This is my best guess.

I think it will be difficult to find the "exact" English translation of an internal company organization, so I'm providing you my best guess.

Hope this helps.

investigative commission of Inspection and Evaluation Guidelines for Reactor Internals of Nuclear Plant

http://ci.nii.ac.jp/naid/110002527184

My answer is based on my findings below:

検討会 = investigative committee
点検評価ガイドライン (for) inspection and evaluation guidelines
炉内構造物等 = reactor internal structures (please see websites below)

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V...

The Burg spectrum estimation of the parameter method distinctively traces the modes of the reactor's internal structures with the order of 160 tested by χ2 (chi) distribution andF distribution.

http://www.world-nuclear.org/info/inf06.html
The decades-long test and analysis program showed that less radioactivity escapes from molten fuel than initially assumed, and that this radioactive material is not readily mobilized beyond the immediate internal structure.

http://www.rapid-response-consulting.com/expert/jdr.aspx
Reactor internal structures inspection and evaluation Component Evaluations

PDF]
Mechanical Structure Design Features of the KALIMER-600 Sodium ...
File Format: PDF/Adobe Acrobat - View as HTML
The reactor internal structures of the KALIMER-600 are composed of the core ..... has the compact reactor internal structures and small vessel compared to ...
www.iasmirt.org/iasmirt-2/SMiRT19/S19_FinalPapers/S02_1.pdf