sep.21 2007, oslo, norwayy. kadi1 cern, switzerland 20-21 september 2007, nuclear risks - safety and...

Sep.21 2007, Oslo, Norway Y. Kadi 1

Y. KadiCERN, Switzerland

20-21 September 2007, Nuclear Risks - Safety and Security, Oslo, Norway

From Waste to Value :Accelerator-based Inherently Safe Nuclear

Power


A new primary energy source

By 2050, the world’s consumption (+ 2%/y) should reach 34 TW, of which 20 TW should come from new energy sources: A major innovation is needed in order to replace the expected “decay” of the traditional energy sources!

This implies a strong R&D effort, which is the only hope to solve the energy problem on the long term. This R&D should not exclude any direction a priori! Renewables Nuclear (fission and fusion) Use of hydrogen

Can nuclear energy play a major role?

Nuclear energy has the potential to satisfy the demand for a long time (at least 15 centuries for fission, essentially infinite for fusion if it ever works), and is obviously appealing from the point of view of atmospheric emissions.


Which type of nuclear energy?

Nuclear fusion energy: not yet proven to be practical. Conceptual level not reached (magnetic or inertial confinement?). ITER a step, hopefully in the right direction.

Nuclear fission energy: well understood, and the technology exists, with a long (≥ 50 years) experience, however, present scheme has its own problems:

• Military proliferation (production and extraction of plutonium);

• Possibility of accidents (Chernobyl [1986]; Three Mile island [1979]);

• Waste management. However, it is not given by Nature, that the way we use

nuclear fission energy today is the only and best way to do it. One should rather ask the question:Could nuclear fission be exploited in a way that is acceptable to Society?

To answer this question, Scientists around the world have carried out, since the 1990’s, an extensive experimental programme which has led to a conceptual design of a new type of nuclear fission system, driven by a proton accelerator, with very attractive properties.


Historical Background

The idea of producing neutrons by spallation with an accelerator has been around for a long time:

In 1950, Ernest O. Lawrence at Berkeley proposed to produce plutonium from depleted uranium at Oak Ridge. The Material Testing Accelerator (MTA) project was abandoned in 1954.

In 1952, W. B. Lewis in Canada proposed to use an accelerator to produce 233U from thorium, in an attempt to close the fuel cycle for CANDU type reactors.

Concept of accelerator breeder : exploiting the spallation process to breed fissile material directly soon abandoned.

Ip ≈ 300 mA

Renewed interest in the 1980's and beginning of the 1990's, in particular in Japan (OMEGA project at Japan Atomic Energy Research Institute), in the US (Hiroshi Takahashi et al. proposal of a fast neutron hybrid system at Brookhaven for minor actinide transmutation and Charles Bowman a thermal neutron molten salt system based on the thorium cycle at Los Alamos), and in Europe (SPIN program at the French-CEA).


Transmutation of nuclear waste

Direct use of spallation neutrons ?

E fp=qfp⋅Epηsp

⋅1

ηbηT[MeV]

Where : qfp = fraction of FP to be transmuted (99Tc, 129I, 135Cs, 90Sr, 85Kr and 93Zr ≈ 28%)

Ep = incident proton energy (1000 MeV)sp = spallation neutron yield (≈ 30 for Pb target)b = electrical efficiency for accelerating protons (≈ 50%)T = thermal efficiency (≈ 33%)

E fp=0.28×100030

×1

0.5×0.33≈60 MeV

This would represent 60/200 ≈ 30% of the total fission energy produce not economical !


Basic Principle of Energy Amplifier Systems

One way to obtain intense neutron sources is to use a hybrid sub-critical reactor-accelerator system called Accelerator-Driven System:

The accelerator bombards a target with high-energy protons which produces a very intense neutron source through the spallation process.

These neutrons can consequently be multiplied (fission and n,xn) in the sub-critical core which surrounds the spallation target.


Neutron Multiplication

In and ADS ?

