EP2668831A1

EP2668831A1 - Tunable fusion blanket for load following and tritium production

Info

Publication number: EP2668831A1
Application number: EP12739212.4A
Authority: EP
Inventors: Jeffery Fredrick LATKOWSKI; Kevin James KRAMER; James Alexander DEMUTH; Kevin Morris
Original assignee: Lawrence Livermore National Security LLC
Current assignee: Lawrence Livermore National Security LLC
Priority date: 2011-01-28
Filing date: 2012-01-30
Publication date: 2013-12-04
Also published as: JP2014508289A; CN103340019A; CA2822075A1; WO2012103548A1; RU2013133629A

Abstract

A fusion chamber for an inertial confinement fusion power plant is disclosed. The chamber includes regions for the flow of coolant around the exterior of the chamber, together with compartments of high temperature refractory metal alloys such as tungsten and vanadium which contain tin or other materials having the desired neutron interaction properties. The tin can be inserted and removed to increase or decrease the thermal power output and increase or decrease the corresponding tritium breeding ratio.

Description

Tunable Fusion Blanket for Load Following and Tritium Production

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0001] The United States Government has rights in this invention pursuant to Contract No. DE-AC52-07NA27344 between the U.S. Department of Energy and Lawrence

Livermore National Security, LLC, for the operation of Lawrence Livermore National Laboratory.

CROSS-REFERENCE TO RELATED APPLICATION

[0002] This United States Patent Application is related to and claims priority from commonly assigned earlier filed United States Provisional Patent Application entitled "Tunable Fusion Blanket Offering the Ability to Produce Extra Tritium and Load Follow," filed January 28, 201 1 , as U.S. Application No. 61/437,508, and Patent Cooperation Treaty Application entitled "Inertial Confinement Fusion Chamber," filed November 8, 201 1, as PCT Serial No. US2011/059814. Each of these applications is incorporated by reference herein.

BACKGROUND OF THE INVENTION

[0003] This invention relates to the production of electrical power using fusion reactions. In particular, the invention relates to a fusion chamber for an inertial confinement fusion power plant in which continuous real-time adjustment of fusion power and tritium production rates are enabled.

[0004] The National Ignition Facility (NIF), the world's largest and most energetic laser system, is now operational at Lawrence Livermore National Laboratory (LLNL) in

Livermore, California. One goal of operation of the NIF is to demonstrate fusion ignition for the first time in the laboratory. Initial experiments are calculated to produce yields of the order of 20 MJ from an ignited, self propagating fusion burn wave. The capability of the facility is such that yields of up to 150-200 MJ could ultimately be obtained. The NIF is designed as a research instrument, one in which single "shots" on deuterium-tritium containing targets are performed for research. A description of the NIF can be found in Moses et al, Fusion Science and Technology, Volume 60, pp 11-16 (201 1) and references therein.

[0005] There is a rapidly growing need for power, and especially for clean power. At LLNL a project known as Laser Inertial-confinement Fusion Energy, (often referred to herein as "LIFE") is working toward introduction of fusion based electric power plants into the U.S. economy before 2030, and in a pre-commercial plant format before that. LIFE technology offers a pathway for the expansion of carbon-free power around the world. It will provide clean carbon-free energy in a safe and sustainable manner without risk of nuclear

proliferation.

[0006] One challenge with respect to LIFE, just as with any technology for generating electrical power to be distributed to large numbers of consumers, is the requirement for differing amounts of power to be provided at different times, e.g. at different times of day, month and year. Consumers expect to have highly reliable electric power, necessitating that power plants produce more power, for example, for air conditioning, during warmer months or days, than at other times of the year. The result is that utilities providing that electrical power must be able to increase and decrease the amount of electric power produced by their facilities. Thus, among the challenges with respect to fusion power, is providing mechanisms by which a reliable long-lived fusion chamber can be provided in which the fusion reactions occur, yet which can provide greater or lesser amounts of heat at different times for generation of electric power.

