Harnessing the medical benefits of nuclear technology
The South African Nuclear Energy Corporation SOC Ltd (Necsa) houses the country’s
only nuclear research reactor which is by far Africa’s largest producer of a range of medical isotopes that are used for diagnostic purposes and the therapeutic treatment of cancer.
Before the nuclear research reac- tor starts its 30-day cycle, Linina Bedhesi is entrusted with the job of performing calculations to ensure that the system operates safely.
The 27-year-old is a reactor ana-lyst at Necsa and her job entails using calculation codes to carry out safety analysis for the reactor's core.
She performs heat and spent fuel calculations for the South African Fundamental Atomic Research Installation 1 (SAFARI-1).
SAFARI-1 is a 20 megawatt tank-in- pool type material testing nuclear research reactor. It is owned and operated by Necsa and located at Pelindaba, 30 kilometres west of Pretoria.
Benefits of medical isotopes
Millions of people have benefited from the medical isotopes originating from SAFARI-1. Patients in South Africa and internationally are treated with typical radioisotopes. For the isotopes to be produced and for SAFARI-1 to keep running, Bedhesi performs core-follow calcu- lations to establish the amount of fuel burnt during the reactor's cycle. Without these calculations, the reac- tor cannot start.
“Heating calculations are impor- tant for the safety of the reactor. We need to know the amount of heat released per fission reaction and the spatial distribution of heat so that we can implement cooling in high temperature regions,” she explained.
“If we know that, we can imple- ment cooling in the reactor. And this is one of the biggest safety calculations that is needed,” she added.
For spent fuel calculations, Bed- hesi uses a calculational computer code to calculate what amount of uranium and plutonium is present in a spent fuel assembly for storage purposes.
Other scientists or technicians who do operational work at SA- FARI-1 send Bedhesi data about the cycle under operation.
If any safety parameter is not met, it will compromise the safety of the reactor and the process cannot be initialised if Bedhesi tells the scien- tists at SAFARI-1 that it is not safe.
She works with three colleagues who perform the same calcula- tions to ensure that no mistakes are made and that there is consistency. The nuclear reactor has a built-
in feature called a scram, which automatically shuts down when something irregular happens during the process.
Whenever that happens, the scientists ask Bedhesi and her team if they should allow the reactor to reach the parameters deemed safe.
“We will then do the calculations and generate a report. Sometimes we will include a section of observations in the report to tell them that it is not consistent with what we are used to seeing, and they should decide whether to start up or not,” she said.
Living her dream
Bedhesi was appointed as a reac- tor analyst at Necsa in August 2017 and it is already a job that is close to her heart.
She does not mind driving for about 45 minutes every morning to work and she certainly does not mind the wildlife she gets to see regularly.
“There are zebras and monkeys here at Necsa. It is a very refreshing sight,” she said.
She holds an undergraduate degree in Nuclear Science and Engineering from the University of Witwatersrand (Wits). Bedhesi also has an Honours Degree in Physics from Wits and is in the process of obtaining an MSc (Physics). Prior to enrolling at Wits, she had a scholarship to study biology in India.
A couple of years ago, she found herself reading a brochure on BSc Nuclear Science and Engineering. “While reading the brochure, I found myself more interested in the nuclear sciences. I think it is because my parents had a history of cancer. It was just an emotional journey for me,” she said.
Cancer patients undergo different types of therapy in hospitals and often medical professionals use isotopes, which are produced by SAFARI-1.
Determined to succeed
“I registered for this course. I saw a picture of SAFARI-1 in the brochure and told myself that one day I will work at Necsa. At the end of my second year of study, I contacted Necsa’s human resource section and asked if I could do vacation work and I was granted the op- portunity. That is how my journey began, in December 2013,” she said.
When her peers went home for school holidays, Bedhesi made her way to Necsa to gain work experience.
“I also did my Honours project at Necsa, and am continuing with my Masters work here as well,” she said. She said there is a huge gap of knowledge between her seniors and the juniors in the field, which needs to be filled.
“There are many people in the late years of their careers and there are very young people. There is also a lack of skills,” she said.
However, Bedhesi said the nuclear science field is very reward- ing and her hard work pays off.
She gets to attend international conferences and to present her work to people from across the globe.
“During my time at Necsa, I have obtained two awards at the South African Institute of Physics Con- ference for my MSc work. I also received two postgraduate merit awards from Wits University. My work is extremely exciting, and I enjoy the challenges that come with it,” she said. What is most exciting for her is that a female scientist is given the same opportunity as males in the science field, although she feels that science is still very much male- dominated globally.
“I was the only female that gradu- ated in physics in my class in 2015 at undergraduate level,” she said.
Healing the world through nuclear
The production of medical iso- topes is one of the most important functions of the reactor. There is an isotope that Necsa is a key distribu- tor of, and it is called the Molybde- num-99 (Mo-99). It is used for diag- nostic imaging, cancer research or generally in nuclear medicine.
Necsa supplies a third of the Mo- 99 demand globally. In 2014, it was said to be the third largest producer of Mo-99 in the world. The work done at SAFARI-1 is not only impacting on South Africa but many parts of the globe.
Mo99 originally had to be im- ported into South Africa weekly, but since 1993, with its unique ability to manage virtually the entire nuclear production cycle, Necsa has become the sole local and an important international supplier of Mo-99.
Necsa also produces Iodine-131 and Lutetium-137, among many other isotopes, and these are also used in diagnostic imaging and therapy.