Assessment of Exposure Dose according to Outflow rate

V. Radiological Safety Assessment of Worker

5.5 Assessment of Exposure Dose according to Outflow rate

Figure 27. Spatial dose according to outflow rate from zeolite and activated carbon storage tank

Figure 28. Spatial dose according to outflow rate from spent resin mixture separator

Figure 29. Spatial dose according to outflow rate from spent resin storage tank

Figure 30. Spatial dose according to outflow rate from microwave reactor

Figure 31. Spatial dose according to outflow rate from spent resin feed hopper

In the case of leakage of spent resin mixture from the facility, the dose assessment of workers was performed. As shown in Table 20, The dose rates were derived as 2.20E-01 mSv/h ~ 3.10E-01 mSv/h, 2.50E-01 mSv/h ~ 3.30E-01 mSv/h, 2.00E-01 mSv/h ~ 3.00E-01 mSv/h, 2.70E-01 mSv/h ~ 3.50E-01 mSv/h, and 2.70E-01 mSv/h ~ 3.30E-01 mSv/h for SRMS, ZAST, SRFH, MWR, and SRST, respectively when the close worker remove the leaked spent resin mixture. The case of leakage from MWR caused the most exposure to workers. Doses for 250 hours of work per year were conservatively derived as 5.50E+01 mSv, 6.25E+01 mSv, 5.00E+01 mSv, and 6.75E+01 mSv for SRMS, ZAST, SRFH, MWR, and SRST, respectively. Therefore, these values exceeded the maximum dose limit. However, in realistic assessment, the range of dose rate was derived from 4.17E-02 mSv/h to 7.29E-02 mSv/h.

The annual doses (1.04E+01 mSv ~ 1.82E+01 mSv) were lower than the dose limit in terms of external exposure regardless of the outflow rate and leakage part.

Table 20. Dose rate of workers while removing radioactive materials according to outflow rate due to leakage in treatment facility (mSv/h)

Outflow rate

Assessment

type SRMS ZAST SRST MWR SRFH

10 %

Conservative 2.20E-01 2.50E-01 2.70E-01 2.70E-01 2.00E-01 Realistic 4.58E-02 5.21E-02 5.63E-02 5.63E-02 4.17E-02 20 %

Conservative 2.30E-01 2.60E-01 2.80E-01 2.80E-01 2.10E-01 Realistic 4.79E-02 5.42E-02 5.83E-02 5.83E-02 4.38E-02 30 %

Conservative 2.40E-01 2.70E-01 2.80E-01 2.90E-01 2.20E-01 Realistic 5.00E-02 5.63E-02 5.83E-02 6.04E-02 4.58E-02 40 %

Conservative 2.50E-01 2.80E-01 2.90E-01 3.00E-01 2.30E-01 Realistic 5.21E-02 5.83E-02 6.04E-02 6.25E-02 4.79E-02 50 %

Conservative 2.60E-01 2.90E-01 2.90E-01 3.00E-01 2.40E-01 Realistic 5.42E-02 6.04E-02 6.04E-02 6.25E-02 5.00E-02 60 %

Conservative 2.70E-01 2.90E-01 3.00E-01 3.10E-01 2.50E-01 Realistic 5.63E-02 6.04E-02 6.25E-02 6.46E-02 5.21E-02 70 %

Conservative 2.80E-01 3.00E-01 3.10E-01 3.20E-01 2.60E-01 Realistic 5.83E-02 6.25E-02 6.46E-02 6.67E-02 5.42E-02 80 %

Conservative 2.90E-01 3.10E-01 3.20E-01 3.30E-01 2.70E-01 Realistic 6.04E-02 6.46E-02 6.67E-02 6.88E-02 5.63E-02 90 %

Conservative 3.00E-01 3.20E-01 3.20E-01 3.40E-01 2.80E-01 Realistic 6.25E-02 6.67E-02 6.67E-02 7.08E-02 5.83E-02 100 %

Conservative 3.10E-01 3.30E-01 3.30E-01 3.50E-01 3.00E-01 Realistic 6.46E-02 6.88E-02 6.88E-02 7.29E-02 6.25E-02