[0007] In the technology described herein, a fusion power plant is provided with a fusion chamber into which capsules containing deuterium and tritium fuel are introduced multiple times per second. As the individual fuel capsules contained within hohlraums ("targets") reach the center of the chamber, banks of lasers fire on the targets, heating and compressing the fuel to create a fusion reaction. Heat from the fusion reaction is captured by coolant circulating around the chamber. This heat is then used to generate electricity. A desired aspect of plant operation is production of tritium to replace that burned in previous targets.

[0008] Our approach to the architecture of the fusion chamber utilizes a segmented tubular design for the first wall, as described in more detail in the commonly assigned patent application "Inertial Confinement Fusion Chamber" referenced above. That design provides a fusion chamber with efficient thermal coupling, low mechanical stress, and a high strength to weight ratio. The modular approach of the fusion chamber also decouples it from the optical system, allowing rapid removal and replacement of the blanket and first wall modules with only a need to make and break plumbing connections, not reconfigure accurate optical pathways. The fusion chamber is cooled with liquid lithium coolant circulating through individual segments of the fusion chamber.

[0009] This invention offers the operator of a fusion power plant the added flexibility of adjusting the tritium breeding ratio and thermal power by means of filling or emptying regions within the fusion blanket. These adjustments allow for fusion plant load-following, enabling the fusion blanket to be tuned to deliver different amounts of thermal power and corresponding electric power to the grid in real-time, and to also control the amount of tritium production.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 illustrates the fusion chamber and its segmented design;

[0011] Figure 2 is a perspective view of one-half of one segment of the fusion chamber;

[0012] Figure 3 is a cross-sectional view of one segment of the fusion chamber shown in Figure 2; and

[0013] Figure 4 is another cross-sectional view of a segment of the fusion chamber shown in Figure 2 illustrating additional compartments used to provide control over output power and tritium breeding.

DETAILED DESCRIPTION OF THE INVENTION

[0014] Figure 1 is a diagram illustrating the overall design of a fusion chamber 20 as may be used for implementation of our invention. This chamber 20 will be situated within a fusion power plant such as described in our co-pending United States patent application entitled "Inertial Confinement Fusion Power Plant Which Decouples Life-Limited

Components From Plant Availability," filed November 8, 201 1 , as serial number

PCT US2011/059820, the contents of which are herein incorporated by reference.

[0015] As shown in Figure 1 , the chamber consists of multiple identical sections 100. Each section 100 can be factory built and shipped to the power plant site using conventional transportation equipment. Within an on-site maintenance facility, described in our co- pending application referenced immediately above, the modular chamber sections are mounted within a common support frame. The fully assembled chamber and frame are then transported for installation within a vacuum vessel surrounding the chamber. Installation of the chamber requires only the connection of cooling inlet pipes and outlet pipes to each quarter-section of the chamber, which is independently plumbed.

[0016] Figure 2 is a perspective view of a one-half segment 100 of the fusion chamber 10. As illustrated, the segment has a first wall which consists of parallel arranged tubes 1 10 which cover the underlying structure, and through which lithium coolant is circulated. The beam port openings 120 in the segment are also illustrated. Lithium is sent first to a plenum that feeds coolant to one-quarter of the full chamber. Coolant is first routed to the first wall tubes, where it experiences the highest heat flux. Upon exiting from the first wall tubes, the lithium is circulated into the blanket entry port 130. Coolant existing the blanket does so through port 140. The four one-quarter sections of the full chamber are independently plumbed.

[0017] To enable the laser beams to reach chamber center forty-eight openings 120 totaling about 5% solid-angle are provided. At the beam ports, the first wall pipes are routed radially outward and then they wrap around on the back side of the blanket. Additional openings are provided at the top and bottom of the chamber for interfaces with the target injection system and the debris clearing / vacuum pumping / target catching systems, respectively.

[0018] Figure 3 is cross section through the mid-point of an ordinary segment 100, that is a segment which does not include the features of this invention. Depending upon the extent to which adjustment of power production and tritium breeding are desired, only some segments of the fusion chamber may include the features of this invention. On the other hand, greater flexibility can be achieved by including the features of this invention in all segments of the chamber, one such segment being illustrated in Figure 4 below.

