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36 Credible fusion power-plant studies consider environmental, safety and health issues as the design is conceived. All the studies cited here employ low-activation structural materials and blankets. All minimize the tritium inventory and the sources of chemical energy—for example, by using flibe or Li2O instead of liquid Li. When all these steps have been taken into account, the activation is calculated, and its impact on maintenance, routine off-site dose rates, accidental doses, waste disposal and the need for costly nuclear-grade construction is assessed.
37 Figure 6 shows the calculated radioactivity of the Cascade reactor as a function of time after a 30-year lifetime. Shown are the activities of the reactor and shield, the target material (assuming a lead hohlraum) and the tritium per kilogram in the inventory. For comparison the inventory of a typical fission plant with the same power is shown. An hour or so after shutdown, tritium is clearly the main radiation source for fusion plants. Other sources of activity will be two or three orders of magnitude smaller than that in a fission plant. Calculations indicate that a fusion plant such as Cascade can meet all safety requirements without any nuclear-grade construction and that all waste produced will be amenable to shallow burial. The waste can thus be disposed of by processes less expensive than those used for fission waste. Note also that the radioactive lifetime of the fusion waste is orders of magnitude shorter than that of fission waste.
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Light-ion-driven fusion power plant designs have been studied. Driving high-gain targets requires intensities greater than 100 TW/cm2. To survive the effects of the target explosion, the diode must be several meters away, and the beams must be transported to the target. The diode on PBFA II is only about 15 cm away from the target. We must develop reliable, long-lifetime diodes that can be pulsed at 1-10 Hz and from which appropriate beams can be extracted.
4. Improve your vocabulary.
Make the following sentences complete by translating the words and phrases in brackets.
a) Central to the economics of any (силовой установки для ядерного синтеза с инерционным удержанием плазмы) is the fusion cycle gain.
b) The generator which (преобразует) thermal (энергию) (в электричество).
с) The drive energy can be delivered by (лазерами) or (ионными пучками).
d) Lasers (позволили) early (дешевым) target experiments to prove some of the (основных характеристик) of inertial confinement fusion.
e) However, the diode’s cost is proportional to the (максимальная потребляемая мощность) required.
f) Thus for good (эффективность) light must be extracted during (всё время накачки)
g) The ions are generally (ускоряют) in a single (этап).
h) Beams with these (характеристики) have not yet (продемонстрировали) the required (яркость).
i) The current (предел) is reached when (силы пространственного заряда) of the beam become (равными) to the applied (силы фокусировки).
j) The reactor vacuum requirement is (определяется) by the requirements of (распространения пучка).
V. Reading for General Understanding
A Check the comprehension of the texts “Reactors”, “Target Factory” and
“Environmental. Safety and Health Issues”.
1. A fusion target burns to completion in a few tens of picoseconds to 100 psec.
a) You are quite right.
b) No, you are wrong. A fusion target does not burn to completion. Some part of it remains.
c) Both of you are not right. A fusion target burns to completion in a few nanoseconds.
2. Neutrons carry away about a half of the thermonuclear energy.
a) You are mistaken. Neutrons carry always about two-thirds of the thermonuclear energy. B)It’absolutely true.
c) Neutrons carry away almost three-forths of the thermonuclear energy.
3. After exiting the reactor the granule bed is dryed with helium and transported around the loop, where heat and tritium are extracted.
a) You are mistaken. The granule bed is fluidized with hydrogen and transported around the loop, where heat and tritium are extracted.
b) The fluidized bed is transported along the loop, where heat and tritium are extracted.
c) After exiting the reactor the granule bed is fluidized with helium and transported around a loop, where heat and tritium are extracted.
4. The vapour fills the reactor and reaches a steady pressure in a time on the order of tens of microseconds.
a) You are right.
b) No, you are mistaken. The vapour fills the chamber and reaches a critical pressure in a time on the order of tens of microseconds.
c) You are wrong. The vapour fills the chamber and reaches a steady pressure in a time on the order of tens of microseconds.
