Ciao Pigi, of course you know Bitcoin and Bitcoin Cash are two separate currencies, so if you send Bitcoin to your Bitcoin Cash address, or vice-versa, your wallet won't receive the transaction correctly.
I think that Kraken staff will need to manually sweep the funds from the incorrect receiving wallet, into the correct wallet.
Here's how: since you sent BTC to a BCH wallet, Kraken staff will have to export the BCH private keys from "your Kraken BCH wallet", and import them into "your Kraken BTC wallet" (recovering those BTC into your Kraken BTC wallet).