A dose constraint proposal for members of the public taking into account multi-unit nuclear power plants in Korea

Abstract

In the 2007 recommendations, the International Commission on Radiological Protection (ICRP) changed from a process-based system of practices and intervention to a system based on the characteristics of the radiation exposure situation. In addition, the ICRP now recommends the application of source-related dose constraints under a planned exposure situation as a tool for the optimization of measures to protect the workers and members of the public. In this study, an analysis of radioactive effluents from Korean nuclear power plants and a public dose assessment were conducted using these source-related dose constraints. As a result, this analysis suggests appropriate dose constraints for members of the public taking into account the operation of multi-unit nuclear reactors at a single site in Korea.

Keywords:

• dose constraint
• radiation dose
• radiation protection
• nuclear power plants
• radioactive effluents
• public dose assessment

1. Introduction

The International Commission on Radiological Protection (ICRP) issued the new 2007 recommendations as ICRP Publication 103, reinforcing the principle of the optimization of measures of protection [1]. The International Atomic Energy Agency (IAEA) also revised its basic safety standards (BSS) to take into account ICRP Publication 103 [2]. In Korea, the Korea Institute of Nuclear Safety (KINS), the Korean nuclear regulatory body, completed a long-term research project in 2011 to apply ICRP Publication 103 to revise the procedures of regulatory guidance according to the new IAEA BSS Series No. GSR Part 3 (Interim) [3]. It is expected that nuclear safety laws will be amended based on the research results after 2013 [3].

ICRP Publication 103 categorizes three types of exposure situations: planned exposure situations, emergency exposure situations, and existing exposure situations [1]. Appropriate guidance for each situation is also provided [1,4]. Furthermore, the revised recommendations emphasize dose constraints under planned exposure situations and reference levels under emergency and existing exposure situations as the key aspects of the principle of optimization. Radiation exposure to members of the public adjacent to nuclear power plants (NPPs) is an example of a planned exposure situation. The ICRP recognizes that it is possible to achieve optimization for members of the public through the establishment of appropriate dose constraint levels for prospective and predicted doses occurring as a result of the operation of a NPP [1,4].

In order to determine the appropriate dose constraint levels for members of the public, this study investigated the concept of dose constraints as defined in ICRP Publication 103 and in the Korean regulatory guidance while also investigating the current status of the implementation of dose constraints at Korean NPPs. In addition, the annual release of radioactive effluents into the environment and its corresponding dose levels for members of the public were analyzed. Finally, this study suggests acceptable and appropriate dose constraints for members of the public taking into account the operation of multi-unit nuclear reactors at a single site in Korea.

2. Concept of the ICRP's dose constraints

According to ICRP Publication 103, dose constraints are used for limiting individual doses during the process of the optimization of protection measures [1]. The constraints stipulate that radiation exposure levels should be kept as low as reasonably achievable (ALARA), taking into account economic and societal factors [1]. Dose constraints are prospective and source-related restrictions on individual doses from a source under a planned exposure situation such as the planning stages of the construction and operation in an NPP to the extent individual doses can be forecast so as to ensure that the constraints will not be exceeded [1]. Furthermore, the ICRP recommends the implementation of reference levels under emergency and existing exposure situations [1]. Table 1 displays the system of protection as put forth in ICRP Publication 103 depending on the type of exposure situation and the category of exposure [1].

Table 1. Dose constraints and reference levels used in the ICRP 103 recommendations.

Type of situation	Occupational exposure	Public exposure	Medical exposure
Planned exposure	Dose limit	Dose limit	Diagnostic reference level^c
	Dose constraint	Dose constraint	(Dose constraint^d)
Emergency exposure	Reference level^a	Reference level	NA^c
Existing exposure	NA^b	Reference level	NA^c

^aLong-term recovery operations should be treated as part of planned occupational exposure.

^bExposures resulting from long-term remediation operations or from protracted employment in affected areas should be treated as part of planned occupational exposure, even though the source of radiation is existing.

^cPatients.

^dComforters, carers, and volunteers in research only.

^eNot applicable.

