My Report

INTRODUCTION: ITER ITER(International Thermonuclear Experimental Reactor) is a joint international research and development project that aims to demonstrate the scientific and technical feasibility of fusion power. The partners in the project - the ITER Parties - are the European Union (represented by EURATOM), Japan, the People´s Republic of China, India, the Republic of Korea, the Russian Federation and the USA. ITER will be constructed in Europe, at Cadarache in the South of France. One of the important missions of the ITER is to validate the design concepts of tritium breeding blankets relevant to a power producing reactor like DEMO. ITER will demonstrate the feasibility of the breeding blanket concepts that would lead to tritium selfsufficiency and higher grade heat extraction in future which is necessary for DEMO. TBM Requirements : Several requirements of TBM are as below, 1. Tritium breeding to demonstrate the feasibility of the process and to ultimately enable the extrapolation to a full size blanket and the validation of analytical tools. 2. High grade heat production and removal to demonstrate the feasibility of electricity production. 3. verification of on-line tritium recovery and control systems; 4. validate and calibrate the design tools and the database used in the blanket design process including neutronics, electromagnetic, heat transfer, and hydraulics; 5. demonstrate the integral performance of blanket systems under different loading conditions; 6. observe possible irradiation effects on the performance of the blanket modules.

In addition as a part of the TBM is a FW component comparable with the ITER Shielding Blanket and must fulfil the following functions: 1. Remove the surface heat flux and the nuclear heating within the allowable temperature, stress and deformation limits. 2. Reduce the nuclear responses in the vacuum vessel structural material for the ITER fluence goal. 3. Contribute to the protection of superconducting magnets against excessive nuclear heating and radiation damage. 4. Contribute to the passive stabilisation of the plasma. 5. Provide a maximum degree of mechanical and structural self-support to: (1) minimise the loads transmitted to the vacuum vessel, and (2) decouple the operating temperature ranges between the test blanket system, and the vacuum vessel. INDIAN LLCB-TBM (Test Blanket Module) : India has proposed the Lead-Lithium cooled Ceramic Breeder (LLCB) as the blanket concept. LLCB concept is different from other concepts and it includes the feature of both solid and liquid type concepts. The LLCB blanket concept consist of lithium titanate as ceramic breeder (CB) material in the form of packed pebble beds and Pb-Li eutectic as multiplier, breeder and coolant for the CB zones. The outer box however is cooled by helium. To assess the performance LLCB TBM will be tested from day-one operation of ITER in one-half of a designated test port. The tests in ITER include the simultaneous function of all subsystems including the TBM as well as its ancillary system. A set of engineering scaling experiments will be proposed in ITER to understand the heat removal capability of leadlithium eutectic especially in the MHD environment, in compliance with ITER Safety requirements and guidelines.

ENGINEERING DESCRIPTION The LLCB TBM is designed for one vertical half of TBM port as shown in the figure.

The front surface is having a height of 1.66m and a width of 0.484m. The Plasma side is coated with 2mm Beryllium. The radial extent of TBM is 0.55m supported at the back side with flexible support keys and shear keys for guiding. A water cooled SS316 shield is placed at the back side of TBM for radiation shield. Initial design of the TBM module has been made and detailed analysis is on the way to achieve the testing parameters of TBM. First wall covers the three sides, top and bottom plates cover two sides and back side plates the sixth side.

LLCB TBM Design The preliminary design of the LLCB Test Blanket Module has been discussed here. The overall dimensions of the TBM are 1.66 m (pol) x 0.484 m (tor) x 0.534 m (rad). As per the ITER guidelines a clear space of 20 mm has been provided between the TBM and surrounding frame structure.

FIG- The LLCB ITER-TBM Module

Figure: The Sectional views of LLCB TBM

Ceramic Breeder Zones And Pb-Li Flow Path : There are five breeder zones are proposed in this concept, these breeder zones form Pb-Li path. These breeder zones are filled with Li2TiO3 pebbles of size 1mm for tritium breeding. The tritium is extracted by Helium purge gas at a pressure of 1.2 bar (abs) passes into the breeder zones from the top and bottom plates. Pb-Li enters from the bottom manifold into the first pass between the first breeder zone and and first wall backside. The thickness of each channel is 50mm for reducing the Pb-Li velocity so that MHD effects are minimized. The internal surface along the Pb-Li path is coated with 2mm Alumina for minimizing the MHD effects.

