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Title: A tritium vessel cleanup experiment in TFTR

Abstract

A simple tritium cleanup experiment was carried out in TFTR following the initial high power deuterium-tritium discharges in December 1993. A series of 34 ohmic and deuterium neutral beam fueled shots was used to study the removal of tritium implanted into the wall and limiters. A very large plasma was created in each discharge to ``scrub`` an area as large as possible. Beam-fueled shots at 2.5 to 7.5 MW of injected power were used to monitor tritium concentration levels in the plasma by detection of DT-neutrons. The neutron signal decreased by a factor of 4 during the experiment, remaining well above the expected T-burnup level. The amount of tritium recovered at the end of the cleanup was about 8% of the amount previously injected with high power DT discharges. The experience gained suggests that measurements of tritium inventory in the torus are very difficult to execute and require dedicated systems with overall accuracy of 1%.

Authors:
; ; ; ; ; ;  [1];  [2];  [3]
+ Show Author Affiliations
  1. Princeton Univ., NJ (United States). Plasma Physics Lab.
  2. Los Alamos National Lab., NM (United States)
  3. JET Joint Undertaking, Abingdon (United Kingdom)
Publication Date:
Research Org.:
Princeton Univ., NJ (United States). Plasma Physics Lab.
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
34437
Report Number(s):
PPPL-3081; CONF-9406270-5
ON: DE95009399; TRN: 95:009745
DOE Contract Number:
AC02-76CH03073
Resource Type:
Technical Report
Resource Relation:
Conference: 21. EPS conference on controlled fusion and plasma physics, Montpellier (France), 27 Jun - 1 Jul 1994; Other Information: PBD: Mar 1995
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION; TFTR TOKAMAK; TRITIUM RECOVERY; THERMONUCLEAR FUELS; THERMONUCLEAR REACTOR WALLS; LIMITERS; CLEANING; EXPERIMENTAL DATA; VACUUM SYSTEMS; INVENTORIES

Citation Formats

Caorlin, M., Kamperschroer, J., Owens, D.K., Voorhees, D., Mueller, D., Ramsey, A.T., La Marche, P.H., Barnes, C.W., and Loughlin, M.J.. A tritium vessel cleanup experiment in TFTR. United States: N. p., 1995. Web. doi:10.2172/34437.
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Caorlin, M., Kamperschroer, J., Owens, D.K., Voorhees, D., Mueller, D., Ramsey, A.T., La Marche, P.H., Barnes, C.W., & Loughlin, M.J.. A tritium vessel cleanup experiment in TFTR. United States. doi:10.2172/34437.
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Caorlin, M., Kamperschroer, J., Owens, D.K., Voorhees, D., Mueller, D., Ramsey, A.T., La Marche, P.H., Barnes, C.W., and Loughlin, M.J.. Wed . "A tritium vessel cleanup experiment in TFTR". United States. doi:10.2172/34437. https://www.osti.gov/servlets/purl/34437.
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@article{osti_34437,
title = {A tritium vessel cleanup experiment in TFTR},
author = {Caorlin, M. and Kamperschroer, J. and Owens, D.K. and Voorhees, D. and Mueller, D. and Ramsey, A.T. and La Marche, P.H. and Barnes, C.W. and Loughlin, M.J.},
abstractNote = {A simple tritium cleanup experiment was carried out in TFTR following the initial high power deuterium-tritium discharges in December 1993. A series of 34 ohmic and deuterium neutral beam fueled shots was used to study the removal of tritium implanted into the wall and limiters. A very large plasma was created in each discharge to ``scrub`` an area as large as possible. Beam-fueled shots at 2.5 to 7.5 MW of injected power were used to monitor tritium concentration levels in the plasma by detection of DT-neutrons. The neutron signal decreased by a factor of 4 during the experiment, remaining well above the expected T-burnup level. The amount of tritium recovered at the end of the cleanup was about 8% of the amount previously injected with high power DT discharges. The experience gained suggests that measurements of tritium inventory in the torus are very difficult to execute and require dedicated systems with overall accuracy of 1%.},
doi = {10.2172/34437},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Mar 01 00:00:00 EST 1995},
month = {Wed Mar 01 00:00:00 EST 1995}
}
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Technical Report:
View Technical Report (0.46 MB)
DOI:  10.2172/34437
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  • ; ; ; ...
    In the summer/fall of 1996 after nearly three years of D-T operations, TFTR underwent an extended outage during which large port covers were removed from the vacuum vessel in order to complete upgrades to the tokamak. Following the venting of the torus, a three tier system was developed for the outage in order to reduce and control the free tritium in the vacuum vessel so as to minimize the exposure to personnel during port cover removal and reinstallation. The first phase of the program to reduce the free tritium consisted of direct flowthrough of room air through the vacuum vesselmore » to the molecular sieve beds using the Torus Cleanup System. Real time measurements of the effluent tritium concentration were used to derive the amount of tritium removed from the torus. Once the free tritium in the vessel had been reduced to approximately 50 Ci, a second phase was initiated using a 55 Gallon Drum Bubbler System for the direct processing of the vacuum vessel to further lower the tritium level in the torus. Tritium oxide is absorbed by the bubbler system with the exhaust vented to one of the tritium monitored HVAC ventilation stacks. To preclude the release of tritium to the Test Cell location of TFTR and to minimize the exposure of workers, a variable flow exhaust system was employed in order to maintain a negative pressure in the vacuum vessel between 0.05" and 1.5" w.c. during the removal of port covers ranging in size from approximately 5 to 1000 in(superscript2). These systems were completely successful in reducing and controlling the free tritium in TFTR and were instrumental in maintaining ALARA (As Low As Reasonably Achievable) exposures to tritium during the 1996 outage. These systems are again being utilized during the safe shutdown and decommissioning of TFTR which commenced in April of 1997. This paper describes in detail the configuration of these systems and the data obtained during the outage and safe shutdown of TFTR.« less

