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Irradiation tests of 3M™Novec™ fluids
Pe t r G O R B O UNOV, I T E P ( Mo s c o w) ,
f o r L HCb Sci Fi Tr a c ke r a n d CE R N «P F C A l t e r n a t iv e s » p r o je c t s
• Novec as replacement for PFCs in
(mono-phase) cooling systems
• Radiation resistance of liquids
• Gamma-irradiations at IONISOS
• Neutron irradiations at CHARM
• Summary of results
P. Gorbounov Novec radiation tests
Material Irradiation Tests meeting 14 June 2017
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3M™ Novec™ fluids
• 3M Novec fluids [1]: environment-friendly alternatives to perfluorocarbons (PFC), like
C6F14.. Global Warming Potential: 7000-9000(C6F14), ~1 (Novec 649), ~300 (Novec 7100).
• Like C6F14, Novec fluids can be used at CERN in mono-phase cooling applications. Typically,
such systems operate either in no-radiation environments (brine systems), or at low to
medium total dose environments - from O(100 Gy) to O(1o kGy ). With the typical “diluton
factor” of 1/10, the expected dose range for the coolant is O(10 Gy) to ~1 kGy.
• Novec 649 and Novec 7100 fluids [1] were introduced >20 years ago and are widely used in
the industry. However, their radiation resistance was practically not studied.
• Examples of potential near-term apps: LHCb SciFi (~100 Gy, N649 the baseline coolant [2,3]),
LHCb RICH electronics cooling ( <1 kGy), ATLAS and CMS brine systems (no radiation)
• The present study, initiated by the LHCb SciFi Tracker and performed within the framework
of the CERN “PFC Alternatives” project, was aimed to explore a wider dose range for future
applications: 1 kGy, 10 kGy and 100 kGy
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Goals, figures of merit, irradiation plan
• Questions :
•
What is the rate of radiation-induced degradation (“radiation resistance”) of the fluid ?
•
What are the main degradation products?
•
Which of them are detrimental to the cooling system and personnel (corrosive, toxic)?
•
Purification methods? Compatibility with materials?
• Radiation resistance of liquids?
• Unlike with solids (detectors, electronics, construction materials), cooling liquids are easily replaceable
• The destruction rate should be of the same order as for C6F14 (~0.07 %/10 kGy [3]), up to 10-fold less
resistance is acceptable;
• The amount of the detrimental radiolysis products should be within the capacity of the online purification
system;
• Gamma irradiation tests: (N649+N7100) * 2(redundancy) * (1 kGy + 10 kGy + 100 kGy): 12 samples
• Compatibility of irradiated liquids with metals: tested with high gamma doses and low neutron doses
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Gamma irradiations at IONISOS (I)
• Gamma-irradiations (to avoid container activation)
• After evaluation of several irradiation facilities (including Cranfield(UK),
Fraunhofer Inst. (GE), Radlib (Spain), GIF++ (CERN)), we selected…
• IONISOS, the commercial industrial material sterilization facility in
Dagneux (FR). 3 Co-60 units. The dose rates 0.5 kGy/h for the lowest dose
and 2 kGy/h for the medium and high doses. Very convenient (close to
CERN). See more in CERN presentations by Ionisos, e.g. Indico 512823
• Contact: [email protected] .
• The irradiation service costs 1685 Euros (all included), fast delivery (2-3
weeks), rigorous dose control, certificates… Highly recommended!
• Our orders: DAI 6164180 (October 2015) and
6380272 (May 2016)
SS containers: manufactured by EN-CV.
Cleaning and filling: TE-VSC-SCC
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Gamma irradiations at IONISOS (II)
• C6F14 and Novec fluids have a excellent compatibility with metals and hard plastics
• To study the effect of the radiolysis products on various metals (SS304, SS316, copper, titanium) the
metal samples half-immersed into C6F14, Novec 649 and 7100, in glass test tubes, were also irradiated
Observations:
• Glass test tubes 145 mm x OD25 mm, with Alu caps and
PE stoppers, by Bolium.com
• ParaFilm used for sealing the tubes turned out to be
non-radiation resistant: turned into gel under 100 kGy
• Using PE stoppers was not a good idea: in contact with
fluoride, PE could produce HF
• The “100 kGy” samples showing the visible surface
changes were analysed with SEM at CERN EN-MME-MM
• All materials irradiated at IONISOS were tested by the
CERN RP and found to have zero residual activation.
