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 http://hepmail.phys.sinica.edu.tw/~texono/

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

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 90,131802 (2003) N coherent scattering (at LHB’s talk) Explore the mixing angle -- Dozens of international experiments ( CHOOZ et al.)

All require a better understanding of the reactor antineutrino spectrum

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.

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 2 per fission

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

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.

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

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

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

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

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

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 --0.95%; 54Fe --4.2%; 58Ni --6.3%; 112Sn --0%. In RC: 50Cr --0.01%; 54Fe --0.1%; 58Ni --0.63%; 112Sn --0%. 50Cr, 54Fe, 58Ni, 112Sn 51Cr + e- 51V + νe 55Fe + e- 55Mn + νe 59Ni + e- 59Co + νe 113Sn + e- 113In + νe activation isotopes in reactor structure material RC 4967tons、stainless steel 1040tons、Zr-alloy 63 tons

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

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－1 (C.L. 68%)

…… 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,

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

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;

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 sin2 accuracy.