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Nuclear Waste Management

The optimism of the 1950s in nuclear power foresaw two things: 1. nuclear power would provide nearly limitless, inexpensive energy, and 2. technological advances would solve the problem of nuclear waste and other risks.

Nuclear fission

Needless to say, neither of these has been achieved: far from it: 1. Nuclear power never produced more than 5% of world electricity, and is one of the most expensive forms of energy, and 2. technology has not done very much to alleviate the burden of half a million tonnes of useless waste, leaving the world with a dangerous, hard to manage legacy for thousands of years.

After more than half a century, a stockpile of political, economic and environmental liabilities have accumulated to mountainous dimensions.

Here is a brief overview of the current situation with regards radioactive waste management:

Types of Waste

High-Level Radioactive Waste

There are 7 long-lived radio-isotopes in spent nuclear fuel: selenium-79, zirconium-93, technetium-99, palladium-107, tin-126, iodine-129, and caesium-135.

IsotopeHalf-life /MyDecay modeDecay energy /MeVDecay productYield (U-235) /%Note
${\table {79};{34}}$Se0.327 $^{*1}$$β^{-}$0.15${\table {79};{35}}$Br0.045bio-accumulating with nitrate
${\table {93};{40}}$Zr1.53$β^{-}$ γ0.091${\table {93};{41}}$Nb5.46low soil mobility, suitable for geological storage
${\table {99};{43}}$Tc0.211$β^{-}$0.294${\table {99};{44}}$Ru6.14environmentally mobile, significant component of nuclear waste, may be transmuted artificially
${\table {107};{46}}$Pd6.5$β^{-}$0.033${\table {107};{47}}$Ag1.25not amenable to disposal by nuclear transmutation, less environmentally mobile I and Tc
${\table {126};{50}}$Sn0.230$β^{-}$ γ4.050${\table {126};{51}}$Sb0.108gamma emitted from decay product (antinomy-126)
${\table {129};{53}}$I15.7$β^{-}$ γ0.194${\table {129};{54}}$Xe0.841high long-term risk since environmentally mobile and long-lived, potential for transmutation (neutron bombardment or lasers) under study
${\table {135};{55}}$Cs2.3$β^{-}$0.269${\table {135};{56}}$Ba6.911disposal by nuclear transmutation difficult, intense medium-term radiation

$^{*1}$ Uncertainty in the half-life of Selenium-79 gives measurements/estimates in the range $6.5 × 10^4$ to $1.13 × 10^6$ years.

Fuel Types

RGPu = reactor grade plutonium; WGPu = weapons-grade plutonium; MOX = Mixed Oxide Fuel

Fuel$t_{1/2}$Source
Pu-239weapons, enriched U-238
U-235enriched natural uranium ore
U-233Thorium

Two systems are proposed for handling waste from muclear fission in reactors: geological storage and transmutation.

Transmutation

An example of transmutation is the conversion of technetium-99c. The target is bombarded with neutrons to create the isotope technetium-100Tc, which ahas a very short half-life, decaying to the non-radioactive ruthenium-100.

Storage

The fuel in a nuclear reactor core generates heat from the chain reaction of neutrons from one fission event striking other nuclei, which in turn undergo fission, generating neutrons, which strike other nuclei... and so on, millions of times per second.

When a nuclear reactor is shut down, the fuel rods are removed and placed in a temporary storage tank, under water. The water cools the rods and absorbs the neutrons which are still leaving the uranium or plutonium fuel. Although the chain reaction has ceased, since most of the neutrons are being absorbed by the water, and not reaching the nuclei of other uranium atoms, there is still a fair amount of heat being produced by the beta decay of the fission products in the fuel, as they go through a reaction chain, forming a series of unstable isotopes, till a stable isotope.

This decay heat is initially 7% of the chain reaction energy, and within a day is only 4%. The rate of heat generation slowly decreases over time. Although compared to the reactor chain reaction heat, the fuel rods need to be kept for a matter of years before it is ready to be placed in more permanent storage.

Globally, by 2020 445 kt (approx. 20 000 $m^3$) of spent fuel (IAEA estimate). Storage is so far only in temporary water tanks, but storage capacity is exhausted.

Intermediate Storage

Mismanagement and Disasters:

From the first commercial nuclear power station at Calder Hill, north-east England, 1956, till the 1990s, more than 100,000 tonnes of radioactive waste was simply dumped at sea.

Long-term storage

Risks and Solutions

EU Regulations

EU wanted to pass a directive obliging member states to identify a permanent repository site by 2008, and have it operational by 2018. The Directive was turned down by pressure.

France, Belgium, Germany and Switzerland are researching deep storage. Sweden and Finnland are expected to have their sites ready by 2017 and 2020.

Sweden is testing techniques at its Äspö Hard Rock Laboratory, at Öskarshamm.

Vienna Joint Convention on Radioactive Waste, 1997

Download: Vienna Joint Convention (1997) full text - English (pdf 67 kB)

Full name: Joint Convention on the Safety of Spent Fuel Management and on the Safety of Radioactive Waste Management

German Nuclear Waste Plan

Reference: Gesetz über die friedliche Verwendung der Kernenergie und den Schutz gegen ihre Gefahren (Atomgesetz), Absatz 2c: Nationales Entsorgungsprogramm

Absatz 2d: Grundsätze der nuklearen Entsorgung

Switzerland Nuclear Waste plan

France

Eastern Europe Legacy

UK

Sellafield: Reprocessing at Dounreay creates potentially dangerous stock of purified HEU.

USA

The US has strict restrictions on the export of HEU, and in 1993 reneged on a promise to retake HEU when it has been spent in research reactors around the world.

In 1983, Yucca Mountain, Nevada, 150 km north-east of Las Vegas, was nominated as the permanent respository site. US Senate overrode state veto. However, in 2005 the DOE (dept. of Energy) discovered that a USGS (US Geological Survey) hydrologist had fabricated data about water flows through Yucca Mountain, chosen for its dryness.

Content © Andrew Bone. All rights reserved. Created : September 2, 2015 Last updated :January 15, 2016

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