Dose constraints were introduced for the first time in ICRP Publication 60 to resolve inequalities in radiation exposure levels during optimization processes [5]. This concept was not mandatory in ICRP Publication 60, but had been made mandatory by the time of ICRP Publication 103 [1,5]. A dose constraint serves as an upper bound of the predicted dose during the optimization of protection measures for the pertinent source [1]. In addition, dose constraints will always be lower than the pertinent dose limit. The action necessary if a dose constraint is exceeded includes determining whether the protection had been optimized, whether the appropriate dose constraint had been selected, and whether further steps to reduce doses to acceptable levels would be appropriate. However, this is not applicable to regulatory requirements [1,4]. The dose constraints for occupational exposure are set voluntarily by the nuclear licensee, taking into account the optimization measures necessary to lower the individual dose below the dose constraint [3,6]. For public exposure, the dose constraint can be set by the regulatory body taking into account an upper bound of the annual doses that members of the public could receive from the planned operation of a specified controlled source [1,4,6]. Furthermore, the ICRP recommends that a specific dose constraint value may then be established by a process of generic optimization that takes into account national or regional attributes as well as preferences, where appropriate, with consideration of international guidance and good practices elsewhere [1]. For example, the ICRP suggests that acceptable dose constraint levels for occupational and public exposure are less than 20 and 1 mSv y⁻¹, respectively. In the case of radioactive waste disposal and prolonged exposure, levels of less than 0.3 mSv y⁻¹ and less than 0.3–1 mSv y⁻¹ are suggested, respectively, as dose constraints for public exposure [1,6,7].

3. Preparation for the implementation of ICRP's dose constraints

At the end of 2010, KINS published regulatory guidance pertaining to the basic concept of dose constraints [8]. This guidance requires that dose constraints for workers and members of the public should be set such that individual doses are kept ALARA under a planned exposure situation. According to this guidance, an individual dose level, which exceeds the dose constraint set for occupational exposure, means that the optimization of protection measures is not implemented fully and that additional action should be taken to reduce individual doses [8]. Thus, this constraint has two functions; the first is to prevent individual doses from exceeding dose constraint limits via the optimization of protection measures and the second is to restrict total individual doses so that they do not exceed the dose limit.

As stated above, dose constraints for members of the public should be set by the government or by a regulatory body [1,3,6]. The nuclear licensee should control radioactive effluent into the environment taking into account the dose constraints provided by the regulatory body [1]. Particularly, the concept of a ‘representative person’ is necessary for the implementation of dose constraints for members of the public because the radiation source can expose unknown numbers of the general public. Furthermore, KINS created separate regulatory guidance for such a representative person, providing a definition of such a representative person and a means of calculating the associated dose [9]. According to this guidance, a representative person is defined as a representative individual of highly exposed individuals in the population. This term replaces ‘average member of the critical group’, which was described in the previous ICRP [9].

In contrast to dose constraints for occupational exposure, the constraints for members of the public can be misused as a regulatory limit because a regulatory body sets the dose constraints for members of the public. However, the difference between a dose constraint and a dose limit is that constraints are not applicable to regulatory requirements [4,6]. Although the KINS guidance defines the concept, its implementation, and action for dose constraints, specific values for the constraints are not given [8].

4. Radioactive effluents from NPPs and their dose estimations

The standards for dose levels pertaining to members of the public due to radioactive effluent materials from NPPs have already been implemented in Korea [10]. These standards are applicable during both normal operations and accidents at NPPs, and they have been used as constraints in a manner similar to the usage of ICRP's dose constraints for members of the public [10,11]. According to government notice in Korea, the annual dose standards, the so-called design objective values, for members of the public include specific numbers [11]. Table 2 shows the dose level standards for members of the public as applied in the design of nuclear facilities. In this notice, the term dose constraint is not used officially; however, the standards are used as dose constraints in practical because they include the concept of the ICRP's dose constraint.

Table 2. Standards applied to the design of nuclear facilities (at the boundary of the exclusion area).

Classification	Item	Annual dose limits per unit	Annual dose limits per site
Gaseous radioactive effluents	Air absorbed dose by gamma ray	0.1 mGy y^−1	For the operation of multiple nuclear reactor facilities at one site
	Air absorbed dose by beta ray	0.2 mGy y^−1	Effective dose: 0.25 mSv y^−1
	Effective dose by external radiation exposure	0.05 mSv y^−1	Thyroid equivalent dose: 0.75 mSv y^−1
	Skin equivalent dose by external radiation exposure	0.15 mSv y^−1
	Human organ equivalent dose by particle radioactive substances, ^3H, ^14C and radioiodine	0.15 mSv y^−1
Liquid radioactive effluents	Effective dose	0.03 mSv y^−1
	Human organ equivalent dose	0.1 mSv y^−1

