skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Pellet Fueling and Control of Burning Plasmas in ITER

Abstract

Pellet injection from the inner wall is planned for use on ITER as the primary core fueling system since gas fueling is expected to be highly inefficient in burning plasmas. Tests of the inner wall guide tube have shown that 5mm pellets with up to 300 m/s speeds can survive intact and provide the necessary core fueling rate. Modeling and extrapolation of the inner wall pellet injection experiments from today's smaller tokamaks leads to the prediction that this method will provide efficient core fueling beyond the pedestal region. Using pellets for triggering of frequent small edge localized modes is an attractive additional benefit that the pellet injection system can provide. A description of the ITER pellet injection system capabilities for fueling and ELM triggering are presented and performance expectations and fusion power control aspects are discussed.

Authors:
 [1];  [2];  [1];  [1];  [1];  [1];  [1];  [3];  [1]
  1. ORNL
  2. General Atomics
  3. ITER International Team, Garching, Germany
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
981757
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Nuclear Fusion; Journal Volume: 47; Journal Issue: 5
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; EDGE LOCALIZED MODES; EXTRAPOLATION; FORECASTING; GUIDE TUBES; PELLET INJECTION; PELLETS; PERFORMANCE; SIMULATION

Citation Formats

Baylor, Larry R, Parks, P. B., Jernigan, Thomas C, Caughman, John B, Combs, Stephen Kirk, Foust, Charles R, Houlberg, Wayne A, Maruyama, S., and Rasmussen, David A. Pellet Fueling and Control of Burning Plasmas in ITER. United States: N. p., 2007. Web. doi:10.1088/0029-5515/47/5/008.
Baylor, Larry R, Parks, P. B., Jernigan, Thomas C, Caughman, John B, Combs, Stephen Kirk, Foust, Charles R, Houlberg, Wayne A, Maruyama, S., & Rasmussen, David A. Pellet Fueling and Control of Burning Plasmas in ITER. United States. doi:10.1088/0029-5515/47/5/008.
Baylor, Larry R, Parks, P. B., Jernigan, Thomas C, Caughman, John B, Combs, Stephen Kirk, Foust, Charles R, Houlberg, Wayne A, Maruyama, S., and Rasmussen, David A. Mon . "Pellet Fueling and Control of Burning Plasmas in ITER". United States. doi:10.1088/0029-5515/47/5/008.
@article{osti_981757,
title = {Pellet Fueling and Control of Burning Plasmas in ITER},
author = {Baylor, Larry R and Parks, P. B. and Jernigan, Thomas C and Caughman, John B and Combs, Stephen Kirk and Foust, Charles R and Houlberg, Wayne A and Maruyama, S. and Rasmussen, David A},
abstractNote = {Pellet injection from the inner wall is planned for use on ITER as the primary core fueling system since gas fueling is expected to be highly inefficient in burning plasmas. Tests of the inner wall guide tube have shown that 5mm pellets with up to 300 m/s speeds can survive intact and provide the necessary core fueling rate. Modeling and extrapolation of the inner wall pellet injection experiments from today's smaller tokamaks leads to the prediction that this method will provide efficient core fueling beyond the pedestal region. Using pellets for triggering of frequent small edge localized modes is an attractive additional benefit that the pellet injection system can provide. A description of the ITER pellet injection system capabilities for fueling and ELM triggering are presented and performance expectations and fusion power control aspects are discussed.},
doi = {10.1088/0029-5515/47/5/008},
journal = {Nuclear Fusion},
number = 5,
volume = 47,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • Pellet injection is the primary fueling technique planned for core fueling of ITER [ITER Technical Basis 2002 ITER EDA Documentation Series (Vienna: IAEA)] burning plasmas. Efficient core plasma fueling with deuterium and tritium D-T is a requirement for achieving high fusion gain and it cannot be achieved with gas fueling. Injection of pellets from the inner wall has been shown on present day tokamaks to provide efficient fueling and is planned for use on ITER. Modeling of the fueling deposition from inner wall pellet injection using the Parks ExB drift model indicates that pellets have the capability to fuel wellmore » inside the separatrix. Gas fueling calculations show very poor neutral penetration due to the high density and wide scrape off layer. Isotopically mixed D-T pellets can provide efficient tritium fueling that will minimize tritium wall loading when compared to gas puffing. Currently the performance of the ITER inner wall guide tube design is under test with initial results indicating that pellet speeds in excess of 300 m/s will lead to fragmented pellets. The ITER pellet injection technology requirements and remaining development issues are discussed along with a plan to reach the design goal for employment on ITER.« less