  • The problems of tritium permeation through and loading of the TFTR vacuum vessel wall structural components are considered. A general analytical solution to the time dependent diffusion equation which takes into account the boundary conditions arising from the tritium filling gas as well as the source function associated with implanted energetic charge exchange tritium is presented. Expressions are derived for two quantities of interest: (1) the total amount of tritium leaving the outer surface of a particular vessel component as a function of time, and (2) the amount retained as a function of time. These quantities are evaluated for specificmore » TFTR operating scenarios and outgassing modes. The results are that permeation through the vessel is important only for the bellows during discharge cleaning if the wall temperature rises above approximately 150/sup 0/C. At 250/sup 0/C, after 72 hours of discharge cleaning 195 Ci would be lost.« less

  • The transmission of neutral beams through plasmas expected in the Tokamak Fusion Test Reactor (TFTR) has been investigated. An analytical expression for the transmission coefficient of a 120 keV deuterium beam through a tritium plasma was used and a model for the flux profile of the TFTR Neutral Beam System designed by LBL/LLL was developed and incorporated. The plasma is assumed to have a parabolic profile and is characterized by a major radius of 310 cm, a minor radius of 57 cm, and a central plasma density of greater than or equal to 0.4 x 10/sup 14/ cm-/sup 3/. Tomore » protect the stainless steel vacuum vessel walls of the TFTR device, tungsten plates are located inside the vessel. The loading of the tungsten protective plates during normal operation is well below the neutral beam fluxes which would melt the tungsten. The TFTR Neutral Beam System will inject a total of 20 MW of 120 keV deuterium atoms from twelve sources, as well as approximately 12 MW of 60 keV deuterium atoms. The fluxes anticipated on the tungsten plates due to an unattenuated beam which would be incident at an angle of 45/sup 0/ are less than or equal to 6.5 kW/cm/sup 2/. The fluxes due to an attenuated beam are calculated to be less than or equal to 0.35 kW/cm/sup 2/. For the maximum injection time of 0.5 second, a fault condition in which the plasma was not formed at the time of injection could induce a surface temperature very near the melting point of tungsten. For the standard 0.1 second injection time anticipated for TFTR, a similar fault condition would not cause the temperature to rise to more than 2000 K which is well below the melting point (3640 K) of tungsten.« less

  • The TFTR vacuum vessel is to be protected with tungsten plates from the effects of neutral beam impingement. A thermal analysis is performed to determine the maximum allowable beam intensity (power per unit area) under normal and faulted operating conditions. In order to permit a faulted pulse, or unattenuated injection, to occur after normal pulse series, the maximum neutral beam energy flux should be below 10 kW/cm/sup 2/ depending on the beam design configuration, to prevent the melting of the plates. The analyses were performed using an injection time of 0.5 second and a cycle time of 300 seconds.

  • A structural evaluation of the TFTR Device Vacuum Vessel components was undertaken in order to verify the vessel adequacy in the prescribed operating environment. The products of this investigation appearing in this report include; (1) An evaluation of the required vessel wall thickness for the vessel design operating environment of one atmosphere external pressure and 93/sup 0/C (200/sup 0/F) uniform temperature. (2) A verification of vessel integrity to preclude a fatigue type failure for reactor startup and shutdown cyclic life in the design environment. (3) A verification of stiffening ring structural integrity. (4) A discussion of the design guidelines tomore » be used in providing adequate penetration reinforcement when the desired penetration spacing has been defined.« less