The notice also requires that the dose for members of the public due to radioactive effluents and radiation from NPPs should be estimated periodically and compared with the annual dose limits [12]. In this process, the dose for members of the public is calculated as the projected dose prior to the discharge of radioactive effluents from NPPs, and the estimation of the dose for members of the public per reactor unit and site is finally calculated using the actual effluent data at NPPs [13,14]. Korean NPPs use KDOSE 60, a computing code, for dose estimations [13,14]. The criteria in KDOSE 60 are based on the method of US NRC Regulatory Guide 1.109 and the dose coefficients of ICRP Publication 60 [5,14,15]. This code has three main parts: GAS for dose calculations due to gaseous effluents, LIQ for dose calculations due to liquid effluents, and XQDQWQ for calculations of the atmospheric diffusion parameters [14]. This code calculates the most conservative estimate of the dose received by members of the public using the maximum individual approach. Other specific parameters including population information, meteorology, and effluent release activity surrounding plants are taken from the annual reports on radioactive material release from the individual NPPs. The exposure pathways from liquid and gaseous effluents are also based on Regulatory Guide 1.109 and include some site-specific considerations [14,15]. The dose estimation pathways for members of the public due to the transportation of radioactive materials are shown in Figures 1 and 2 [13,14]. Although radionuclides differ depending on the NPP, the major radionuclide for gaseous and liquid effluents is tritium, and most of the public doses are from tritium [16].

Figure 1. Pathway of gaseous radioactive effluents.

Figure 2. Pathway of liquid radioactive effluents.

5. Dose estimation for members of the public during the licensing process for the construction of a new NPP

Evaluations of the effects of radiation and radioactive effluents on the surrounding environment are required during the licensing process for the construction and the operation of a new NPP [11,12]. During this process, dose levels at the boundary of the exclusion area, with the assumption of hypothetical accidents such as a loss-of-coolant accident, should meet the annual dose standard. Its results are also used to judge whether or not the distance of the boundary of the exclusion area from the NPP is appropriate [17–19]. For an assumption of normal operation, the dose levels at the boundary of the exclusion area should be less than the annual dose standard as well. For hypothetical accidents, the annual thyroid and whole-body dose standards at the boundary of the exclusion area are 3000 and 250 mSv, respectively [11]. With the assumption of normal operation, the annual dose standards of the effective dose and that for the thyroid at the boundary of the exclusion area are 0.25 and 0.75 mSv y⁻¹, respectively [11]. These values serve as practical dose constraints for new NPPs during the stages of construction and operation in Korea.

6. Operation of multi-unit reactors at a single site

In Korea, the number of multi-unit reactors at a single site is increasing continuously because it is very difficult to find new NPP sites. Currently, four NPP sites are available in Korea [13,20]. At the Kori site, six reactors are currently in operation, two reactors are under construction, and the construction of an additional two reactors is planned. At the Hanbit (formerly Yonggwang) site, six reactors are in operation. At the Wolsong site, four CANDU reactors are in operation and one PWR reactor is in operation and one PWR reactor is under preliminary operation. A tritium removal facility (TRF) is also in operation at the Wolsong site. At the Hanul (formerly Ulchin) site, six reactors are in operation, but two reactors are under construction and the construction of two reactors is planned. Tables 3 and 4 depict the current NPP operation, construction, and planning situations [20].

Table 3. Power reactors currently operating in Korea.

Reactor	Type	Net capacity (MWe)	Commercial operation
Kori 1	PWR^a-Westinghouse	587	April 1978
Kori 2	PWR-Westinghouse	650	July 1983
Kori 3	PWR-Westinghouse	950	September 1985
Kori 4	PWR-Westinghouse	950	April 1986
Shin-Kori 1	PWR-OPR^b1000	1000	February 2011
Shin-Kori 2	PWR-OPR1000	1000	July 2012
Wolsong 1	PHWR^c-Candu	679	April 1983
Wolsong 2	PHWR-Candu	700	July 1997
Wolsong 3	PHWR-Candu	700	July 1998
Wolsong 4	PHWR-Candu	700	October 1999
Shin-Wolsong 1	PWR-OPR1000	1000	July 2012
Hanbit 1	PWR-Westinghouse	950	August 1986
Hanbit 2	PWR-Westinghouse	950	June 1987
Hanbit 3	PWR-OPR1000	1000	March 1995
Hanbit 4	PWR-OPR1000	1000	January 1996
Hanbit 5	PWR-OPR1000	1000	May 2002
Hanbit 6	PWR-OPR1000	1000	December 2002
Hanul 1	PWR-Framatome	950	September 1988
Hanul 2	PWR-Framatome	950	September 1989
Hanul 3	PWR-OPR1000	1000	August 1998
Hanul 4	PWR-OPR1000	1000	December 1999
Hanul 5	PWR-OPR1000	1000	July 2004
Hanul 6	PWR-OPR1000	1000	April 2005
Total: 23		20,716

