Neutron production
Ulli Köster, ILL
What is a neutron ?
1. a subatomic particle
2. a matter wave
Neutrons are everywhere
13% neutrons
Bound neutrons are everywhere
45% neutrons
Carbon-12
98.9%
6 protons
6 neutrons
Carbon-13
1.1%
6 protons
7 neutrons
Big Bang Nucleosynthesis
Free neutrons have become rare
The Neutron’s Circle of Life
1. How neutrons are born
2. How neutrons are conformed to use
3. How neutrons die
4. What neutrons are good for
(except neutron scattering and nuclear spectroscopy)
How neutrons are born
1. Alpha-induced reactions: 9Be(α,n)12C +5.7 MeV
How neutrons are born
1. Alpha-induced reactions: 9Be(α,n)12C +5.7 MeV
2. Deuteron fusion: d(d,n)3He +3.3 MeV, t(d,n)4He +17.6 MeV
How neutrons are born
1. Alpha-induced reactions: 9Be(α,n)12C +5.7 MeV
2. Deuteron fusion: d(d,n)3He +3.3 MeV, t(d,n)4He +17.6 MeV
3. Photo-dissociation: 9Be(γγ ,n)2α -1.66 MeV
How neutrons are born
1. Alpha-induced reactions: 9Be(α,n)12C +5.7 MeV
2. Deuteron fusion: d(d,n)3He +3.3 MeV, t(d,n)4He +17.6 MeV
3. Photo-dissociation: 9Be(γγ ,n)2α -1.66 MeV
4. Spontaneous fission:
252Cf(sf)134Te+115Pd+3n
+212 MeV
How neutrons are born
1. Alpha-induced reactions: 9Be(α,n)12C +5.7 MeV
2. Deuteron fusion: d(d,n)3He +3.3 MeV, t(d,n)4He +17.6 MeV
3. Photo-dissociation: 9Be(γγ ,n)2α -1.66 MeV
4. Spontaneous fission:
252Cf(sf)134Te+115Pd+3n
5. Neutron-induced fission:
+212 MeV
235U(n,f)134Te+99Zr+3n
+185 MeV
γp
np
n th
How neutrons are born
1. Alpha-induced reactions: 9Be(α,n)12C +5.7 MeV
2. Deuteron fusion: d(d,n)3He +3.3 MeV, t(d,n)4He +17.6 MeV
3. Photo-dissociation: 9Be(γγ ,n)2α -1.66 MeV
4. Spontaneous fission:
252Cf(sf)134Te+115Pd+3n
5. Neutron-induced fission:
6. Beta-delayed n emission:
+212 MeV
235U(n,f)134Te+99Zr+3n
+185 MeV
87Br(β- )87Kr*→
→ 86Kr+n +1.3
MeV
How neutrons are born
1. Alpha-induced reactions: 9Be(α,n)12C +5.7 MeV
2. Deuteron fusion: d(d,n)3He +3.3 MeV, t(d,n)4He +17.6 MeV
3. Photo-dissociation: 9Be(γγ ,n)2α -1.66 MeV
4. Spontaneous fission:
252Cf(sf)134Te+115Pd+3n
5. Neutron-induced fission:
235U(n,f)134Te+99Zr+3n
6. Beta-delayed n emission:
7. Spallation:
208Pb(p,3p
20n)185Au -173 MeV
+
200
Fr
1.4 GeV p
fragmentation
+
238
11
U
Li
+
X
fission
n
p
+
144
Ba
+
92
Kr
+185 MeV
87Br(β- )87Kr*→
→ 86Kr+n +1.3
High energy nuclear reactions
spallation
+212 MeV
MeV
Spallation + Fragmentation + Fission
W. Wlazło et al., Phys. Rev. Lett. 84 (2000) 5736.
T. Enqvist et al., Nucl. Phys. A 686 (2001) 481.
How neutrons are born
1. Alpha-induced reactions: 9Be(α,n)12C +5.7 MeV
2. Deuteron fusion: d(d,n)3He +3.3 MeV, t(d,n)4He +17.6 MeV
3. Photo-dissociation: 9Be(γγ ,n)2α -1.66 MeV
4. Spontaneous fission:
252Cf(sf)134Te+115Pd+3n
5. Neutron-induced fission:
6. Beta-delayed n emission:
7. Spallation:
208Pb(p,3p
+212 MeV
235U(n,f)134Te+99Zr+3n
+185 MeV
87Br(β- )87Kr*→
→ 86Kr+n +1.3
20n)185Au -173 MeV
MeV
A nuclear chain reaction
A single-pulse neutron source
Uncontrolled
chain reaction
of fast-neutron
induced fission
≈25 kg of 93% 235U
235U(n,f)
cross-section as function of energy
Moderation
A controlled nuclear chain reaction
using thermal neutron induced fission
1. Moderate neutrons
2. Control neutron
losses
40*2.5 = 100
100
103
98
89
85
40
80
neutron numbers are given for a typical PWR reactor
≈0.6% of fission neutrons are beta-delayed by 12 s on average
⇒slows down reactor kinetics (∆k = 0.001) from ≈0.05 s to ≈80 s
⇒ essential for reliable control of reactor power
40*2.5 = 100
100
103
98
89
85
40
80
Research reactor
Components of a nuclear reactor
1. Fuel
2. Moderator
3. Control rods
4. Coolant
5. Pressure vessel
6. Containment
7. Steam generator (for power plants) or
experimental facilities (for research reactors)
Moderator
elastic collisions with light atoms (mass A):
average energy loss En+1 - En = 2 En A/(A+1)2
ln(En) – ln(En+1) = ξ = 1 – (A-1)2/(2A) * ln[(A+1)/(A-1)]
Moderating power:
Moderating ratio:
Light water (H2O)
Heavy water (D2O)
Beryllium (Be)
Graphite (C)
Polyethylene (CH2)x
ξΣ scatter
1.28
0.18
0.16
0.064
3.26
ξΣ scatter/Σ abs.
