CA1160428A - Process for the extraction of tritium from heavy water - Google Patents

Process for the extraction of tritium from heavy water

Info

Publication number
CA1160428A
CA1160428A CA000320154A CA320154A CA1160428A CA 1160428 A CA1160428 A CA 1160428A CA 000320154 A CA000320154 A CA 000320154A CA 320154 A CA320154 A CA 320154A CA 1160428 A CA1160428 A CA 1160428A
Authority
CA
Canada
Prior art keywords
tritium
heavy water
column
water
liquid
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
CA000320154A
Other languages
French (fr)
Inventor
Allan H. Dombra
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Atomic Energy of Canada Ltd AECL
Original Assignee
Atomic Energy of Canada Ltd AECL
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Atomic Energy of Canada Ltd AECL filed Critical Atomic Energy of Canada Ltd AECL
Priority to CA000320154A priority Critical patent/CA1160428A/en
Priority to IL58977A priority patent/IL58977A/en
Priority to GB8000902A priority patent/GB2039866B/en
Priority to FR8001095A priority patent/FR2446798A1/en
Priority to DE19803001967 priority patent/DE3001967A1/en
Priority to BE0/199055A priority patent/BE881265A/en
Priority to JP561880A priority patent/JPS55132622A/en
Priority to SE8000447A priority patent/SE439476B/en
Priority to IT8067086A priority patent/IT8067086A0/en
Application granted granted Critical
Publication of CA1160428A publication Critical patent/CA1160428A/en
Expired legal-status Critical Current

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Classifications

    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01BNON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B4/00Hydrogen isotopes; Inorganic compounds thereof prepared by isotope exchange, e.g. NH3 + D2 → NH2D + HD

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Catalysts (AREA)
  • Separation By Low-Temperature Treatments (AREA)
  • Physical Or Chemical Processes And Apparatus (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

TITLE

PROCESS FOR THE EXTRACTION OF TRITIUM
FROM HEAVY WATER

INVENTOR
Allan H. Dombra ABSTRACT OF THE DISCLOSURE
A process for the extraction of tritium from a liquid heavy water stream comprising contacting the liquid heavy water with a countercurrent gaseous deuterium in a column packed with a water-repellent catalyst such that tritium is transferred by isotopic exchange from the liquid heavy water stream to the gaseous deuterium stream, passing the gas enriched in tritium from the column through means for removing tritium therefrom and returning the gas lean in tritium to the column, and obtaining a liquid heavy water output from the column, said heavy water being reduced in tritium content.

Description

1 ~"S~0~28 ~his invention rela-tes to a process for the extraction of tritium from a liquid heavy water stream.
Nuclear power reactors of -the type using heavy water (D20) as coolant and moderator incur a progress-ive build-up of tritiated heavy water (DTO) in the D2O and this can lead to problems oE controlling radiation exposure at the nuclear power stations. This D2O impurity is produced continuously in the reactor as the D2O is subjected to neutron irradiation. In present Canadian nuclear generating stations, the average tritium levels are the order of 1 curie per kg of D2O in the primary heat transport systerns and over 10 curies per kg of D2O in the moderator systems and these levels are rising. Thus the tritiumj while present in comparatively minute quantities~ because of its radioactiv.ity nonetheless poses signi~icant radiation problems where~er D2O leaks occur or where it is purged from the system.
At the present time tritium oxide tor "tritium water") can be enriched by various processes such as vacuum distillation or electrolytic cascade ~several stages of water electrolysis). However, these processes are not very suitable because of high toxicity of tritium oxida~
safety risks, low separation factor fo~ water distillation J
or high power consumption for the electrolysers. A more practical method is to either convert the tritiated heavy water to the elemental form, for example, ~-y water electrolysis or to e~tract tritium from water b~ catalytic exc~lange with a deuterium stream.
A process for removing protium and tritium from hea~y water by vapour-phase catalytic exchange is described in United States Patent No.3,505,nl7 issued to E. Roth on April 7~ 1970 Although the process described and claimed in this patent includes the steps oE tapping
2 8 the heav~ water contained in a nuclear reactor and subjec-ting said tapped heavy water to an iso-tope exchange reaction with gaseous deuterium, it is obvious from the disclosure that the "tap~ed heavy water" is heavy water vapour. Because the exchange is between water vapour and gas, the two streams ~low to the exchange column concurrently and the process must operate at elevated temperatures (80 to 400C using catalysts). This process involves the use of evaporators and condensers at each equilibrium exchanye step and this is most disadvantageous.
A process for hydrogen isotope concentration between liquid water and hydrogen gas is described in United States Patent No. 3,981,976 issued September 21, 1976 to W.H. Stevens and assigned to ~tomic Energy of Canada Limited. This patent points out that the process~may be used to reduce the tritium concentration, present as DTO, in heavy water that has been used in an operating nuclear reactor.
This is achieved by increasin~ the concentration of tritium in liquid water by donation from gaseous deuterium derived from the liquid water. The deuterium is produced from heav~ water in a deuterium gas generator.
It is an object of the present invention to provide a process ~or extraction oi tritium ~rom liquid h~avy water that operates at or near ambient temperatures and pressures.
It is another object of the invention to provide a process for removal of tritium from liquid heavy water that extracts, rather than concentrates, tritium from heavy water.
It is another object of the invention to provide a process for extraction of tritium from liquid heavy water tha-t operates without the need for evaporating ~2-.

