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According to a US Nuclear Lab (LBL), tritiated water (HTO) enters the body through breathing, ingestion, skin absorption from contaminated air and water, and “experiments show that exposure to tritiated water results in mutations and cell disruptions that can lead to cancer, heritable genetic defects, and reproductive and developmental effects [Straume, 1993]….although the health effects of the beta doses from tritium are believed to be qualitatively similar to health effects of gamma rays, the beta rays are believed to be more potent per unit energy deposition than gamma rays“. (See more at bottom of the page.)

Nonetheless, dumping Fukushima tritiated (radioactive) water into the Pacific and now evaporating it into air have continued to be practiced and proposed for Fukushima. Why? The reason seems unfathomable. Perhaps they don’t want word to get out that tritiated water can be filtered because it is obviously cheaper to just dump it into the air, ground and waterways, as the nuclear industry does the world over? And, governments-nuclear industry might have to clean up tritium contamination? A 2014 US DOE document states that it will continue to dump tritiated water into “slow-moving” groundwater at Hanford because filtering would cost between 12 cents to 50 cents per liter, for the energy, and less than one cent to dump it into groundwater.[1]

Tritiated water is highly corrosive so storage containers need to be monitored and frequently replaced. A half life of 12.7 years still means that it will be radioactive for well over 100 years, but that it degrades quickly enough that it must be replaced for nuclear weapon upkeep.

Japan has companies on the ground at Fukushima filtering the water, including tritium, or pretending to do so. Are the companies that inept? They have proven so for the filtration of radionuclides which are easier to filter. Is Japan diverting the tritium for weapons? Tritium is required for manufacture and upkeep of nuclear weapons. But, there are also tritium processing plants, which allow the recovery of Helium 3 from tritium, which is worth between $100 and 2,000$ per liter: “Helium-3 Recovery – Tritium radioactively decays to helium-3, which has become a precious commodity. One reason for the tremendous growth in demand for helium-3 is its use in neutron detection equipment that is being installed all over the world to protect our nation and its allies from terrorism. SRTE recovers, purifies, and bottles this valuable byproduct of tritium, and is the sole source of helium-3 gas in the United States.” http://www.srs.gov/general/news/factsheets/tritium_esrs.pdf
“Current US industrial consumption of helium-3 is approximately 60,000 liters (approximately 8 kg) per year;[27] cost at auction has typically been approximately $100/liter although increasing demand has raised prices to as much as $2,000/liter in recent years.” http://en.wikipedia.org/wiki/Helium-3 Tritium has actually sold for much more. But, tritium and helium 3 must be extracted from the water. It is not $2,000 per liter of tritiated water, but rather of the helium 3.

On the most basic level, separation of tritiated and non-tritiated water can be achieved due to differing characteristics, such as different freezing-melting points.

Health hazards of tritium are discussed below the following description of the Palladium Membrane Filter.

Here is one technology for filtering tritiated water. Westinghouse is currently owned by Toshiba:
“WSRC-TR-2001-00364
Design, Construction and Testing of a Practical-Scale Palladium Membrane Reactor for Cracking Tritiated Water

D. W. Howard and K. L. Sessions
Westinghouse Savannah River Company
Aiken, SC 29808

S. A. Birdsell
Los Alamos National Laboratory
Los Alamos, NM

This document was prepared in conjunction with work accomplished under Contract No. DE-AC09-96SR18500 with the U.S. Department of Energy.

Abstract

A palladium membrane reactor (PMR) system has been successfully designed, constructed, tested, and put into service at the Savannah River Site for recovering elemental tritium from tritiated water on Disposable Molecular Sieve Beds (DMSB), filled during tests of the Tokamak Fusion Test Reactor. This PMR system is the first known large-scale application of the PMR to routine, production recovery of tritium from tritiated water.

This PMR incorporated several new design features to achieve high conversion efficiency of tritiated water to elemental tritium, while operating at the high flow rates and low pressure drops needed for a practical production-scale operation. The PMR demonstrated >98% conversion of water to elemental hydrogen during “cold” (non-tritium) tests.

During the first integrated system test with tritiated water, over 4.8 lbs. of tritiated water were processed in a period of about 150 hours of continuous operation, recovering approximately 2400 liters of mixed ‘hydrogen’ isotopes (H, D, & T). The system is now in routine operation recovering tritium from the legacy of DMSBs generated during the Princeton tests. Future plans for the PMR system are to process over a dozen DMSBs, containing about 75 lbs. of tritiated water, recovering about 38000 liters of mixed hydrogen isotopes (primarily D).