58
21000
130
200
122
The first nuclear reactor on Earth
Isotopic abundance
100.0%
10.0%
1.0%
235U
238U
0.1%
-5000
-4000
-3000
-2000
Time before now (My)
Choice of coolant
coolant = moderator
⇒ passive regulation
⇒ intrinsic safety
RBMK:
graphite moderator
water cooling
⇒ positive void
coefficient !
-1000
0
RHF fuel element
8.6 kg 235U, 93% enriched
27
8 December 1987: Intermediate-Range Nuclear Forces Treaty
1 warhead = 25 kg HEU = 3 fuel elements for ILL
The ILL reactor contributes to permanent disarmament!
The reactor core and vessel
Fuel element :
-Ri = 14 cm
-Re = 19 cm
Vessel:
- R = 125 cm
Beam tubes :
-13 Horizontal
-4 inclined
Sources
-VCS
-HCS
-HS
BD : 25 janv ier 2008
Some comments on recent events…
Reactor fuel elements = 1st barrier
pencil
assembly
UO2 pellets
2nd barrier: primary cooling circuit
3rd barrier: containment
Thermal neutron induced fission
Nuclear decay heat
Fukushima 2 and 3: 784 MWe, 2300 MWth
150 MW
35
9
5 3
Nuclear decay heat
ILL: 57 MWth
3.7 MW
0.9
0.2 0.1
Decay heat can be passively cooled by natural convection!
Secondary reactions
Safety features of the ILL reactor
Double safety hull with
ventilation and filtration
Hydrogen
recombination
Water reservoir
inside hull
Redundance
Safety features of Generation 3+ reactors (EPR)
Molten core
catcher area
Double safety hull with
ventilation and filtration
Heat
removal
system
Hydrogen
recombination
Water reservoir inside hull
Redundance:4
individual
systems
Power reactor
⇔
Research reactor
• heat used to produce
• neutrons used for
electricity
applications
• neutrons just to maintain • heat not used
chain reaction
• needs high power,
high temperature and
high pressure for good
thermal efficiency
• BWR: 75 bar, 285°C
• PWR: 155 bar, 315°C
• operates at lower power,
low temperature (ILL 30-48°C)
and low pressure (<14 bar)
• vessel and all inserts made
from pure Al-alloy
• 25 cm thick steel
pressure vessel ⇒
• modular and exchangeable
defines lifetime (40..60 y)
⇒ no finite lifetime
ILL: Replacement of the reactor vessel 1990-94
ILL: Replacement of the reactor vessel 1990-94
The risk profile of power versus research reactors
ILL reactor
Power reactor
Tav erage=39 °C
p: few bar
Spallation neutron source versus reactor
Advantage for reactor
• higher time-averaged flux (for high-flux reactor)
• flux very constant over time
• larger irradiation volume possible (multiple fuel elements)
• much lower electricity bill
Advantage for spallation neutron source
• pulsed operation much easier
• much higher peak flux for TOF applications
• does not carry “reactor” in its name
Urban legend:
“Reactors are dirty, spallation neutron sources are clean.”
Back to physics:
the neutron as a tool to study fission
LOHENGRIN Setup
Experimental setup (straight beam)
Experimental setup (bent beam)
RED Magnet
Target position
Condenser
Reactor wall
Reactor core
Introduction of new target
Light water pool
Main magnet
Heavy water vessel
Container for used targets
Neutron tomography beamline
1m
11Li
production in thermal neutron induced fission?
235U
+ n ⇒
11Li
+
140Xe
+
85Br
+
85
A
235
+
1
=
11
+
140
Z
92
+
0
=
3
+
54
∆M (MeV)
40.919
8.071
40.801
-72.990
+
35
-78.610
Q (MeV) = (40.919 + 8.071) – (40.801 – 72.990 – 78.610) = +159.8
Detection of rare ternary particles
Exotic!???
Exotic
1013 per s produced
worldwide in nuclear
power plants!