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Post-irradiation study of fluids
• Outsourcing! Technical Specifications [4].
• Good links with 3M, the Novec fluids manufacturer, at the NDA level. Leading
Novec specialists (Ph. Tuma, J.Owens) from 3M St-Paul/MN visited CERN
twice. 3M offered to study our samples for free.
• Three other external chemical laboratories were selected for the postirradiation analysys tender (DO-29750EP, completed on March 1, 2016) .
•
CEA Saclay, France - Laboratoire de Radiolyse et de la Matière Organique (LRMO) - refused
•
ICPE-CA, Bucharest, Romania – National R&D Institute for Electrical Engineering 23.7 kEUR
•
ILK, Dresden, Germany – Institute for Ventilation and Cooling, winner! ~15.62 kEUR
• One set of 2015’ samples went to 3M, the other - to ILK. The 2016’ samples
went to ICPE-CA, where the full analysis was performed (final report: May
2017). 3M completed their analyses by end of 2016 (confidential report).
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Results from gamma-irradiations
•
•
•
•
•
Overall, Novec fluids have a high radiation resistance comparable (or
better) with C6F14
Novec 649 having the thermo-physical properties very similar to
C6F14, was superior to Novec 7100
• 8 times less fluoride production
• No toxic gases detected in the liquid phase (vs COF2 and traces
of PFB in N7100)
Final report (under preparation by the “PFC Alternatives” team) [5]
SEM analysis report [6]
Endoscopic inspection of the interior walls of the test containers [7]
View of the SS container inner
wall at the liquid-headspace
border (Novec 7100, 100 kGy)
P. Gorbounov Novec radiation tests
Material Irradiation Tests meeting 14 June 2017
Ti-1 Ti-2 SS-1 SS-2 Cu-2 Cu-1
(“1” = C6F14, “2” = Novec 649)
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Mixed-field irradiation at CHARM (I)
• SciFi tracker: the photodetectors are predominantly exposed to neutrons (~1 Mev, 1…2·1012/cm2 or ~100-200 Gy)
• Coolant will be only partially exposed to this radiation (“dilution factor”) – neglected for this test
• Goal: effect of neutron-irradiated Novec fluids on common metals (SS 304 and 316, copper, aluminium,
titanium). Technical specification: P.Gorbounov [8], executive summary: E. Guillermain [8].
“Of our interest is the state of the metal strips: signs of surface degradation or deposits, the difference between
the part immersed in the fluid and the one exposed to the headspace gas. The surface analysis will be performed
by the CERN Metallurgy group”
• Preparation for the CHARM irradiations: we benefitted from the fantastic support by Elisa, Robert Froeschl and
Salvatore Danzeca. Container for test tubes half-filled with test fluids, with test metal strips, was made of PE
plates and perforated aluminium sheets (see next slide)
• Irradiations: 20-29 June 2016, at the position “9” selected by the CHARM team (predominantly neutrons). Total
achieved fluence was 1.8E12 (1 MeV eq).
• Post-irradiation treatment by the RP service was way too long: it took ~2 months .
• The metal samples, classified by the RP as “slightly radioactive” (<0.1 uSv/h, ~20-40 BGO counts/s), were visually
inspected and analysed with SEM (this was not very conclusive [7])
• Net result: irradiated Novec fluids exhibited similar or better compatibility with metal, compared to the
reference fluid C6F14. SS316 and Aluminium had the best resistance to all fluids.
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Mixed-field irradiation at CHARM (II)
27 test tubes, with different combinations of
fluids, metals and moisture content
P. Gorbounov Novec radiation tests
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fluid
headspace
Mixed-field irradiation at CHARM (II)
316
304
Cu Al
Ti
C6F14 wet
316
Al
304
Cu
Ti
316
Ti
N649 wet
Al
304
C6F14 dry
Ti
316
304
Al
Cu
N649 dry
“dry” – fluids were dried to RH<10%
“wet” – fluids were saturated with water (up to RH>95%)
NB: RH was measured with a capacitive moisture sensor IST LinPicco Basic A05-GS (www.ist-ag.com)
NB: PE stopper was the likely cause of HF-induced corrosion in the upper (headspace) part of strips
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Ti
Summary and acknowledgements
• The study of the radiation resistance of Novec fluids, relative to the reference C6F14 (PFC) fluid, is
completed
• The study was initiated by the LHCb SciFi Tracker upgrade project and performed within the
framework of the CERN “PFC Alternatives” project
• On behalf of these two projects, I thank all competent CERN services for the excellent support
• Our personal thanks are to Markus Brugger for his help in selection of the irradiation facilities and
contacting IONISOS; to Robert Froeschl for providing a human interface to the RP services, to
Salvatore Danzeca for his assistance in performing the CHARM irradiations and to Elisa Guillermain
for her invaluable help in organizing the irradiations.
