D型照射リグの設計報告書

Design of uninstrumented irradiation subassembly type-D (UNIS-D)

岡本 薫; 宮川 俊一; 三次 岳志 ; 北村 了一

Okamoto, Kaoru; Miyakawa, Shunichi; Mitsugi, Takeshi; Kitamura, Ryoichi

本書は、高速実験炉「常陽」MK-III炉心以降に使用する新型の燃料照射試験用オフライン照射リグであるD型照射燃料集合体(以下、D型照射リグと呼ぶ。)の開発についてまとめたものである。D型照射リグは、燃料要素の再装荷能力、照射条件設定能力、既存照射リグとの燃料保持構造の互換性及び各種コンパートメントの装填能力を有しており、従来の照射リグに比べ継続照射試験時の取り扱い性能の向上、照射温度条件設定数の拡大、構造上の課題への対応を図っている。D型照射リグは、内部に燃料要素を納める二重の円筒管(以下、コンパートメントと呼ぶ。)を最大18本装填することが可能なコンパートメント型照射リグである。D型照射リグには、B型照射リグで使用している型コンパートメント(燃料要素装填数最大5本)及びD型照射リグ用に開発した型コンパートメント(燃料要素装填数1本)の2種類を混在させ装填することが可能である。集合体内には、型コンパートメントを最大6本、型コンパートメントを最大18本装填可能である。また、コンパートメント毎に照射温度条件を設定可能なので、D型照射リグ1体で最大18の互いに異なる条件を設定することが可能であり、構造設計の妥当性及び要求性能を満たしていることを確認した。

In the needs of the fuel irradiation test in "Joyo" MK-III core, there have been required that the irradiation of high performance fuel at high liner heat rate to high burn-up range, or the irradiation of advanced fuel such as MA fuel and Vipac fuel. In order to carry out these irradiation tests, newly designed irradiation subassembly is required with special features of; (1)Capability of the re-assembling after post-irradiation examination, even if the number of fuel in the identical irradiation condition decreases because of intermediate inspection. (2)Enhanced flexibility of the irradiation temperature setting ( in the present, UNIS-B's has 6 cases on the maximum). (3)Sufficient flexibility for the coolant flow distribution in the subassembly by extending variety of the flow rate setting. UNIS-D is a fuel irradiation subassembly which has been developed from above viewpoints. It is a compartment loading type irradiation subassembly that is able to load maximum of 18 compartments. Two types of compartments -type and -typc arc prepared for UNIS-D. Thc sufficient consideration has also been made on the rc-assembling. A -type is the same compartment as the existing UNIS-B's and a -type is the newly designed one for UNIS-D. Three to five fuel pins are loaded into a -type compartment and only one pin is loadcd into a -type compartment. It is possible to carry out the irradiation test in a maximum of 18 test temperature conditions within a subassembly, since it has the sufficient flexibility for the coolant flow distribution. As for the development of UNIS-D, we have finished the detailed structure design and the design verification by the water flow examination, which confirmed that the UNIS-D exceeded its required performances in use and that its structure design was satisfactory.