How to calculate the protective distance of industrial X-ray flaw detection theoretically

Industrial X-ray flaw detection health protection standards: lol :victory: When conducting transillumination inspection according to Section 5.2.2, the air kerma rate around the inspected object can be classified as a control area within the range of more than 40 μGy·h-1. For special circumstances, please refer to Appendix B (Normative Appendix). A clearly visible "No entry into X-ray area" warning sign must be hung on the boundary of the control area, and flaw detection operators should operate outside the boundary, otherwise protective measures must be taken. 5.2.3 When conducting transillumination inspection, the air kerma outside the boundary of the control area can be classified as a management area if the air kerma rate is above 4 μGy·h-1. Warning signs, such as signal lights, bells, and warning ropes, must be set up on the boundary, and a clearly visible "No Entry for Unrelated Personnel" warning sign must be hung. If necessary, a dedicated guard must be set up. Attention should also be paid to controlling the presence of members of the public who frequently stay near the boundaries of the management area. Determination of the control area and management area for X-ray on-site flaw detection operations B.1 The air kerma rate at the boundary of the control area is set as 4OμGy·h-1, which is calculated based on three-tenths of the annual effective dose limit for radiation workers (15mSv) and the actual startup time per week is 7.5h. If the actual start-up time t per week is greater than 7.5h, the air kerma rate at the boundary of the control area should be calculated according to the following formula: K=300/t………………………………(B.1) where: K—the air kerma rate at the boundary of the control area, μGy·h-1; t—the actual start-up time per week, h 300-15 mSv is evenly distributed to the value of 50 weeks per year, that is, 300 μSv. At the same time, the air kerma rate at the boundary of the management area also changes accordingly.

First of all, the standards cited above have expired, and the air kerma rates have been revised to 15 and 1.5.； Secondly, as shown in B1, how to calculate the distance?