LBNF LongBaseline Neutrino Facility Tritium Management and Facility
LBNF Long-Baseline Neutrino Facility Tritium Management and Facility Issues Jim Hylen US-Japan Meeting on Accelerators and Beam Equipment for High -Intensity Neutrino Beams 19 March 2019
Outline • Tritium basics • Tritium lessons from Nu. MI (FNAL’s operating high-power n beam) • How LBNF design incorporates Nu. MI lessons learned for Tritium • LBNF Tritium Risk due to differences between Nu. MI and LBNF - Gas in target pile: Air for Nu. MI, semi-sealed Nitrogen for LBNF - Identified risk is high HTO in target pile air during access • Two-prong mitigation strategy to protect workers during access - (i) Pull air away from workers during access - (ii) Continuously purge Tritium during running - Prototype continuous-purge-during-running – add H 2 O to N 2? 2 3/19/2019 Jim Hylen | Tritium Management LBNF
Tritium Basics • Tritium (3 H) decays to 3 He by beta emission, beta has average energy 5. 69 ke. V and maximum 18. 6 ke. V. • Half-life is 12. 32 years. • Highly mobile, has high diffusion coefficient through metals • If there is water around, Tritium mostly ends up as HTO • The beta will not make it through your skin • Harmful if ingested by drinking or breathing HTO, or absorption through skin • Tritium released as HT has significantly less human uptake than HTO, so trying to shift release in that direction would be consistent with ALARA • For neutrino beamline, Tritium is nearly all produced by spallation in the shielding 3 3/19/2019 Jim Hylen | Tritium Management LBNF
Tritium release limits for Fermilab 1 Ci = 3. 7 x 1010 Bq • Sanitary Sewers - 5 Ci/yr - 9, 500 p. Ci/ml • Surface water - 1, 900 p. Ci/ml • Class 1 groundwater - Non-degradation (taken as “detectable” = 1 p. Ci/ml) - (aside: general drinking water limit is 20 p. Ci/ml) • Dose through air to public (Maximally Exposed Offsite Individual) - 0. 1 mrem in a year (summed with all other FNAL air release radiation) - Roughly 3000 Ci of HTO release to air would give 0. 1 mrem to MEOI • Dose through air to workers - Defined Air Concentration on next slide 4 3/19/2019 Jim Hylen | Tritium Management LBNF
DAC (Defined Air Concentration) 1 m. Sv = 100 mrem • DAC is amount of radiation in air that: Would gives 5 rem dose to workers in 2000 hr work year. = 2. 5 mrem/hr, = 100 mrem in 40 hr work week. • For tritium in form of HTO, DAC corresponds to 20 p. Ci/cc of air. • At 25 C, 100% RH, it translates to about 852, 000 p. Ci/ml of water At FNAL, we don’t let water get tritiated much beyond 800, 000 p. Ci/ml, so that leaks/spills can’t get the air above a DAC. • Work restrictions required if Tritium in air > DAC (see backup) Note we are trying to design to stay below DAC 5 3/19/2019 Jim Hylen | Tritium Management LBNF
Tritium release experience at Nu. MI In recent years, measured release of Nu. MI tritium: • 90% evaporated up roof stack, air exhaust • 7% through underdrains to sump, then used as cooling water, eventually evaporates from cooling ponds • 2% collected from target cooling water, barreled and disposed off-site • 1% collected from horn water cooling system, barreled and disposed off-site • Small amounts collected in Air Handling Units; to sewer for now • Tiny amounts blow down on ground; it re-evaporates naturally 6 3/19/2019 Jim Hylen | Tritium Management LBNF
Nu. MI, as background for tritium discussion Evaporator of condensate ~ 250 gallon/day Absorber dehumidifier condensate is pumped to target hall, mixed with target pile condensate Underdrain water all flows to MINOS sump, then pumped to CUB cooling towers and ICW ~ 100 gallon/minute (ii) Decay Pipe SR 3 EAV 1 EAV 2, EAV 3 (iii) (i) EAV 1, EAV 2, EAV 3 (and sometimes SR 3) are air exhausts Target hall to EAV 2 gives time for short-lived isotopes to decay Tritium producing particle shower power is deposited ~ 1/3 in each of (i) target hall, (ii) decay pipe, and (iii) absorber at end of decay pipe 7 Jim Hylen | Tritium Management 3/19/2019