1. Introduction

A Palladium Membrane Reactor (PMR) system to recover tritium from tritiated water has been successfully demonstrated on a laboratory scale at the Tritium Systems Test Assembly (TSTA) at Los Alamos National Laboratory [1]. Large quantities of tritiated water waste exist world-wide because the predominant method of cleaning up tritiated streams is to oxidize the tritium to tritiated water, which can be collected with high efficiency onto molecular sieves and stored for subsequent processing and/or disposal.

The PMR is also under consideration for the tritium processing plant for the International Thermonuclear Experimental Reactor (ITER), which would contain tritiated impurities such as water and methane. The tritium will require recovery from these impurities for economic and environmental reasons.

The PMR is a combined permeator and catalytic reactor. Heterogeneous catalysts are used to foster reactions such as water-gas shift reaction,

Q2O + CO = Q2 + CO2

and methane steam reforming,

CQ4 + Q2O = 3 Q2 + CO

where Q represents any of the hydrogen isotopes H, D, and/or T. Thermodynamics limit these reactions to only partial completion. A Pd/Ag membrane, which is exclusively permeable to hydrogen isotopes, is incorporated into the catalyst bed of the reactor. A vacuum maintained on the permeate side of the membrane, continuously removes the product hydrogen isotopes, and enables the reactions to proceed toward completion.

Previous papers [2, 3, 4] have reported the results of various PMR laboratory-scale testing. Tests have been performed on simulated fusion fuels without tritium, simulated fusion fuel with tritium, and tritiated water, at flow rates up to (1100 sccm total gas; 500 sccm of Q2O; and/or 40 sccm of CQ4).

The Savannah River Site (SRS) currently has in storage a large number of Disposable Molecular Sieve Beds (DMSBs) containing tritiated water recovered from the experimental runs at the Princeton Tokamak Fusion Test Reactor. These DMSBs are being processed to recover the tritium. The previous processing method required the desorbed water, driven off the DMSB by heating, to be reacted with heated Mg metal to convert the Q2O to Q2, which was then isotopically separated. The use of heated Mg to convert the Q2O to Q2, has multiple disadvantages: generation of contaminated solid waste, periodic shutdown (with hands-on, contaminated maintenance) to replace spent Mg, and low flow rate.

The present paper reports on the design, construction, and testing of a Palladium Membrane Reactor, now installed at the Savannah River Site and used for production-scale recovery of tritium from tritiated water. This PMR system has now eliminated the generation of solid waste, eliminated the need for replacement of spent Mg, and has shortened the processing time for each DMSB. This PMR was the product of a collaborative effort between the Savannah River Site and Los Alamos National Laboratory. The PMR was designed by LANL personnel, constructed by Johnson Matthey Inc., and tested by LANL and SRS personnel at LANL. SRS personnel designed the instrumentation, auxiliary equipment, and support equipment. The PMR was installed, started, and put into production operation by SRS personnel.

2. PMR Design
Figure 1 Palladium Membrane
Figure 1 shows a schematic drawing of the SRS PMR. This PMR was designed to be similar to the 1st stage PMR described by Birdsell & Willms [1] used for tritiated water processing, but having increased Pd/Ag tube permeation area and an increased ratio of permeation area to catalyst volume. The SRS PMR contains 16 tubes (vs. 6 for the LANL unit), each 28.25 inches long by 0.25 inch OD, but has a higher ratio of tube surface area to catalyst volume than the 1st stage of the LANL PMR system. In regards to the ratio of tube surface area to catalyst volume, the SRS PMR was designed to be more similar to the 1st stage PMR of LANL’s cold test bench PMR system, described by Birdsell, Willms, and Wilhelm [3].

The reactor body is approximately 30.5 inches long by 3.5 inch OD, constructed of 347 stainless steel. The SRS PMR contains approximately 4000 gms of Pt/a-Al2O3 catalyst (Engelhard A-16825). The catalyst pellets are approximately 0.125 inch diameter by 0.125 inch long. The catalyst surrounds the Pd/Ag tubes within the reactor body.

The sixteen Pd/Ag tubes are arranged on two concentric circles. The inner circle contains five tubes and the outer circle contains eleven. The tube arrangement was designed so that the majority of points in the catalyst bed would less than 0.3 inches from the nearest tube surface, and that no point would be more than 0.5 inch from the nearest tube surface. This was intended to minimize concentration gradients within the catalyst bed. The top end of each tube is sealed, and the bottom end passes through the bleed end cap assembly and is open to the vacuum manifold that routes to the product pumping system.