  • Pellet injection is the primary fueling technique planned for central fueling of the ITER burning plasma, which is a requirement for achieving high fusion gain. Injection of pellets from the inner wall has been shown on present day tokamaks to provide efficient fueling and is planned for use on ITER [1,2]. Significant development of pellet fueling technology has occurred as a result of the ITER R&D process. Extrusion rates with batch extruders have reached more than 1/2 of the ITER design specification of 1.3 cm3/s [3] and the ability to fuel efficiently from the inner wall by injecting through curvedmore » guide tubes has been demonstrated on several fusion devices. Modeling of the fueling deposition from inner wall pellet injection has been done using the Parks et al. ExB drift model [4] shows that inside launched pellets of 3mm size and speeds of 300 m/s have the capability to fuel well inside the separatrix. Gas fueling on the other hand is calculated to have very poor fueling efficiency due to the high density and wide scrape off layer compared to current machines. Isotopically mixed D/T pellets can provide efficient tritium fueling that will minimize tritium wall loading when compared to gas puffing of tritium. In addition, the use of pellets as an ELM trigger has been demonstrated and continues to be investigated as an ELM mitigation technique. During the ITER CDA and EDA the U.S. was responsible for ITER fueling system design and R&D and is in good position to resume this role for the ITER pellet fueling system. Currently the performance of the ITER guide tube design is under investigation. A mockup is being built that will allow tests with different pellet sizes and repetition rates. The results of these tests and their implication for fueling efficiency and central fueling will be discussed. The ITER pellet injection technology developments to date, specified requirements, and remaining development issues will be presented along with a plan to reach the design goal in time for employment on ITER.« less
  • Pellet injection from the inner wall is planned for use on ITER as the primary core fueling system since gas fueling is expected to be highly inefficient in burning plasmas. Tests of the inner wall guide tube have shown that 5mm pellets with up to 300 m/s speeds can survive intact and provide the necessary core fueling rate. Modeling and extrapolation of the inner wall pellet injection experiments from today's smaller tokamaks leads to the prediction that this method will provide efficient core fueling beyond the pedestal region. Using pellets for triggering of frequent small edge localized modes is anmore » attractive additional benefit that the pellet injection system can provide. A description of the ITER pellet injection system capabilities for fueling and ELM triggering are presented and performance expectations are discussed.« less
  • The paper reports on simulation of pellet-fueled plasmas in a fusion reactor. The simulations have been performed by means of the ASTRA transport code. We have studied physical modeling of pellet injection as well as the numerical conditions to resolve pellet injection correctly. As a first step the essential mechanisms for density control have been studied based on simplified assumptions with a generic source of additional heating. The experience gained has been used to simulate advanced scenarios including internal transport barriers. It has been confirmed that it is possible to drive the plasma of a next-generation tokamak into a high-Qmore » regime and to maintain it in a steady-state regime. Nevertheless, the pellet injection parameters required are rather demanding and imply a significant technological improvement of pellet injectors. Those investigations represent an improvement of simulations done earlier with a control of the central density at constant profile.« less
  • The results of development of a pellet fueling system for the International Thermonuclear Experimental Reactor (ITER) at St. Petersburg Technical University and the Efremov Institute are summarised. A pellet injection stand with ITER-like parameters, a continuous extrusion stand, a tritium pellet injector and other facilities are described. Physical problems of the pellet fueling are considered.