)42~

and condensin~ heavy water at each e~uili~rium stage.
It is ano-ther object of the invention to provide a process for extraction of tritium from liquid heavy water that does not require a deuterium gas generator.
These and other objects of the invention are achieved by a process for the extraction of tritium from a liquid heavy water stream comprising: contactlng the hea~y water with a countercurrent gaseous deuter1um stream in a column packed with a water-repellent catalyst such that tritium is transferred by isotopic exchange from the liquid heavy water stream to the gaseous deuterium stream.
In drawings which illus-trate an emhodiment of the invention, Figure 1 is a flow diagram of the extraction process, and Figure 2 is a representative equilibrium diagram for the process, Referring to figure 1, a liquid heavy ~ater feed is passed through a purificakion stage 10. Depending on the quality of the feedwater, khe feédwater purification stage will include a filkering syskem ko remove suspended solids, an ion-exchange system to remove ionic compounds and a standard degassing system to remove dissolved gases such O~ and N2. If the feedwater is contaminated with oil or other organic ma-terials, it will be purified by charcoal adsorption or chemicals methods. Normally, the hea~y wate withdrawn from reactor systems is relatively clean and will he passed only through a filtering and an ion-exchan~e system.
The tritium to deuterium (T/DI atom radio (XO) in khe heavy water stream is in -the order of parts per millium (typically n ~ o ppml and the principle tritium-deuterium species, are DTO and D2O. After puri~ication, the liquid _3_ ~-~ 1$~)~28 stream is fed to the top of a catalytic isotope exchange column 11 in which the tritium is extracted from the liquid ¦ stream by contacting it with a counter flowing gaseous stream ¦ of DT - D2 in the column packed wi-th a water-repellent ¦ catalyst. The process is operative with any type of catalyst that is water~repellent but the preferred type is that described in United States Patent No. 3,888,974 issued June 10, 1975 to W.H. Stevens and assigned to Atomic Energy of Canada Limited. This catalyst consists of at least one catal~tically active metal selected from Graup VIII of the Periodic Table having a substantially liquid-water-repellent organic resin or polymer coating thereon which is permeable to water vapour and hydrogen ~as. This type of catalyst is also described in -the aforementioned Patent No. 3,981,976 and United States Patent No. 4,025,560 issued May 24, 1977 to John H. Rolston et al and assigned to Atomlc Energy o~ Canada Limited. After passing through the column the detritiated liquid heavy water (T/D = Xn~ is returned to the nuclear ~
reactor or other source. : :
The deuterium gas tT/D = yO) entering the bottom of the column 11 is lean in tritium (DT component) and after leavlng the column is enriched in tritium ~DT).
This gas (T/D = Yl) is purified.in gas purification stage 12 and sent to a cryogenic distillation stage 13 that lowers the concentration of the DT-T2 in the gas after which it is returned to the bottom of the column 11. The ~eedgas purification system for the cryogenic uni.t is designed to remove traces of impurities which condense and solidi:[y as the temperature of the feedstream drops (moisture, CO2, N2~ 2 CO). Typically, the feedgas puri.~icat;.on ~rain includes molecular sieve driers/ xe4enerati~e hcat exchangers and cryogenic silica gel or charcoal adsorbers. Distillation ~4-stage 13 ~ives 2s output a concentrated D'r-T2 gas stream which would normally be withdrawn into suitable containers, The cryogenic D2 distillation stage 13 may be replaced with other isotopic sepa.ation processes such as therm~l diffusion or gas chromatography.
The overall reaction in the catalytic isotope exchange column can be representecl as follows:

