Heat a large saucepan over medium heat, add oil and onion, cook for 2 minutes, stirring occasionally.
Add carrot and celery, cook for 5 minutes, stirring occasionally, season to taste.
Add 2 litres of water and bring to a simmer. Simmer for 10 minutes.
Add rice and cook for 45 minutes, or until tender.
Add chicken and cook for 2-3 minutes until cooked through.
In a medium bowl, whisk the lemon juice into the eggs. Slowly add about a cup of the liquid from the hot soup to the egg mixture while whisking. Pour the egg mixture into the soup, while stirring until fully incorporated.