In the case of remote work, similarly, leakage from MWR caused the most exposure to workers (7.50E-03 mSv/h ~ 8.20E-03 mSv/h for conservative assessment and 1.50E-03 mSv/h ~ 1.71E-03 mSv/h for realistic assessment). Considering these values for the annual doses (250 hours and 2,000 hours), 1.80E+00 mSv ~ 2.05E+00 mSv and 1.44E+01 mSv ~ 1.64E+01 mSv for conservative assessment and 3.75E-01 mSv ~ 4.27E-01 mSv and 3.00E+00 mSv ~ 3.42E+00 mSv for realistic assessment were derived, respectively. The annual doses (2,000 hours) of remote worker were less than the dose limit, which was conservatively evaluated, regardless of the outflow rate. Therefore, the radiological safety of the remote worker was confirmed in the event of leakage of spent resin mixture from the facility.

Table 21. Dose rate of workers in remote room according to outflow rate due to leakage in treatment facility (mSv/h)

Outflow rate

Assessment

type SRMS ZAST SRST MWR SRFH

10 %

Conservative 7.20E-03 7.30E-03 7.30E-03 7.50E-03 7.20E-03 Realistic 1.50E-03 1.52E-03 1.52E-03 1.56E-03 1.50E-03 20 %

Conservative 7.30E-03 7.40E-03 7.40E-03 7.60E-03 7.30E-03 Realistic 1.52E-03 1.54E-03 1.54E-03 1.58E-03 1.52E-03 30 %

Conservative 7.40E-03 7.50E-03 7.40E-03 7.60E-03 7.40E-03 Realistic 1.54E-03 1.56E-03 1.54E-03 1.58E-03 1.54E-03 40 %

Conservative 7.50E-03 7.60E-03 7.50E-03 7.70E-03 7.40E-03 Realistic 1.56E-03 1.58E-03 1.56E-03 1.60E-03 1.54E-03 50 %

Conservative 7.60E-03 7.70E-03 7.60E-03 7.70E-03 7.50E-03 Realistic 1.58E-03 1.60E-03 1.58E-03 1.60E-03 1.56E-03 60 %

Conservative 7.70E-03 7.80E-03 7.70E-03 7.80E-03 7.60E-03 Realistic 1.60E-03 1.63E-03 1.60E-03 1.63E-03 1.58E-03 70 %

Conservative 7.80E-03 7.80E-03 7.80E-03 7.90E-03 7.70E-03 Realistic 1.63E-03 1.63E-03 1.63E-03 1.65E-03 1.60E-03 80 %

Conservative 7.80E-03 7.80E-03 7.80E-03 7.90E-03 7.70E-03 Realistic 1.65E-03 1.65E-03 1.63E-03 1.67E-03 1.63E-03 90 %

Conservative 8.00E-03 8.10E-03 7.90E-03 8.10E-03 7.90E-03 Realistic 1.67E-03 1.69E-03 1.65E-03 1.69E-03 1.65E-03 100 %

Conservative 8.10E-03 8.20E-03 8.00E-03 8.20E-03 8.00E-03 Realistic 1.69E-03 1.71E-03 1.67E-03 1.71E-03 1.67E-03

Table 22. Annual dose (mSv) of workers in remote room according to outflow rate due to leakage in treatment facility (250 h)

Outflow rate

Assessment

type SRMS ZAST SRST MWR SRFH

10 %

Conservative 1.80E+00 1.83E+00 1.83E+00 1.88E+00 1.80E+00 Realistic 3.75E-01 3.80E-01 3.80E-01 3.91E-01 3.75E-01 20 %

Conservative 1.83E+00 1.85E+00 1.85E+00 1.90E+00 1.83E+00 Realistic 3.80E-01 3.85E-01 3.85E-01 3.96E-01 3.80E-01 30 %

Conservative 1.85E+00 1.88E+00 1.85E+00 1.90E+00 1.85E+00 Realistic 3.85E-01 3.91E-01 3.85E-01 3.96E-01 3.85E-01 40 %

Conservative 1.88E+00 1.90E+00 1.88E+00 1.93E+00 1.85E+00 Realistic 3.91E-01 3.96E-01 3.91E-01 4.01E-01 3.85E-01 50 %

Conservative 1.90E+00 1.93E+00 1.90E+00 1.93E+00 1.88E+00 Realistic 3.96E-01 4.01E-01 3.96E-01 4.01E-01 3.91E-01 60 %