DT(g~ + D2(Q) ~-- D2(g) ~ DT(Q) . (1) The equilibrium constant K for the above reaction (,expressed in terms of equilibrium mole fractions o~ the' .reaction species) is as follows:

~ 7 [ .D,TO(Q)~ (2) : LDT(g) ~ ~ D2O(Q)'~
Since at low concentrations of DT and DTO, the mole fractions of D2 and D2O are nearly constant and approach unity, the above equation (2) can be simpli~ied as follows:
K = T/D atom ratio i.n the.liqui.d.DTO~.~ .O phase :
' T/D atom ra-tio in the gasëous DT-D2 phase ( ) provided the liquid phase is in equilibrium with the gas phase. '' Equation.(3) is also used co,mmonly to define~
the s~paration factor ~ ~or the exchange of isotopic species between the liquid and gas phases. Therefore, K = ~ in this case.
The e~uation for K based on partition function ratios given by Bron J et al in the paper "Isotopic Partition Function Ra-tios Involving H2, ~2~ H2S~H2Setand NH3", Z. Nat~lrforsch, Vol. 23a, pgs ~29-136, 19'73 is as follows:
ln k = 0.05352 + 0.2~362 (300/T~ + 0.462~1 (.300/T)' - 0.27574 (300/~3 ~ 0.062~0 (300/~ (4 whe.re T = Temperature, Kelvin ~ ~0428 This shows -that the separation actor at ambient temperature is approximately 1.6 ~ = 1.6387 at 25C).
These very use~ul separation ~actor levels are obtained in the present process provided that:
(1) water-repellènt catalysts are used~
(2) the atom ratio T/D in gas entering the column~ yO, is smaller than the atom ratio T/D in the liquid entering the column, XO, that is XO > yO.
As shown in Figure 2, the atom ratio T/D in 1~ liquid entering the` column, x , is greater than the atom ratio T/D in the gas entering the column, yO, that is xO > ~0;
the atom xatio T/D in the gas leaving the column, yl,~is greater than in the gas entering the column, that is, :

Yl > YO- ~s tritium is stripped from the liquid phase : ~.
xO > xn, where xn is T/D ratio in the liquid leaving the col~ . Figure 2 represents a simplified graphical deter-mination of thè number of equilibiriuM stages required to achieve a given extraction of tritium from the l.iquid-phase (frequently referred to as the ~cCabe-Thiele diagram~. It O involves alternative use of two plots: one representing a materials balance for each equilibrium sta~e, referred to as the operating line, and the other representing the ;
e~uilibrium T/D ratio in the liquid phase (x) and in the gas phase (y~, referred to as the equilibrium curve. A :
r~aterial balance for the exchange tower can be expressed by the following equation representing the terminal points of the o~erating line, that is, xO and Yl at the top of the tower and xn, y at the bottom of the tower:

L(.xo - xn) = G(Yl Yo ~ where L and G are molar liquid and gas flow rates, respectively, I lG~)428 ~ o achi.eYe the transfer of tritium .~rom the liquid to the gas phase, the operat~ng llne must always be below the equilibrium curve (Y~o ~ YO, Y1 ~ yO and xO ~ xn).

Claims

I claim:
1. A process for the extraction of tritium from a liquid heavy water stream containing 0.1 to 10 ppm of tritium comprising:
a) passing the liquid heavy water from which tritium is to be extracted through a purification stage, b) contacting the purified heavy water with a countercurrent gaseous deuterium stream in a column packed with a catalyst, consisting of at least one catalytically active metal selected from Group VIII of the Periodic Table and having a substantially liquid-water-repellent organic resin or polymer coating thereon which is permeable to water vapour and hydrogen gas, such that tritium is transferred by isotopic exchange from the liquid heavy water stream to the gaseous deuterium stream, c) passing the gas enriched in tritium from the column through a gas purification stage, d) passing the purified gas through a cryogenic distillation stage to remove tritium therefrom and returning the gas lean in tritium to the column, and e) obtaining a liquid heavy water output from the column, said heavy water being reduced in tritium content.
CA000320154A 1979-01-22 1979-01-22 Process for the extraction of tritium from heavy water Expired CA1160428A (en)