[0019] In Figure 3 the first wall tubing 1 10 is illustrated, along with the underlying structure 150. Liquid lithium coolant enters the tubing 1 10 through a plenum 160 which is coupled to all of the tubes of the segment 100. A similar plenum (not shown) on the other side of the segment collects the liquid lithium after it has passed through the tubing 110. Once lithium exits the first wall tubing 1 10, it may be recirculated into the underlying structure 150 for additional heating of the coolant. In an alternate implementation all of the lithium is recirculated, which results in the need for only one cooling loop for segment 100. If desired, the first wall tubing 1 10 and the underlying structure 150 can be independently plumbed to satisfy different cooling requirements and/or enable the use of alternate coolants.

[0020] Cooling of the underlying structure 150 is designed such that the coldest coolant is delivered to the structural materials. This is accomplished through use of "skin cooling" with the coolant entering the blanket at the top and flowing down at high speed through smaller cooling channels. The coolant turns around when it reaches the bottom of the blanket and then flows up through the bulk region 170 at much lower speed. The low temperature and high speed in the skin region provides the most effective cooling. The blanket coolant is introduced through port 130 and extracted from a similar port 140.

[0021] As described in more detail in the patent applications referenced herein, coolant entering the first wall tubes at 470°C will leave the first wall and enter the underlying structure (blanket) at approximately 510°C. The coolant reaches approximately 550°C at the bottom of the blanket. With bare steel, the coolant heats up at the top of the blanket to an outlet temperature of 575°C. Higher temperatures can be achieved through use of nonstructural insulating panels. For example, tungsten is compatible with liquid lithium to more than 1300°C. Our design used bare steel and provides lithium at an exit temperature of 575°C. By appropriate selection of materials, however, a future fusion chamber design would allow even higher temperatures.

[0022] The fusion chamber is designed according to the ASME piping code. Specifically, the chamber is designed to one-third of a given material's ultimate tensile strength, two-thirds of its yield strength, two-thirds of its creep rupture strength and a 0.01% creep rate per 1000 hours. Temperature-dependent properties are used in such evaluations.

[0023] Our invention provides a fusion chamber that offers the operator of the power plant the flexibility of adjusting the tritium breeding ratio and the thermal power by filling or draining regions within the fusion blanket. These real-time adjustments may be required when it is desired to produce additional tritium, for example, to overcome shortages resulting from lower-than-expected production, or higher-than-expected losses, or to produce tritium to fuel new fusion facilities. These adjustments allow for the fusion power plant to load follow, enabling it to be tuned to deliver different amounts of thermal power, and corresponding electrical power, to the grid in real time.

[0024] The real-time adjustment of the tritium breeding ratio and the thermal output power is accomplished by filling compartments, e.g. compartment 170, in the fusion blanket with tin or other materials that have the desired neutron interaction properties. The material can be inserted and removed to the desired level to increase or decrease the thermal power output and increase or decrease the corresponding tritium breeding ratio. The materials used can be stagnant, flowing liquid, or movable solids. If desired, additional neutron producing materials such as beryllium or beryllium titanium (Bei₂Ti) can further improve performance. By enabling the fusion blanket to capture neutrons and energy released from the fusion reaction, the collected energy may be converted to tritium for new fusion fuel production and to thermal power in the form of flowing high temperature coolant.

[0025] Figure 4 illustrates one implementation of the compartments 200. The

compartments 200 are formed from high temperature refractory metal alloys to allow maximum thermal power production while maintaining high strength in the structural components. These alloys include tungsten and vanadium, as well as other materials. The compartments can be selectively filled and emptied with high temperature resistant materials such as tin or gadolinium,

[0026] In previous inertial fusion energy engines, thermal power was proposed to be reduced by reducing fusion target output, reducing the repetition rate of the fusion source, or dumping excess thermal power using cooling towers. Each of these approaches negatively impact the economics of the power plant. In contrast, our approach enables adjustment of thermal power and tritium production without negatively impacting the economics of the power plant.

