- Email: [email protected]
Present status of nuclear containments and ISI in Korea
Progress in Nuclear Energy 51 (2009) 761–768
Contents lists available at ScienceDirect
Progress in Nuclear Energy journal homepage: www.elsevier.com/locate/pnucene
Review
Present status of nuclear containments and ISI in Korea Jihong Park a, *, Jaekeun Hong b a b
Industrial Technical Support Division, Korea Institute of Materials Science, 66 Sangnam-Dong, Changwon, Kyeongnam, 641-831, Republic of Korea Structural Materials Division, Korea Institute of Materials Science, 66 Sangnam-dong, Changwon, Kyeongnam, 641-831, Republic of Korea
a b s t r a c t Keywords: Nuclear containments Inservice inspection Nuclear power plants Inspection technology
Since the first nuclear power plant started in commercial service in 1978 in Korea, 20 units have been operated and maintained, and most recently several units were under construction and planned to be constructed in order to meet the demand of more electricity. The importance of nuclear containments always has been one of the hottest issues for the safety and protection of nuclear power plants. From 1970s to present year, various types of nuclear containments have been constructed until now. With the changes of times, nuclear containment systems have undergone a remarkable change, and finally a Korea standard nuclear power plant was defined. For those reasons, various regulatory issues, inspection technologies, technical requirements for periodic inspection have been applied differently depending on the specific nuclear containment types. In this study, overall status of nuclear power plants, development stages of nuclear containment systems, and inservice inspections in Korea were researched. Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction Nuclear power plants should be designed and operated in order for the safety assurance, safety design, facilities, and maintenance to be certainly guaranteed. Since Chernobyl and TMI nuclear accidents, the importance of nuclear containments always has been one of the hottest issues for the safety and protection of nuclear power plants until now. The most important role of nuclear containments is to prevent radioactive substances from leaking out, acting as final barrier in nuclear power plants. Since 1970s in Korea, several typed nuclear power plants were introduced and constructed with change of times. As a matter of course, various typed nuclear containments have been developed with change of times. In this paper, overall status of nuclear power plants, development stages of nuclear containment systems and inservice inspections performed recently including performing organizations, inspection technologies and regulatory requirements mainly from a standpoint of Korea standard nuclear containments were described briefly. 2. Status of nuclear power plants The Korea Government had worked out a long term policy on the demand and supply of energy. At long last the Korea Ministry of Science and Technology (MOST) promulgated the ‘‘Atomic Energy Act’’ for the peaceful use of nuclear energy in 1958 (MOST,1958). Since
* Corresponding author. Tel.: þ82 55 280 3419; fax: þ82 55 280 3409. E-mail address: [email protected] (J. Park). 0149-1970/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.pnucene.2009.05.005
the first nuclear power plant ‘‘Kori unit 1’’ was started in commercial service in 1978, at present 20 unit nuclear power plants have been operated and maintained in Korea (Jihong P. et al., 2007a,b). Also in order to meet the demand of more electric energies required by industries, most recently 4 units were started to be constructed in New Kori and New Wolsong sites. And already additional several units were planned to be constructed. All of those nuclear power plants in Korea are owned by only one unique utility, ‘‘Korea Hydro Nuclear Power Company (KHNP)’’ (KHNP, 2007). Since the electric generation output from the first nuclear power plant, ‘‘Kori Unit 1’’ with 587 MWe, the electrical capacity gradually have increased up to 1000 MWe at present, and it was planned to reach 1400 MWe in the near future (Jihong P. et al., 2007a,b). At present year 2009, the electric generation output from nuclear power plants (20 units) in service accounts for 40–45 percent of total electricity generation output including hydroelectric, thermal power, and others. Korea stands 6th in the world as regards the output of nuclear electric power. At the beginning stage of nuclear power plant constructions in Korea, various reactor types such as Westinghouse (U.S.), AECL (Canada), Framatome (France) were adopted to be constructed. Since Yonggwang Unit 3, ‘‘Korea Standard Nuclear Power Plants (KSNP)’’ were started to be constructed and settled down. Overall status of Korea nuclear power plants were described briefly in Table 1. 3. Nuclear containment systems Since 1970s in Korea, nuclear containment systems have been developed mainly as following 4 stages:
762
J. Park, J. Hong / Progress in Nuclear Energy 51 (2009) 761–768
Table 1 Status of nuclear power plants in Korea. Name of units
Reactor type
Commission
Kori
Unit Unit Unit Unit
1 2 3 4
Busan
587 650 950 950
PWRa (Westinghouse)
1978. 1983. 1985. 1986.
04. 07. 09. 04.
29. 25. 30. 29.
Wolsong
Unit Unit Unit Unit
1 2 3 4
Gyeongbuk
679 700 700 700
PHWRb (AECL)
1983. 1997. 1998. 1999.
04. 07. 07. 10.
22. 01. 01. 01.
Yonggwang
Unit Unit Unit Unit Unit Unit
1 2 3 4 5 6
Jeonnam
PWR (Westinghouse)
1986. 1987. 1995. 1996. 2002. 2002.