2·10-10 per fission
Neutron (particle) physics:
the neutron as an object
Neutron Decay
• clean semi-leptonic decay
νe
p(udu)
W
• clear theoretical understanding:
only 3 free parameters in
Standard Model
• ratio of coupling constants
• and its phase
• Quark mixing from the
Cabibbo-Kobayashi-Maskawa matrix
n(udd)
τ −1 ∝ Vud (1 + 3λ2 )
2
λ=
gA
gV
Vud
Ideal system for precision measurements
e-
Why is neutron-decay important?
neutron-decay provides key input for many disciplines:
astrophysics, cosmology and particle physics
From cold to ultracold neutrons
Ultracold neutrons
nuclei in surface
T ≈ 2 mK
E ≈ 100 neV
v ≈ 5 m/s
λ ≈ 1000 Å
neutron
Typically:
99.99 % - elastic reflection
0.009% - inelastic scattering
to the thermal energy range
0.001% - absorption
UCN
Total reflection under any angle on suitable materials
like Be, Ni, C ⇒ possibility to store for long time
The UCN facility PF2 at ILL
Neutron turbine
A. Steyerl (TUM - 1985)
Vertical guide tube
Cold source
Reactor core
56
Measurements of the neutron lifetime τn
exponential decaylaw : N = N0e−λt
or, ultimately, measure the exponential decay directly
Storage experiments w ith UCN
Beam experiments w ith cold neutrons
“counting the surviving neutrons”
“ UCN bottle”
“counting the dead neutrons”
1
1
N (t 1 )
=
⋅ ln
τm t 2 - t 1
N( t2)
N(t 21 )
e
l
nβ
1
1
1
1
1
= +
+
+
+ ...
τm τβ τ wall τ leak τvacuum
0 (experiment)
1
τ wall
= µ ⋅ v eff
0 (extrapolation)
N0
1
1
=
τm τβ
l
nβ =
Two relative measurements
dN
N − v⋅τ
=− 0e n
dt
τn
Two absolute measurements
A “typical” UCN storage experiment at ILL – MamBo I
Glass w alls:
H=0.3 m, W=0.4 m
L=0.5m … 0.01 m
(surface A and volume V sizeable)
1
1
1
= +
+ ...
τ m τβ τ wall
τ wall → number of wall collisions,
i.e. mean free path λ
Measure storage lifetime τst
for different volume to surface ratios V/A
and extrapolate for V
∞
1
τ wall
→0
“GRAVITRAP” Neutron Lifetime Experiment
at the PF2/MAM beam position in the ILL
6σ
P. Geltenbort
878.5(8) s
60
Magnetic confinement
• For µ n = -60.3 neV/T, a 2T field generates a 120 neV barrier.
• Force due to field gradient, F = -µ (dB/dz), repels only one spin state.
• Use permanent magnets.
• Step 3: 3D confinem ent
• Step 1: 1D confinem ent
- top (gravity)
- bottom (magnetic shutter)
1 – permanent magnets
2 – magnetic poles
• Step 2: 2D confinem ent
UCN: Particle physics with “human dimensions”
Speed: some m/s
Jumps up to 2.5 m high
Magnetic field:
1 T may repel
UCN 0.6 m high
≈ 10 min half-life
≈ 15 min lifetime
Scales of temperature and energy in neutron physics
Ultra cold
nanoparticles
20 nK
10-12
Cold
moderators
10-3
? 1 3
10 10
10-7
10-3 10-1
VUCN
Reactor
moderators
Temperature, K
107
Neutron energy, eV
Fission
Quantum states of neutrons in the
Earth’s gravitational field
Neutrons as a tool for medicine
The Nuclear Medicine Alphabet
SPECT
Camera
PET-Scanner
β+
γ
Auger-e-
α
β-
Cancer and efficiency of treatments
At time of diagnosis
Diagnosed
Cured by:
Surgery
Radiation therapy
Surgery+radiation therapy
All other treatments and
combinations incl.
chemotherapy
Fraction cured
Primary
With
tumor metastases
58%
42%
Total
100%
22%
12%
6%
5%
69%
12%
45%
Over one million deaths per year from cancer in EU.
⇒ improve early diagnosis
⇒ improve systemic treatments
Immunology approach
Target
(antigen)
Antibody
Roelf Valkema, EANM-2008.
Multidisciplinary collaboration
to fight cancer
Target
Peptide,
antibody,
etc.
Linker
Receptor
Radionuclide
Immunology
Structural biology
Coordination
chemistry
Nuclear physics
and
radiochemistry
Nuclear medicine and medical physics
1,4,7,10-tetraazacyclododecantetraacetate
Helmut Maecke, EANM-2007.
Roelf Valkema, EANM-2008.
Lymphoma therapy: RITUXIMAB+177Lu
F. Forrer et al., J Nucl Med 2013;54:1045.
Alternative production route to
177Lu
• Free of long-lived isomer
• Non-carrier-added quality
• “Needs” high-flux reactor
The rising star
for therapy
Acknowledgements
Thanks for transparencies from:
Hartmut Abele
Roger Brissot
Bruno Desbriere
Peter Geltenbort
Bastian Maerkisch
Valery Nesvishevsky
Anatoli Serebrov
Oliver Zimmer