Water Radiolysis Issues T. Sekiguchi 2019. 10. 24 Contents 2 - - PowerPoint PPT Presentation

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Water Radiolysis Issues T. Sekiguchi 2019. 10. 24 Contents 2 - - PowerPoint PPT Presentation

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Water Radiolysis Issues T. Sekiguchi 2019. 10. 24 Contents 2 Water radiolysis Hydrogen recombination system Operation status Issues Summary October 24, 2019 11th Workshop on Neutrino Beam and Instrumentation (NBI2019)

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SLIDE 1

Water Radiolysis Issues

  • T. Sekiguchi
  • 2019. 10. 24
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SLIDE 2

October 24, 2019 11th Workshop on Neutrino Beam and Instrumentation (NBI2019)

Contents

  • Water radiolysis
  • Hydrogen recombination system
  • Operation status
  • Issues
  • Summary

2

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SLIDE 3

October 24, 2019 11th Workshop on Neutrino Beam and Instrumentation (NBI2019)

Horn Cooling Water System

  • Water cooling of horn conductors
  • Water spray onto IC ⇒ collected in drain tank ⇒ pump up
  • Two independent pumps for water circulation
  • Water supply pump
  • Water suction pump @ 7~8 m above horns
  • Supply and suction flow rates are balanced manually

3

inner conductor

  • uter

conductor Drain tank Pump up

Buffer tank Pump Suction pump He vessel Height ~8m Service Pit Machine Room H2O He

He gas line

He

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SLIDE 4

October 24, 2019 11th Workshop on Neutrino Beam and Instrumentation (NBI2019)

Horn Operation History

4 Recovery from Big Earthquake Horn replacement Target He pipe replacement

3.52s 3.2s →3.04s 2.56s 2.48s 2.48s 2.48s 2.48s

0.2

0.2x107 0.5x107 0.8x107 1.2x107 0.8x107 0.5x107 0.1x107 1st-gen. horns 2nd-gen. horns

Hydrogen problem (2010.Mar) Corrosion problem (2012.Jun) Water drop problem (2012.Oct) Power supply problem (2011.Dec)

Cycle

Neutral grounding problem (2014.Oct) Neutral grounding problem (2016.Feb.&Apr.)

1020

2.48s 1.3x107 1.7x107

Hydrogen problem (2017.Oct) Water drop problem (2018.Mar) Capacitor problem (2017.Mar)

2.48s # horn pulse

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SLIDE 5

Water Radiolysis

  • Beam exposure to horn cooling water produces hydrogen gas
  • Water radiolysis
  • Ionization and excitation of H2O molecule by beam exposure
  • Primary products：eaq-, OH, H, H2, H2O2 ⇒ Final products : H2, O2, H2O2
  • Production ratio : H2, O2, H2O2 = 1.3 : 0.1 : 0.99 ⇒ very small O2 production
  • H2O2 naturally decomposes, yielding O2
  • 2H2O2 → 2H2O + O2

5

  • Y. Katsumura, Isotope News, No.746,

48-49 (2016)

  • Y. Katsumura, Radiation Chemistry, No.81, 2-7 (2006)
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SLIDE 6

Hydrogen Production and Recombination

  • Measured production rate
  • ~260 L (4.7%) / 1019 POT @ 485 kW
  • Hydrogen removal by recombination : 2H2 + O2 → 2H2O
  • Catalyst : Alumina pellet with 0.5% Pd
  • H2 produced inside horns → Forced He (+H2) circulation through catalyst
  • H2 production rate greatly reduces to 5.8 L (0.1%) / 1019 POT
  • However, H2 still gradually increases → He flushing once per 1~2 weeks
  • H2 concentration : 1%→0.1%

6

Buffer tank Pump Suction pump He vessel Height ~8m Service Pit Machine Room H2O He He gas line H2 Beam

Forced circulation

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SLIDE 7

Hydrogen Removal System

7

0.2 m3 1.4 m3 2.7 m3 0.6 m3

400 L/min

H2 recombination catalyst Alumina pellet with 0.5% Pd

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SLIDE 8

Hydrogen Removal System

8 400 L/min

  • He flushing to be performed once a week (or two weeks)
  • He flushing system
  • He buffer tank (~5.5m3) in TS machine room
  • Pure He gas injected to water tank ⇒ Horns ⇒ He buffer tank
  • Old He gas stored for a week and exhausted to outside ⇒ short-lived nuclei to decay
  • One He flushing ⇒ 2/3 of entire He gas can be replaced with flesh He gas

He buffer tank (~5.5m3)