Fig. Schematic of the LLCB blanket concept

Attractive features of the LLCB Concept  It uses lead as the neutron multiplier instead of beryllium, thus making it beryllium free. 

The use of tons of highly toxic beryllium as neutron multiplier with its limited resources makes it imperative to handle and reprocess it.

 There is an inherent simplicity arising from the absence of internal grid cooling circuit, as it is no longer needed.  This will reduce a number of complex joints drastically and can improve the plant availability. Key advantages of the LLCB concept :  For a given radial depth, it has more tritium breeding when compared to a pure Pb-Li based concept. This is because of the improved utilization of the low energy neutrons, which breed tritium with Li-6. The radial depth is a non-trivial parameter in reactor design, because the space requirements behind the blanket are always stringent. Every small increase in the size of the vessel and magnets are quiet expensive.  The heat transfer coefficient (HTC) between the CB and the Pb-Li is a very crucial parameter and unique to LLCB. Currently the worst-case estimates (laminar flow) have been assumed (average HTC = 4347 W/m2k). It is possible to excite turbulence in such a highly sheared velocity profile by creating some high electrical conductivity paths on the CB zone partitions. The LLCB concept will give us valuable data on the HTC and allow a good extrapolation to self-cooled Pb-Li concepts, which are currently not being tested on ITER.  There is an inherent simplicity arising from the absence of internal grid cooling circuit, as it is no longer needed. This will reduce a number of complex joints drastically and can improve the plant availability. The breeder box can also be easily removed after cutting the purge circuit and disposed to radio active waste storage in DEMO for passive cooling.  No Beryllium is a distinct advantage, because of the greatly reduced toxic

inventory from a public acceptance point of view.

TRITIUM EXTRACTION SYSTEM PRESENT DESIGN

Introduction : In LLCB concept Tritium Extraction System (TES) has very important role to recover the bred tritium from the module. TES for LLCB concept is for all tritium-laden streams. Presence of tritium in various streams (lead lithium, purge gas, helium first wall coolant) flowing in tritium blanket module is either generated by neutron lithium interaction or due to permeation through the solid boundaries. In LLCB concept, consists of two breeding zones,  Lead-Lithium and  the solid ceramic breeder zone. It is estimated that, tritium will be produced at a rate of ~52.2 mg/day in liquid breeder and ~35 mg/day in solid breeder. Tritium Extraction System (TES) is designed for a capacity of 100 mg/day as against an estimated production rate of ~87.2 mg/day. As there is no concrete estimation of tritium permeation to helium coolant system. CPS (Coolant Purification System), which is similar to a tritium purge gas extraction system is designed for safer side with same capacity of 35 mg/day. Primary tritium extraction starts from TBM to purge gas in TBM solid pebble bed itself in case of solid breeder and in the Extractor column in case of liquid Pb-Li breeder. Further, purge gas is cleaned-up from dusts, oxygen, moisture and other impurities before processing it to tritium recovery. Purge gas is then recycled to TBM after adding makeup helium and hydrogen in it. Recovered tritiated hydrogen gas is stored into getter bed and sent to Hydrogen Isotope Separation System (HISS) for separation of tritium from hydrogen. LLCB TBM Tritium Extraction System Design Consideration : The important function of TES is to extract entire tritium produced in Pb-Li and Ceramic breeder zones of LLCB TBM. for improved future designs data are also taken care by designing the system for higher extraction capacity identification and quantification of impurity generated while operating the TBM.

Single tritium extraction & processing system will be designed for this combined helium stream. This philosophy is based on the estimated individual helium flow rates required for each tritium-laden stream of TBM. Tritium permeation from lead lithium stream to helium first wall coolant is expected to be negligible due to high mass transfer resistant liquid boundary layer and the high operating pressure of helium coolant. Nevertheless, provision is made to extract tritium from bleed stream, in case there is any permeation with longer time of operation. Helium coolant stream containing permeated tritium will be handled in separate cooling purification loop due to very large operating pressure and flow requirements. Tritium accountancy for individual stream of TBM will be done separately in port cell. Tritium transfer from lead lithium to helium stream will also be placed in transfer cask housed in a port cell. Instrumentation and control panels along with tritium monitors will be outside port cell in the adjoining area of port cell. TES design is based on general ITER guidelines and constraints in ITER building space. Partial pressure of tritium in any stream is not allowed to exceed one Pascal to limit the tritium permeation. Lead lithium inventory in TBM is not allowed to exceed 300 liters. Tritium removal or transfer from lead lithium efficiency for helium is 95%. As a first step basic design philosophy is based on using well-proven and rugged methods of adsorption desorption. In addition CPS will not be designed for continuous mode operation due to very low tritium extraction requirement.