Conservative 1.93E+00 1.95E+00 1.93E+00 1.95E+00 1.90E+00 Realistic 4.01E-01 4.06E-01 4.01E-01 4.06E-01 3.96E-01 70 %

Conservative 1.95E+00 1.95E+00 1.95E+00 1.98E+00 1.93E+00 Realistic 4.06E-01 4.06E-01 4.06E-01 4.11E-01 4.01E-01 80 %

Conservative 1.98E+00 1.98E+00 1.95E+00 2.00E+00 1.95E+00 Realistic 4.11E-01 4.11E-01 4.06E-01 4.17E-01 4.06E-01 90 %

Conservative 2.00E+00 2.03E+00 1.98E+00 2.03E+00 1.98E+00 Realistic 4.17E-01 4.22E-01 4.11E-01 4.22E-01 4.11E-01 100 %

Conservative 2.03E+00 2.05E+00 2.00E+00 2.05E+00 2.00E+00 Realistic 4.22E-01 4.27E-01 4.17E-01 4.27E-01 4.17E-01

Table 23. Annual dose (mSv) of workers in remote room according to outflow rate due to leakage in

treatment facility (2,000 h) Outflow

rate

Assessment

type SRMS ZAST SRST MWR SRFH

10 %

Conservative 1.44E+01 1.46E+01 1.46E+01 1.50E+01 1.44E+01 Realistic 3.00E+00 3.04E+00 3.04E+00 3.13E+00 3.00E+00 20 %

Conservative 1.46E+01 1.48E+01 1.48E+01 1.52E+01 1.46E+01 Realistic 3.04E+00 3.08E+00 3.08E+00 3.17E+00 3.04E+00 30 %

Conservative 1.48E+01 1.50E+01 1.48E+01 1.52E+01 1.48E+01 Realistic 3.08E+00 3.13E+00 3.08E+00 3.17E+00 3.08E+00 40 %

Conservative 1.50E+01 1.52E+01 1.50E+01 1.54E+01 1.48E+01 Realistic 3.13E+00 3.17E+00 3.13E+00 3.21E+00 3.08E+00 50 %

Conservative 1.52E+01 1.54E+01 1.52E+01 1.54E+01 1.50E+01 Realistic 3.17E+00 3.21E+00 3.17E+00 3.21E+00 3.13E+00 60 %

Conservative 1.54E+01 1.56E+01 1.54E+01 1.56E+01 1.52E+01 Realistic 3.21E+00 3.25E+00 3.21E+00 3.25E+00 3.17E+00 70 %

Conservative 1.56E+01 1.56E+01 1.56E+01 1.58E+01 1.54E+01 Realistic 3.25E+00 3.25E+00 3.25E+00 3.29E+00 3.21E+00 80 %

Conservative 1.58E+01 1.58E+01 1.56E+01 1.60E+01 1.56E+01 Realistic 3.29E+00 3.29E+00 3.25E+00 3.33E+00 3.25E+00 90 %

Conservative 1.60E+01 1.62E+01 1.58E+01 1.62E+01 1.58E+01 Realistic 3.33E+00 3.38E+00 3.29E+00 3.38E+00 3.29E+00 100 %

Conservative 1.62E+01 1.64E+01 1.60E+01 1.64E+01 1.60E+01 Realistic 3.38E+00 3.42E+00 3.33E+00 3.42E+00 3.33E+00

Figure 32. Comparison of annual dose of worker in remote room according to outflow rate and leakage part - 2,000 hrs (unit: mSv)

A committed effective dose was evaluated for the worker removing spent resin mixture leaked from the spent resin treatment facility considering conservative and realistic assessment. Assessments were performed for the cases where the worker wore and did not wear the air-purifying respirator, and for each part, the outflow rate that exceeded the worker's annual dose limit was derived. Table 24 represents the results of the committed effective dose when the worker who does not wear an air-purifying respirator removes the leaked spent resin mixture. In realistic assessment, the dose range was derived as 4.33E-03 mSv ~ 3.92E+00 mSv without APF. In conservative assessment, the leakage of 100 % of spent resin from the MWR had the most effect on workers with 1.88E+01 mSv. Although the APF was not considered, the annual dose limit was all satisfied regardless of the outflow rate and leakage part.