He+H2 He+H2 He+H2 He+H2

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SLIDE 9

Hydrogen Removal System

9 400 L/min

He buffer tank (~5.5m3) Pure He gas

  • He flushing to be performed once a week (or two weeks)
  • He flushing system
  • He buffer tank (~5.5m3) in TS machine room
  • Pure He gas injected to water tank ⇒ Horns ⇒ He buffer tank
  • Old He gas stored for a week and exhausted to outside ⇒ short-lived nuclei to decay
  • One He flushing ⇒ 2/3 of entire He gas can be replaced with flesh He gas

He He He He He+H2

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SLIDE 10

Hydrogen Removal System

10 400 L/min

He buffer tank (~5.5m3) Exhaust to

  • utside
  • He flushing to be performed once a week (or two weeks)
  • He flushing system
  • He buffer tank (~5.5m3) in TS machine room
  • Pure He gas injected to water tank ⇒ Horns ⇒ He buffer tank
  • Old He gas stored for a week and exhausted to outside ⇒ short-lived nuclei to decay
  • One He flushing ⇒ 2/3 of entire He gas can be replaced with flesh He gas

He+H2 He+H2 He+H2 He+H2

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SLIDE 11

Prospect for 1.3 MW

  • Operation criteria
  • Keep H2 concentration below 3%
  • H2 explosion limit in air = 4%
  • Prospect for 1.3 MW
  • H2 concentration < 1% in 1 week operation @ 485 kW ⇒ < 3% @ 1.3 MW
  • Current production rate can be acceptable even with 1.3 MW beam
  • But there exists some problems that need to be solved for a safe operation

11

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SLIDE 12

Ion Exchanger Effect on H2 Concentration

  • H2 production rate rapidly increased after Ion exchanger replacement
  • Moderate production rate for old IE, but water conductivity increased ⇒ IE’s lifetime
  • IE resins may be degraded due to oxidization by H2O2

12

IE replacement Dual IE Single IE

Run6 2015 Feb.~May Run7 2016 Feb.~May

Run period Run6 Run7 Run8 Run9-1 Run9-2 Run9-3 Configuration Single (old) Single (new) Single (old) Dual (new) Single (new) Single (new) Beam power ( kW ) 330 390 470 450 475 485 H2 concentration (%) 0.4 2.5 1.5 4.0 1.0 2.4 Production rate ( % / 1019 POT) 0.173 0.683 0.215 0.832 0.299 0.137

Run8 2016 Oct.~2017 Apr. Run9 2017 Oct.~2018 May.

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SLIDE 13

October 24, 2019 11th Workshop on Neutrino Beam and Instrumentation (NBI2019)

Water Conductivity Trend

  • Water conductivity
  • A strange behavior during dual IE operation
  • Low conductivity during single IE operation
  • Conductivity got increased around middle of April
  • This indicates lifetime of IE ⇒ ~6.0 x 1020 POT (or 2~3 months)

13

Beam ON Beam ON Dual IE Single IE Single IE October November December March April May 1 2 3 4 5 1 2 3 4 5 2017 Oct ~ Dec 2018 Mar ~ May

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SLIDE 14

October 24, 2019 11th Workshop on Neutrino Beam and Instrumentation (NBI2019)

Effect of H2O2

  • Hydrogen peroxide (H2O2)
  • Production rate is close to that of H2 (H2 : H2O2 = 1.3 : 1)
  • It corrodes IE resins ⇒ degradation of IE with presence of H2O2
  • Can be decomposed naturally : 2H2O2 ⇒ 2H2O + O2
  • Catalyst can accelerate the decomposition
  • Resultant O2 can work as a source O2 for the recombination
  • Measurement of H2O2 concentration
  • ~10 mg/L ⇔ estimated : ~500 mg/L @ 3.9x1020 POT
  • This indicates that most of H2O2 produced was decomposed
  • Even this small concentration of H2O2 can affect the IE resins

14

No dilution 1/10 dilution No dilution

Sensitive to 0.05-5mg/L Sensitive to 3-700mg/L

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SLIDE 15

Problems and Countermeasures

  • Problems
  • Short lifetime of IE due to H2O2 ⇒ IE replacement causes high H2 production rate
  • H2 gradually increases due to small O2 concentration
  • Dissolved O2 in cooling water (~1.9mg/L)
  • Can create superoxide O2- (eaq- + O2 → O2-), which can accelerate water

radiolysis ⇒ dissolved O2 should be removed

  • Countermeasures
  • Need ion exchanger resins which are tolerant to H2O2
  • O2 degasifier to remove dissolved O2
  • Inject O2 gas to solve the lack of O2 for recombination ⇒ Safety control is an issue