LLCB TBM Tritium Extraction process description Process flow sheet for LLCB concept is shown in figure. Helium with 0.1% hydrogen is used as purge gas to sweep tritium, which is generated in solid pebble bed as well as in gas liquid contactor placed in port cell for transferring tritium from lead lithium to helium stream. Tritium rich helium streams after being cooled and accounted for tritium are sent to tritium building for tritium extraction. Tritium extraction for helium coolant is done separately in CPS in TCWS vault building. Two major activities are performed in port cell for LLCB TBM. First major activity is to transfer tritium from lead lithium stream to helium stream. This is achieved in gas liquid contactor using stainless steel structured packing. Tritium accountancy of each stream is also done in port cell. Tritium rich purge helium gas of pebble bed and helium from lead lithium extractor are combined together and sent to tritium extraction system in tritium building. Return helium after tritium extraction is recycled back in coaxial pipes. Tritium extraction loop basically consist of AMSB for moisture removal and cryogenic molecular sieve bed for hydrogen isotope removal. Regeneration is done in a closed loop to avoid extra inventory handling of purge gas at final moisture removal stage or hydrogen isotope separation stage. Sufficient loading time is taken to take care of higher regeneration time requirement and to reduce the frequency of loading unloading cycle. Preliminary Design Parameters of LLCB TES system LLCB TBM TES consists of mainly four systems. (1) Lead-Lithium system: Liquid Coolant cum Breeder (Lead-Lithium) circulation and tritium transfer from it to Helium purge gas (2) Purge gas system: Purge gas (both for solid as well as liquid breeder) circulation, purification and hydrogen isotope separation system (3) Tritium extraction system: Hydrogen isotope extraction and storage system including sending them to isotope separation system for tritium recovery (4) Coolant purification system: First wall coolant (Helium gas) purification system to extract hydrogen isotopes including tritium from coolant Helium gas.

Pb-Li loop will be located at Port Cell along with TMS (Tritium Management System). The Pb-Li loop consists of Re-circulation pump, Tritium extractor column cum sump, LeadLithium to Helium heat exchanger, Cold trap, Helium/Helium heat exchanger (recuperator), filter and heaters. Tritium monitoring system consists of a metal reducing bed, ion chambers and its electronic measuring system. Purge gas system will be located at Tritium Building. It will be encapsulated in a glove box. It consists of Helium to water heat exchanger, Atmospheric adsorber beds, filter, Cryogenic Helium/Helium heat exchanger (recuperator), Cryogenic adsorber beds, Helium purge gas buffer tank, Purge gas re-circulation blowers, Cold trap, Atmospheric adsorber bed regeneration blower and liquid storage tank. Apart from these equipments this system also includes Tritium monitoring system and other instrumentation. Tritium extraction system also will be located at Tritium Building but in a separate glove box. It consists of Filter, Expansion Tank, Regeneration Blower, reducing Metal Bed, PalladiumSilver Membrane assembly, Vacuum Pump, Getter Bed, Sequential Gas Chromatograph and Heat Calorimeter. Coolant Purification System (CPS) is similar to tritium extraction system, which will be located at TCWS building. Only a small bleed of coolant helium gas will be taken to CPS for recovery of permeated tritium into the coolant gas system. Apart from these there will be a small Control and Monitoring Room located at Tritium Building with all required electrical and instrumentation panels for operation and control of Tritium Extraction System

