Cover letter for PhD program

Hi, friends, I am now applying my phd program. The following letter is my phd cover letter. I am not sure if it is OK or not. And I am worrying about my writing English. So it will be very helpful if some friends could correct some mistakes in it. I will appreciate it very much.
Dear Sir or Madam:
I am applying to your PhD in Nuclear Physics program of Faculty of Science, Department of Physics. My career ambition is to become a doctor researching Radiation Science and Protection.
In University, I graduated with Nuclear Engineering and Environment Physics, University of Science and Technology as my majors. I am continuing my academic career with the study of “Radiation science” at *** University. In Jun 2017, I will graduate with a Master of degree with an expected average score above 96 percent. While I rank in the first student, I am trying to keep the first rank until graduating.
After getting Bachelor degree, I worked as a technician at ***Agency for Radiation and Nuclear Safety for 1.5 years, where I taught “radiation safety” short course for the facilities staffs and built “emergency response plan”. In a business trip in Vientiane, the capital of Lao Republic, we discovered an orphan source in a family of scrap metal dealers by chance. The family has 6 people lived with the radiation source in 3 years. They have nothing knowledge about what is radiation and how it effects to their heath. Perhaps, with farmers like them, they are not eligible to pay attention to radiation problems. They said that it looks like a story on Mars and Venus it is very strange problem that they never know, but they said that their heath is showing signs of declined markedly, especially 5 years old girl she frequently sick. We explained to them the dangerous of radioactive sources and the consequences can happen. They were too surprised and then they shocked and scared and cried. They said that they will know nothing and continuingly living with this source if they are not meet us. In addition, in the poor countries like Lao, Cambodia and my country-****** also, scientific and technical qualification are limited though the governments are big efforts. The difficulties on financial and strong skills human are still big problems in poor countries. That trip was inspiring me to continue studying and researching on radiation safety in particular and nuclear physics in general. By maybe, there are many other similar families who are living with dangers that they know nothing.
In 2015, I received full scholarship at ***** University, South Korea. I am currently studying and researching on ***** Laboratory, Department of Nuclear Engineering. I am doing a project on “D*******************************” that applies to looking for the orphan radiation source.
I want to study at **** University because of your outstanding educational system, focus on gathering relevant work experience and your excellent facilities. From speaking with some people who are studying and living in ****, I am confident of my decision. With many distinguish scientists as professors, I know that I will gain expert knowledge at the forefront of discovery.
I have built a strong background in radiation and nuclear physics and your program covers areas of research that matches my interests. In addition, diligence, persistence, cooperation and honesty are my intrinsic personalities. I am confident that I will be suitable for your research program and I am confident that I will bring a high level of energy and enthusiasm to your program. I am sure to exceed your expectations, because of both my academic and interpersonal skill as well as my efforts to contribute to radiation and nuclear field in ***** as well as poor countries after coming back.
Should you want further information, please contact me. Thank you very much for your time and consideration.
I am looking forward to hearing from you.
Your sincerely.