08. 06. 03. 01. 05. 12.
25. 10. 31. 01. 21. 24.
Unit Unit Unit Unit Unit Unit Unit Unit Unit Unit
1 2 3 4 5 6 1, 3, 1, 1,
Gyeongbuk
Ulchin
New Kori New Wolsong New Ulchin a b
Location
2 4 2 2
Busan Gyeongbuk
Capacity (MWe)
950 950 1000 1000 1000 1000 950 950 1000 1000 1000 1000 1000 1400 1000 1400
PWR (Doosan/CE)
PWR (Framatome) PWR (Doosan/CE)
1988. 09. 10. 1989. 09. 30. 1998. 08. 11. 1999. 12. 31. 2004. 07. 29. 2005. 04. 22. Under construction Planned Under construction Planned
PWR: pressurized water reactor. PHWR: pressurized heavy water.
(a) First stage; Metal containments (b) Second stage; Prestressed concrete containments with grouted tendons (c) Third stage; Prestressed concrete containments with ungrouted tendons (d) Forth stage; KSNP containments
3.1. 1st stage (metal containment) First at the beginning stage, the nuclear containments of the first two nuclear power plants, Kori Unit 1 & 2 were designed as metal containment buildings with design pressure of 43–45 psi. The containments were composed of inside metal structure with 1½ in (38 mm) thickness and outside traditionally reinforced concrete structures with 75–80 mm thickness with having a shallow-dome roof on cylindrical wall (Fig. 1). Especially the inside metal structures play an important role of pressure retaining and preventing leakage of radioactive substance.
shapes of containment buildings are torispherical or shallow-dome roofs on cylindrical walls. Grouted (Bonded) post-tensioned concrete is the descriptive term for a method of applying compression after pouring concrete and the curing process. The procedure is that the concrete is cast around aluminum curved duct, to follow the area where otherwise tension would occur in the concrete element. Then a set of tendons is fished through the duct and the concrete is poured. Once the concrete has hardened, the tendons are tensioned by hydraulic jacks that react against the concrete member itself. When the tendons have stretched sufficiently, according to the design
3.2. 2nd stage (prestressed concrete containment with grouted tendons) At the second stage for nuclear containment constructions, prestressed concrete systems were adopted, which is a method for overcoming traditional concrete’s natural weakness in tension. Prestressing tendons generally with high tensile steels are used to provide a clamping load which produces a compressive stress that offsets the tensile stress that the concrete compression member would otherwise experience due to a bending load. Prestressing tendon is a separate continuous multi-wire or multi-strand tensioned element anchored at both ends to an end tendon anchorage assembly. The nuclear containments, Wolsong Unit 1, 2, 3, 4 and Ulchin Unit 1 & 2 were designed as prestressed concrete containments with grouted (bonded) tendon systems (Fig. 2). The
Fig. 1. 1st Stage, metal containment.
J. Park, J. Hong / Progress in Nuclear Energy 51 (2009) 761–768
763
Fig. 2. Prestressed concrete with grouted (Bonded) tendon system.
specifications, they are anchored in position and maintain tension after the jacks are removed, transferring pressure to the concrete. The duct is then grouted to protect the tendons from corrosion. In case of Ulchin Unit 1 & 2, inside metal liner plates and outside concrete structures play roles of preventing leakage of radioactive substances and pressure retaining in containment building respectively. On the contrary, in case of Wolsong Unit 1, 2, 3, 4, epoxy coatings instead of using metal liner plates were applied to prevent leakage of radioactive substances due to relatively lower design pressure (18 psi) compared with those of other containments. The specifications of the second stage nuclear containment systems were described in Table 2.
3.3. 3rd Stage (prestressed concrete containment with ungrouted tendons) Compared with the 2nd stage, the 3rd stage nuclear containments were designed as prestressed concrete containments with ungrouted (unbonded) tendon systems (Fig. 3). Ungrouted (unbonded) post-tensioned concrete containment differs from those of grouted (bonded) by providing each individual tendon permanent freedom of movement relative to the concrete. To achieve this, each individual tendon was coated with corrosion protection medium (grease) and covered by a sheathing duct. Kori Unit 3 & 4 and Yonggwang Unit 1 & 2 were designed as prestressed concrete containments with ungrouted (unbonded) tendon systems with having a hemispherical-dome roof on cylindrical wall. Outside concrete structures mainly perform pressure retaining role,
and inside metal liner plates play roles of preventing leakage of radioactive substances. The specifications of 3rd stage nuclear containment systems were described in Table 3.