Tritium extraction from the lead-lithium eutectic alloy : In this system In Pb-Li eutectic alloy, Li is as breeder material. High energy neutron from the plasma side strikes on it and finally tritium that is produced within that alloy. should be separated from that Pb-Li eutectic alloy. By extracting tritium from that alloy we make that alloy tritium free and through different treatment we can refill that alloy in the TBM. From the above figure we can say that tritium etraction from the Pb-Li ayyols need simple process in which following equipments are included,  Helium cooled heat exchanger  Circulating pump  Gas-Liquid extractor  Pb-Li storage tank  Pb-Li Cooler  Cold trap  Blower  Filter unit Stream of tritium produced within the Pb-Li alloy in the module having high temp is sent to the gas liquid extractor in which concentration of the tritium in the alloy is 0.0187 ppm .The operating temp of the extractor is 753 K. This extractor is installed in the port cell. The feed is fed to the extractor from the top at the flow rate of 2.15 Lit/sec.and helium gas containing 0.1% H2 is blowing by a blower from the bottom of the extractor at the flow rate of 7.5 Nl./s.So in this way counter current gas liquid extraction will be take place.Here tritium is transferd from the Pb-Li to He gas by countercurrent mass transfer (Extraction) operation. The tritium transfer efficiency from the Pb-Li to He gas is considered to be 95%. He purging from the bottom of the extractor carries tritium that is released from the Pb-Li is obtained from the top of the extractor that He gas if contain some amount of HTO,H2O or LiOH those matter should be removed from the gas.For that cold trap is provided with the check valve.First of all that gas passes from that cold trap to condense all these matter to make gas free from such matters. Now He contain hydrogen isotopes and very little amount of other composition is sent to the TES tritium extraction system for the further separation of the tritium from the He purge gas.

Flow sheet of Tritium Extraction System for the Pb-Li eutectic alloy.

Pb-Li from the bottom of the extractor is stored into Pb-Li storage tank. The operating pressure and temp of the storage tank are 0.8 MPa and 753 K respectively. Storage capacity of it is 300 Lit. The temp of the Pb-Li alloy inside the tank is around 753 K so before refilling it into TBM channel, Its temp can be reduced by passing it through Pb-Li Cooler or He cooled heat exchanger. In which He gas is passing through the tube side and Pb-Li is passing through the shell side for the effective heat transfer. Finally Pb-Li after cooling is circulated in the TBM channel by circulating pump.

PRELIMINARY DESIGN PARAMETERS REQUIRED FOR TES IN Pb-Li LOOP (1) Gas-Liquid contactor(Extractor). SERVICE

TRITIUM EXTRACTION

Design capacity

100 mg/day

T-transfer efficiency to He

95%

Operating Temp

753 K

Operating Pressure

0.8 MPa

Pb-Li flow rate

2.15 Lit/sec

He flow rate

7.5 Nl/s

(2) Pb-Li Storage tank: SERVICE

STORAGE OF PBLI

Capacity

300 Lit

Operating Temp

753 K

Operating Pressure

0.8 MPa

00

Storage tank

(3) Pb-Li Cooler Or He Cooled Heat Exchanger : SERVICE

PB-LI/HE COOLER

He Coolant flow

0.75 Kg/Sec

Inlet He/Pb-Li Temp

30oC/480oC

Outlet He/Pb-Li Temp

180oC/300oC

Type

Shell and Tube

He-In

Pb-Li In

He Out

Pb-Li Out

(4) Pb-Li Transfer Pump :

SERVICE

PB-LI CIRCULATION IN LLCB LOOP

Type

Centrifugal

MOC

SS

Operating Temp

300oC

Head required

10 m(Pb-Li)

Discharge Flow

4.5 Lit/sec

(5)Filter Unit :

PRE FILTER

TO REMOVE PARTICLES UP TO 3 Μ SIZE

Max ∆P Allowable

500 Pa

Filter type

Fiber glass media

FINE FILTER

To remove particles below 3 μ size

Max ∆P Allowable

500 Pa HEPA

Filter type

High Efficiency Perticulate Air

Pre filter

Fine filter

Tritium Extraction from He Purge gas : Tritium generated in the ceramic pebble bed made of Li2TiO3 is purged out by purging He gas containing 0.1% H2 gas for the effective separation of the H 2-Isotopes from the breeder material. The partial pressure of the H2 is around 110 Pa and during the tritium extraction process it may be varied up to 200 Pa.It is assumed that most of the tritium generated in the CB zones are in the form of the HT and HTO..So to convert that HTO into HT, H2 is mixed with the He purge gas.