The bleed end cap is attached to the bottom of the reactor body. A ten-micron stainless steel filter separates the catalyst from the bleed end cap. The Pd/Ag tubes penetrate through the filter and the entire bleed end cap assembly and are welded to the outer surface of the bleed end cap. The byproduct gas (unreacted CO and H2O, unpermeated H2, and CO2) flows out of the catalyst bed, through the ten micron filter, and into the bleed end cap where it is pumped away by the by-product exhaust pump train. The ten-micron filter was intended to provide sufficient pressure drop to prevent channeling of the gas through the catalyst bed near the by-product exhaust port.

The vacuum manifold is welded to the outer portion of the bleed end cap assembly. The open end of each Pd/Ag tube connects to this vacuum manifold allowing the hydrogen that permeates into the tube to be removed from the reactor via the vacuum manifold and product pumping system.

A heating and insulating jacket surrounds the reactor body. The jacket has three separate heating elements. The first (top) element or zone is designed to heat the inlet portion of the reactor and is approximately six inches long. The second zone is approximately 18 inches long, and the bottom zone is approximately 6 inches long. There are two thermocouples associated with each heating zone; one thermocouple measures the temperature of the heating element while the other measures the skin temperature of the reactor body. Additionally 4 thermocouples measure temperatures within the catalyst bed: one on the centerline of the bed near the feed inlet, and 3 others 0.1 inch in from the ID of the reactor body spaced at 120° angular positions and approximately equal axial intervals. These thermocouples were intended to allow precise adjustment of a uniform temperature in the PMR.

3. PMR System
Figure 2 PMR Process Flow
Figure 2 shows the overall process flow diagram of the PMR system.

The PMR system is exhausted through three sets of pumps. Three Normatex scroll pumps (Model PV-12) arranged in parallel exhaust the product gas (hydrogen isotopes) from the vacuum manifold. Based on the PV-12’s performance curve, the three pumps in parallel were intended to achieve a suction pressure of approximately 1 torr at a flow rate of 0.5 std. liter per minute. The three scroll pumps discharge into a train of 4 Metal Bellows pumps (Model MB-151) arranged in series. The discharge from this pump train is collected into storage tanks for later isotopic separation. The byproduct gas (H2O, CO2, CO and residual H2) is exhausted by a train of 4 Metal Bellows pumps (Model MB-151) arranged in series and configured to pull the gas through a molecular sieve bed. The molecular sieve bed is intended to remove the unreacted water from the byproduct stream; the remaining gas is compressed by the pump train and discharged into storage tanks for further processing.

The carbon monoxide (research grade; minimum purity 99.99%) is supplied to the PMR process from a gas cylinder, through a pressure regulator, check valve, and a set of three automatic valves in a Block-and-Bleed configuration. The carbon monoxide supply can either be routed to the PMR through the DMSB (sweep mode) where the flowing CO helps to sweep the desorbed water vapor out of the DMSB, or be routed directly to the reactor inlet (bypass mode) to mix there with the stream of desorbed water.

Flow rates of both water vapor and carbon monoxide are measured and controlled by mass flow controllers and a PLC that adjusts the flow rate set points to maintain an excess of approximately 5%-20% CO in the PMR feed.

The PMR’s normal operating conditions will be between 400 –500 C, and 600 – 1000 torr, and flow rates from 100 – 3000 sccm.

Instrumentation for monitoring the performance of the PMR system includes a mass spectrometer sample point for the byproduct gas downstream of the byproduct molecular sieve bed, and two moisture meters on the byproduct stream, one upstream and one downstream of the byproduct molecular sieve bed. These two moisture meters provide the control of the residual moisture in the gas exiting the PMR, and indicate when the byproduct molecular sieve bed has become saturated and requires changeout.

3. Testing

3.1 Initial Testing

After fabrication by Johnson Matthey Inc., the PMR was installed in support and auxiliary equipment at LANL similar to the final equipment at SRS, and put through a “cold” (non-tritium) test regimen to check out the equipment, to condition the catalyst and to verify design performance. Diagnostic instrumentation at LANL used a gas chromatograph instead of a mass spectrometer.

The PMR was leak tested, and heated to operating temperature. The catalyst was dried by flowing dry argon through the PMR at operating temperature. The catalyst was conditioned by flowing a 5% oxygen in argon mixture through the PMR, followed by a 5% hydrogen in argon mixture, both at operating temperature. The permeation rate of hydrogen through the PD/Ag tubes was determined by supplying a mixture of 50% hydrogen in argon to the feed and measuring the flow rate of hydrogen gas in the product stream.