3.4. 4th stage (KSNP containment) At the final stage, KSNP (Korea Standard Nuclear Power Plants) was settled down (Fig. 4). KSNP was optimized power reactor 1000 and based on the model system 89 of ABB-CE. The nuclear containment systems of KSNP were modified and improved from the 3rd stage ones. 8 units (Yonggwang Unit 3–6 & Ulchin Unit 3–6) operated and additional 8 units (New Kori Unit 1–4, New Wolsong Unit 1–2, & New Ulchin 1–2) under construction or planned were designed as KSNP. KSNP containments with having a hemispherical-dome roof on cylindrical wall were composed of inverted U shaped vertical tendons and hoop shaped horizontal tendons located in the cylinder and dome (Fig. 5 and 6). The numbers of horizontal tendons (with one tendon having a 240 loop) and vertical tendons were 96 and 135 respectively. The schematic diagram and roles of anchorage components of tendon system were briefly shown in Fig. 7 and Table 4. Each tendon has 55 multi-element strands (1/2 in diameter of each strand), and the stand materials used are ASTM A 416 Grade 270, low relaxation, seven-wire twisted strands (Fig. 8). With evolution from the 3rd to the 4th stage nuclear containments, the major changes were as follows. With increasing of containment size, the number of tendons installed was changed from 72 vertical and 117 horizontal tendons to 96 vertical and 165 horizontal
Table 2 The specifications of 2nd Stage containment systems. Item
Unit Ulchin Unit 1, 2
Wolsong Unit 1, 2, 3, 4
Design code Shape No. of buttress Concrete wall thickness Design pressure Height Metal liner plate thickness No. of tendons (each group)
RCC-G part 1 Torispherical dome roof on cylindrical wall 4 90 cm 58 psi 59.4 m 6 mm 144 (Vertical tendons) 280 (Hoop tendons) 174 (Dome tendons)
Strand type No. of strands (each tendon) Anchoring method Sheath filler
7wire (0.5 in diameter) 19 & 37 Wedge Cement grout
CAN/CSA Shallow-dome roof on cylindrical wall 4 107 cm 18 psi 51.89 m Epoxy coating 124 (Vertical tendons) 163 (Hoop tendons) 141 (Dome Tendons) 126 (basemat tendons) 7wire (0.5 or 0.25 in Diameter) 1, 37 & 35 Buttonhead Cement grout
764
J. Park, J. Hong / Progress in Nuclear Energy 51 (2009) 761–768
Fig. 3. Prestressed concrete with ungrouted (Unbonded) tendon system.
Table 3 The specifications of 3rd stage containment systems. Item unit
Kori unit 3,4 & Yonggwang unit 1,2
Design code Shape No. of buttress Concrete wall thickness Design pressure Height Metal liner plate thickness No. of tendons (each group)
ASME Hemispherical-dome roof on cylindrical wall 3 122 cm 60 psi 63.35 m 6.35 mm 72 (Vertical tendons) 117 (Horizontal tendons) 7wire (0.5 in diameter) 50, 53 & 55 Wedge Grease
Strand type No. of strands (each tendon) Anchoring method Sheath filler
Fig. 5. Inverted U shaped vertical tendons (side view).
Fig. 4. KSNP containment.
tendons. And the number of strands per each tendon was changed from 50 or 53 to 55. About the third stage containments, two kinds of tendon anchorages were designed. One (Fig. 9) is designed for examination of prestress force (tendon force) measurement only, and the other (Fig. 10) is designed for examination of material test (yield strength, ultimate tensile strength, breaking strength, elongation, physical property, & etc.) of tendon-strands. Namely, the inspection tendons
Fig. 6. Hoop shaped horizontal tendons (top view).
J. Park, J. Hong / Progress in Nuclear Energy 51 (2009) 761–768
765
Fig. 7. Anchorage components in tendon system.
Table 4 Roles of anchorage components in tendon system. Designation
Description
Bearing plate Anchorhead Shim plate
Protecting the exterior concrete surfaces Anchoring the tendon-strands Adjusting & buffing plate between bearing plate & anchorhead Preventing the anchored wedges from ejecting out Element for fixing & anchoring the tendon-strands Seven-wire twisted prestress element Tunnel for tendon-strands & prevention from leaking of grease Storage and protection for grease & anchorage ends Access tunnel for injection of grease Venting of inside air/gas and draining of inside water
Retainer plate Wedge Strand Sheathing duct Grease cap Grease injection access Vent & drain
during inservice inspection were predesignated for prestress force measurement and material test separately. Especially for material test of tendon-strand, tendon anchorage should be designed that at least one tendon-strand could be detensioned and removed. In the 4th stage containments, tendon anchorages were designed so that all tendons could be available for both prestress force measurement and material test during inservice inspection (Fig. 11).