The main chemical reaction which takes place in the breeder is as below, H2 + HTO

HT + H2O

(Isotope Exchange Reaction)

Generally tritium produced in the crystal grains of the Lithiated pebbles and from that it is released to He Purge gas as below

(1) Tritium formation reaction in crystal grain; (2) Diffusion of tritium in crystal grain; (3) interaction of tritium with irradiation defects in crystal grain; (4) tritium transfer from bulk to surface water through interfacial layer; (5) absorption of tritium into the bulk of crystal grain;

(6) Adsorption and desorption of tritium on grain surface; (7) Isotope exchange reactions between gaseous hydrogen, H2, in the gas stream and tritium on grain surfaces (isotope exchange reaction 1) H2(gas phase) + T2O(surface) ↔ T2 (gas phase) + H2O(surface) (8) Isotope exchange reactions between water vapor, H2O, in the gas stream and tritium on the grain surfaces (isotope exchange reaction 2) H2O(gas phase) + T2O(surface) ↔ T2O(gasphase) + H2O(surface); (9) Water formation reactions when H2 is added to the blanket purge gas; (10) Transfer of hydrogen isotopes and water through pores of sintered pellets; (11) Transfer of hydrogen isotopes and water through a boundary layer formed on the surface of sintered pellets to the gas stream. Now Tritium released by this way is carried our from that by He Purge gas, So He Contains some impurities like HTO, H2O and LiOH etc. Those impurities should be removed from it therefore the gas is sent to the TES (Tritium Extraction System) Tritium Extraction System (TES) receives Tritiated He gas from various regions like,  Pb-Li Extractor – Top stream contains Tritiated He gas..  He purge gas purged out from the CB Zones.  Tritium that is permeated in the He cooled equipments that tritium is mixed with He

coolant so tritium should be removed from the He is sent to the TES for the separation. Tritiated He from the different zones is treated in the TES to separate hydrogen isotope from the He Purge gas and then after hydrogen isotopes are sent for further separation of H-D-T. Separated helium gas still contains little amount of tritium so before recycling that gas it must be purified into CPS. After purifying that helium it is reused as a purge gas for the further operation in the ceramic breeder zones.

Process Description : Tritiated helium gas from the various zones is filtered in to the filter to remove particulate matter from the gas. There are two type of the filters. Particulates up to 3 μ size are removed by the prefilter having Fibre glass as a filter media. Then particulates having size below 3μ is further removed by the fine-filter. There are two filter of each, In which one filter is in working condition and other should be in standby mode which is used when previous one is sent for the maintenance. They are connected in the parallel. The maximum allowable pressure drop across the filters is around 500 Pa. Then particulate free gas composition is sent to the water cooled heat-exchanger. It is also shell and tube heat exchanger in which water is circulated in tube side while hot gas is passed through the shell side for the effective heat transfer. Helium gas mixture is cooled from 180oC to 30oC.and temp changes from 23 oC to 25 oC for the water. Now He gas composition having 30 oC temp is sent to the AMSB (Atmospheric Molecular Sieve Adsorber Bed) Adsorber to remove some moisture from the gas .Before the gas is sent to the AMSB first of all it is passed through the MFC and IC to measure the tritium concentration and mass flow regulation. Here MFC is necessary before the Heat exchanger to regulate constant flow rate of 31.5 Nm3/hr for the helium gas mixture. Ionization Chamber (IC) is also installed with the MFC to measure the tritium concentration. The AMSB is operated at 30oC temp and at 0.12 MPa pressure .He gas mixture having 11.5 ppm moisture content is fed to the AMSB from the bottom at the flow rate of 31.5 Nm3/hr.AMSB has molecular sieve 5A as a adsorbent in which water vapors or moisture is trapped and hence removed them from the gas mixture .After 7 days of working operation regeneration of the AMSB is carried out at a temp of 250 oC by heating the bed by an electric heater operated at 1 KW. After the regeneration Tritiated water is released from the bottom of the AMSB Tritiated He gas come out from the AMSB still contains some amount of HTO.H2O and LiOH. These impurities should be removed from the gas mixture so after the AMSB the gas composition is passed through the cold trap. There are two functions of the cold trap; They are.. (1) used for the removal of the HTO.H2O and LiOH from the He gas. (2) used for the removal of the HTO.H2O and LiOH from the regenerated gas from the AMSB.

Working function of AMSB and Cold Trap (In Loading Condition)

Moisture free process Gas

Atm. Adsorpt Bed

Blower

Process gas out

Process Gas

LN2 out

LN2 In Cold Trap

The Cold trap is one type of jacketed vertical tank which is cooled by liquid N2 flowing from the jacket. The operating temp of the cold trap is -193 oC and operating pressure is 0.12 MPa. Tritiated He gas is flowing from the cold trap at the flow rate of 2 Nm3/hr.Impurities like, HTO.H2O and LiOH are condensed at such a low temp and formed ice in the frozen area of the cold trap. In this way HTO.H2O and LiOH are removed from the Tritiated gas, This gas is further recycled through AMSB for the effective separation. This is the loading operation of the cold trap.