Nu. MI target hall, target pile ~ 50 m TARGET HALL Beam Decay Pipe Target pile: volume containing shielding steel & concrete covers In target pile: 25, 000 cfm recirculating air cools target pile shielding Design Water Drainage Path is dimple mat underneath target pile ~ 300 cfm ( ~ 8 m 3/minute) air leak from target pile to target hall during operation Target hall: ~ 1, 200 cfm exhaust to passageway next to decay pipe Dehumidification in pile loop and at door to passageway intercepts most HTO (not original installation, dehumidification was added as tritium mitigation) 8 Jim Hylen | Tritium Management 3/19/2019
Schematic of main Nu. MI Tritium release path Takes target hall HTO humidity, condenses it, then evaporates it from roof All of this dehumidification and evaporation equipment was added to Nu. MI as upgrades to deal with Tritium. 2 Cooling coil Condensate To decay passage To DK Tgt pile Give short-lived radioisotopes in air time to decay (Target pile) 9 Jim Hylen | Tritium Management 3/19/2019
1 Ci = 3. 7 x 1010 Bq Nu. MI Tritium Production and Release MARS Ci/1020 POT 24 11 2. 5 0. 22 0. 03 ? ? 1. 3 1. 7 - 4. 2 41 - 44 6 ~ 26 Monte Carlo Produced in target pile steel decay pipe concrete decay pipe steel chase air decay pipe helium absorber horns Target TOTAL MARS Monte Carlo of Tritium production in Nu. MI (120 Ge. V proton beam) Ci/1020 POT Measured Release 2008 – 2011 at 300 k. W Ci/1020 POT Measured Release 2016 at 520 k. W Release jumped non-linearly with beam power as steel temperature ~ 100 C, and is approximately equal to M. C. production rate in steel components 10 Jim Hylen | Tritium Management 3/19/2019
Diffusion scales – sanity check From literature search, get typical range of diffusion constants. The average distance that tritium moves in time t is <X> = sqrt( 4 D t ). Plug in Tritium lifetime as t, and compare to typical distance scales. Diffusion constant ( cm 2/s ) Ave. distance in Tritium lifetime ( cm ) Distance Scale Nu. MI (cm) Distance Scale LBNF (cm) Steel in Target Pile 2 – 8 x 10 -5 176 - 353 10 - 65 10 (cooling panel) Concrete in Decay Region 2 – 22 x 10 -7 18 -58 137 – 300 to outside 560 to outside Yes, most of the Tritium in steel will get to the surface of the steel, can release to air. But most Concrete Tritium decays before it can get outside. (Can go inside). 11 Jim Hylen | Tritium Management 3/19/2019
Tritium concentration in dehumidifier water, evaporated to air 1) Large jump in tritium release when Duratek steel shielding got to ~ 100 C 12 Jim Hylen | Tritium Management Yearly shutdown 300 k. W ops Yearly shutdown ml er air n p of tio r cc tra pe en not nc Co ater, w of No beam, upgrade for NOVA Yearly shutdown 540 k. W ops (not smooth exponential in diffusion versus temperature) 2) Lower emissions during beam-off 700 k. W ops 3/19/2019
Tritium near Nu. MI target hall Some tritium from roof-top exhaust is blown down to soil Some tritium from roof-top exhaust is drawn into nearby Air Handling Unit intakes We have monitored those locations MI-8 bldg. (spares production) Nu. MI bldg. above tgt. hall 13 Jim Hylen | Tritium Management 3/19/2019
Blow down to soil & AHU intakes • Under certain weather conditions, get blowdown from the NUMI stacks; see some tritium in samples of soil around the building. Lots of clay between that surface and the groundwater layer, so we do not mitigate. Most of it evaporates over time. See it on different sides of building depending on wind pattern. Range of samples: • 14 <1 p. Ci/ml up to 15 p. Ci/ml in water Air intake to building Air Handling Units (AHUs) are on roofs. Sometimes the AHUs produce condensate (depending on temperature and humidity). That condensate can have significant tritium content, depending on wind etc. It currently contributes to the tritium going to the sewer line. Discussions are underway about possibly mitigating this. MI-65 AHU condensate water tritium: ranges from 0. 01% to almost 1% of evaporated concentration MI-8 AHU condensate water tritium: ranges from 0. 001% to 0. 01% of evaporated concentration Jim Hylen | Tritium Management 3/19/2019
