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					   Neutron and Beta/Gamma
Radiolysis of Supercritical Water
              NERI Project 02-060

      Argonne National Laboratory
              David Bartels
              Chuck Jonah
        University of Wisconsin
               Paul Wilson
              Mark Anderson
              Robert Agasie
How much Oxygen and Hydrogen
Peroxide is produced in the radiolysis
of supercritical water at various
temperatures and pressures???

Can radiolysis be suppressed by
adding hydrogen?
Water Properties
          Microheterogeneity




Tucker, S.C. and Maddox, M.W., J.Phys. Chem. B, 1998, 102, 2437.
              Electron Radiolysis

(e-)aq                                       (+ H O --> H O+ + OH)
                                                   2       3
                   +    18eV e-              +
              H2O                   H2O
                                                               3MeV e-

                                   30eV e-
              7 eV e-


                    *                 +
              H2O                 H2O                          (e-)aq


  (H + OH )



                                                  (e-)aq
                                                       +
                                                 (+ H3O --> H + H O)
                                                                  2
      Neutron Radiolysis
                  O H                       recoil ion
ca. 2 MeV                    dense track

   n              H                             p+

       fast ion
H2O               H2, O2, H2O2, HO2., OH, H, (e-)aq

       in reactor, use:
       H2 + OH                       H + H2O
       H + H2O2                      H2O + OH
       H + O2                        HO2.
       & etc.
Reaction Set for Radiolysis of Water
Apparatus for Supercritical Water
      Radiolysis Studies
    
          MAIN FEED
            TANK


                        PREHEATER



                                 SCW CELL
              PUMPS,    
              PULSE                          DETECTOR
            DAMPENERS

                                              PRESSURE
                            e-               REGULATOR

                                    COOLER
        SECONDARY
         FEED TANK                       EFFLUENT
                                        COLLECTION
     Optical Cell for Supercritical
          Water Radiolysis
                 Sapphire windows
                                       2 cm




Spring washers         Gold Gaskets   Electron Beam Access
Sample Kinetics Data --
O2 Reaction with (e-)aq
Hydrated Electron Reaction with
           Oxygen
Density dependence of several
      reactions at 380C
Ratio of H atoms to electrons formed
            in radiolysis
                       10
                            8
                            6                380º C
                            4
                                                               360-380 ºC
   GH/Ge Yield Ratio




                            2
                                                                            < 300º C
                                gas phase - room temperature
                        1
                            8
                            6

                            4


                            2


                       0.1
                          0.0          0.2        0.4      0.6         0.8         1.0
                                                 density [g/cc]
       Reaction of OH Radical with H2




Why should this “simple” reaction slow down at higher temperature?
                                                             Light-Water Radiolysis in U-2 Loop, NRU Reactor

                                                1.2x10-4                                                                    6x10-5
                                                                                     Inlet O-17




            Hydrogen Concetration in moles/kg




                                                                                                                                       Oxygen Concentration in moles/kg
                                                                                     Outlet O-17
                                                    10-4                                                                    5x10-5
                                                                                     Mixer


                                                8.0x10-5                                                                    4x10-5



                                                6.0x10-5                                                                    3x10-5

                                                              Hydrogen
                                                4.0x10-5                                                                    2x10-5



                                                2.0x10-5     Critical Hydrogen Concentration                                    10-5

                                                                                                  Oxygen

                                                      0                                                                           0
                                                      15.2         15.3       15.4           15.5          15.6   15.7   15.8

                                                                                     Time in hours


Data from NRU Reactor U-2 Loop experiment, showing slow decrease of hydrogen as
it was titrated with a slow addition of oxygen, until the sudden onset of radiolysis
indicated by the rapid appearance of oxygen (from Elliot et al. 1997). The slight
mismatch in stoichiometry between the oxygen and hydrogen arises from instrument
calibration errors, and/or loss of oxygen on pipework. The latter was frequently
observed. The temperature at the reactor outlet was 307.5°C.
                           University of Wisconsin
                          Supercritical Water Neutron
                               Radiolysis Loop

                                                                                               DAQ
      section 1              section 2                      section 3              section 4
                      Neutron shield      Heating section                                            HPLC          water
          92 cm                  48 cm                       94 cm                   89 cm           pump          reservoir
                                              Preheater




Irradiation   Graphite       Pb                      6 cm
volume        moderator      gamma/beta                                                                                H2O
                             shielding                                  Water shielding               water bath       sampling

				
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posted:9/22/2011
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