1. Reactor anti-neutrinos and neutrinos
Lin Shin-Ted
ON Behalf of TEXONO Collaboration, Institute of Physics, Academia Sinica
@NTU PSM. 18 Jan. 2006
Taiwan EXperiement On NeutrinO

2. Outline of my talk Why Reactor ? Anti-neutrinos from Reactor
Reactor operation data
The spectrum
Cross check and Uncertainty of anti-neutrino beam
Neutrinos from Reactor
How can it be produced?
M-C simulation of reactor e flux
Some physics potential of reactor neutrino experiment

3. Why Reactor ? Reactor as Electron Neutrino source.
It’s rich and under control.
e- scattering
-- to determine the Weinberg angle and possibility to observe the destructive interference term in Standard Model (at MD’s talk)
Search for and neutrino decay lifetimes
-- H.B.Li et al. TEXONO Collaboration PRL 90, (2003)
N coherent scattering (at LHB’s talk)
Explore the mixing angle
-- Dozens of international experiments ( CHOOZ et al.)

4. All require a better understanding of the reactor antineutrino spectrum

5. Reactor as anti-neutrino source
is produced by beta-decay
744 kinds of different daughter nuclei are involved in the fission.
235U
238U
239Pu
241Pu
weight
1.5%
98.0%
0.42%
0.08%
Thermal
48.5%
7.5%
36.5%
8.5%
Since the cross section of fission is higher than neutron capture on 235U as well as Pu.

6. What happens at reactor?
Probably fission? Probably NOT!
It can absorb 0.6 neutron per fission via reaction
The dash line is the spectrum
due to beta decay following neutron capture on 238U. It can provide per fission

7. Anti-Neutrino beam in KS reactor
The flux of is 6.13*10^12/cm2/s
The different isotopes spectrum and
Neutron capture on 238U
The fission rate for each isotope get from INER’s simulation

8. Cross check and monitoring on beam
Check the total thermal energy based on total fission rate from INER.
The mass of 239Pu and 241Pu increase with time, however, 235U and 238U decrease !
Monitoring the total thermal output from KS power plant.

9. Uncertainty of neutrino beam
The relation of exposure time
Above 3MeV, the antineutrino spectrum is quiet robust with exposure time during two year of irradiation.
As irradiation time goes by, the fission rate would decrease under supposing constant power.
Shortly, It’s well-control in high energy anti-neutrino spectrum(3-8MeV)
Exposure time
1:experimental result 2:Estimated spectrum
3: known 23 nuclei (exp.) 4: Estimated
Adapted by P. Vogel in PRC 24,4 1981

10. Calculation and cross check
Coordinating KS data base and get the fission rate from INER.
According the Vogel model and normalized the number of neutrino to estimate the neutrino spectrum.
Do a series of checks related to the other information
Number of Anti-neutrino check
Ntot =Nf + Nc +Nbr
Eth = Etot – Ebr – Enu + Enc Where Eth: thermal energy Etot : total fission energy Ebr : long lived fragments Enu : neutrino energy Enc : neutron capture energy

11. Structural materials of reactor Electron capture or + decay
Reactor as “ne“ Source
Fission Material
Fission Products
Neutrons
odd-odd nuclei
Structural materials of reactor
Electron capture or + decay
νe Emission
Captured
Mostly rich in neutrons
¯ Decay back to  stable valley
Anti-neutrino Emisson

12. Direct fission product Direct fission product
Source of reactor electron neutrino Z
104Tc
18m
103Tc
50s
104Ru
stable
103Ru
39d
104Rh
42s
103Rh
104Pd
－decay of
fission product n EC － N
Direct fission product
Fission products
Structure material
7E-10 -
3E-10
<3E-8
235U
Y(Z, N)×PEC
(Per fission)
1.7E-6
1.3E-5
239Pu
1E-7
1.2E-8
6.0
1.26
128I
4E-8
0.3
0.88
110Ag
1E-9
1.7
1.9
108Ag
7E-8
0.4
1.15
104Rh
<1E-5
0.2
87Sr
1.4E-5
0.005
0.53
86Rb
Y(Z, N)
PEC(%)
QEC(MeV)
Direct fission product

13. Source of reactor electron neutrino
Neutron activation
fission products
QEC(MeV) σn
(barns)
PEC(%)
Y(Z, N)
(Per fission)
Y(Z, N)×PEC
235U
239Pu
104Rh
1.15
146
0.4
3.2
6.8
1.3E-4
2.7E-4
110Ag
0.88 89
0.3
0.03
1.1
9E-7
3.3E-5
122Sb
1.62
6.2
2.2
0.012
0.043
2.6E-6
1.0E-5
128I
1.26
6.0
0.12
0.52
6.9E-5
3.1E-4

14. Source of reactor electron neutrino
Candidate isotopes:
50Cr in RC , SS & Zr-alloy;
54Fe in RC , SS & Zr-alloy;
58Ni in RC , SS& Zr-alloy;
112Sn in Zr-alloy;
In SS:
50Cr %;
54Fe --4.2%;
58Ni --6.3%;
112Sn --0%.
In RC:
50Cr %;
54Fe --0.1%;
58Ni %;
112Sn --0%.
50Cr, 54Fe, 58Ni, 112Sn
51Cr + e V + νe
55Fe + e Mn + νe
59Ni + e Co + νe
113Sn + e In + νe
activation isotopes in reactor structure material
RC 4967tons、stainless steel 1040tons、Zr-alloy 63 tons

15. Geometry description of M-C simulation
Reactor core: 624 lattices;
Fuel rod: 72 rods in each lattice;
Mass of UO2: 138 tons;
Nuclear fuel material: UO2;
enrichment of 235U : 3 %;
Height of the fuel rod: 400cm;
Radius of the fuel rod: 0.45cm;
UO2
Zr-alloy
Control rods And water

16. n-absorption: Thermal neutron capture cross-section
Simulation (MCNP) result
Fission neutrons are mostly absorbed by fuel rods and control rods;
Electron neutrino are mainly contributed by Cr-50 in control rods;
n-absorption: Thermal neutron capture cross-section
94% of the captured neutrons are thermal neutrons.
Neutrino flux at detector position
due to Cr-50 is: 5.0×108 cm-2s-1
This analysis has published by BXin et al.
(TEXONO Collaboration) in PRD 2005
51Cr + e-  51V + νe
t/mn≥1.3 s·eV－ (C.L. 68%)

17. …… Physics potential Physics potential
Can we increase the flux of the electron neutrinos emitted from a reactor ? ……
2 fuel rods replaced by Cr-50 rods …
1 fuel rod replaced by Cr-50 rods,

18. The reactor still work well
Physics potential
Physics potential
The reactor still work well
Neutrino flux can be enhanced up to 103 times

19. Number of target nuclei
Physics potential
Physics study of /Charged current with Reactor
71Ga(ne, e－)71Ge
CC event rate
target materials
isotope
Nature enrichment
（％）
Number of target nuclei
(1027)
X(ne, e－)Y
Event rate
（counts/day）
Gallium
71Ga
39.89
33.7
3.4
Indian
115In
95.7
49.9
20.8
Ytterbium
176Yb
12.7
4.3
6.64
Molybdenum
100Mo
9.63
5.8
3.64
Neutrino flux: 2×1011cm-2s-1 ;
10 tons target materials in nature;

20. Physics potential
Monitoring of unwarranted plutonium production during the reactor operation
-- an issue of paramount importance in the control of nuclear proliferation.
Maximally-loading reactor core with 51Cr sources. Event rates per 500-ton-year for the far detector L= 340m. Their achievable one sigma and sin accuracy.