

First wall (FW) HCS is meant for extracting heat from the TBMrst wall. The TBM first wall is cooled by high-pressure primary

Fig. 2. Exploded view of LLCB TBM module.

and Design 87 (2012) 1009– 1013

helium, which rejects heat subsequently to ITER water-cooling sys-tem. The primary helium, cooling system (PHCS) is designed toremove the peak heat load of 300 kW.

The block diagram of the system is shown in Fig. 3. In normaloperation, the helium gas enters into TBM FW at 300 C and 80 barpressure and comes out at about 340 ◦C. This hot gas flows throughrecuperator where it gets cooled by cold helium coming out fromcirculator outlet. The recuperator outlet helium is forwarded tohelium/water heat exchanger where it rejects heat to ITER waterloop. The cold water at 28 ◦C is heated up in the main heat exchangerby absorbing the heat transferred from the hot helium of the loop.Helium will come out from He–water heat exchanger at less than70 ◦C. this cold helium passes through the dust filter and to the cir-culator inlet. The cold helium is circulated again in the system withthe circulator. The circulator works as a flow circulation device tak-ing a high pressure suction and discharge to overcome the systempressure drop. The electric heater inline to the TBM FW inlet will beworking as per the mode of operation of ITER. It is a supplementaryheat source in case of incomplete recuperation and for the purposeof baking process and testing of loop. A tritium monitoring system(TMS) is provided at the inlet and outlet of TBM to monitor thetritium permeation in TBM.

Besides the FWHCS, there is another helium circuit named aslead–lithium–helium cooling system (LLHCS). LLHCS is meant forextracting heat from the lead–lithium cooling system and theliquid-metal heat exchanger (LMHX) is the interface for the twothermally dependent systems, i.e. LLCS and the LLHCS. The LLHCSis designed to remove the peak heat load of 0.557 MW.

3.2. Lead–lithium cooling system (LLCS) [4]

LLCS is an important loop of TBM for liquid Pb–Li blanket design.The loop is used to perform the dual role, such as extract the nuclearheat and tritium generated in the TBM. LLCS is a closed loop sys-tem in which, the tritium enriched hot Pb–Li coming out of TBMis directly fed to the heat exchanger, for the removal of heat byusing helium coolant. A small stream of cooled Pb–Li is then sentfor the tritium extraction system, in a detritiation column. Purgehelium gas stream is used for removal of tritium from the liquidmetal. The detritiated Pb–Li stream from detritiation column is thenmixed with the main Pb–Li stream. The combined stream goes tothe pump sump tank. The sump tank is fitted with centrifugal pump.A gas space is provided at the top of the sump tank to protect themechanical seal of the pump. This Pb–Li flow is pumped back to theTBM by maintaining the temperature of 300 ◦C at the entrance ofTBM with the help of an electric heater.

Pb–Li in circulation gets contaminated with some magnetic aswell as non-magnetic impurities. Small flow of about 2% of mainPb–Li flow is passed through cold trap and the magnetic trap forpurification. The measurement of impurities is done using pluggingindicator. The block diagram of the system is shown in Fig. 4.

3.3. Tritium extraction system (TES)

TES for the LLCB TBM has very important role to recover bred tri-tium from the TBM module. TES for LLCB concept is combined for alltritium-laden streams of TBM circuit. Presence of tritium in variousstreams (lead–lithium, purge gas, helium primary and secondarycoolants) flowing in TBM is either generated by neutron lithiuminteraction or due to permeation through the solid boundaries. InLLCB concept, there are two breeding zones, liquid lead–lithium

zone and the solid ceramic breeder zone. It is estimated that, tri-tium will be produced at a rate of ∼52.2 mg/FPD in liquid breederand ∼35 mg/FPD in solid breeder. TES is designed to extract bred aswell as permeated tritium from LLCB TBM.

P. Chaudhuri et al. / Fusion Engineering and Design 87 (2012) 1009– 1013 1011

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Fig. 3. Block diagr

TES consists of mainly three subsystems:

Lead–lithium system: Liquid coolant cum breeder (Pb–Li) circula-tion and tritium transfer from it to helium purge gas.Helium purge gas system: Purge gas (both for solid as well as liquidbreeder) circulation, purification and hydrogen isotope separa-tion.Tritium extraction system: Hydrogen isotope extraction and stor-age system including sending them to isotope separation systemfor tritium recovery.

Primary tritium extraction starts from TBM to purge gas in TBMolid pebble bed itself in case of solid breeder and in the Extractorolumn in case of liquid Pb–Li breeder. Further, purge gas is coolednd cleaned-up from dusts, oxygen, moisture and other impuritiesefore processing it to tritium recovery. Purge gas is then recycledo TBM after adding makeup helium and hydrogen in it. Recoveredritiated hydrogen gas is stored into getter bed and sent to hydro-en isotope separation system (HISS) for separation of tritium from

ydrogen.

TES is designed to extract entire tritium produced in Pb–Lind ceramic breeder zones of LLCB TBM. Tritium produced inoth the breeder zones is first transferred to helium purge gas

Fig. 4. Block diagram of LLCS of LLCB TBM.

