Lok Sabha Question No. 3830 (UNSTARRED), answered on 2015-08-12
Subject: Technological Challenges of Nuclear Programmes
Ministry: ATOMIC ENERGY
Asked by: HARISHCHANDRA DEORAM CHAVAN

## GOVERNMENT OF INDIA DEPARTMENT OF ATOMIC ENERGY

## LOK SABHA UNSTARRED QUESTION NO.3830

TO BE ANSWERED ON 12.08.2015

## TECHNOLOGICAL CHALLENGES OF NUCLEAR PROGRAMMES

3830.  SHRI  HARISHCHANDRA  CHAVAN:

Will the PRIME MINISTER be pleased to state:

- (a) the details of technological challenges and concerns before India's third stage civil nuclear programme;
- (b) whether the development of the prototype fast breeder reactor would enable the country to harness its vast thorium reserves and if so, the details thereof; and
- (c) the details of safety measures that have been designed for the fast breeder reactors?

## ANSWER

THE  MINISTER  OF  STATE  FOR  PERSONNEL,  PUBLIC  GRIEVANCES  & PENSIONS AND PRIME MINISTER'S OFFICE (Dr. JITENDRA SINGH) :

- (a) The  third  stage  of  India's  nuclear  power  programme  envisages  large-scale use of domestic thorium resource and substantial R&D work has been carried out  in  various  areas  of  thorium  fuel  cycle.  As  a  part  of  this  work,    thorium based  fuel  has  been  produced  for  irradiation  in  research  reactors  and Pressurised  Heavy Water  Reactors  (PHWRs).  The  irradiation  experience  of the thoria based fuels in the research reactors and PHWRs have generated considerable  data  and  understanding  on  thoria  fuel  behavior  aspects.  The irradiated thoria assemblies from research reactors have also been reprocessed to obtain Uranium-233 and this has been used for fabrication of fuel  for  a  30  kWth  research  reactor  KAMINI  at  Kalpakkam.  Power  Reactor Thorium  Reprocessing  Facility (PRTRF)  was  recently  commissioned  in Bhabha Atomic Research Centre (BARC) and this is being used to reprocess the  PHWR  irradiated  thoria  fuel  bundles.    The  R&D  programmes  in  the Department of Atomic (DAE) are well advanced and address some important challenges  for  use  of  thorium  on  an  industrial  scale  is  in  the  area  of

reprocessing,  waste  management,  remote  fuel  fabrication  and  advanced materials for high temperature and corrosive environments. To provide further thrust  to  this  programme,  a  300  MWe  closed  fuel  cycle  based  Advanced Heavy  Water  Reactor  (AHWR),  which  will  produce  most  of  its  power  from thorium based fuel, has been designed and developed in BARC. This will be a technology  demonstrator  reactor  and  will  provide  sufficient  experience  on large scale use  of thorium  well before  the time  period  envisaged  for construction  of  Thorium-Uranium-233  reactor  systems  as  part  of  the  three stage programme.

- (b) Since Thorium does not contain fissile material, it cannot be directly used as a nuclear  fuel.    The  large  scale  use  of  thorium  as  part  of  third  stage  of  our nuclear  power  programme  will,  therefore,  begin  after  adequate  generation capacity using fast breeder reactors under the second stage is established. The Prototype Fast Breeder Reactor (PFBR) being constructed at Kalpakkam is  the  forerunner  of the  second stage. This will pave  way for deployment of additional  Commercial  Fast  Breeder  Reactors  to  attain  the  desired  nuclear power  generation  capacities,  and  providing  the  required  additional  fissile material, plutonium, to launch the thorium based third stage. The development of PFBR is, therefore, an important step towards harnessing the vast thorium reserves in the country at a later date.
- (c) Fast  Reactors  are  designed  with  several  redundant  and  diverse  safety measures:
- i. All  the  sodium systems are of welded construction of high quality. The material  used  is  stainless  steel,  which  provides  leak  before  break,  i.e. any large break of a pipeline, if it happens, will be preceded by a minor leak of sodium, which is detectable by sensitive leak detectors and the sodium from the affected line drained into storage tanks.
- ii. The  primary  sodium  system,  which  cools  the  core  directly,  is  always made with double walls. Thus, even if there is a small leak from the main wall,  it  will  be  contained  within  the  second  wall,  and  the  core  will  be

ensured  to  be  fully  submerged  in  sodium.  The  high  boiling  point  and extremely  good  thermal  conductivity  of  sodium  ensure  that  the  heat  is removed and sodium boiling and core melt are avoided.

- iii. The core cooling is always done by more than one pump, to avoid any loss of flow incident.
- iv. All reactors are provided with multiple shutdown systems operating on at least two diverse principles, which ensure that the reactor gets shutdown whenever there is an order to shutdown. The shutdown commands are automatic  or  manual.  Automatic  shutdown  is  initiated  by  the  signals derived  from  several  parameters  like  power,  global  temperature,  fuel outlet temperature, rate of rise of power etc. Manual shutdown is initiated by pressing a button.
- v. The  reactor is so designed  that  the  energy  released  due  to  an improbable core melt down is absorbed by the Reactor Vessel itself. A small quantity of sodium is likely to be ejected out from the reactor top if the  core  melts;  the  reactor  is  provided  with  a  Reactor  Containment Building  to  contain  the  ejected  sodium  and  prevent  its  release  to  the public. In sodium cooled reactors, there is no hydrogen generation in the primary  sodium  and  hence  there  is  no  risk  of  hydrogen  explosion  and associated failure of the Reactor Containment Building.
- vi. The reactors are designed with passive provisions to cool the core even if  there  is  no  pumping  of  the  coolant  as  during  a  power  failure.  Steam generators, in which there is high pressure water on one side and low pressure sodium on the other, can liberate sodium if there is a leak. The steam  generators  are  provided  with  very  sensitive  hydrogen  detectors and immediately drained both on water side and sodium side.

*****