NUCLEAR WASTE AND REMEDIATION STRATEGY Course Seminar CE 641 - PowerPoint PPT Presentation

NUCLEAR WASTE AND REMEDIATION STRATEGY Course Seminar CE 641 Presented by Aniruddh Jain Roll No: 09304018 M.Tech 1st Year

WHAT IS NUCLEAR ENERGY • Nuclear energy is the energy released by the splitting (fission) or merging together (fusion) of the nuclei of atom(s). ΔE = Δm.c ² In which ΔE = energy release Δm = mass defect c = the speed of light in a vacuum Nuclear Fusion Nuclear Fission

NUCLEAR ENERGY FACTS AND FIGURES On the morning of 6th August,1945 HIROSHIMA • A atom bomb named "Little Boy" was dropped at 8:15 am local time • Due to the bombing, 90% of the Hiroshima's buildings were either damaged or completely destroyed. • "Practically all living things, human and animal, were literally seared to death," the Japanese radio broadcaster reported. • A fireball with a radius of 200 meters was generated whose surface temperature reached about 8000 degree centigrade • DEATH TOLL 140,000 It contained 64 kg of uranium, of which 0.7 kg underwent nuclear fission, and of this mass only 0.6 g was transformed into energy. That is with a efficiency of only 1.5 % Hiroshima before and after

NUCLEAR ENERGY FACTS AND FIGURES Continued……. • On the morning of August 9, 1945 another bomb “Fat Man” was dropped on the city of Nagasaki • Death toll 80,000 Some energy equivalents • 1 ton of uranium= 10000 to 16000 tons of oil • One kilogram of uranium-235 can theoretically produce about 20 trillion joules of energy (2 × 1013 joules); as much energy as 1500 tonnes of coal. URANIUM AVAILIBILITY • about 40 times as abundant as silver • more plentiful than antimony, tin, cadmium, mercury ,and it is about as abundant as arsenic or molybdenum NAGASAKI BEFORE & AFTER

HENCE THE RACE OF POWER AND ENERGY HAS LEAD TO THE DEVELOPEMET OF NUCLEAR ENERGY AND ALONG WITH IT HAS LEAD TO THE GENERATION OF HIGHLY HAZARDOUS NUCLEAR WASTE WHICH HAS POSED A BIG QUESTION OF NUCLEAR WASTE MANAGEMENT IN FRONT OF THE DEVELOPED WORLD

TYPES OF RADIO ACTIVE WASTES Exempt waste and very low level waste • Not harmful to people or the surrounding environment • Consist mainly of demolished material (concrete, plaster, bricks, metal etc) produced during dismantling operations on nuclear industrial sites. • Therefore disposed of with domestic refuse Low level waste • Generated from hospitals & industry, as well as the nuclear fuel cycle which Contains small amounts of mostly short-lived radio activity • No shielding required • Contains only 1% of radio activity & 90% of volume of total waste Intermediate level waste • Comprises of chemical sludge and metal fuel cladding, contaminated material from reactor decommissioning • Contains 4% of radioactivity & 7% of volume of total waste High level waste • Consists of the fission product & transuranic elements generated in the reactor core • Highly radio active and requires cooling and shielding • Contains 95% of the radioactivity & 3% of volume of total waste

INTERESTING FACT 1000 MW light water reactor • Produces 200-350 cubic meter of LLW and ILW • 20 cubic meter of HLW For the same capacity plant • 400000 tones of ash is produced

MANAGING HLW FROM USED FUEL • Storage Mostly in ponds at reactor sites which are usually 7 meter deep to allow 3 meter of water over to fully shield it • Some storage is in dry casks of vaults with air circulation and the fuel is surrounded by concrete which eventually after 40-50 year has one thousand of its original radioactivity. Thus making handling easy and finally disposing it permanently • It also gives a chance to our future generation to get something out of it. • If processed it is vitrified to borosilicate glass and eventually disposed deep underground

TREATMENT AND CONDITIONING OF NUCLEAR WASTES Converting Radioactive waste materials to suitable forms for subsequent management, such as transportation, storage and final disposal Incineration • Segregation is done of combustible waste and then is incinerated at 1000º • Resulting ash undergoes cementation or Bituminization • However this technology is subject to public concern Compaction Volume Reduction technology where that is used mainly for LLW volume reduction Volume reduced upto a factor 5

