04 Protection
Weekly design limit P
Convert an annual effective-dose limit to a weekly shielding design goal.
Listen
Listen · English
Simulation
Weekly design limit P — Change the numbers; the scene follows.
Where it works
Treatment vault
Primary barrier
In the bunker maze and barriers — time, distance, TVL, WUT, and weekly controlled-area dose.
Open this machineFormula
Typical values
Variables
Results
P
Weekly design goal
0.02mSv/week
P
Weekly design goal
2.0000e-5Gy/week
Explanation
What it means
Shielding design goals are weekly. Divide the annual limit by 50 working weeks: public 1 mSv/y → 0.02 mSv/week; many clinics design controlled areas to 5 mSv/y (0.1 mSv/week) even though the occupational limit is 20 mSv/y. This is a working relation in Radiation protection.
Where it is used
Clinically it sits on the Treatment vault — Primary barrier. In the bunker maze and barriers — time, distance, TVL, WUT, and weekly controlled-area dose. Protection equations are the wall, the occupancy factor, and the badge: time, distance, shielding, and WUT. They turn a room into a legal design.
Treatment vault · Open this machineHow to use it
Feed P (Gy/week) into the barrier-transmission calculator. NCRP 151 still uses 50 weeks, not 52. Change one input and watch the curve and the simulation follow.
Symbols
- P_yearAnnual limit1 mSv/y
Worked example
A typical case from the default values: P_year = 1 mSv/y (Annual limit). Substituting into the relation gives P = 0.02 mSv/week; P = 2.0000e-5 Gy/week. These are teaching numbers — align them with your machine.
Typical values give
- P = 0.02mSv/week
- P = 2.0000e-5Gy/week
Where it comes from
The displayed formula is the working relation. Convert an annual effective-dose limit to a weekly shielding design goal. Usual reference: NCRP 151. Derive it in the specialty lesson, then return here to pin the numbers.
Reference: NCRP 151
Assumptions & limits
Design goal, not a personal dose limit. ALARA may justify a lower P. Pregnant-worker limits are separate.
Pitfalls
Tenth-value layers are for the broad beam in that material and that energy — not a photocopy from another bunker. Occupancy T is not a guess; it is a use pattern. Inverse-square fails against a large scatter source. Design goal, not a personal dose limit. ALARA may justify a lower P. Pregnant-worker limits are separate.
Keep this
Time, distance, shielding — in that order — then calculate the wall. Design goal, not a personal dose limit. ALARA may justify a lower P. Pregnant-worker limits are separate.
In this specialty