4. Inservice inspections All of the nuclear power plants should be inspected periodically according to the ‘‘Regulation on Inservice Inspection of Nuclear Reactor Facilities’’ by Notice of the Ministry of Science and Technology (MOST), Korea government (MOST, 2004). This Notice stipulate technical regulations such as standards, codes, inspection periods, and others. Because of various types of nuclear containments, several appropriate codes, standards and procedures are applied differently depending on the specific nuclear containment types. ‘‘Long Term Inservice Inspection Plan of Containment
Building’’ (KHNP, 1985–2004) and ‘‘Technical Specification and Inspection Procedure for Inservice Inspection of Containment Building’’ (KOPEC, 1978–2006) were issued and approved by the utility (KHNP) and enforcement authority (MOST) respectively. And fundamentally all the required technical regulations were contained in those documentations. Main technical requirements and inspection items were summarized briefly in Table 5. The main performing body for inservice inspection (ISI) in nuclear containments is ‘‘Korea Hydro & Nuclear Power Company (KHNP)’’ cooperated with several industries. And all of these inservice inspection plans, performances, procedures and documentations should be reviewed, witnessed and supervised by Korea Institute of Nuclear Safety (KINS) and Korea Institute of Materials Science (KIMS) as entrusted regulatory agency and authorized nuclear inspection agency respectively. Finally all of the records and results of inservice inspections should be reported and approved by the Atomic Energy Bureau, Ministry of Science and Technology. The examination categories, contents and frequency of inservice inspections in KSNP nuclear containments were summarized briefly in Table 6. 5. Discussions With evolution of nuclear power plants in Korea from 1970s to present year, there have been remarkable changes of containment systems and inservice inspections. First, the noticeable change with transition from the 1st stage (metal containments) to the 2nd stage containments (prestressed concretes with grouted tendons) was conversion of traditional concrete to prestressed concrete system. Consequently it could overcome traditional concrete’s natural weakness in tension. Second, with transition from the 2nd stage (grouted tendon systems) to the 3rd stage containments (ungrouted tendon systems), real tendon prestress force measurement (in situ) during inservice inspection could be available. In the 2nd stage containments, real prestress force measurement of grouted tendon system was not available even
Fig. 8. Seven-wire strand.
766
J. Park, J. Hong / Progress in Nuclear Energy 51 (2009) 761–768
Fig. 9. Tendon anchorage for prestress force measurement only.
though simulated test beam methods (indirect prestress force measurement) were used. In the grouted tendon system of the 2nd stage containments, adjustment of tendon force and replacement of tendon in need were not available. In the meantime, adjustment of tendon force and replacement of tendon in need were available in the 3rd stage containments (ungrouted tendon system). Third, with transition from the 3rd stage to the 4th stage containments (KSNP), perfect random selection of tendons (representative tendon sampling) for inservice inspection (ISI) could be available. In the 3rd stage containments, inspection tendons were already predesignated for prestress force measurement and material test separately. On the contrary in the 4th stage KSNP containments, any tendon could be selected for tendon prestress force measurement and material test during ISI. The assurance of perfect random selection of tendons is basic concept of inservice inspection and also strongly required by Korea regulatory authority. And in the 3rd stage containments, new tendonstrand should be replaced after removal of 1 tendon-strand for
Fig. 11. 4th Stage tendon anchorage.
material test. However in the 4th stage containments, replacement of new tendon-strand is not necessary because the containment was designed to ensure safety margin of prestress force with sufficient number of tendon-strands. In many cases, the technical requirements of ISI in KSNP containments are similar with those of ASME, US NRC Regulatory Guide, CAN/CSA, RCC-G & etc. However, more severe and strictly conservative concepts were applied and contained in the
Fig. 10. Tendon anchorage for material test.
Table 5 Main inspection items & technical requirements for ISI. Containment system
Main inspection items
1st stage Kori 1–2
Main technical requirements
Metal containment Concrete Surface Integrated leak rate test Local leak rate test
Notice of the Ministry of Science & Technology Long term ISI plan of containment building Technical specification & inspection procedure - ASME Sec. XI, Div.1 IWE (ASME, 1989–2004a) - FSAR (KHNP, 1978–2005)
2nd Stage Wolsong 1w4
Concrete surface Indirect prestress force test (test beam method) Integrated leak rate test Local leak rate test
Notice of the Ministry of Science & Technology Long term ISI plan of containment building Technical specification & inspection procedure - CAN/CSA-N287.7 (CSA, 1980) - U.S. NRC Regulatory guide 1.90 (U.S. NRC, 1977) - FSAR
2nd Stage Ulchin 1–2
Liner plate Leak resistance test Strength test
Notice of the Ministry of Science & Technology Long term ISI plan of containment building Technical specification & inspection procedure - RCC-G Part 3 (AFCEN, 1981) - ASME Sec. XI, Div.1 IWE - FSAR
3rd Stage Kori 3–4
Yonggwang 1–2 4th Stage Yonggwang 3–6 Ulchin 3–6 New Kori 1–4 New Wolsong 1–2
Concrete surface Liner plate Integrated leak rate test Local leak rate test Tendon Anchorage Prestress force test Material test:
Notice of the Ministry of Science & Technology Long term ISI plan of containment building Technical specification & inspection procedure -
- Strand - Grease - Free water
US NRC Regulatory guide 1.35 (U.S. NRC, 1990) ASME Sec. XI, Div.1 IWE ASME Sec. XI, Div.1 IWL (ASME, 1989–2004b) ACI 201 (ACI, 1992) FSAR ASTM & APHA
Table 6 ISI examination categories, contents and frequency. Categories
Contents