5. The beams can be bent out of the direct path with granules that are themselves out of the line of sight.
a) You are right. It is quite right.
b) You are wrong. The beams can be bent out of the direct path with magnets.
c) It is not so. The magnets are on the line of sight.
6. Some granules may collide due to the shock.
a) You are mistaken. Some granules may break down into several parts.
b) It’s not true. The granules may break apart due to the shock.
c) Some granules may break in two due to the shock.
7. The gain at low drive energy depends upon the breaking down of the capsule.
a) The gain at low drive energy depends upon the inner surface of the capsule.
b) The gain at low drive energy depends upon the coating of the capsule.
c) You are wrong. The gain at low drive energy depends upon the surface finish of the capsule.
8. The cost of a reactor test facility will be driven by the cost of the driver, so it is critical to obtain ignition at large drive energy.
a) It is critical to obtain ignition at maximum drive energy.
b) It is critical to obtain ignition at minimal drive energy.
c) It is critical to obtain ignition at small drive energy.
9. Such small reactor should not be expensive to construct or operate.
a) It’s true.
b) It’s wrong. Such small reactor should not be cheap to operate.
c) It’s not quite right. Such small reactor should be rather simple in design.
B Pick out from the texts “Reactors”, “Target Factory” all the word combinations with the following words (terms) and give their Russian equivalents.
target plant
debris bed
energy technique
pulse gas
power vapour
reaction vacuum
beam waste
VI. Reading for Detail and Language Study.
A Find in the texts above-mentioned the English equivalents for the following phrases.
| Источник энергии | Простота |
| Силовая установка | Способность |
| Выгоды и проблемы | Скорость пучка |
| Справляться с ч-л | Радиус отверстия для пучка |
| Керамические гранулы | Магнитное поле |
| Лазер на твёрдом теле | Удлинять |
| Запускающее устройство | Содержать |
| Мишень | Термоядерная энергия |
| Луч | Скорость осаждения |
| Горение | Испарять |
| Микровзрыв | Проникать |
| Распространение луча | Поглощать |
| Частота повторения импульсов | Нагрузка на стенку реактора |
| Ускоритель | Слой |
| Лёгкие ионы | Извлекать |
| Тяжёлые ионы | Зеркало |
| Лазерный диод | Расстояние |
| Импульсный режим | Диаметр |
| Газовая среда | Угол освещения |
| Кпд | Прямая бомбардировка нейтронами |
| Свет | Смачивать |
| Требуемая энергия | накачивать |
| Надёжность | Замена |
| Ток | Толщина |
| Яркость | метод |
В Translate the following words and expressions
a) target factory;
b) reactor vacuum requirement;
c) power balance equation
d) net annual energy
e) cost reduction
f) overlapping narrow absorption band
g) energy transfer time
h) desired extraction time
i) conventional high-energy accelerators
j) beam velocity
k) target debris
C Translate the text “Environmental, Safety and Health Issue” in written form.
VII Oral Practice
A Answer the questions on the texts
1. What is fusion?
2. What are the problems facing inertial confinement fusion?
3. How many components does an inertial fusion power plant have?
4. In what way can the power plant output be varied?
5. What is the fusion cycle gain?
6. What can deliver drive energy?
7. What are the advantages of Nd: glass lasers?
8. Why is the use of the KrF laser made complicated?
9. How large is the anticipated pumping time?
10.What happens in a light-ion accelerators?
11.How many steps are needed to accelerate the ions?
12.Why heavy ion accelerators are the best candidates for a reactor driver?
13.What kinds of heavy-ion accelerators are studied in Europe and the USA? Why? What are their advantages?
14.Name heavy ions.
A
R e a c t o r s
1. What types of reactors do you know?
2. What are the advantages and disadvantages of Sombrero, Osiris and Cascade reactors?
B