Pfi =η fp⋅ϕ∗⋅kν(1−k)

⋅iC

⋅E f

Where : k = neutron multiplication factor* = source importance (≈ 1.5) = neutrons emitted per fission (≈ 2.5)Ef = energy generated per fission (≈ 3.1x10-10 W)i = accelerator currentC = charge of a proton (= 1.6x10-19 C)

E fp=ηsp⋅

kν(1−k)

⋅E f −Ep

ηb ⋅ηT

ηsp (1−k)⋅η fp+k

(1−k)⋅ (1−

kν

)⋅η fp−qfpν

⎛

⎝ ⎜

⎞

⎠ ⎟

⎡

⎣ ⎢

⎤

⎦ ⎥

In order for the process to be self-sufficient

k≥1

1+ηsp⋅ηb ⋅ηT ⋅E f

ν ⋅Ep

≈0.7


The FEAT experiment

3.6 tons of natural uranium


Main FEAT results


Physics of Sub-Critical Systems


Advantages of Sub-Critical Systems

1. EAs operate in a non self-sustained chain reaction mode

minimises criticality and power excursions

• EAs are operated in a sub-critical mode stays sub-critical whether

accelerator is on or off extra level of safety against

criticality accidents

1. The accelerator provides a control mechanism for sub-critical systems

more convenient than control rods in critical reactor

safety concerns, neutron economy

1. EAs accept fuels that would not be acceptable in critical reactors

Minor Actinides High Pu content LLFF...

1. EAs operate in a non self-sustained chain reaction mode

minimises criticality and power excursions

• EAs are operated in a sub-critical mode stays sub-critical whether

accelerator is on or off extra level of safety against

criticality accidents

1. The accelerator provides a control mechanism for sub-critical systems

more convenient than control rods in critical reactor

safety concerns, neutron economy

1. EAs accept fuels that would not be acceptable in critical reactors

Minor Actinides High Pu content LLFF...

Figure extracted from C. Rubbia et al., CERN/AT/95-53 9 (ET) showing the effect of a rapid reactivity insertion in the Energy Amplifier for two values of subcriticality (0.98 and 0.96), compared with a Fast Breeder Critical Reactor.

2.5 $ (k/k ~ 6.510–3) of reactivity change corresponds to the sudden extraction of all control rods from the reactor.

There is a spectacular difference between a critical reactor and an EA (reactivity in $ = /; = (k–1)/k) :


Energy Amplifiers vs Critical Reactors

Main objective is to reduce the production of nuclear waste (TRU)

Energy Amplifier : sub-critical fast neutrons Thorium + 233U +TRU (Pu + Minor Actinides)

Reactor : critical slow neutrons Uranium + Pu


Fast neutrons and high burn-up

Fast neutrons allow a more efficient use of the fuel by allowing an extended burnup

Fast neutrons allow a more efficient use of the fuel by allowing an extended burnup


Evolution of radiotoxicity of nuclear waste

TRU constitute by far the main waste problem [long lifetime – reactivity]. The system should be optimized to destroy TRU. Same as optimizing for a system that minimises TRU production. Interesting for energy production!

Typically 250kg of TRU and 830 kg of FF per Gwe


Nuclear waste:

TRU:(1.1%)produced by neutron capture;dominated by plutonium: destroy them through fission

235U 236U 237U 238U 239U 240U

237Np 238Np 239Np 240Np

238Pu 239Pu 240Pu 241Pu 242Pu 243Pu

241Am

243Am

6.75 d 23.5 mn 14.1 h

2.12 d 2.35 d 61.9 mn(7.2 mn)

14.3 yr 4.96 h

582 15

2100

78 742 1100 200

3

98.3 5.11 440 2.75 22

180 2.75 68

540 269 290 380 18.5 90

242Am

580 74

γγ

γ γ90Br 90Kr 90Rb 90Sr 90Y

143Xe 143Cs 143Ba 143La 143Ce 143Pr

γ β− β−

(neutron)

Fission Fragments

Gamma Radiation

Stable

Stable

235U

γ β− γ β− γ β− γ β−

143Nd

γ β− β−γ β− γ β− γ β−

90Zr

n

n

n

n

0.3 s 1.78 s 14.33 s 14.2 mn 33 h 13.57 d

1.92 s 32.32 s 2.63 mn 28.78 y 64.1 h

Fission Fragments:(4%)the results of fissions transform them into stable elements through neutron captureNote:

thermal fission resilient element

s

Note: thermal fission resilient element

s

The strategy consists in using the hardest possible neutron flux, so that all actinides can fission instead of accumulating as waste.


