Cal. Gov. Code § 21491

A person who is entitled to receive a monthly allowance as a survivor of a deceased person may designate a beneficiary to receive the pro rata allowance payable following his or her death. The beneficiary designation shall be filed by the survivor with the board in writing in order to be effective, and the designation shall be subject to all laws applicable to designations of beneficiaries. A survivor may revoke his or her beneficiary designation at any time. A beneficiary designation by a survivor shall not be subject to the automatic revocation of designation provisions of Section 21492.