GST reversal on import debit note raised

We have imported 100 No's raw material.we have paid custom duty with IGST on it. and taken credit of IGST.Aftermonth 40 no's found rejected. we have raised debit note to the foreign supplier.But in this caserejecres material is not being sent back to the foreign suppliers due to high cost. it has been discussed with the foreign supplier. he told to keep with us and scrap out here. we have removed them from our live stock to scrap stock. Should we reverse the IGST taken ceisit on 40 no's rejected material?