Principle of LLFP destruction


Experimental Setup


TARC Results (2)


Energy Amplifiers vs Critical Reactors

Main objective is to reduce the production of nuclear waste (TRU)

Energy Amplifier : sub-critical fast neutrons Thorium + 233U +TRU (Pu + Minor Actinides)

Reactor : critical slow neutrons Uranium + Pu


Radiotoxicity

The radiotoxicity of spent fuel reaches the level of coal ashes after only 500 years, and is similar to what is predicted for future hypothetical fusion systems


General Features of Energy Amplifier Systems

Subcritical system driven by a proton accelerator:

Fast neutrons (to fission all transuranic elements) Fuel cycle based on thorium (minimisation of nuclear waste) Lead as target to produce neutrons through spallation, as neutron moderator and as heat carrier Deterministic safety with passive safety elements (protection against core melt down and beam window failure)


Detailed Features of Energy Amplifier Systems


R&D Activity in Europe

Vast R&D activity in Europe over last 10 years: 12 countries, 43 institutions

EU 31 MEuros

Member States 100 MEuros

Vast R&D activity in Europe over last 10 years: 12 countries, 43 institutions

EU 31 MEuros

Member States 100 MEuros


In FP5, a complementory combination of test facilities was set up in Europe.

EUROTRANS is

fully using these test facilities.

STELLA LoopCEA

CIRCE LoopENEA

TALL LoopKTH

CIRCO LoopCIEMAT

CorrWett LoopPSI

VICE LoopSCK-CEN

CHEOPE LoopENEA

DEMETRA: Test Facilities


Gelina @ Geel (UE-Belgium)

GSI @ Darmstadt (Germany)

Cyclotron @ Uppsala (Sweden)

nTOF @ CERN (Switzerland)and its TAS γ-calorimeter

Neutron capture (n,γ) resonances in one actinide

NUDATA: Experimental Facilities


F. G

roes

chel

et a

l. (P

SI)

MEGAPIE Project at PSI

0.59 GeV proton beam

1.3 MW beam power Goals: Demonstrate

feasablility One year service

life Operating since

August 2006

Proton Beam

MEGAPIE TARGET


80 MW LBE-cooled XADS80 MW LBE-cooled XADS 80 MW Gas-cooled XADS80 MW Gas-cooled XADS 50 MW LBE-cooled XADS 50 MW LBE-cooled XADS ((MYRRHA) MYRRHA)

The eXperimental Accelerator-Driven System (XADS) in the 5° FP of the EU


Worldwide ProgramsProject Neutron Source Core Purpose

FEAT(CERN)

Proton (0.6 to 2.75 GeV)(~1010p/s)

Thermal(≈ 1 W)

Reactor physics of thermal subcritical system (k≈0.9) with spallation source

TARC(CERN)

Proton (1.5 & 2.75 GeV)(~1010p/s)

Fast(≈ 1 W)

Lead slowing down spectrometry and transmutation of LLFP

MUSE(France)

DT(~1010n/s)

Fast(< 1 kW)

Reactor physics of fast subcritical system

YALINA(Belorus)

DT(~1010n/s)

Fast(< 1 kW)

Reactor physics of thermal & fast subcritical system

MEGAPIE(Switzerland)

Proton (600 MeV)+ Pb-Bi (1MW)

----- Demonstration of 1MW target for short period

TRADE(Italy)

Proton (140 MeV)+ Ta (40 kW)

Thermal(200 kW)

Demonstration of ADS with thermal feedback

TEF-P(Japan)

Proton (600 MeV)+ Pb-Bi (10W, ~1012n/s)

Fast(< 1 kW)

Coupling of fast subcritical system with spallation source including MA fueled configuration

SAD(Russia)

Proton (660 MeV)+ Pb-Bi (1 kW)

Fast(20 kW)

Coupling of fast subcritical system with spallation source

TEF-T(Japan)

Proton (600 MeV)+ Pb-Bi (200 kW)

-----Dedicated facility for demonstration and accumulation of material data base for long term

MYRRHA(Belgium)

Proton (350 MeV)+ Pb-Bi (1.75 MW)

Fast(35 MW)

Experimental ADS

EADF(Europe)

Proton (600 MeV)+ Pb-Bi (4-5 MW)

Fast(100-300 MW)

Prototype Energy Amplifier

Reference EAProton ( ≈ 1 GeV)+ Pb-Bi (≈ 10 MW)

Fast(1500 MW)

Energy Production & Transmutation of MA and LLFP


Conclusions

Can atomic power be green ? Physics suggests it can !!

Present accelerator technology can provide a suitable proton accelerator to drive new types of nuclear systems to destroy nuclear waste (including nuclear weapons) and/or to produce energy.

An Energy Amplifier could destroy TRU through fission at about x4 the rate at which they are produced in LWRs. LLFF such as 129I and 99Tc could be transmuted into stable elements in a parasitic mode, around the EA core, making use of the ARC method.

Next step: DEMO ? when ? where ?

sep.21 2007, oslo, norwayy. kadi1 cern, switzerland 20-21 september 2007, nuclear risks - safety and...

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