This is how I used to do it (although haven't needed to for some time):
You need:
Bincrypt
360 Flash Tool.
KeyVault Modder
The corrupt NAND dump
The donor NAND dump (Should be same model mobo as corrupt one - preferably the same kernel but not necessarily)
Both nands CPU keys
Open bincrypt and place your CPU Key (from the bad NAND) in the 'CPU Key' box. Click 'Raw Flash Bin' and make sure the 'Extract' has a dot in it. Then click 'Decrypt' under 'Operation'. Then click 'Process', open the bad NAND, and then name the kv whatever you like.
Bincrypt again: Now place the donor CPU key in the CPU key box, and follow the same steps as above.
Now open KeyVault Modder and open your KeyVault from the bad NAND, you should be able to view the information, although some bits may be missing. Don't worry, but note the stuff that's there down.
BinCrypt again: Place your original (bad) CPU key in the CPU Key box. Click 'Raw Flash Bin' and 'Replace'. Under 'Operation' click 'Encrypt', then click 'Process'. Select your donor NAND dump, then select the donor keyvault when asked.
This has injected the donor keyvault signed with your 'bad' CPU key

Open 360 Flash Tool, click 'Keys' and pop your 'bad nand' CPU key in there. Open the 'bad nand' dump, and note down all the LDV values in the order they appear.
Now open 360 Flash Tool, Click Keys, place your 'bad nand' CPU Key on the line intended, open up the now 'good nand' dump you've injected your CPU key into. Click Ok, it will probably say 'bad kv' (not always though). Then click 'Patch', tick the 'Patch Headers', and enter the LDV values you noted down above, in the order you wrote them in. Also tick the 'Patch Keyvault' box (if you can - if not, click 'ok' which will patch the info, then open the 'patch' window again and it should allow you). Under the 'Patch Keyvault' you need to enter your bad nand dumps region, drive type, and drive key. Click ok, and you're done

Probably massively out of date, but dragged it up from an email I sent someone a while back........