Liner plate Shell/dome/embedment Pressure retaining welds Penetrations/hatch Seals/moisture barriers Dissimilar metal welds Pressure retaining bolting
-
Degradation Corrosion Crack Abrasion/Erosion Loss of coating Material loss. Leak tightness Peeling Blistering Strikes Discontinuity Localized leak rate test Integrated leak rate test Cracks Degradation Grease leakage Abnormal behavior Compressive strength Reinforcing steel corrosion Differential settlement
-
-
Corrosion Damage Deformation Dent Slippage
-
Crack Fracture Balance Scratch Grease leakage
-
Prestress force measurement Color Smell Crack Chemical analysis Elongation
-
Viscosity Corrosion Physical damage Yield strength Tensile strength
LLRT ILRT Concrete Exterior concrete surface (dome, shell & buttress) Tendon anchorage area
Anchorage hardwares Bearing plate Shim plate Wedge Gasket ring Retainer plate Grease injection access Tendon Material test Grease Free water Strand/wire
Anchorhead Strand/wire Grease cap Vent cock
Frequency Aging Pitting Wear Bolt tightness Deformation Flaw Flaking Discoloration Distress Gouges Dents
w7 Times per 10 years
Every 3~5 years - Chemical analysis - Distress - Damage
1, 3, 5 & every 5 years following SIT
1st unit: 1, 5, 10 & every 10 years following SIT 2nd unit: 1, 5 & every 10 years following SIT
768
J. Park, J. Hong / Progress in Nuclear Energy 51 (2009) 761–768
‘‘Technical Specification and Inspection Procedure for ISI of Containment Building’’ (KOPEC, 1978–2006). Overall inservice inspection results of most Korea nuclear containments did not show any serious evidence of damage, degradation, corrosion, grease leakage and loss of prestressing force even though 20 units have been operated since 1978. In minor cases, the presence of free water and grease degradation in the tendon cap might be presumed due to the grease injection during installation in rainy season. The first nuclear power plant, Kori unit 1 was designed with 30 year lifetime, and it has been operated since 1978. Now the extension for further use of Kori unit 1 is hot issue and under review by the utility (KHNP) and government (MOST). Several years ago, ‘‘Korea Electric Power Industry Code (KEPIC)’’ (KEA, 2005a, b) corresponding with ASME was issued, and it is under plan to be adopted as main technical standard and code for inservice inspection of nuclear power plants in Korea.
6. Conclusions At present, 20 unit nuclear power plants have been operated and maintained in Korea since the first nuclear power plant ‘‘Kori unit 1’’ was started in commercial service in 1978. And most recently, 8 units were started to be constructed and planned. From 1970s to present year, nuclear containment systems have been evolved mainly as following 4 stages. 1st stage (metal containment), 2nd stage (prestressed concrete containment with grouted tendons), 3rd stage (prestressed concrete containment with ungrouted tendons), and finally 4th stage (KSNP containment) was settled down. With evolution of nuclear containment systems, structural integrity, reliability of inspection, and estimation of lifetime extension could be much improved even though the shortcomings of high cost of installation, extended inspection items & technical requirements, and high cost of inspection remained. All of the nuclear containments should be inspected periodically according to the ‘‘Regulation on Inservice Inspection of Nuclear Reactor Facilities’’ by the Notice of the Ministry of Science and Technology (MOST), Korea. For periodic inservice inspection, technical requirements, inspection items, frequencies, and procedures are applied differently depending on the specific nuclear containment types. Even though various mixed codes and standards have been used for inservice inspection (ISI) of nuclear containments until now, ‘‘Korea Electric Power Industry Code (KEPIC)’’ is under progress as main technical code for inservice inspection of nuclear power plants in Korea. Since 1978, overall inservice inspection results of most Korea nuclear containments did not show any serious degradation evidence. The first nuclear power
plant, ‘‘Kori unit 1’’ which was designed with 30 year lifetime is under approval for lifetime extension. Acknowledgements The authors would like to express thanks to all the colleagues in Korea Authorized Nuclear Inspection Center, Korea Institute of Materials Science (KIMS) for the encouragement and excellent guidance during research. And we must express deep appreciation to the president and staffs of KHNP Co., Ltd. for support and assistance for a long time. References American Concrete Institute (ACI), 1992. Guide for Making a Condition Survey of Concrete in Service ACI 201. American Society of Mechanical Engineers (ASME), 1989–2004a. Requirements for Class MC and Metallic Liners of Class CC Components of Light Water Cooled Power Plants ASME Sec. XI, Div.1 IWE, New York, USA. American Society of Mechanical Engineers (ASME), 1989–2004b. Requirements for Class CC Concrete Components of Light Water Cooled Power Plants ASME Sec. XI, Div.1 IWL, New York, USA. Canadian Standards Association (CSA), 1980. Inservice Testing and Examination Requirements for Concrete Containment Structures for CANDU Nuclear Power Plants CAN/CSA-N287.7, Mississauga, Canada. French Society for Design and Construction Rules for Nuclear Island Components (AFCEN), 1981. Design and Construction Rules for Civil Works of 900 MWe PWR Power Plants, RCC-G Part 3, France. Jihong, P., Jaekeun, H., Byunghoon, L., Youngho, S., 2007a. Present status of nuclear containments in Korea. In: Proceedings of 15th International Conference on Nuclear Engineering, April 22–26, Nagoya, Japan. Jihong, P., Jaekeun, H., Banuk, P., 2007b. Nuclear Containment Systems and Inservice Inspection Status of Korea Nuclear Power Plants. In: Proceedings of International Congress on Advances in Nuclear Power Plants, May 13–18, Nice, France. Korea Hydro & Nuclear Power Company (KHNP), 1978–2005. Final Safety Analysis Report Korea. Korea Hydro & Nuclear Power Company (KHNP), 1985–2004. Long Term Inservice Inspection Plan of Containment Building Korea. Korea Hydro & Nuclear Power Company (KHNP), 