RECENT DESIGNS FOR ADVANCED FUSION-REACTOR BLANKETS

A series of reactor design studies based on the Tokamak configuration have been carried out under the direction of Professor Robert Conn of UCLA. They are called ARIES-I through IV. The key mission of these stu dies is to evaluate the attractiveness of fusion assuming different de grees of advancement in either physics or engineering development. Thi s paper discusses the directions and conclusions of the blanket and re lated engineering systems for those design studies. ARIES-I investigat ed the use of SiC composite as the structural material to increase the blanket temperature and reduce the blanket activation. Li2ZrO3 was us ed as the breeding material due to its high temperature stability and good tritium recovery characteristics. To reduce the activation caused by the using of Zr, isotopic tailoring is required. Also, W was selec ted as the divertor target. The activation caused by the Zr and W, eve n with isotopic tailoring, reduced the safety advantage for the SiC bl anket. The ARIES-IV is a modification of ARIES-I, The plasma was in th e second stability regime. Li2O was used as the breeding material to r emove Zr. A gaseous divertor was used to replace the conventional dive rtor so that high Z divertor target is not required. We investigated t he possibility of breeding without the use of Be. However, tritium sel f sufficiency could not be assured with the uncertainties in the neutr onic data. The safety advantage of ARIES-IV was enhanced by the remova l of the high activation materials. The physics of ARIES-II was the sa me as ARIES-IV. The engineering design of the ARIES-II was based on a self-cooled lithium blanket with a V-alloy as the structural material. Even though it was assumed that the plasma was in the second stabilit y regime, the plasma beta was still rather low (3.4%). To achieve an a cceptable neutron wall loading, the magnetic field is rather high. Thi s put an extra burden on a self-cooled liquid metal blanket. It was de termined that a self-cooled lithium blanket with bare walls was not ac ceptable for a reactor with ARIES-II type parameters. Therefore, an in sulating coating is required to assure an acceptable design window to reduce the MHD pressure drop. The ARIES-III is an advanced fuel (D-He- 3) tokamak reactor. The reactor design assumed major advancement on th e physics, with a plasma beta of 23.9%. A conventional structural mate rial is acceptable due to the low neutron wall loading. From the radia tion damage point of view, the first wall can last the life of the rea ctor, which is expected to be a major advantage from the engineering d esign and waste disposal point of view. Organic coolant was selected a s the reactor coolant to reduce the operating temperature compared to He, and to reduce the coolant pressure and improve thermal efficiency compared to water. However, the use of organic coolant raised safety a nd decomposition concerns.