15

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SLIDE 16

Problems and Countermeasures

  • Problems
  • Short lifetime of IE due to H2O2 ⇒ IE replacement causes high H2 production rate
  • H2 gradually increases due to small O2 concentration
  • Dissolved O2 in cooling water (~1.9mg/L)
  • Can create superoxide O2- (eaq- + O2 → O2-), which can accelerate water

radiolysis ⇒ dissolved O2 should be removed

  • Countermeasures
  • Need ion exchanger resins which are tolerant to H2O2
  • O2 degasifier to remove dissolved O2
  • Inject O2 gas to solve the lack of O2 for recombination ⇒ Safety control is an issue

16

To be considered

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SLIDE 17

October 24, 2019 11th Workshop on Neutrino Beam and Instrumentation (NBI2019)

H2O2 Resistant Ion Exchanger

  • H2O2 is problematic for nuclear reactor business
  • H2O2 resistant ion exchanger developed for nuclear reactor
  • Pd-doped ion exchanger can decompose H2O2 and ⇒ Pd works as a catalyst
  • therefore can extend lifetime of ion exchanger

17

  • T. Izumi et al (2018)
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SLIDE 18

October 24, 2019 11th Workshop on Neutrino Beam and Instrumentation (NBI2019)

  • New resin
  • Resins produced by LANXESS and its performance proved

by EBARA

  • I contacted the person in charge of the new resin and he was

very interested in the application of this resin

  • As a trial, this resin was put into one IE bottle for a test
  • 4L of the old resins were replaced with new ones
  • To be tested during next beam time

18

Remove existing resins Put new resins Completed IE bottle

New resin (~4L) is overlaid Existing resin (~46L) 50 L in total

H2O2 Resistant Ion Exchanger

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SLIDE 19

October 24, 2019 11th Workshop on Neutrino Beam and Instrumentation (NBI2019)

O2 Degasifier System

19 P P P H-Ex Chiller F F DO Evacuate O2 (also H2O) Tank (~2L)

H2O (HTO)

  • Degasifier system installed
  • Concerns
  • H2O (HTO) also evacuated
  • Water in small tank gradually

increased ⇒ Need drain

  • HTO should not be exhausted to

the air

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SLIDE 20

October 24, 2019 11th Workshop on Neutrino Beam and Instrumentation (NBI2019)

O2 Degasifier System

20 P P P H-Ex Chiller F F DO Evacuate O2 (also H2O) Tank (~2L)

H2O (HTO)

Drain tank (~74L)

Overflow

  • Degasifier system installed
  • Concerns
  • H2O (HTO) also evacuated
  • Water in small tank gradually

increased ⇒ Drain tank added

  • HTO should not be exhausted to

the air

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SLIDE 21

October 24, 2019 11th Workshop on Neutrino Beam and Instrumentation (NBI2019)

O2 Degasifier System

21 P P P H-Ex Chiller F F DO Evacuate O2 (also H2O) Tank (~2L)

H2O (HTO)

Drain tank (~74L)

Overflow

  • Degasifier system installed
  • Concerns
  • H2O (HTO) also evacuated
  • Water in small tank gradually

increased ⇒ Drain tank added

  • HTO should not be exhausted to

the air ⇒ Return to water tank

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SLIDE 22

October 24, 2019 11th Workshop on Neutrino Beam and Instrumentation (NBI2019)

O2 Degasifier System

22 P P P H-Ex Chiller F F DO Evacuate O2 (also H2O) Tank (~2L)

H2O (HTO)

Drain tank (~74L)

Overflow

  • Degasifier system installed
  • Concerns
  • H2O (HTO) also evacuated
  • Water in small tank gradually

increased ⇒ Drain tank added

  • HTO should not be exhausted to

the air ⇒ Return to water tank

Still under preparation. To be used for beam in FY2020

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SLIDE 23

October 24, 2019 11th Workshop on Neutrino Beam and Instrumentation (NBI2019)

Summary

  • Beam exposure to the horn cooling water creates H2, O2, H2O2
  • H2 is removed by H2 recombination using catalyst
  • H2 concentration is currently < 1% per week @ 485 kW, which can

indicates < 3% even at 1.3 MW

  • It is likely that ion exchanger resins are oxidized by H2O2 and lifetime is

2~3 months

  • New ion exchanger resins tolerant to H2O2 are introduced and will be

tested in next beam time

  • Dissolved O2 in the water can affect H2 production rate. O2 degasifier is

under preparation.

23