^aPressurized water reactor.

^bOptimized power reactor.

^cPressurized heavy water reactor.

Table 4. Reactors under construction, on order, or planned in Korea.

Reactor	Type	Gross capacity (MWe)	Start construction	Commercial operation
Shin-Wolsong 2	PWR-OPR^a1000	1000	October 2005	July 2014
Shin-Kori 3	PWR-APR^b1400	1400	September 2007	August 2014
Shin-Kori 4	PWR-APR1400	1400	September 2007	September 2014
Shin-Hanul 1	PWR-APR1400	1400	April 2010	April 2017
Shin-Hanul 2	PWR-APR1400	1400	April 2010	February 2018
Shin-Kori 5	PWR-APR1400	1400	September 2014	December 2019
Shin-Kori 6	PWR-APR1400	1400	September 2014	December 2020
Shin-Hanul 3	PWR-APR1400	1400	November 2015	June 2021
Shin-Hanul 4	PWR-APR1400	1400	November 2015	June 2022
Total: 9		12,200

^aOptimized power reactor.

^bAdvanced power reactor.

7. Analysis of radioactive effluents from NPPs and dose levels for members of the public

Radioactive effluents from operating NPPs in Korea have been analyzed. The total radioactivity of effluents for five years from 2006 to 2010 was 3.29×10¹⁵ Bq: 2.31×10¹⁵ Bq coming from the Wolsong site (approximately 70% of the total radioactivity), 4.56×10¹⁴ Bq coming from the Hanbit site (14%), 2.73×10¹⁴ Bq coming from the Hanul site (8%), and 2.53×10¹⁴ Bq coming from the Kori site (8%). These results also show that the main contributor as a radioactive effluent material is tritium. The annual radioactive effluents from 2006 to 2010 are shown in Table 5 [13,21–24].

Table 5. Annual radioactive effluents from Korean nuclear power plants (years: 2006–2010) (unit: Bq).

	Site
Year	Kori	Hanbit	Wolsong	Hanul	Total
2006	6.54×10^13	6.75×10^13	4.93×10^14	5.25×10^13	6.78×10^14
2007	4.94×10^13	7.74×10^13	5.25×10^14	6.25×10^13	7.14×10^14
2008	4.56×10^13	1.36×10^14	4.78×10^14	4.48×10^13	7.04×10^14
2009	4.67×10^13	9.26×10^13	4.53×10^14	5.37×10^13	6.46×10^14
2010	4.63×10^13	8.27×10^13	3.59×10^14	5.94×10^13	5.47×10^14
Total	2.53×10^14	4.56×10^14	2.31×10^15	2.73×10^14	3.29×10^15

The average dose for members of the public for five years from 2006 to 2010 due to radioactive effluents was 0.00502 mSv y⁻¹. This value, the dose for the members of the public, is much lower than the annual dose standard for a site, 0.25 mSv y⁻¹, accounting for only 2.01%. For the effective dose, the average dose for five years was only 0.5% of the annual effective dose limit for members of the public, 1 mSv y⁻¹; the values were 0.00602 mSv y⁻¹ for the Kori site, 0.00550 mSv y⁻¹ for the Hanbit site, 0.00632 mSv y⁻¹ for the Wolsong site, and 0.00221 mSv y⁻¹ for the Hanul site. Most of the dose for members of the public was due to gaseous effluents, and its main pathways for exposure were the ingestion of crops and the inhalation of air. Furthermore, main contributor to the public dose was tritium. Table 6 shows the dose results for members of the public due to radioactive effluent materials from 2006 to 2010 [13,21–24].