However, on the aspect of ALARA, when performing work on the MWR, wearing a respirator or performing a work shift may conservatively satisfy the dose limit.

Table 24. Committed effective dose of workers without air-purifying respirator according to outflow rate due to leakage in treatment facility (mSv)

Outflow rate

Assessment

type SRMS ZAST SRST MWR SRFH

10 %

Conservative 5.82E-02 2.08E-02 3.30E-02 1.88E+00 5.53E-02 Realistic 1.21E-02 4.33E-03 6.87E-03 3.92E-01 1.15E-02 20 %

Conservative 1.16E-01 4.16E-02 6.59E-02 3.77E+00 1.11E-01 Realistic 2.43E-02 8.66E-03 1.37E-02 7.85E-01 2.30E-02 30 %

Conservative 1.75E-01 6.24E-02 9.89E-02 5.65E+00 1.66E-01 Realistic 3.64E-02 1.30E-02 2.06E-02 1.18E+00 3.45E-02 40 %

Conservative 2.33E-01 8.32E-02 1.32E-01 7.53E+00 2.21E-01 Realistic 4.85E-02 1.73E-02 2.75E-02 1.57E+00 4.60E-02 50 %

Conservative 2.91E-01 1.04E-01 1.65E-01 9.42E+00 2.76E-01 Realistic 6.07E-02 2.17E-02 3.43E-02 1.96E+00 5.76E-02 60 %

Conservative 3.49E-01 1.25E-01 1.98E-01 1.13E+01 3.32E-01 Realistic 7.28E-02 2.60E-02 4.12E-02 2.35E+00 6.91E-02 70 %

Conservative 4.08E-01 1.46E-01 2.31E-01 1.32E+01 3.87E-01 Realistic 8.49E-02 3.03E-02 4.81E-02 2.75E+00 8.06E-02 80 %

Conservative 4.66E-01 1.66E-01 2.64E-01 1.51E+01 4.42E-01 Realistic 9.70E-02 3.46E-02 5.49E-02 3.14E+00 9.21E-02 90 %

Conservative 5.24E-01 1.87E-01 2.97E-01 1.70E+01 4.97E-01 Realistic 1.09E-01 3.90E-02 6.18E-02 3.53E+00 1.04E-01 100 %

Conservative 5.82E-01 2.08E-01 3.30E-01 1.88E+01 5.53E-01 Realistic 1.21E-01 4.33E-02 6.87E-02 3.92E+00 1.15E-01

Table 25 represents the results of the committed effective dose when the worker who wears an air- purifying respirator removes the leaked spent resin mixture. As for the committed effective dose, the leakage from MWR had the highest with 3.77E-02 mSv ~ 3.77E-01 mSv, and the leakage from SRMS had the second highest with 1.16E-03 mSv ~ 1.16E-02 mSv. In realistic assessment, MWR had the dose range with 7.85E-03 mSv ~ 7.85E-02 mSv, and SRMS had the range with 2.43E-04 mSv ~ 2.43E-03 mSv. Relatively lower values were obtained for wearing respirator compared to without wearing respirator. Therefore, if leakage occurs, it is expected that the respirator must be considered.

Table 25. Committed effective dose of workers with air-purifying respirator according to outflow rate due to leakage in treatment facility (mSv)

Outflow rate

Assessment

type SRMS ZAST SRST MWR SRFH

10 % Conservative 1.16E-03 4.16E-04 6.59E-04 3.77E-02 1.11E-03 Realistic 2.43E-04 8.66E-05 1.37E-04 7.85E-03 2.30E-04 20 % Conservative 2.33E-03 8.32E-04 1.32E-03 7.53E-02 2.21E-03 Realistic 4.85E-04 1.73E-04 2.75E-04 1.57E-02 4.60E-04 30 % Conservative 3.49E-03 1.25E-03 1.98E-03 1.13E-01 3.32E-03 Realistic 7.28E-04 2.60E-04 4.12E-04 2.35E-02 6.91E-04 40 % Conservative 4.66E-03 1.66E-03 2.64E-03 1.51E-01 4.42E-03 Realistic 9.70E-04 3.46E-04 5.49E-04 3.14E-02 9.21E-04 50 % Conservative 5.82E-03 2.08E-03 3.30E-03 1.88E-01 5.53E-03 Realistic 1.21E-03 4.33E-04 6.87E-04 3.92E-02 1.15E-03 60 %

