Reactor anti-neutrinos and neutrinos

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

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 90,131802 (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. is produced by beta-decay 744 kinds of different daughter nuclei are involved in the fission. Reactor as anti-neutrino source Since the cross section of fission is higher than neutron capture on 235U as well as Pu.

6. What happens at reactor? • Probably fission?ProbablyNOT! • 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

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. Exposure time 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) Uncertainty of neutrino beam 1:experimental result 2:Estimated spectrum 3: known 23 nuclei (exp.) 4: Estimated Adapted by P. Vogel in PRC 24,4 1981

10. 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 Calculation and cross check Eth = Etot – Ebr – Enu + EncWhere Eth: thermal energyEtot : total fission energyEbr : long lived fragmentsEnu : neutrino energyEnc : neutron capture energy

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

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

13. Source of reactor electron neutrino Neutron activation fission products

14. Source of reactor electron neutrino Candidate isotopes: • 50Crin RC , SS & Zr-alloy; • 54Fe in RC , SS & Zr-alloy; • 58Niin 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 isotopesin 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 Control rods And water Zr-alloy

16. Simulation (MCNP) result Fission neutrons are mostly absorbed byfuel rods andcontrol rods; Electron neutrinoare mainlycontributed byCr-50 in control rods; n-absorption: Thermal neutron capture cross-section 94% of the capturedneutrons 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%)

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. Physics potential Physics potential The reactor still work well Neutrino flux can be enhanced upto103 times

19. Physics potential Physics study of /Charged current with Reactor 71Ga(ne, e－)71Ge CC event rate • Neutrino flux: 2×1011cm-2s-1 ; • 10 tons target materials in nature;

20. 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. Physics potential