Table 6. Annual public dose by radioactive effluents from Korean nuclear power plants (years: 2006–2010) (effective dose per site, unit: mSv).

	Site
Year	Kori	Hanbit	Wolsong	Hanul	Total
2006^a	0.00664	0.00485	0.00348	0.00165	0.00416
2007^a	0.01510	0.00604	0.00579	0.00209	0.00726
2008^a	0.00460	0.00957	0.00831	0.00190	0.00609
2009^a	0.00226	0.00433	0.00707	0.00209	0.00394
2010^b	0.00152	0.00274	0.00696	0.00333	0.00364
Average	0.00602	0.00550	0.00632	0.00221	0.00502
Comparison to the design criteria of nuclear facilities^c	2.41%	2.20%	2.53%	0.89%	2.01%
Comparison to the annual public dose limit^d	0.60%	0.55%	0.63%	0.22%	0.50%

^aAge group: adult; number of reactors: 20.

^bAge group: infant (five-year old); number of reactors: 21.

^cAnnual dose limit per site of standards applied to the design of nuclear facilities: 0.25 mSv y⁻¹ (effective dose).

^dAnnual public dose limit: 1 mSv y⁻¹ (effective dose).

8. Dose estimation for new NPPs

Dose estimations during the licensing process for a new NPP have two parts; the first is a dose estimation value for accidents assuming hypothetical accidents at the boundary of the exclusion area and second is a dose estimation value for normal operations taking into account general operational situations at NPPs. Regarding dose estimations for accidents, a dose is calculated while taking into account severe exposure under a loss-of-coolant accident. For dose estimations under normal operations, a dose is calculated conservatively by adding up the dose using the expected source term with a hypothetical fuel defect of 0.12% for the main reactor and the maximum dose from the history of other reactors. Contrary to the hypothetical assumption, the average level of fuel defect under normal operation at Korean NPPs is 0.000106% [25]; the hypothetical value is much higher than the real value. The estimated dose was also determined by summing the dose from the existing NPPs and the dose from the new NPPs. The expected maximum number of total NPPs at a single site in Korea is currently 10, and most of the new NPPs have an increased capacity up to 1400 MWe. Thus, this estimated dose will be much higher than the current dose coming from NPPs under normal operation.

It was found that the dose for accidents was 0.25–0.4 mSv for the whole body and 20–40 mSv for the thyroid, with sufficient margins compared with dose standards [17–19]. In contrast to the dose for accidents, the dose for normal operations was 0.202 mSv y⁻¹ for the construction licensing process for Shin-Hanul NPP units 1 and 2. This value includes the dose coming from the six existing reactors at the Hanul site. For Shin-Wolsong NPP unit 1, the dose was estimated as 0.221 mSv y⁻¹ for the operation licensing process. This value includes the dose coming from the six existing reactors and the TRF. Thus, the dose was nearly 90% of the annual dose standard for normal operation taking into account the operation of multi-unit reactors at a single site. The dose estimation results for the approval of a license for a new NPP are displayed in Table 7 [17–19].

Table 7. Assessment results of licensing for construction and operation of Korean nuclear power plants in 2011.

License	Condition	Classification	Dose limits (mSv)	Assessment result (mSv)
Construction of Shin-Hanul 1 and 2	Emergency	Thyroid dose	3000	42.1
		Whole-body dose	250	0.356
	Normal operation	Thyroid dose	0.75	0.286
		Effective dose	0.25	0.202
Operation of Shin-Kori 2	Emergency	Thyroid dose	3000	28.3
		Whole-body dose	250	0.250
	Normal operation	Thyroid dose	0.75	0.447
		Effective dose	0.25	0.138
Operation of Shin-Wolsong 1	Emergency	Thyroid dose	3000	25.0
		Whole-body dose	250	0.23
	Normal operation	Thyroid dose	0.75	0.309
		Effective dose	0.25	0.221

9. Establishment of dose constraints for members of the public

Korean NPPs have already applied dose standards akin to dose constraints in an effort to estimate the effect of radiation and radioactive effluents coming from NPPs for members of the public. These standards are based on the 10 CFR Part 50 Appendix I, part of the US NRC regulations pertaining to radioactive effluents and 40 CFR 190 Subpart B, part of the US Environmental Protection Agency regulations pertaining to environmental standards [26,27]. Since the United States was the primary supplier to NPPs in Korea, most Korean regulations on NPP licensing have been based on US NRC regulations. These regulations take into account a maximum of three reactors at a single site [28]. According to the regulations, the annual dose standards for members of the public due to radioactive effluents from uranium fuel cycle facility are 0.75 mSv y⁻¹ for the thyroid and 0.25 mSv y⁻¹ for the effective dose; however, it also should be noted that if more than three reactors exist at a single site, the dose could exceed the annual dose standard [28].