During Nu. MI operation, MI-65 ventilation AHU condensate up to 1, 720 p. Ci/ml, AHU 1, AHU 2, AHU 3 fairly similar Evaporator ~ 500, 000 p. Ci/ml of water in air 600 cfm AHU 3 AHU 1 Hi-Bay 6, 000 cfm AHU 2 stair AHUs release condensate to sewer shaft Shield door EAV 2 Evap Absorber Condensate Target Hall Pile Dehum Target Pile 15 Jim Hylen | Tritium Management 3/19/2019
9/11/2018 short circuit to AHU during access Target pile open, target hall shield door open, pile dehumidifier off AHU 3 AHU 1 Hi-Bay AHU 2 EAV 2 Evap 24, 300 p. Ci/ml of water in air stair 950 / 819 / 17, 500 p. Ci/ml HTO condensate to sewer spikes but at acceptable levels 4% of DAC in target hall to workers so not problematic at Nu. MI 16 Jim Hylen | Tritium Management shaft 41, 500 p. Ci/ml of water in air Shield door Target Hall Absorber Condensate Pile Dehum Target Pile 66, 600 p. Ci/ml of water in air 3/19/2019
Lessons learned from Nu. MI • Large Tritium release from target pile steel shielding – The Tritium release can be very temperature dependent • Was non-linear with beam power – Must route this release in a controlled fashion • (in early Nu. MI running, much exchange onto damp concrete) • Underdrains must be maintainable for life of facility • Must control secondary pathways as well – Should not send building AHU condensate to sewer – Need to consider access periods • Getting rid of tritium during running reduces HTO problem during access periods • Prompts new strategy; as go to higher beam power, during access pull target pile air away from workers to reduce exposure to HTO. 17 Jim Hylen | Tritium Management 3/19/2019
LBNF systems and Tritium: LBNF layout Target Horns Target Hall 1. 2 MW, eventually 2. 4 MW proton beam, producing neutrinos Decay Region Absorber region Hadron absorber protons Muon absorber 221 m 18 3/19/2019 Jim Hylen | Tritium Management LBNF
LBNF Tritium production at 2. 4 MW (MARS Monte Carlo) At 56% uptime per year, M. C. predicts producing 846 Ci/year ( = 3. 1 x 1013 Bq/yr = 31 TBq/yr) of which 500 Ci/yr is in target pile steel 19 3/19/2019 Jim Hylen | Tritium Management LBNF
LBNF Air release to public MEOI OK for LBNF for air-release • If all the Tritium in the target pile steel comes out and goes up the stack as HTO, it will take up 17% of Fermilab’s air release radiation budget. This is about what we expect from Nu. MI experience. • If ALL the Tritium produced at LBNF goes up the stack, it would be 28% of the lab’s air release budget. Larger than desired, but not really problematic. • We want to investigate trying to release some as HT rather than HTO as a cheap way to reduce the dose to MEOI (ALARA), but if that does not work it is not a large risk to the project. • We are also deliberately adopting strategy of trying to continuously get rid of the Tritium in the target pile steel, rather than build up an inventory that might catastrophically release at some point. 20 3/19/2019 Jim Hylen | Tritium Management LBNF
LBNF areas • Will discuss target hall • Some slides on Decay pipe region & Absorber region are in backup 21 3/19/2019 Jim Hylen | Tritium Management LBNF
LBNF target shield pile in target hall • Central chase for components is 2. 2 m/2. 0 m wide, 34. 3 m long, nitrogen-filled • Bulk steel is inside N 2 vessel, N 2 cooled • 4” inner layer of shielding water-cooled; replaceable cooling panels 22 3/19/2019 Jim Hylen | Tritium Management LBNF