[0027] In the illustrated embodiment of Figure 4, tin is employed within the tungsten chambers 200. The tin is stagnant, but it can be pumped into position or drained (or otherwise inserted and removed) to change the fusion engine from "power mode" with the tin present, to "tritium breeding mode" with the tin removed. Our analysis of the tritium breeding ratio and the gain of the bulk material are shown in the table below. With an all liquid lithium cooled blanket, that is, with all segments of the fusion chamber being as illustrated in Figure 3, the tritium breeding ratio and gain are shown in the first row. With tungsten compartments containing tin (and emptied of tin), the tritium breeding ratio and gain are shown in the second and third rows of the table. Finally with tungsten compartments loaded and drained with a Bei₂Ti/Sn blanket, the results are shown in the last two rows of the table. Design Tritium Breeding Ratio Gain

All Lithium Blanket 1.48 1.12

Loaded Tin Blanket 1.15 1.21

Drained Tin Blanket 1.33 1.14

Loaded Be^Ti/Sn Blanket 1.02 1.32

Drained Bej₂Ti/Sn Blanket 1.18 1.27

[0028] In contrast to prior approaches, our invention allows real-time adjustment. The fusion thermal power produced and tritium production rate can be constantly tracked and traded off with operating conditions as needed to product excess tritium for new plant startup or to reduce power production of the plant during low demand periods.

[0029] The foregoing has been a description of a preferred embodiment of the invention. It will be appreciated that variations may be made in the manner by which the materials are added to or removed from the fusion blanket to enable control of the thermal power output and the tritium breeding ratio. Accordingly, the scope of the invention as defined by the appended claims.

Claims

What is claimed is:

1. A fusion chamber comprising:

a plurality of segments which when fitted together form the fusion chamber, each segment including:

a first wall positioned to face a central area of the chamber within which fusion reactions occur;

an blanket region disposed behind the first wall and including passages therein for receiving fluid coolant; and

wherein at least one of the segments includes an additional region within which a high temperature resistant material can be provided for capturing additional neutrons from a fusion reaction within the chamber.

2. A fusion chamber as in claim 1 wherein the additional region comprises a compartment for containing the high temperature resistant material.

3. A fusion chamber as in claim 2 wherein the high temperature resistant material comprises tin.

4. A fusion chamber as in claim 2 wherein the high temperature resistant material comprises beryllium.

5. A fusion chamber as in claim 2 wherein the high temperature resistant material comprises beryllium titanium (Bei₂Ti).

6. A fusion chamber as in claim 2 wherein the high temperature resistant material comprises gadolinium.

7. A fusion chamber as in claim 2 wherein the compartment comprises at least one of tungsten and vanadium.

8. A fusion chamber as in claim 1 wherein the first wall of each segment comprises a set of tubes arranged in parallel across a front wall of the segment, each tube extending from a first plenum disposed behind the front wall to a second plenum disposed behind the front wall, the plenums adapted to be coupled to a supply of fluid coolant for cooling the set of tubes.

9. A fusion chamber as in claim 1 wherein each one of the segments includes the additional region within which a high temperature resistant material can be provided for capturing additional neutrons from a fusion reaction within the chamber.

10. A fusion chamber as in claim 1 wherein each segment further includes at least two openings to allow a laser beam to pass through the segment to a central region of the chamber and supporting structure to support that segment in position to form the fusion chamber.

1 1. A fusion chamber as in claim 1 wherein the fluid coolant comprises liquid lithium.

12. In a fusion chamber having a first wall positioned to face a central area of the chamber within which fusion reactions occur and including a blanket region disposed behind the first wall which includes passages for receiving fluid coolant, a method of adjusting the output power of the fusion chamber comprising:

controllably inserting into and removing from the blanket a material for capturing additional neutrons from the fusion reactions.

13. A method as in claim 12 wherein the step of controllably inserting into and removing from the blanket a material for capturing additional neutrons from the fusion reactions further controls breeding of tritium in the blanket region.

14. A method as in claim 12 wherein the blanket region further includes compartments for the material for capturing additional neutrons.

15. A method as in claim 14 wherein the material comprises tin or gadolinium.

16. A method as in claim 15 wherein the fluid coolant comprises lithium.