Conservative 6.99E-03 2.49E-03 3.96E-03 2.26E-01 6.63E-03 Realistic 1.46E-03 5.20E-04 8.24E-04 4.71E-02 1.38E-03 70 %

Conservative 8.15E-03 2.91E-03 4.62E-03 2.64E-01 7.74E-03 Realistic 1.70E-03 6.06E-04 9.62E-04 5.49E-02 1.61E-03 80 %

Conservative 9.32E-03 3.33E-03 5.27E-03 3.01E-01 8.84E-03 Realistic 1.94E-03 6.93E-04 1.10E-03 6.28E-02 1.84E-03 90 %

Conservative 1.05E-02 3.74E-03 5.93E-03 3.39E-01 9.95E-03 Realistic 2.18E-03 7.80E-04 1.24E-03 7.06E-02 2.07E-03 100 %

Conservative 1.16E-02 4.16E-03 6.59E-03 3.77E-01 1.11E-02 Realistic 2.43E-03 8.66E-04 1.37E-03 7.85E-02 2.30E-03

Table 26 represents the results of the committed effective dose when the worker who wears an air- purifying respirator removes the leaked spent resin mixture for 250 h per year. In SRMS, ZAST, SRST, and SRFH, the dose limit of the worker was satisfied regardless of the outflow rate. When 20 % of the outflow from MWR (1.88E+01 mSv) occurred, the dose limit of worker was satisfied. However, in realistic assessment, the dose range was derived as 2.17E-02 mSv ~ 1.96E+01 mSv, which is less than the dose limit in terms of internal exposure.

Table 26. Committed effective dose of workers for annual work (250 h) with air-purifying respirator according to outflow rate due to leakage in treatment facility (mSv)

Outflow rate

Assessment

type SRMS ZAST SRST MWR SRFH

10 %

Conservative 2.91E-01 1.04E-01 1.65E-01 9.42E+00 2.76E-01 Realistic 6.07E-02 2.17E-02 3.43E-02 1.96E+00 5.76E-02 20 %

Conservative 5.82E-01 2.08E-01 3.30E-01 1.88E+01 5.53E-01 Realistic 1.21E-01 4.33E-02 6.87E-02 3.92E+00 1.15E-01 30 %

Conservative 8.73E-01 3.12E-01 4.95E-01 2.83E+01 8.29E-01 Realistic 1.82E-01 6.50E-02 1.03E-01 5.89E+00 1.73E-01 40 %

Conservative 1.16E+00 4.16E-01 6.59E-01 3.77E+01 1.11E+00 Realistic 2.43E-01 8.66E-02 1.37E-01 7.85E+00 2.30E-01 50 %

Conservative 1.46E+00 5.20E-01 8.24E-01 4.71E+01 1.38E+00 Realistic 3.03E-01 1.08E-01 1.72E-01 9.81E+00 2.88E-01 60 %

Conservative 1.75E+00 6.24E-01 9.89E-01 5.65E+01 1.66E+00 Realistic 3.64E-01 1.30E-01 2.06E-01 1.18E+01 3.45E-01 70 %

Conservative 2.04E+00 7.28E-01 1.15E+00 6.59E+01 1.93E+00 Realistic 4.25E-01 1.52E-01 2.40E-01 1.37E+01 4.03E-01 80 %

Conservative 2.33E+00 8.32E-01 1.32E+00 7.53E+01 2.21E+00 Realistic 4.85E-01 1.73E-01 2.75E-01 1.57E+01 4.60E-01 90 %

Conservative 2.62E+00 9.35E-01 1.48E+00 8.48E+01 2.49E+00 Realistic 5.46E-01 1.95E-01 3.09E-01 1.77E+01 5.18E-01 100 %

Conservative 2.91E+00 1.04E+00 1.65E+00 9.42E+01 2.76E+00 Realistic 6.07E-01 2.17E-01 3.43E-01 1.96E+01 5.76E-01

Dalam dokumen Radiological Safety Assessment of Workers for 1 ton/day Spent Resin Treatment Facility (Halaman 65-83)