Cold trap in Un-Loading Condition

Cold Trap

Central Electric Heater

Tritiated Water Storage

Tank

To CECE (WDS)

During the unloading operation of the cold trap, whatever aerosol or ice formed in the frozen area of the cold trap is removed. An electrical heater is provided at the centre of the cold trap. By heating the frozen area of the cold trap the formed ice is melted and collected as a Tritiated water in the Tritiated water storage installed at the bottom of the cold trap. There are two Tritiated water storage tanks. once one storage tank if filled with the Tritiated water then it is sent to the WDS (Water Ditritiation System) for the final separation of the tritium from the water At same time another one is put in operation for the collection of Tritiated water.

Finally Moisture free tritiated He gas from the top of the AMSB is filtered and sent to the cryogenic Recuperator for the further cooling. Recuperator is also one type of shell and tube type He/He heatexchanger He-H2 Make up

Shell Side

Tube side

Recuperator

CMSB

Process Gas from the Atm Adsorption bed and from the Cold Trap

From the figure we can say that tritiated He gas is passing through the tube side at the flow rate of 31.5 Nm3/hr which is cooled by the returned He gas from the CMSB flowing from the Shell side. The tritiated He gas is cooled by returned He gas from 30 oC to – 170 o C, while the returned He gas from the CMSB in heated by the tritiated gas from -193 oC to 10oC. So by using Recuperator we can complete two processes within single operational equipment Like, (1) Tritiated He gas is cooled from 30 oC to – 170 o C, And (2) He gas from the CMSB in heated by the tritiated gas from -193 oC to 10oC.

Now Tritiated He gas from the Recuperator is sent to the Cryogenic Molecular Sieve Adsorber Bed (CMSB) for the H2 isotope separation .Tritiated He gas having H2 isotope contents of 230 ppm and temp of -170oC is fed to the CMSB from the top at the flow rate of 31.5 Nm3/hr.The operating temp and pressure of the CMSB is -196 oC.and 0.12 MPa respectively. CMSB contains Molecular Sieve 5A as a adsorber media that allows to pass the gas molecules through it which having molecular size less than 5A.It is cooled by LN2 Continuously flowing from the helical tubes installed in the CMSB. There are two basic operation of the CMSB for the effective separation of the H2 isotopes, Like, (1) CMSB in loading condition (2) CMSB in Un-loading condition / Regeneration. (1) CMSB in loading condition The processed gas is passed through an adsorber bed (CMSB) operated at liquid nitrogen (LN2) temperature (-196°C). The bed is filled with 5A zeolite pellets which adsorb molecular hydrogen as well as gaseous impurities and residual moisture. The bed contains filters on the down-stream and upstream side to prevent particulate material from being transferred during loading or unloading operations. In addition, the bed is equipped with an electrical heater. The second bed provides additional adsorption capacity; it can be also used when the first bed is being unloaded or regenerated Process gas from Recuperator LN2

LN2

CMSB

He gas to the recuperator

CMSB

(2) CMSB in Un-loading condition / Regeneration Expansion Tank Filter

CMSB

5A zeolite pellets Ele,Heater

CMSB

Hot Mg metal bed

Blower

N2 &O2 Remove Pd/Ag Diffuser

He from Pd/Ag Diffuser

Getter Bed

Un loading or regeneration is carried out after the loading period . The regeneration time should be around 8 hrs.During the regeneration The CMSB is heated at the temp of 70 oC by means of the heater installed at the bottom of the CMSB.During the regeneration the LN2 flow in the CMSB must be stopped for the effective separation. Regeneration temp will be increased with respect to time. When the temp reaches at 150 K the hydrogen isotopes from the zeolite bed will be desorbed, here when temp increased the pressure will be increased inside the CMSB. So to maintain the pressure inside the CMSB, Expansion tank is provided which is prefilled with the 50 KPa He which is needed as a carrier gas for the H2 isotopes during the further un-loading process.at the end of the regeneration the expansion tank is evacuated and refilled with 50 KPa He.