Target pile design choices Replaceable water cooling panels are used for innermost steel layer Bulk shielding is cooled by 35, 000 ft 3/minute flow of N 2 gas Lessons learned being applied: • Concrete is all outside the N 2 vessel • Vessel includes all gas in high radiation (containing short-lived air-activation) • Steel (emitting tritium) is all in vessel • Continuously purge tritium by slow N 2 release (1 to 7 cfm, = ~ 0. 1 m 3/minute) 23 3/19/2019 Jim Hylen | Tritium Management 6. 2 m LBNF
LBNF Target pile release, during operation Designing toward continuous slow direct release to air during operation • Because no 41 Ar, and slow release of 11 C, 13 N, 15 O, can have short direct path • Has stainless vessel around steel shielding (which Nu. MI does not have) • No damp concrete that was problematic for Nu. MI Will still have roof evaporator for any condensate collected, but should be small Release from stack 1091 cfm Target hall Leaks and Gas handling room Air Continuous purge ( 2 to 7 cfm, = ~ 0. 1 m 3/minute) Target pile vessel Steel shielding Pre-target Nitrogen vessel chase Filter chiller dehum. fan 35, 000 cfm N 2 • • • 24 LBNF target hall complex will have geo-membrane barrier around it. Also sits on compressed clay. HTO would take hundreds of years (many tritium decay lifetimes) to percolate to water table. Whereas Nu. MI target hall is below the clay. Requirement to Civil to take precautions with pilings punching through clay. Jim Hylen | Tritium Management 3/19/2019
1 st order estimate of LBNF Target Hall (TH) air tritium concentration Take Nu. MI measured tritium release per 1020 POT, and various Monte Carlo calculations of production, Scale by POT/yr, divide by LBNF TH ventilation over a year Get average tritium concentration in air going through target hall Get estimates above a DAC, but could ramp the ventilation up by say x 5 during access to get below DAC during access But this assumes constant release ! 25 Jim Hylen | Tritium Management 3/19/2019
Nu. MI • Air in target pile is nearly a DAC during operation, but drops by one to two orders of magnitude fairly rapidly at start of a shutdown. (See slide 13 for pattern). • Also, air in target hall is diluted, with 300 cfm leak from pile and 900 cfm fresh from power supply room, raw room, and leaks from shaft and escape passageway, so well below DAC even during operation. • Nu. MI does not have an access Tritium DAC problem. – High release during running – Low release pretty soon after beam shutdown 26 Jim Hylen | Tritium Management 3/19/2019
A tale of three target piles What is experience of actual release pattern from existing target piles ? Target pile gas Gas vent rate during ops Beam power Target pile gas tritium release pattern Nu. MI Air 300 cfm 700 k. W High during running Low during access T 2 K Helium 0 485 k. W Low during running High during access SNS Helium Small continuous 1 MW Low during running High during access N 2 3 to 7 cfm 2. 4 MW ? LBNF design Note: • LBNF uses different gas than Nu. MI in target pile vessel • Gas vent rate for LBNF is two orders of magnitude less than Nu. MI 27 Jim Hylen | Tritium Management 3/19/2019
T 2 K equivalent tritium concentration in air for access is about 2/3 of U. S. DAC. Normal cycle is to run sealed up with helium for half a year, then have half year shutdown. At start of shutdown, have to ventilate the target pile for several weeks with air to get tritium concentration below their “DAC” so they can access. So for target pile tritium release to air, it is inverse of Nu. MI No gas release during operation Tritium release high at start of shutdown Since they have a half-year shutdown each year, spending several weeks to a few months getting the tritium concentration down is not a big problem for them. That does not fit the usual FNAL cycle of ~10 months on / 2 months off Also, if have a horn or target failure during a run, want fast repair/replacemet 28 Jim Hylen | Tritium Management 3/19/2019