Priority Applications (9)

Application Number Priority Date Filing Date Title
CA000320154A CA1160428A (en) 1979-01-22 1979-01-22 Process for the extraction of tritium from heavy water
IL58977A IL58977A (en) 1979-01-22 1979-12-17 Extraction of tritium and protium from heavy water
GB8000902A GB2039866B (en) 1979-01-22 1980-01-10 Process for the extraction of tritium from heavy water
FR8001095A FR2446798A1 (en) 1979-01-22 1980-01-18 PROCESS FOR EXTRACTING THE TRITIUM FROM HEAVY WATER
DE19803001967 DE3001967A1 (en) 1979-01-22 1980-01-21 METHOD FOR EXTRACTION OF TRITIUM FROM HEAVY WATER
BE0/199055A BE881265A (en) 1979-01-22 1980-01-21 PROCESS FOR EXTRACTING THE TRITIUM FROM HEAVY WATER
JP561880A JPS55132622A (en) 1979-01-22 1980-01-21 Method of extracting tritium from liquid heavy water
SE8000447A SE439476B (en) 1979-01-22 1980-01-21 PROCEDURE FOR EXTRACTION OF TRITIUM AND EVENT PROTIUM
IT8067086A IT8067086A0 (en) 1979-01-22 1980-01-22 PROCEDURE FOR THE EXTRACTION OF TRITIUM FROM HEAVY WATER

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CA000320154A CA1160428A (en) 1979-01-22 1979-01-22 Process for the extraction of tritium from heavy water

Publications (1)

Publication Number Publication Date
CA1160428A true CA1160428A (en) 1984-01-17

Family

ID=4113387

Family Applications (1)

Application Number Title Priority Date Filing Date
CA000320154A Expired CA1160428A (en) 1979-01-22 1979-01-22 Process for the extraction of tritium from heavy water

Country Status (9)

Country Link
JP (1) JPS55132622A (en)
BE (1) BE881265A (en)
CA (1) CA1160428A (en)
DE (1) DE3001967A1 (en)
FR (1) FR2446798A1 (en)
GB (1) GB2039866B (en)
IL (1) IL58977A (en)
IT (1) IT8067086A0 (en)
SE (1) SE439476B (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5468462A (en) * 1993-12-06 1995-11-21 Atomic Energy Of Canada Limited Geographically distributed tritium extraction plant and process for producing detritiated heavy water using combined electrolysis and catalytic exchange processes

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3571524D1 (en) * 1985-04-25 1989-08-17 Sulzer Ag Process for the separation and enrichment of tritium from tritiated fluids, especially from cooling water of the primary cycle and the deuterium/tritium streams of a nuclear fusion plant
US10381121B2 (en) 2013-11-13 2019-08-13 Savannah River Nuclear Solutions, Llc Decontamination of tritiated water
US11058994B2 (en) 2019-01-18 2021-07-13 Savannah River National Solutions, LLC Tritium cleanup system and method

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1526867A (en) * 1966-08-09 1968-05-31 Commissariat Energie Atomique Improvements in means for removing protonium and tritium from heavy water
JPS5544786B2 (en) * 1972-05-04 1980-11-14
JPS4918680A (en) * 1972-06-05 1974-02-19
JPS5132800A (en) * 1974-09-11 1976-03-19 Shigeki Awata KAIRYOTABAKOTSUKI FUIRUTAA
DE2905585A1 (en) * 1978-04-13 1979-10-18 Sulzer Ag PROCESS FOR SEPARATION OF THE HYDROGEN ISOTOPES H, D, T IN ORDER TO SELECTIVELY REMOVE INDIVIDUAL ISOTOPES FROM A MIXTURE

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5468462A (en) * 1993-12-06 1995-11-21 Atomic Energy Of Canada Limited Geographically distributed tritium extraction plant and process for producing detritiated heavy water using combined electrolysis and catalytic exchange processes

Also Published As

Publication number Publication date
GB2039866B (en) 1982-12-22
JPS55132622A (en) 1980-10-15
IL58977A (en) 1982-12-31
GB2039866A (en) 1980-08-20
IT8067086A0 (en) 1980-01-22
BE881265A (en) 1980-05-16
SE439476B (en) 1985-06-17
DE3001967A1 (en) 1980-07-31
SE8000447L (en) 1980-07-23
FR2446798A1 (en) 1980-08-14

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