Regeneration should be carried out in three stages, (1) The adsorbed bed is heated at 150 K to desorb hydrogen isotopes. (2) The adsorbed bed is heated at 300 K to desorb water and .remaining hydrogen. (3) The adsorbed bed is heated at 600 K to desorb O2 and N2 from the bed. Now desorbed gases from the top of the CMSB must be purified. First of all the gases if filtered with the filter then is sent to the expansion tank which is necessary to restrict the pressure increased during desorption in the warm up phase of the adsorbed to a value below 0.2 MPa.The tank is prefilled with the 50 KPa He which is needed as a carrier gas for the H 2 isotopes during the further un-loading process.at the end of the regeneration the expansion tank is evacuated and refilled with 50 KPa He. Hot Mg metal bed is connected with that in parallel so gases from the expansion tank is passes through that to remove O2 and N2 from the gases.The function of the hot Mg bed is to restore adsorbed HTO during the regeneration of the CMSB. Now Pure Tritiated He gas is passed through the Pd-Ag metal permeator in which Pd is coated on the Ag.Here Pd is acts as a catalyst that reduces the partial pressure of the H2 isotopes(i.e Tritium) so as per the sieverts law (S α 1/p(1/2) ) solubility of the tritium in the Pd-Ag will be increased so tritium will be easily passed through that permeator and He will be restricted. Tritiated He Gas

Pd/Ag Diffuser

He gas to the CMSB

H2-isotopes

Getter bed

That means, permeator will not allow He to pass through it,So He will be returned from that permeator and sent back to the CMSB to carry further gases desorbed from the bed during regeneration. One heater (1 KW) is installed at the Pd-Ag permeator for the reactivation of the permeator. In this Close cycle, blower is used to circulate these gases. Tritium that is permeated from the Pd-Ag permeator is primary stored in the HIS (Hydrogen Isotope Storage) Getter bed Getter bed is filled with the Pulverized ZrCo or Depleted Uranium.Hydrogen isotopes released from the permeator is stopred in this gettering material bed. Getter bed is operated under two functions; (1) Getter bed at Loading condition (2) Getter bed at Un-loading condition.

(1) Getter bed at Loading condition : Hydrogen isotopes from the permeator is stored into getter bed which is operated at 30 oC and at The pressure of 0.12 Mpa. Hydrogen isotopes(Q2)

H2-isotopes

are stored in the metal(M) getter bed like below reaction, M(s) + (x/2)Q2(g)

MQx(s)

The metal (Zr-Co or depleted uranium) bed has capacity of 3 gm of hydrogen and the weight of that bed based on this capacity is 200 gm.

Getter bed

Material selection of the gettering bed : Those materials which are characterized by very low equilibrium pressure at the room temperature are selected as gettering materials Some gettering materials are ;  Depleted Uranium  Zirconium Iron  Zirconium aluminium  Nickel  Titanium  ZrCo.

ZrCo Getter Bed

According to figure hydrogen gas is diffused into metal which is activated ZrCo powder and is contained in sintered stainless steel tubes to provide a large surface area for ZrCo powder to contact the introduced hydrogen gas. For synthesizing kilograms of ZrCo, Some ZrCo beds have been designed, fabricated and tested for actual use in tritium experiments. One of the major applications of beds is the recovery of large amounts of almost pure gaseous hydrogen isotopes in a short period of time. In this use, the bed is regarded as a vacuum pump that evacuates hydrogen gas tom atmospheric pressure to 10-2 Tort or lower, where residual tritium is negligible from the point of view of inventory control. This type of bed will be utilized in many kinds of experiments that require pure hydrogen isotopes including tritium to be supplied and recovered in each run.

(2) Getter bed at Un-loading condition. Hydrogen isotopes stored in to the getter bed are separated as a Hydrogen / Deuterium and tritium. According to structure of the getter bed it consists a central heater (1 KW) for the. regeneration The ZrCo bed is heated at 500 oC for the desorption of these isotopes

To HISS

CMSB

ZrCo Getter Bed

Electric Heater

There are two getter bed in process which are loaded with the radioactive substance tritium so they are keep in the glove box to minimize the Q2O formation. among these two one is in working operation while another one is kept in stand by mode, It is kept in working operation when first one is sent for regeneration. He gas recycled from the CMSB is fed via recuperator into H2-He buffer tank Or H2-He make up unit where Pure H2 is mixed with the incoming He gas to maintain H2:He ratio. Then this mixture is repurged into CBs of the TBM.