SNS built a system to grab tritium from the helium release stream during operation. During running, they saw very little tritium collected, and very little tritium making its way passed the tritium filter. During target change-outs, the mercury and vessel is exposed to air. Since it is remote changeout (remote driven by the mercury vapor), workers are not exposed to the tritium. The release cycle is thus also inverse of Nu. MI, with couple orders of magnitude more tritium released during shutdown than during operations. 29 Jim Hylen | Tritium Management 3/19/2019
Sealed versus unsealed target pile, and gas used Tritium transport from shielding to gas depends on: • Concentration gradients • Diffusivity of tritium through the solid shielding – Generally exponential in material temperature – Can also have temperature-depending trapping potential threshold effects • Surface effects are large – Paint, other coatings – Mono-layer of water or other contaminants on surface • Effects of gas in contact with the surface – Humidity exchanging H 2 O with surface, … • Radiation may play large role – Lots of Ozone, Nitric acid, OH and other ions running around in Nu. MI during operation Extrapolating from humid air (Nu. MI) to N 2 (LBNF) is not straight-forward • Do we need some H 2 or H 2 O in N 2 to facilitate tritium getting out of the shielding during running? – Need expertise in radiation chemistry / tritium transport to estimate – Probably want a prototype test to confirm estimations 30 Jim Hylen | Tritium Management 3/19/2019
1) Ventilation prong of access mitigation; Recall LBNF Target pile ventilation, during operation: Release from stack 1091 cfm Target hall Leaks and Air handling room Continuous purge ( 2 to 7 cfm) Target pile vessel Steel shielding Pre-target Nitrogen vessel chase Filter chiller dehum. fan 35, 000 cfm N 2 31 Jim Hylen | Tritium Management 3/19/2019
But During target pile or gas handling unit access Ventilation modification to help mitigate high Tritium release in target pile vessel • Pull tritium away from workers in nitrogen vessel • Include filter to pick up contamination before exhaust – so another filter and stack Fresh air for workers 5000 cfm air ? Target hall Target pile vessel Steel shielding Pre-target 32 Filter Gas handling room 5000 cfm ? Nitrogen vessel chase Jim Hylen | Tritium Management Filter chiller dehum. fan 3/19/2019 Fresh air for N 2 -> air
2) Continuous purge prong of T access mitigation; Plan for tritium release study Recall our strategy is to get rid of Tritium during running in N 2 atmosphere, thus reducing Tritium outgassing during access – we want fast transport during running • 1 st step - what is rate-limiting ? (for hot running in N 2, also cool access in air) – – • Diffusion through steel Paint Water layer on surface (does it need replenishing? ) Water (or hydrogen) in gas 2 nd step – – do we need additives to the N 2, and how much ? (ppm through ppt, not huge) • Hydrogen ? Water vapor ? Both ? – What is the temperature dependence, and how should we turn that knob? • 3 rd step – do we do a prototype test to check ? • Iterate if necessary 33 Jim Hylen | Tritium Management 3/19/2019
Take-aways • Going into LBNF design, we have a LOT of experience handling tritium in Nu. MI, which is very similar to LBNF • The differences: - LBNF is 2400 k. W / 700 k. W = 3. 4 times the beam power of Nu. MI - LBNF target pile vessel will be filled with N 2; Nu. MI was air - LBNF gas purge rate will be 2 to 7 cfm; Nu. MI was 300 cfm • We still want to continuously get rid of Tritium up exhaust during running and have low Tritium evaporation during access • We are executing a Tritium mitigation plan to assure that the above differences are accounted for and if necessary compensated for. - Specifically, for example, do we need some humidity in the target pile to facilitate tritium transport during running? - Do we also want to purposely adjust the shielding temperature during running versus shutdown? 34 3/19/2019 Jim Hylen | Tritium Management LBNF