2007. Homepage. www.khnp.co.kr Korea. Korea Power Engineering Company (KOPEC), 1978–2006. Technical Specification and Inspection Procedure for Inservice Inspection of Containment Building Korea. Korea Electric Association (KEA), 2005a. Inservice Inspections of MC and Metallic Liner, Korea Electric Power Industry Code (KEPIC) MIE Korea. Korea Electric Association (KEA), 2005b. Inservice Inspections of Containment Structures, Korea Electric Power Industry Code (KEPIC) MIL Korea. Ministry of Science and Technology (MOST), 1958. Atomic Energy Act Korea. Ministry of Science and Technology Korea (MOST), 2004. Regulation on Inservice Inspection of Nuclear Reactor Facilities, Notice No. 2004-13 Korea. United States Nuclear Regulatory Commission (U.S. NRC), 1977. Inservice Inspections of Prestressed Concrete Containment Structures with Grouted Tendons, U.S. NRC Regulatory Guide 1.90 USA. United States Nuclear Regulatory Commission (U.S. NRC), 1990. Inservice Inspections of Ungrouted Tendons in Prestressed Concrete Containments, U.S. NRC Regulatory Guide 1.35 USA.
Contents lists available at ScienceDirect
Progress in Nuclear Energy journal homepage: www.elsevier.com/locate/pnucene
Review
Present status of nuclear containments and ISI in Korea Jihong Park a, *, Jaekeun Hong b a b
Industrial Technical Support Division, Korea Institute of Materials Science, 66 Sangnam-Dong, Changwon, Kyeongnam, 641-831, Republic of Korea Structural Materials Division, Korea Institute of Materials Science, 66 Sangnam-dong, Changwon, Kyeongnam, 641-831, Republic of Korea
a b s t r a c t Keywords: Nuclear containments Inservice inspection Nuclear power plants Inspection technology
Since the first nuclear power plant started in commercial service in 1978 in Korea, 20 units have been operated and maintained, and most recently several units were under construction and planned to be constructed in order to meet the demand of more electricity. The importance of nuclear containments always has been one of the hottest issues for the safety and protection of nuclear power plants. From 1970s to present year, various types of nuclear containments have been constructed until now. With the changes of times, nuclear containment systems have undergone a remarkable change, and finally a Korea standard nuclear power plant was defined. For those reasons, various regulatory issues, inspection technologies, technical requirements for periodic inspection have been applied differently depending on the specific nuclear containment types. In this study, overall status of nuclear power plants, development stages of nuclear containment systems, and inservice inspections in Korea were researched. Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction Nuclear power plants should be designed and operated in order for the safety assurance, safety design, facilities, and maintenance to be certainly guaranteed. Since Chernobyl and TMI nuclear accidents, the importance of nuclear containments always has been one of the hottest issues for the safety and protection of nuclear power plants until now. The most important role of nuclear containments is to prevent radioactive substances from leaking out, acting as final barrier in nuclear power plants. Since 1970s in Korea, several typed nuclear power plants were introduced and constructed with change of times. As a matter of course, various typed nuclear containments have been developed with change of times. In this paper, overall status of nuclear power plants, development stages of nuclear containment systems and inservice inspections performed recently including performing organizations, inspection technologies and regulatory requirements mainly from a standpoint of Korea standard nuclear containments were described briefly. 2. Status of nuclear power plants The Korea Government had worked out a long term policy on the demand and supply of energy. At long last the Korea Ministry of Science and Technology (MOST) promulgated the ‘‘Atomic Energy Act’’ for the peaceful use of nuclear energy in 1958 (MOST,1958). Since
* Corresponding author. Tel.: þ82 55 280 3419; fax: þ82 55 280 3409. E-mail address: [email protected] (J. Park). 0149-1970/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.pnucene.2009.05.005
the first nuclear power plant ‘‘Kori unit 1’’ was started in commercial service in 1978, at present 20 unit nuclear power plants have been operated and maintained in Korea (Jihong P. et al., 2007a,b). Also in order to meet the demand of more electric energies required by industries, most recently 4 units were started to be constructed in New Kori and New Wolsong sites. And already additional several units were planned to be constructed. All of those nuclear power plants in Korea are owned by only one unique utility, ‘‘Korea Hydro Nuclear Power Company (KHNP)’’ (KHNP, 2007). Since the electric generation output from the first nuclear power plant, ‘‘Kori Unit 1’’ with 587 MWe, the electrical capacity gradually have increased up to 1000 MWe at present, and it was planned to reach 1400 MWe in the near future (Jihong P. et al., 2007a,b). At present year 2009, the electric generation output from nuclear power plants (20 units) in service accounts for 40–45 percent of total electricity generation output including hydroelectric, thermal power, and others. Korea stands 6th in the world as regards the output of nuclear electric power. At the beginning stage of nuclear power plant constructions in Korea, various reactor types such as Westinghouse (U.S.), AECL (Canada), Framatome (France) were adopted to be constructed. Since Yonggwang Unit 3, ‘‘Korea Standard Nuclear Power Plants (KSNP)’’ were started to be constructed and settled down. Overall status of Korea nuclear power plants were described briefly in Table 1. 3. Nuclear containment systems Since 1970s in Korea, nuclear containment systems have been developed mainly as following 4 stages:
762
J. Park, J. Hong / Progress in Nuclear Energy 51 (2009) 761–768
Table 1 Status of nuclear power plants in Korea. Name of units
Reactor type
Commission
Kori
Unit Unit Unit Unit
1 2 3 4
Busan
587 650 950 950
PWRa (Westinghouse)
1978. 1983. 1985. 1986.