PRELIMINARY DESIGN PARAMETERS REQUIRED FOR TES FROM He PURGE GAS (1) He-Water Heat-Exchanger :

Water In SERVICE

He-In

HE/WATER COOLER

He Flow

31.5 Nm3/hr

He Tin /Tout

180oC/30oC

Water Tin /Tout

23oC/25oC

Type

Shell& Tube

He Out Water Out

(2) He- Purge gas blower : SERVICE

CIRCULATION OF HE PURGE GAS IN TBM

Discharge flow

35 Nm3/hr

Head required

10 Kg/Cm2

Operating Temp

30oC

Type

Centrifugal

(3) Cryogenic Recuperator : SERVICE

He Tout = -173 oC

HE/HE COOLER 31.5 Nm3/hr

(1) He Tin /Tout

30oC/-173oC

(2) He Tin /Tout

-193oC/10oC

Type

Shell& Tube

He Tout = 10oC

Cryo.Recuperator

He Flow

He Tin=

He Tin = 30oC

-193oC

(4) Atmospheric Molecular sieve Bed : SERVICE

MOISTURE TRAPPING FROM PURGE GAS

Adsorber type

Mol. Sieve 5A

Capacity

49 gm of moisture

He-flow

31.5 Nm3/hr

Operating temp

30 oC

Operating Pressure

0.12 MPa

Moisture content in the purge gas

11.5 ppm

Regeneration time

AMSB

CMSB

Electric Heater

7 days

Regeneration temp

250 oC

Regeneration heater

1 KW

(5) TES Purge gas buffer tank : SERVICE

TES HE BUFFER CUM MAKE-UP UNIT

Capacity

400 Lit

Operating temp

0.12 MPa

Operating pressure

30 oC

(6) Cold Trap : SERVICE

AMSA REGENERATED MOISTURE TRAPPING

He Flow

2 Nm3/hr

Operating temp

-193oC

Operating Pressure

0.12 MPa

Type

LN2 cooled jacketed tank

H2 make-up To T B M

He Buffer tank

(6) Cryogenic Molecular Sieve Bed (CMSB) : SERVICE

TRAPPING OF H2ISOTOPES FROM PURGE GAS

Adsorber type

Mol.Sieve 5A

Capacity

5 gm of H2 isotopes

Process gas in

LN2 Out

LN2In

CMSB

3

He flow

31.5 Nm /hr

Operating temp

-196 oC

Operating Pressure

0.12 MPa

H2 Isotopes content in He purge gas

230 ppm

Regeneration Time

8 hr

Regeneration temp

70oC

Desorbed gas out

C M S B

Electric Heater

He for regeneration

He gas from process gas

(7) Expansion tank : SERVICE

TO MINIMIZE OVERPRESSURE DURING REGENERATION OF CMSA

Capacity

200 lit

Operating Pressure

0.2 MPa

Operating Temp

30 oC

From CMSB

Expansion tank

To Hot Mg metal bed

To Pd/Ag permeator

(8) Membrane Permeator : SEPERATION OF H2 ISOTOPES FROM HE GAS

Membrane type

Pd-Ag membrane

Flow rate of regenerated gas

2 Nm3/hr

Operating pressure

2 Kg/cm2

Operating temp

450 oC

Permeator area

0.25 m2

Tritiated He gas

Pd/Ag Membrane

SERVICE

Returned He

H2-isotopes to Getter bed

(9) Hot metal bed : SERVICE

O2, N2 AND OTHER IMPURITIES REMOVAL BED

Material

Mg flakes

Bed Wt

5 Kg

He flow

2 Nm3/hr

Operating temp

400oC

Operating pressure

0.12 MPa

Regeneration time

7 days

Tritiated He gas contain O2,N2 and other impurities

Hot Mg metal bed

Tritiated He gas

(10) Getter Bed : SERVICE

STORAGE OF H2 ISOTOPES

Bed material

ZrCo / Depleted uranium

Bed wt

200 gm

Loading limit

50% of bed capacity

Operating temp

30 oC

Operating pressure

0.12 MPa o

Regenerated temp

500 C

Desorbed pressure

In the order of bar

CMSB Electric Heater

ZrCo Getter Bed

Coolent Purification System : CPS would be located in the TCWS building. A bleed will be taken from the main coolant loop for purification and separation of tritium purpose. It will contain most of the equipment of main purge gas loop in the TES, except TES purge gas buffer tank, purge gas circulation blower and water cooled heat exchanger. The detailed design work is under progress. Monitoring of hydrogen content in CMSA regeneration gas will be done using sequential gas chromatography (micro GC) instrument. Tritium monitoring in the metal getter bed will be done using heat calorimetry. Hydrogen and tritium monitors will be installed inside glove box for continuous monitoring and alarm.