HCS of LLCB TBM.

streams separately. Since both the tritium laden purge gas streamscontain similar level of tritium concentration, they are combinedtogether and a single tritium extraction and processing system isdesigned for this combined helium purge gas stream. This philoso-phy is based on the estimated individual helium flow rates requiredfor each tritium-laden stream of TBM. Tritium permeation fromlead–lithium stream to helium first wall coolant is expected to benegligible due to high mass transfer resistant liquid boundary layerand the high operating pressure of helium coolant. Nevertheless,provision is made to extract tritium from bleed stream, in case thereis any permeation with longer time of operation. Helium coolantstream containing permeated tritium will be handled in separateCPS due to very large operating pressure and flow requirements.

Tritium accountancy for individual stream of TBM will be doneseparately in port cell. Tritium transfer from lead–lithium to heliumstream will also be placed in transfer cask housed in a port cell.Instrumentation and control panels along with tritium monitorswill be outside port cell in the adjoining area of port cell. TES designis based on general ITER guidelines and constraints in ITER build-ing space. Partial pressure of tritium in any stream is not allowed

to exceed one Pascal to limit the tritium permeation. Lead–lithiuminventory in TBM is not allowed to exceed 300 l. Tritium removalor transfer from lead–lithium efficiency for helium is 95%. As a first

Fig. 5. Process flow sheet of TES of LLCB TBM (nomenclatures are given in AppendixA).

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ig. 6. VV and VVPSS tank pressure during in-VV LLCB TBM coolant leak accident.

tep basic design philosophy is based on using well-proven andugged methods of adsorption desorption. In addition CPS will note designed for continuous mode operation due to very low tritiumxtraction requirement. This will reduce unnecessary operatingoad and complication on CPS.

Process flow sheet for LLCB concept is shown in Fig. 5. Heliumith 0.1% hydrogen is used as purge gas to sweep tritium, which

s generated in solid pebble bed as well as in gas liquid contac-or placed in port cell for transferring tritium from lead–lithiumo helium stream. Tritium rich helium streams after being coolednd accounted for tritium, are sent to tritium building for tritiumxtraction. Tritium extraction for helium coolant is done separatelyn CPS in Tokamak cooling water system (TCWS) vault building.wo major activities are performed in port cell for LLCB TBM. Firstajor activity is to transfer tritium from lead–lithium stream to

elium stream. This is achieved in gas liquid contactor using stain-ess steel structured packing. Tritium accountancy of each streams also done in port cell. Tritium rich purge helium gas of pebble bednd helium from lead–lithium extractor are combined together andent to tritium extraction system in tritium building. Return heliumfter tritium extraction is recycled back.

. Safety analyses of LLCB TBS [5]

In preparation of the regulatory safety files for LLCB TBS, its essential to select a number of postulated off-normal eventequences that have the potential to lead to hazardous conse-uences. The emphasis of the safety assessment is placed on thenalysis of off-normal events. The objective is to demonstrate thathe introduction and operation of the test modules does not addignificantly to the risk of the basic machine. Safety evaluation willnsure that even in case of postulated accidents the individual TBMnd overall ITER system brought back to normal operation withither design provisions/maintenance or replacement of the LLCBBM. The following four groups of loss of coolant accidents (LOCA)re judged to cover all accident scenarios envisaged in incidentsnd accidents involving the LLCB TBS.

Case 1: In-vessel TBM coolant leaks.Case 2: In-TBM breeder box coolant leaks.Case 3: Ex-vessel TBM coolant leaks.Case 4: Complete loss of active TBM cooling.

The assessment addresses a number of concerns or issues thatre directly caused by the TBS failure. These events were selected

Fig. 7. Helium pressure in HCS, LLCS and LLCS dump tank during in TBM breederbox coolant leak.

to address, where applicable, the following ITER reactor safety con-cerns:

(a) Vacuum vessel pressurization.(b) Pressure built-up in port cell and TCWS vault annex.(c) Purge gas system pressurization.d) Temperature evolution in the TBM.

(e) Decay heat removal capability.(f) Tritium and activation products release from the TBM system.(g) Hydrogen and heat production from Be: steam/water, Pb–Li:

steam/water reaction.

An in-house customized computer code is developed for thedeterministic safety analysis. The mathematical simulation of thecode is developed for the calculation of dynamic modes of LLCBTBS ancillary loops with gas compensation for pressure varia-tions. The development allows to perform calculations of all mainspecified normal and emergency modes and modes with vari-ations of parameters of primary and secondary circuits. This isachieved by the choice of calculation scheme and calculation meth-ods. The mathematical models are based on known principles andgenerally accepted assumptions as homogenization of node param-eters, lumped model, thermodynamic equilibrium of phases, etc.The V&V (verification and validation) of the code is being carriedthrough an experimental program having the appropriately scaledlead–lithium liquid metal and helium loop. Some of the resultsobtained from the analyses are reported here.