BACKUP 35 3/19/2019 Jim Hylen | Tritium Management LBNF
DAC, more from FRCM (thanks, Kamran) • If the airborne radioactivity in an area is larger than 1 DAC (during access), or a worker can get more than 12 DAC-hrs (30 mrem) in a week from air born radioactivity without respiratory protection, the area should be posted as AIRBORNE RADIOACTIVITY AREA ( FRCM article 235. 2). • If a worker is expected to get 40 or more DAC-hours in a year (>100 mrem) from internal exposure, then bioassay is required. Chapter 5 of FRCM has a lot more details on internal dosimetry program requirements. • If you don’t want a bioassay program, then you may resort to using respiratory protection equipment for working in an Airborne Radioactivity posted area. 36 Jim Hylen | Tritium Management 3/19/2019
Tritium evaporation from steel There is a publication on temperature and humidity dependence of Tritium release from STAINLESS STEEL We should probably repeat this using shielding type steel Reminder: we want more evaporation during running, less during access 37 Jim Hylen | Tritium Management 3/19/2019
Introduction to Nu. MI decay pipe Tritium study Decay pipe region, 2200 ft long Decay pipe is 2 m diam. Decay pipe passageway (walkway along entire length of decay pipe) Dimple matting Steel Helium Grate every 200 feet with drain to Main Drain 38 Jim Hylen | Tritium Management Main Drain perforated pipe 3/19/2019 LBNF
Nu. MI Saw air-deposited tritium from passageway penetrate into DK concrete shield – substantially reduced (depleted) after dehumidification installed Core samples taken by drilling into decay pipe concrete shield Monte Carlo l Data BEFORE Dehumidification 39 Jim Hylen | Tritium Management Core sample ST 999 (corrected) AFTER Dehumidification ( not normalized) 3/19/2019 LBNF
Tritium strategy – overview (more details later) • Don’t build up an inventory that could catastrophically release • Largest fraction: continuous release to air - Exploring trying to release larger fraction as HT, to be ALARA • Second largest fraction: slow moving in concrete; store to decay • RAW - Barrel and disposed offsite before excessive buildup • Target helium system tritium – needs study, but expectation is to handle it as above, by getting rid of it before it builds to a large inventory 40 3/19/2019 Jim Hylen | Tritium Management LBNF
Tritium – helium in decay pipe • At NUMI, sample of helium in decay pipe showed very low Tritium; Tritium is probably escaping • LBNF will have same style upstream decay pipe window as NUMI, so expect most of the Tritium to go to target pile gas or decay pipe cooling N 2 gas, where it gets purged to outside air • LBNF can periodically sample the Tritium in the decay pipe helium to make sure the inventory did not somehow get huge 41 3/19/2019 Jim Hylen | Tritium Management LBNF
Tritium – Helium in target system • At NUMI, sample of helium in target system helium showed very low Tritium (Tritium could have been high because of evaporation from the target graphite); tritium is probably escaping • Recent LBNF design change to T 2 K style target may affect ability of tritium to get from target to target pile gas. RAL has responsibility for the design of the target helium system. Will have to study if we will have to deliberately introduce a way of removing Tritium if we get too big a build-up. (Membrane, or gettor, or purge? ) • LBNF can periodically sample the tritium in the target helium to make sure the inventory does not somehow get huge 42 3/19/2019 Jim Hylen | Tritium Management LBNF
Decay pipe region • Two concentric steel pipes 4 m diam. , 194 m long • Static helium fill 10% more n compared to air fill • Cooled by flowing 35, 000 ft 3/minute of nitrogen gas • Structure dominated by concrete radiation shield 5. 6 m thick • Annulus N 2 cooling N 2 return 5. 6 m 4 m Helium Concrete Radiation shield Multiple features to keep water out water barriers water drainage Lesson learned from Nu. MI, as requirement to civil: drainage must be maintainable for life of facility 43 3/19/2019 Jim Hylen | Tritium Management LBNF
