[Journal of the Physical Society of Japan Proceedings of the Second International Symposium on Radiation Detectors and Their Uses (ISRD2018) - Tsukuba, Japan (January 23-26, 2018)] Proceedings of the Second International Symposium on Radiation Detectors and Their Uses (ISRD2018) - Neutron Distribution Measurement by the Self-Activation of a CsI Plate with CCD Camera Using a Decaying Self-Activation Imaging Technique