4.1. Case 1: in-vessel TBM coolant leaks

The in-vessel TBM FW coolant leaks are analyzed mainly toaddress ITER vacuum vessel (VV) pressurization and passive decayheat removal capability of TBM. Fig. 6 shows the variation in VVpressure during the accident. Due to FW break of TBM, heliumcomes out and disrupts plasma and subsequent plasma quenchcauses intense heat deposition on the ITER FW and failure of itto cause water ingress into VV. Water at temperature of 148 ◦Cflashes into steam and combined effect of helium and steam causespressurization of VV. When pressure reaches 150 kPa, rupture discbursts and SGM rushes to VVPSS and VV pressure is arrested to

around 150 kPa. Steam gets condensed in water and helium getscollected into the VVPSS vessel. When the water inflow to VV stops,SGM outflow to VVPSS also stops and steam inside VV condensescontinuously to bring down the pressure inside VV. The analysis

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esults show that VVPSS is adequately designed for depressuriza-ion of VV in the accident scenario and that the contribution of TBMW coolant helium in VV pressurization is negligibly small duringhe postulated accident sequence.

.2. Case 2: in-TBM breeder box coolant leaks

In-TBM breeder box coolants leaks are analyzed for assess-ent of pressurization of TBM box and TES caused by release of

BM coolant. The aim is to demonstrate protection of TES fromressurization. Helium from TBM FW coolant circuit causes theressurization of TBM box and hence LLCS of LLCB TBS as shown

n Fig. 7. Due to break in one channel inside TBM, helium comesut impairing the heat removal from TBM and causes pressuriza-ion of LLCS loop. PSV gets opened and lead–lithium starts gettingumped into DT. Dumping of lead–lithium is slower compared toelium ingress into system and LLCS pressure shoots to PHCS pres-ure. Once the entire lead–lithium gets dumped into DT, the path isree for helium, helium enters DT and pressure increases very fastnd reaches DT safety relief valve set pressure at time t = 28 s andelium starts coming out to Port Cell. The TBM box is designed toithstand the pressure of 80 bar.

.3. Case 3: ex-vessel TBM coolant leaks

The ex-vessel components of ancillary systems are considereds extensions of VV and therefore act as primary confinement bar-ier. Ex-vessel ancillary coolant leaks in port cell are analyzed tohow that the pressure transient inside the port cell and TCWSault annex stays within design limits because the port cell actss second confinement barrier.

Fig. 8 gives pressure variation in port cell and TCWS vault annexuring the accident scenario. Port cell pressure spikes at ∼1.5 bar,ressure relief valves between port cell and TCWS vault annexpens at 1.2 bar, depressurizing port cell. Due to postulated simul-

aneous failure of TBM FW port cell air is sucked in to VV resultingn to further depressurization of port cell till port cell and VV pres-ure equalize. In depth explanation of the accident event analyzedan be found in Ref. [4].

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and Design 87 (2012) 1009– 1013 1013

5. Conclusions

The performance of tritium breeding and high-grade heatextraction for LLCB TBM has been evaluated by neutronic analysisand thermal–hydraulic calculations for different internal geomet-rical design variants. The optimum dimensions of CB zones andPb–Li flow has been selected to have the maximum temperaturesof all components used are lies within their respective temperaturewindow. The LLCB TBM auxiliary systems such as, HCS, LLCS, TESprocess design are under progress. Safety analysis of the LLCB TBSis under progress for the contribution to preliminary safety reportof ITER-TBMs. The first order safety analysis for the postulated acci-dents incidents demonstrate that prescribed ITER limits will be metby LLCB design.

Appendix A. Nomenclature

DC detritiation columnCC cooling coilEH electric heaterLMHX liquid metal heat exchangerEM electromagnetic pumpSP sump pumpDT dump tankREC recuperatorC compressorCLR coolerHWHX helium water heat exchangerCOB copper oxide bedB blowerSB storage bottleAMSB atmospheric molecular sieve bedCMSB cryogenic molecular sieve bedCT cold trapCR cryogenic recuperatorET expansion tankHMB hot metal bedM membrane (Pd–Ag)GB getter bedT tankVVPSS vacuum vessel pressure suppression systemPSV pressure safety valveSGM steam–gas mixture

References

1] Design Description Document (DDD) for ‘Indian Lead–Lithium cooled CeramicBreeder (LLCB) Blanket’, version–1.0, Report to the ITER Test Blanket WorkingGroup (TBWG), April 2008.

2] Paritosh Chaudhuri, Chandan Danani, Vilas Chaudhari, R. Srinivasan, E. RajendraKumar, S.P. Deshpande, Current status of design and engineering analy-sis of Indian LLCB TBM, Fusion Engineering and Design 85 (10–12) (2010)1966–1969.

3] S.J. Zinkle, N.M. Ghoniem, Operating temperature windows for fusion reac-tor structural materials, Fusion Engineering and Design 51–52 (2000)55–71.

4] A. Patel, R. Bhattacharyay, R. Srinivasan, E. Rajendrakumar, P. Bhuyan, P. Satya-

channel flow in LLCB TBM, in this issue.5] Vilas Chaudhari, R.K. Singh, Paritosh Chaudhuri, Brijesh Yadav, Chandan Danani,

E. Rajendra Kumar, Analysis of the reference accidental sequence for safetyassessment of LLCB TBM system, in this issue.