As stated above, previous doses for members of the public due to radioactive effluents from Korean NPPs were very low. However, in the licensing process for a new NPP, the estimated dose matches the annual dose standards without a margin. Thus, it is necessary to establish a dose constraint with more of a margin taking into account the result of the analysis of the estimated dose for the licensing of a new NPP, especially one with multi-unit reactors at a single site. In this paper, 0.6 mSv y⁻¹ is suggested as the dose constraint for a single source in Korea, which is approximately 2.5 times the previous constraint for members of the public [29].

Dose constraints can also be established considering the effect of gaseous and liquid effluents per NPP unit in Korea. The ICRP does not differentiate between doses caused by radiation exposure types, such as internal and/or external exposure, and it uses the effective dose to evaluate the overall effect of radiation and radioactive effluents on a human being. Furthermore, the criteria related to the discharge of gaseous and liquid radioactive effluents use the unit of concentration stated in the notice by the regulatory body in order to regulate these discharges. Thus, in this paper, 0.2 mSv y⁻¹ is suggested as the dose constraint for the single NPP unit in Korea [29]. This was determined by summing the doses from gaseous and liquid effluents originally determined in the design of the discharge of gaseous and liquid radioactive effluents. This value is approximately 2.5 times of the sum (0.08 mSv y⁻¹) of the current dose standards for gaseous effluents (0.05 mSv y⁻¹) and liquid effluents (0.03 mSv y⁻¹). At NPPs in Korea, the dose due to liquid effluents is approximately 1.00×10³ times lower than that of the dose due to gaseous effluents; these overall dose standards for gaseous and liquid effluents most likely allow more flexibility to NPP operators.

Increase factor for NPPs at single sites in Korea, (1) $$\frac{10\mathrm{reactors}\left(\mathrm{planned}\right)}{4\mathrm{to}6\mathrm{reactors}\left(\mathrm{current}\right)}\approx 2.5\mathrm{times}\mathrm{of}\mathrm{current}\mathrm{units}$$(1)

Proposed annual dose limit per site, (2) $$0.25{\mathrm{mSv}\mathrm{y}}^{-1}\times 2.5\approx 0.6{\mathrm{mSv}\mathrm{y}}^{-1}$$(2)

Proposed annual dose limit from gaseous and liquid effluents per reactor unit, (3) $$(0.05+0.03){\mathrm{mSv}\mathrm{y}}^{-1}\times 2.5=0.2{\mathrm{mSv}\mathrm{y}}^{-1}$$(3)

Since the regulations on radioactive effluents from NPPs depend on individual nations, it is practically difficult to apply these proposed values to other nations. However, it is expected that the number of reactors at single sites worldwide will increase continuously since it is very difficult to find new NPP sites due to the increase of public anxiety about nuclear power. Thus, from the conceptual perspective, it is inevitable that there will be an increase in the annual dose standards in nuclear power nations if additional NPPs are continuously built at previous sites.

10. Conclusions

According to dose estimations for currently operating NPPs, the dose for members of the public due to radioactive effluents from operating NPPs was approximately 4–8 μSv·y⁻¹, which was less than 3% of the annual dose standard per site of 0.25 mSv y⁻¹ for multiple reactors at a single site, and less than 1% of the annual dose limit for members of the public of 1 mSv y⁻¹. However, the number of reactors at a single site has continuously been increasing. Our analysis indicated that the estimated doses for license approval of new NPPs with multi-unit reactors at a single site, resulted in almost 90% of the annual dose standard (0.202 - 0.221 mSv y^-1). Furthermore, there were no margins to manage the natural fluctuations of radioactive effluents on members of the public. Thus, it is necessary to establish dose constraints for members of the public of 0.6 mSv y⁻¹ per site and 0.2 mSv y⁻¹ per unit taking into account multi-unit reactors at a single site in Korea.

Additional information

Funding

This work was supported by the Korea Hydro & Nuclear Power Co., Ltd.