• We also thank the EN-MME-MM team, especially Anite Perez Fontenla, for performing the SEM and
EDX analysis of the irradiated samples.
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References
1. Novec fluids are reviewed and compared with other liquid coolants. P. Gorbounov, M. Battistin, E. Thomas:
Liquid refrigerants suitable for single-phase detector cooling (case of LHCb SciFi tracker) EDMS 1807709
2. Internal notes, memos, presentations on the Novec fluids, thermal testing. C6K for SciFi Twiki page:
https://twiki.cern.ch/twiki/bin/view/LHCb/C6K
3. Radiolytical characterization of C6F14 at CERN, 2007 , S.Ilie, R.Setnescu, B. Teissandier “Radiolysis effects
in C6F14 fluids”, TS-Note-2007-005, EDMS 642110
4. Technical specification for the post-irradiation study. P. Gorbounov: Technical Specification
Characterization of 3M Novec™ 649 and 7100 fluids: initial chemical purity, radiation resistance,
purification agents, DO-29750/EP, EDMS 1570419
5. Final Report by the “PFC Alternatives” team (M. Battistin et al.), Novec fluids qualification report, EDMS
1751219
6. SEM Analysis of metal samples irradiated with C6F14 and Novec fluids. A.-T. Perez Fontenla (EN-MMEMM) EDMS 1729253/1
7. Endoscopic analysis of test containers, A. Porret (EN-EA-CT),
G:\Departments\EN\Groups\MME\MM\Metallurgy\CND\VT\PV\2016\EP\UAT\LHCb\Novec-containers
8. Technical specifications for the irradiation of Novec fluid s with metal samples at CHARM, June 2016;
EDMS 1816505
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Backup slides
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Why Novec fluids are good candidates to replace C6F14 in
detector cooling systems?
• No alternatives to fluorinated fluids [1]
• C6F14, the thermal fluid of choice for LHC, a potent GHG
• 3M Novec fluids [2] – the only commercially available brand of liquids comparable with PFCs; specially designed
to meet the Kyoto Protocol requirements; sustainable solution
• In 2014 Novec 649 was selected as the baseline coolant for the SciFi Tracker upgrade [SciFi TDR]
• Novec 7100 was added to the validation programme, to represent an alternative Novec chemistry
• C6F14 (PF-hexane):
GWP=9300; 1013 ohm·m; bad coolant;
• Novec 649 (C6-fluoroketone) GWP=1;
inert, rad. Resistant
1010 ohm·m; comparable with C6F14 reacts with liquid water
• Novec 7100 (segregated HFE) GWP=330; 106 ohm·m; 15-20% better coolant
contains CH3 group
~50 CHF/kg
54 CHF/kg
84 CHF/kg
• Novec fluids have the thermo-physical properties similar to C6F14 (especially Novec 649)
• Are widely used in the industry and produced in large quantities (NB: 3M monopoly!)
• Volume resistivity: acceptable for detector cooling applications (better than DI water)
• Warning: Novec fluids contain O. They are less inert and potentially less radiation resistant
than C6F14, hence require a more rigorous monitoring and additional (new) liquid conditioning
elements. This is the cost to pay for low GWP.
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Deliverables Included in the Supply
• studies of the initial purity of the as-provided fluids
• studies of the radiolytical decomposition of the gamma-irradiated with the stress on
detection and identification of toxic and corrosive compounds. Gas and liquid phases!
• evaluation of the efficiency of some classes of purification agents
• a written summary of the results of pilot studies
• final written report (long write-up) describing all analysis results, conditions, procedures
and protocols. The contractor is encouraged to provide his interpretations and
recommendations related to the results.
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