04. 07. 09. 04.
29. 25. 30. 29.
Wolsong
Unit Unit Unit Unit
1 2 3 4
Gyeongbuk
679 700 700 700
PHWRb (AECL)
1983. 1997. 1998. 1999.
04. 07. 07. 10.
22. 01. 01. 01.
Yonggwang
Unit Unit Unit Unit Unit Unit
1 2 3 4 5 6
Jeonnam
PWR (Westinghouse)
1986. 1987. 1995. 1996. 2002. 2002.
08. 06. 03. 01. 05. 12.
25. 10. 31. 01. 21. 24.
Unit Unit Unit Unit Unit Unit Unit Unit Unit Unit
1 2 3 4 5 6 1, 3, 1, 1,
Gyeongbuk
Ulchin
New Kori New Wolsong New Ulchin a b
Location
2 4 2 2
Busan Gyeongbuk
Capacity (MWe)
950 950 1000 1000 1000 1000 950 950 1000 1000 1000 1000 1000 1400 1000 1400
PWR (Doosan/CE)
PWR (Framatome) PWR (Doosan/CE)
1988. 09. 10. 1989. 09. 30. 1998. 08. 11. 1999. 12. 31. 2004. 07. 29. 2005. 04. 22. Under construction Planned Under construction Planned
PWR: pressurized water reactor. PHWR: pressurized heavy water.
(a) First stage; Metal containments (b) Second stage; Prestressed concrete containments with grouted tendons (c) Third stage; Prestressed concrete containments with ungrouted tendons (d) Forth stage; KSNP containments
3.1. 1st stage (metal containment) First at the beginning stage, the nuclear containments of the first two nuclear power plants, Kori Unit 1 & 2 were designed as metal containment buildings with design pressure of 43–45 psi. The containments were composed of inside metal structure with 1½ in (38 mm) thickness and outside traditionally reinforced concrete structures with 75–80 mm thickness with having a shallow-dome roof on cylindrical wall (Fig. 1). Especially the inside metal structures play an important role of pressure retaining and preventing leakage of radioactive substance.
shapes of containment buildings are torispherical or shallow-dome roofs on cylindrical walls. Grouted (Bonded) post-tensioned concrete is the descriptive term for a method of applying compression after pouring concrete and the curing process. The procedure is that the concrete is cast around aluminum curved duct, to follow the area where otherwise tension would occur in the concrete element. Then a set of tendons is fished through the duct and the concrete is poured. Once the concrete has hardened, the tendons are tensioned by hydraulic jacks that react against the concrete member itself. When the tendons have stretched sufficiently, according to the design
3.2. 2nd stage (prestressed concrete containment with grouted tendons) At the second stage for nuclear containment constructions, prestressed concrete systems were adopted, which is a method for overcoming traditional concrete’s natural weakness in tension. Prestressing tendons generally with high tensile steels are used to provide a clamping load which produces a compressive stress that offsets the tensile stress that the concrete compression member would otherwise experience due to a bending load. Prestressing tendon is a separate continuous multi-wire or multi-strand tensioned element anchored at both ends to an end tendon anchorage assembly. The nuclear containments, Wolsong Unit 1, 2, 3, 4 and Ulchin Unit 1 & 2 were designed as prestressed concrete containments with grouted (bonded) tendon systems (Fig. 2). The
Fig. 1. 1st Stage, metal containment.
J. Park, J. Hong / Progress in Nuclear Energy 51 (2009) 761–768
763
Fig. 2. Prestressed concrete with grouted (Bonded) tendon system.
specifications, they are anchored in position and maintain tension after the jacks are removed, transferring pressure to the concrete. The duct is then grouted to protect the tendons from corrosion. In case of Ulchin Unit 1 & 2, inside metal liner plates and outside concrete structures play roles of preventing leakage of radioactive substances and pressure retaining in containment building respectively. On the contrary, in case of Wolsong Unit 1, 2, 3, 4, epoxy coatings instead of using metal liner plates were applied to prevent leakage of radioactive substances due to relatively lower design pressure (18 psi) compared with those of other containments. The specifications of the second stage nuclear containment systems were described in Table 2.
