Supervisor in German Universities I have sent many emails to lecturers within the nuclear field and at different German universities for the sake of supervision. I have attached my CV and complete detailed PhD proposal related to nuclear engineering. I already have a PhD in laser engineering and would like to develop my knowledge in application of high power lasers in nuclear reactors.

Unfortunately I did not receive any reply, even negative ones. I have re-checked my PhD proposal and reviewed my email text, where both seem very good and professional. 

I will be very grateful if you could advise me regarding this issue and how can I get German supervisor for the sake of admission requirements.
A "cold" request sent to a faculty member—sent when there is either no announced opening for a position or no established cycle for admissions—is unlikely to generate a response. This is because of the sheer amount of email that German professors can receive, particularly if they run large research groups. (In many cases, the public email address may not be directly handled by the professor but be filtered by an administrative assistant.) In that case, there's not much you can do.

Your best bet is to look for groups that have announcements for open positions and apply to those. In such cases, you may get a response, but even then there is a possibility you might not hear anything back. It's basically saying "no" without sending a rejection email.