How to Keep a radio button checked after form submission

Here is my problem: I have radio buttons in a loop, in a form (in spring boot) and I would like the radio button that was checked to remain checked after submitting the form and especially when we return to the choice page , just to not be able to recheck the same choice (in JS). Basically, I make a choice, I submit => it sends me to another page but when I return to my page of choice, the previous choice must be disabled.
Form:

<form action="#" th:action="@{/piece}" modelAttribute="piece"  method="post"
     id="formP" onsubmit="">
        <tr th:each="piece: ${pieces}">
            <input type="submit" name="submit" value="${piece.nom}" th:value="'Valider : '+ ${piece.nom}"
             onclick="saveform()"  />
            <label class="radio-image">
                <input type="radio" name="img" th:value="${piece.img}" onclick="check()"  required>
                <img th:src="@{${'/images/'+ piece.img}}" />
            </label>
            <br>
        </tr>
    </form>

Function to retrieve the choice in localStorage:

function check() {
    
    var btnPieceRad = document.getElementsByName('img');
    for (i = 0; i < btnPieceRad.length; i++) {
        if ((btnPieceRad[i].checked)) {
            var valeur = btnPieceRad[i].value;
            localStorage.setItem("radPiece", valeur);
        }
    }
}

I try:

function saveform() {
    var radPiece = localStorage.getItem("radPiece") ;
    radPiece.getElementsByTagName('radio')[radPiece].disabled = true;   
}

Without result
Then I got inspired by the subject How do I disable and check which option that I chose in the radio buttons after form submission?
And I do :

function saveform() {
    var formPiece = document.getElementsByTagName("form");
    formPiece.addEventListener("submit",function(){
        var inputs = formPiece[0].getElementsByTagName("input");
        for(var i=0; i<inputs.length; i++){
            var this_input = inputs[i];
            if( this_input.type=="radio") {
            this_input.disabled = true;
          
        }
        }
    });
}

Without result and I have a sneaky error in the console:Uncaught on this line:
formPiece.addEventListener("submit",function()
Thanks for your help