Decay Pipe Tritium Diffusion Study ( taken from B. Lundberg, May 2013, LBNE-doc 7254) Leak out from concrete Leak into decay pipe N 2 cooling annulus, and purged 44 3/19/2019 Jim Hylen | Tritium Management LBNF
Decay Pipe region protection Danger would be water seeping into the concrete, then carrying Tritium out to the water table Mitigations: Use gas cooling, not water Drainage layer sandwiched by geomembrane systems • Outer geomembrane keeps water out • Drainage layer intercepts any water sneaking passed geomembrane • Inner membrane protects concrete from water in drainage Inner geomembrane system includes sandwiched geonet 45 3/19/2019 Jim Hylen | Tritium Management • Any Tritiated water in drainage is collected, sent to evaporation ponds LBNF
LBNF Absorber Area • The LBNF Absorber will be circulating-air cooled, very much like the current Nu. MI target pile, but without as much water seeping into the absorber area. • The hall is surrounded by grouting and geomembrane. • There is a gap between Absorber floor and walls and the Absorber Hall floor and walls, as a maintainable water and Tritium intercept. • Tritium diffusion is slower in the Aluminum core, but what Tritium comes out will mostly be collected as HTO in the Absorber air-cooling dehumidification system, and evaporated via roof-top stack. This is pretty much a direct copy of the Nu. MI target hall system. • The air from the Absorber hall, which includes air leaks from the Absorber, will be exhausted to the LBNF target hall, and thus up the stack with the target pile exhaust. • Again, AHU condensate will not be sent to sewer 46 3/19/2019 Jim Hylen | Tritium Management LBNF
(Risk) LBNF target pile used to be NUMI x 3. 4, but no longer Why is this issue coming up now? Some history: • Beam to Surf / DUSEL started out as ~ optimized neutrino beam • Due to budget constraints, LBNE turned into Nu. MI target/horns in small target pile Tritium would just be ~ beam power increase x Nu. MI, reasonably well extrapolated, air release levels and access levels OK • LBNE was rejected as too expensive for US • Reborn as LBNF/DUNE international project expand to re-optimized beam with large target pile gas volume • Large air volume in radiation times increase in beam power --> Argon 41 release becomes real headache LBNF changes to semi-sealed target pile with Nitrogen instead of air Eliminates 40 Ar that becomes 41 Ar Reduces O 2 and H 2 O, thus Ozone and Nitric Acid and corrosion Containment time reduces release of 11 C, 13 N, 15 O eliminates need to use Nu. MI as further air cooldown space But can change the Tritium release pattern. • Leave hook of slow purge of N 2 to continuously get rid of tritium 47 Jim Hylen | Tritium Management 3/19/2019
Preventing drains from backing up Found that Nu. MI underdrains were clogging up with sediment. Plug of sediment removed from cross-drain • Danger that target pile and decay pipe regions would flood and water would carry away radioisotopes. • Nu. MI underdrains were not designed with maintenance in mind; cannot reach to physically clean them. Have installed a system to continuously inject chemicals to keep the drainage open. Cycles alternately through: • PBTC (a scale inhibitor) • Sulfamic acid (de-scaler) • Hydrogen Peroxide (biocide) This is working, but rather specific to the clogging material. (Do NOT plan to do this for LBNF). 48 Jim Hylen | Tritium Management Sediment removed from pre-target gutter Lesson learned: Future facilities must design drainage systems that are maintainable for the life of the facility. 3/19/2019
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