Of course there are moral and acceptable reasons to be sterilized. A woman who can not ever be pregnant or give birth because of severe health problems, ie heart problems. There are many, many women who have had to have their uterus removed due to medical problems, thus sterilized. I believe the Catholic Church accepts sterilization in grave circumstances. If I'm wrong, someone please correct me.
Sterlization for those reasons, no matter how grave the reason to never get pregnant again would still be artifical birth control and thus a mortal sin.
We're never allowed to do evil to prevent evil.
"54. But no reason, however grave, may be put forward by which anything intrinsically against nature may become conformable to nature and morally good. Since, therefore, the conjugal act is destined primarily by nature for the begetting of children, those who in exercising it deliberately frustrate its natural power and purpose sin against nature and commit a deed which is shameful and intrinsically vicious. "- Casti Connbui
A couple in this circumstance would be called to total abstinence or strict NFP. Once you allow artifical birth control (which is all sterlization is) for this reason, you're on a slippery slope.
Now indirect sterlization; hysterectomy, the removal of the tube for a tubal pregnancy, that kind of thing; that is allowed.