No value accessor for form control with name: Got this error while trying to bind ngmodel in ion-radio button

Ionic Framework ionic-v3
1 
<ion-list  radio-group *ngFor="let appr of getApprovalsArray">
        <ion-row>
            <ion-col><b>{{appr.wfdc_doc_brief}}</b></ion-col>
        </ion-row>
            <ion-row style="border-bottom: 2px solid #444345!important;">
                <ion-col>
                    <ion-label>Approve</ion-label>
                    <ion-radio [(ngModel)]="processAppr.wfdc_act" value="A" name="wfdc_act" [ngModelOptions]="{standalone: true}"></ion-radio>
                </ion-col>
                <ion-col>
                    <ion-label>Forward</ion-label>
                    <ion-radio [(ngModel)]="processAppr.wfdc_act" value="F" name="wfdc_act" [ngModelOptions]="{standalone: true}"></ion-radio>
                </ion-col>
                <ion-col>
                    <ion-label>Return</ion-label>
                    <ion-radio [(ngModel)]="processAppr.wfdc_act" value="R" name="wfdc_act" [ngModelOptions]="{standalone: true}"></ion-radio>
                </ion-col>
                <ion-col>
                    <ion-label>Cancel</ion-label>
                    <ion-radio [(ngModel)]="processAppr.wfdc_act" value="C" name="wfdc_act" [ngModelOptions]="{standalone: true}"></ion-radio>
                </ion-col>
                <ion-col>
                    <ion-label>Wait</ion-label>
                    <ion-radio checked [(ngModel)]="processAppr.wfdc_act" value="W" name="wfdc_act" [ngModelOptions]="{standalone: true}"></ion-radio>
                </ion-col>
            </ion-row>
  </ion-list>