Question

(a) Dose rate estimates for a mission to Mars consist of 1.9 mSv/d during each 180-d outbound and return flight, and 0.7 mSv/d while on Mars for nearly 2 y. What fraction or multiple of the annual ICRP occupational dose limits do the astronauts receive during total flight time and while exploring the planet each year? (b) How many days before the occupational dose limit is reached on the International Space Station where the dose rate is approximately 0.25 mSv/d?

Final answers are 14 and 5

Answer 1

The occupational dose limit for normal conditions specified by ICRP is 20 mSv /year. (From their website)

a) the mission to mars takes 180 days of total travel time.

The dosage got during this time is 1.9 mSv per day.

So, the total dosage for 180 days = 180*1.9= 342 mSv

On the mars, the dose is 0.7 mSv per day.

The mission is for 2 years.

So, the total dose got on mars = 2*365*0.7 = 511 mSv

Total time for the mission = 180+365*2 = 910 days = 2.493 years.

Total dosage during this time = 342+ 511 = 853 mSv

So, the average dosage got is

Dose/time = 853/2.493 = 342.158 mSv/year

We need to find how many times of 20 is this number.

So, 342/20 = 17 times.

b)The occupational dosage limit is 20 mSv / year.

The radiation in the international space Station is 0.25 mSv per day.

So, the number of days before this limit is reached is

N= 20/0.25 = 80 days.

note:- your answers might be wrong. Especially the part b. Because astronauts stay in the ISS for almost 80-90 days. If the occupational hazard is reached within 5 days, it is 100% sure that all the astronauts will have cancer by the time they reach back to earth, which is not true