TREATMENT AND CONDITIONING OF NUCLEAR WASTES Continued……. Cementation • Solid waste placed into containers is added with grout and then allowed to set. • The monolithic block is suitable for storage and disposal. • Generally used for LLW and ILW

TREATMENT AND CONDITIONING OF NUCLEAR WASTES Continued……. Vitrification • Nuclear waste here in is incorporated into molten glass (borosilicate) which is stable and insoluble. • Insitu vitrification has also been investigate as a means of “fixing” activity in contaminated ground as well as creating a barrier to prevent further spread of contamination • Use for immobilization of HLW

STORAGE AND DISPOSAL OPTIONS Near-surface disposal at ground level, or in caverns below ground level (at depths of tens of meters) • Disposal of waste with or without engineering barriers • Affected by long term climate changes • Hence typically used for LLW & ILW with a radionuclide context of short half-life( upto about 30 years)

STORAGE AND DISPOSAL OPTIONS Continued Deep geological disposal • Long time scale of radioactivity of waste led to this idea Isolations provided by a combination of engineered & natural barriers (rock, salt, clay) • A repository is comprised of mined tunnels or tunnels or caverns into which packaged waste would be placed • Some cases (e.g. wet rock) containers are surrounded by bentonite or cement to provide another barrier

DEEP GEOLOGICAL DISPOSAL Methods, Proposed sites & Case Histories Disposal in strong fractured rocks The Swedish proposed disposal concept uses a copper container with a Steel insert to contain the spent fuel. After placement in the repository About 500 m deep in the bedrock the container would be surrounded by a Bentonite clay buffer. Disposal in clay The Belgian disposal concept proposes that spent fuel and HLW is placed in high integrity steel containers and then emplaced in excavated tunnels within a ductile clay. Yucca Mountain Located in the remote Nevada desert, is the proposed site for the Construction of A US national repository to store spent fuel and high-level waste from nuclear power and military defense programmes. The repository would exist 300 meter underground in an unsaturated layer of volcanic tuff rock. Containment relies on extremely low water table which lies 300m below the repository.

Yucca Mountain

DEEP GEOLOGICAL DISPOSAL Continued…. Methods & Proposed sites & Case Histories Disposal in layered salt strata The Waste Isolation Pilot Plant in New mexico for defence transuranic Waste has been operational since 1999. For this repository natural rock salt is excavated from a several meters thick layer, sandwiched between other types of rock, 650 below ground level. The wastes placed in these excavations contain large volumes of long-lived ILW. A feature of salt Environments is the very low rate of groundwater flow and the gradual Self-sealing of the excavations due to creep of the salt.

OTHER IDEAS FOR DISPOSAL AND WHAT CAN BE THE FUTURE TRENDS Long-term above ground storage • Not currently planned to be implemented anywhere Disposal in outer space • Investigations now abandoned due to cost and potential risks of launch failure Deep boreholes Deep bore holes drilled from the surface to depths of several kilometers of diameter less than 1m. Containers would be separated from each other by a layer of bentonite or cement. The top two Km would be sealed with material such as bentonite , asphalt and concrete. Rock Melting The HLW could be placed in a deep borehole. The heat of the waste can Melt the surrounding rock which on cooling will encase the waste & thus the Waste is distributed throughout the large volume of rock.

Containers release enough heat to create a melt zone around the borehole. As the waste decays and cools, the melt zone resolidifies around the containers, entombing the waste forever. Deep Bore Hole Disposal

OTHER IDEAS FOR DISPOSAL AND WHAT CAN BE THE FUTURE TRENDS Disposal at subduction zone Where one denser section of the Earth’s crust moving towards and Underneath another lighter section. This is marked by an offshore trench. The idea for this option would be to dispose of wastes in the trench region Such that they would be drawn deep into the Earth.

Disposal at sea Has been tried in certain countries but this method is not permitted by a number of international agreements. Sub seabed disposal It is been investigated by many countries but not yet implemented . Disposal in ice sheets For this option containers of heat-generating waste would be placed in stable ice sheets such as those found in Greenland and Antarctica. The containers would melt the surrounding ice and be drawn deep into the ice sheet, where the ice would refreeze above the wastes creating a thick barrier. Direct injection Tried in USA and Russia but is not very popular