A Plan of Purification System for Lithium Loop of Advanced Fusion Neutron Source

A purification system for lithium loop is one of critical issues to design the accelerator-driven (IFMIF-type) fusion neutron source. It is written in IFMIF Intermediate Engineering Design Report that the levels of nonmetallic impurities such as nitrogen, oxygen, carbon, hydrogen isotopes and tritium should be less than 10, 10, 10, 10 and 1 wt.ppm, respectively, although there is little basis reported. To achieve the above impurities levels, especially nitrogen and hydrogen isotopes including tritium, it takes long time for purification before the main operation which generate neutron, and the data for these purification systems are so far insufficient to make an execution drawing. Therefore, a purification plan of lithium loop for Advanced Fusion Neutron Source (A-FNS) is suggested for early realization of A-FNS in Japan as below. In the suggested plan, the impurities levels of nitrogen and hydrogen isotopes including tritium are eased to 400 and 80 wt.ppm, respectively, while oxygen and carbon are the same as above. It is considered that the problems of nitrogen impurities would be plugging and erosion/corrosion, and those of hydrogen isotopes be plugging and tritium inventory in lithium. However, it is considered that the plugging would not be brought about, and the erosion/corrosion and the tritium inventory would not become critical to the lithium loop system under the operation temperature between 523 to 573 K and under the suggested impurities level. As the results, it is found that only a cold trap system for the purification system is necessary at first, and the hot trap system including nitrogen trap and hydrogen trap would become necessary after 4 or 5 years operation. That is, the adoption of the present suggestion could bring 4 to 5 years extension for the completion of the purification system in the execution drawing.30th Symposium on Fusion Technolog

A sophisticated remote maintenance method for the target assembly of Advanced Fusion Neutron Source

A key conception of the remote maintenance (RM) method is presented of the target assembly (TA) of Advanced Fusion Neutron Source (A-FNS). The RM method, newly proposed here, is aimed at (i) enhancing the modularity of the TA RM and (ii) keeping the compatibility with the materials irradiation tests, compared to the preceding TA RM design of International Fusion Material Irradiation Facility (IFMIF). A 3-dimensional kinematics simulation indicates that the clearance of 50 mm between the TA and high flux test module (HFTM) brings the independent removal from and installation in the test cell, regardless of the presence of the test modules in the test cell. A neutronics performance of the HFTM with the enlarged clearance is also studied. The gradient of the calculated neutron irradiation damage is found to be decreased and satisfies a users’ requirement of the irradiation environment when the clearance is enlarged from 2 to 52 mm. These simulation results suggest that the proposed TA RM method will enhance not only the modularity of the TA, but also improve the materials irradiation test environment.The 30th Symposium on Fusion Technology (SOFT 2018

新しい先進核融合中性子源ターゲットアセンブリ遠隔保守概念の提案

先進核融合中性子源(A-FNS)のターゲットアセンブリ(TA)の新しい遠隔保守概念を発表した。本概念は試験セル内機器の遠隔保守性の向上を目的としている。基本的アイデアは、TAと試験モジュール(TM)のクリアランスをIFMIF設計から大幅に広く取った点と遠隔保守機器のTAへのアクセスをTM側からビームダンプ側に変更した点である。3次元機構解析を実施し、既存のIFMIF設計での試験セルのサイズを変更することなく、本遠隔保守概念が成立することを明らかにした。さらに中性子輸送計算を行い試験片の中性子はじき出し損傷量を評価し、中性子照射試験に供するに十分な量であることを明らかにした。第12回核融合エネルギー連合講演

先進核融合中性子源材料照射試験モジュール設計

核融合原型炉炉材料の中性子照射特性試験を行うことを目的として、先進核融合中性子源(A-FNS)施設の設計活動を行っている。A-FNS用に、ハニカム型の容器に円柱形状のキャプセルを設置した材料照射試験モジュールを設計した。キャプセル内には微小試験片を装填し、液体金属を充填する。キャプセル周囲にはシースヒータを設置、キャプセルとハニカム型容器間にはヘリウムガスを流動し、試験片の照射温度を250～550℃に制御する。モンテカルロコードを用いた中性子輸送計算を行い、材料照射試験モジュールの核特性を評価した。微小試験片の中性子はじき出し損傷量は、20dap/fpy～5dpa/fpyとなり、本評価結果に基づき照射実験計画を確立した。第12回核融合エネルギー連合講演