CO and H2O feeds that were similar to the design operating conditions were used for performance testing of the PMR. Water was sorbed onto a spare DMSB, which was subsequently used to supply the water vapor to the PMR system. This permitted demonstration of the ability to control the delivery of water vapor to the PMR. Both the sweep and bypass modes of mixing the CO and water vapor were tested and proved satisfactory. Better than 98% conversion of the water vapor to molecular hydrogen and removal from the fed stream was demonstrated at flow rates up to 500 sccm of water vapor.

3.2 Startup Testing at SRS

After initial testing at LANL, the PMR was shipped to SRS and installed into the pre-fabricated, permanent support and auxiliary equipment, in the tritium-processing production environment. The system was then put through a period of initial testing and checkout, which included leak-checking and electrical functionality.

The system was then subjected to a period of non-heated, non-tritium functional testing. This regimen verified operability of all valves, mass flow controllers, instrumentation, etc.

3.3 Integrated System Tests with Tritium

The first test with tritium used a DMSB containing approximately 4.8 lbs. of tritiated water, and was expected to yield approximately 2400 STP liters of hydrogen molecular isotopes if fully desorbed and converted. The first test was run with the CO feed in the bypass mode, and with an 8% excess of CO. Flow rates up to 500 sccm of water were used. A total of 1608 STP liters of molecular hydrogen isotopes were collected in the product tank, and the average water feed rate was 220 sccm. A total of 1584 liters of byproduct gas were collected, with an average composition of 9.5% CO, 88.3% CO2, and 0.3% molecular hydrogen isotopes. During this test no attempt was made to completely purge the feed DMSB of water.

Subsequent tests have operated the PMR with the CO feed in the sweep mode, which permits a more complete purging of the last water out of the DMSB. This mode of operation has been successfully demonstrated.

4. Routine Production Operations

The PMR system is now in routine production operation recovering hydrogen isotopes from the tritiated water on the DMSBs. Maximum sustained feed rates seem to be limited to about 390 sccm of water vapor, which seems to be limited by the pumping capacity of the product pump train, specifically the Metal Bellows pumps. There are indications that one or more of the Metal Bellows pumps may be malfunctioning. Currently, the PMR system is being used to recover hydrogen isotopes from the inventory of 14 DMSBs from the Princeton Tokamak Fusion Test Reactor. These DMSBs are estimated to have a total of about 70 lbs. of tritiated water, and are expected to yield about 35,700 STP liters of molecular hydrogen isotopes (primarily D).

In the future, the PMR system can be modified to process tritiated water from other offsite and onsite sources. The modifications required are mainly small piping configuration changes to physically connect other geometries of molecular sieve beds to the feed inlet.

5. Conclusions

This PMR system is the first known large-scale application of the PMR process to a routine, production recovery of tritium from tritiated water. This system achieves a high throughput rate of water, and produces no solid waste, thus reducing environmental impacts. It requires less contact maintenance than alternative processes, thereby reducing radiological exposure. The PMR offers a means to process the tritiated water in a more cost effective and environmentally friendly manner than alternative processes.

The design and construction of this PMR were straightforward. No unexpected difficulties in testing or operation have been found. The design appears to be scalable to higher flow rates and/or lower concentrations of hydrogen in the byproduct. The main limitation in achieving either of these goals may lie in the ability of tritium-compatible vacuum pumps to achieve lower pressures in the vacuum manifold at higher throughputs.

6. Acknowledgment

This document was prepared in connection with work done under Contract No. DE-AC09-96SR18500 with the U.S. Department of Energy.

7. References

S. A. Birdsell and R. S. Willms, Tritium Recovery from Tritiated Water with a Two-Stage Palladium Membrane Reactor, Fusion Engineering and Design, Vol. 39-40, ISFNT-4; 4th International Symposium on Fusion Nuclear Technology, Tokyo (Japan), 6-11 Apr. 1997.
R. S. Willms, S. A. Birdsell, and R. C. Wilhelm, Recent Palladium Membrane Reactor Development at the Tritium Systems Test Assembly, Fusion Technology, Vol. 28, No. 3, (1995) pp. 772-777.
S. A. Birdsell, R. S. Willms, and R. C. Wilhelm, Ultra-High Tritium Decontamination of Simulated Fusion Fuel Exhaust using a 2-Stage Palladium Membrane Reactor, Fusion Technology, Vol. 30, No. 3, Part 2A, (1996) pp. 905-910.
S. A. Birdsell, R. S. Willms, Effect of Inlet Conditions on the Performance of a Palladium Membrane Reactor, Proceedings of the 17th IEEE/NPS symposium on furion engineering, San Diego, CA, (Oct. 6-10, 1997) pp. 301-303.” http://sti.srs.gov/fulltext/tr2001364/tr2001364.html
[1] Regarding costs of filtration: “2014 EVALUATION OF TRITIUM REMOVAL AND MITIGATION TECHNOLOGIES FOR WASTEWATER TREATMENT, DOE/RL-2014-10, REVISION 0. AND HANFORD FEDERAL FACILITY AGREEMENT AND CONSENT ORDER (TRI-PARTY AGREEMENT) MILESTONE M-026-07”

Health Hazards of Tritium-HTO (Tritiated Water)

“4.5 Human Contact with Tritium Releases
For releases of tritium from the NTLF, pathways leading to internal exposures of tritium include:
� HTO vapor entering the body through respiration
� Tritium in water, breast milk, or foods ingested and absorbed through the gastro-intestinal tract
� HTO vapor in air taken up through the skin
� HTO in water taken up through the skin during dermal contact with the contaminated water; e.g., while swimming and wading.
[…]
Because few studies are available on tritium-induced health injury in humans, health-risk estimates for tritium must be based on the large number of experiments with animals and cell cultures [Straume, 1993]. These experiments show that exposure to tritiated water results in mutations and cell disruptions that can lead to cancer, heritable genetic defects, and reproductive and developmental effects [Straume, 1993]. These effects are qualitatively similar to the injuries caused by low linear-energy-transfer (LET) radiations produced by cesium-137 and cobalt-60, such as x-rays and gamma-rays, for which a significant amount of human data is available. The quantitative difference between tritium beta emissions and a standard low-LET radiation is expressed by the relative biological effectiveness (RBE). The RBE for tritium ranges from 1 to 3 [Straume, 1993]. This means that although the health effects of the beta doses from tritium are believed to be qualitatively similar to health effects of gamma rays, the beta rays are believed to be more potent per unit energy deposition than gamma rays.” http://www2.lbl.gov/ehs/esg/tritium/tritium/TritCh4.html
[NB: There are animals in the environment too. It’s not only humans.]

Radiation Biologist, Dr. Ian Fairlie, summarizes the hazards as follows:
“Summary of Part 2: The Radiation Hazards of Tritium

Many scientists have expressed concerns about tritium’s low dose factors and its radiotoxicity: indeed, demurring views about tritium’s official doses have existed for decades (for more recent, see Fairlie, 2007; Harrison et al, 2003, and CERRIE, 2004).

Part 2 reveals that a number of radiation protection precepts and procedures are deficient or inappropriate when determining tritium’s hazards. The report’s main arguments about tritium are summarised below.

1. Tritium’s unusual properties of extremely high mobility, exchangeability, and binding with organic materials are not properly recognised by official dose models.

2. Because of the short range of tritium’s beta particle, tritium’s damage depends on its exact location in the cell. For example, tritium next to a DNA molecule exerts more damage than tritium in, say, extracellular water. At present, it is not possible to model where tritium goes in the body with any accuracy. Official models assume that tritium (HTO) is distributed equally throughout the body, but we don’t know that. Some scientists think we should use safer models, in case equal distribution turns out to be wrong.

3. Tritium is often described as a “weak” beta-emitter, but in radiation biology, so-called “weak” beta particles are more effective (i.e., dangerous) than energetic ones. This is especially the case with tritium, but this is not acknowledged in setting its dose factor.

4. Much evidence indicates that tritium’s effectiveness (in radiation biology experiments
comparing tritium with gamma rays) is two or three times that recognised by the ICRP.

5. Little official recognition is given to tritium’s ability to incorporate in organic molecules to high levels as a result of chronic exposures that occur near Candu reactors.

6. Official dose models for organically bound tritium therefore significantly underestimate its doses.

From these points, examining tritium’s doses tends to turn into a critique of current official radiation protection precepts and practices. This is unfortunate, because few people outside of the nuclear industry and its regulators understand these. However, it is important that an effort is made, in order to appreciate the true degree of tritium’s hazards.

In a nutshell, the second part of this report concludes official attitudes on tritium are unscientific and incorrect. It concludes that the recent evidence of tritium’s hazards should be acknowledged by radiation protection agencies in Canada, that a precautionary approach should be adopted with dose factors for HTO and OBT being significantly increased.” http://www.greenpeace.org/canada/Global/canada/report/2007/6/tritium-report-canadian-facilities.pdf. “Tritium Hazard Report: Pollution and Radiation Risk from Canadian Nuclear Facilities” By Dr. Ian Fairlie June 2007, for Greenpeace.
For additional information see: http://www.ianfairlie.org