3.3. 3rd Stage (prestressed concrete containment with ungrouted tendons) Compared with the 2nd stage, the 3rd stage nuclear containments were designed as prestressed concrete containments with ungrouted (unbonded) tendon systems (Fig. 3). Ungrouted (unbonded) post-tensioned concrete containment differs from those of grouted (bonded) by providing each individual tendon permanent freedom of movement relative to the concrete. To achieve this, each individual tendon was coated with corrosion protection medium (grease) and covered by a sheathing duct. Kori Unit 3 & 4 and Yonggwang Unit 1 & 2 were designed as prestressed concrete containments with ungrouted (unbonded) tendon systems with having a hemispherical-dome roof on cylindrical wall. Outside concrete structures mainly perform pressure retaining role,
and inside metal liner plates play roles of preventing leakage of radioactive substances. The specifications of 3rd stage nuclear containment systems were described in Table 3.
3.4. 4th stage (KSNP containment) At the final stage, KSNP (Korea Standard Nuclear Power Plants) was settled down (Fig. 4). KSNP was optimized power reactor 1000 and based on the model system 89 of ABB-CE. The nuclear containment systems of KSNP were modified and improved from the 3rd stage ones. 8 units (Yonggwang Unit 3–6 & Ulchin Unit 3–6) operated and additional 8 units (New Kori Unit 1–4, New Wolsong Unit 1–2, & New Ulchin 1–2) under construction or planned were designed as KSNP. KSNP containments with having a hemispherical-dome roof on cylindrical wall were composed of inverted U shaped vertical tendons and hoop shaped horizontal tendons located in the cylinder and dome (Fig. 5 and 6). The numbers of horizontal tendons (with one tendon having a 240 loop) and vertical tendons were 96 and 135 respectively. The schematic diagram and roles of anchorage components of tendon system were briefly shown in Fig. 7 and Table 4. Each tendon has 55 multi-element strands (1/2 in diameter of each strand), and the stand materials used are ASTM A 416 Grade 270, low relaxation, seven-wire twisted strands (Fig. 8). With evolution from the 3rd to the 4th stage nuclear containments, the major changes were as follows. With increasing of containment size, the number of tendons installed was changed from 72 vertical and 117 horizontal tendons to 96 vertical and 165 horizontal
Table 2 The specifications of 2nd Stage containment systems. Item
Unit Ulchin Unit 1, 2
Wolsong Unit 1, 2, 3, 4
Design code Shape No. of buttress Concrete wall thickness Design pressure Height Metal liner plate thickness No. of tendons (each group)
RCC-G part 1 Torispherical dome roof on cylindrical wall 4 90 cm 58 psi 59.4 m 6 mm 144 (Vertical tendons) 280 (Hoop tendons) 174 (Dome tendons)
Strand type No. of strands (each tendon) Anchoring method Sheath filler
7wire (0.5 in diameter) 19 & 37 Wedge Cement grout
CAN/CSA Shallow-dome roof on cylindrical wall 4 107 cm 18 psi 51.89 m Epoxy coating 124 (Vertical tendons) 163 (Hoop tendons) 141 (Dome Tendons) 126 (basemat tendons) 7wire (0.5 or 0.25 in Diameter) 1, 37 & 35 Buttonhead Cement grout
764
J. Park, J. Hong / Progress in Nuclear Energy 51 (2009) 761–768
Fig. 3. Prestressed concrete with ungrouted (Unbonded) tendon system.
Table 3 The specifications of 3rd stage containment systems. Item unit
Kori unit 3,4 & Yonggwang unit 1,2
Design code Shape No. of buttress Concrete wall thickness Design pressure Height Metal liner plate thickness No. of tendons (each group)
ASME Hemispherical-dome roof on cylindrical wall 3 122 cm 60 psi 63.35 m 6.35 mm 72 (Vertical tendons) 117 (Horizontal tendons) 7wire (0.5 in diameter) 50, 53 & 55 Wedge Grease
Strand type No. of strands (each tendon) Anchoring method Sheath filler
Fig. 5. Inverted U shaped vertical tendons (side view).
Fig. 4. KSNP containment.
tendons. And the number of strands per each tendon was changed from 50 or 53 to 55. About the third stage containments, two kinds of tendon anchorages were designed. One (Fig. 9) is designed for examination of prestress force (tendon force) measurement only, and the other (Fig. 10) is designed for examination of material test (yield strength, ultimate tensile strength, breaking strength, elongation, physical property, & etc.) of tendon-strands. Namely, the inspection tendons
Fig. 6. Hoop shaped horizontal tendons (top view).
J. Park, J. Hong / Progress in Nuclear Energy 51 (2009) 761–768
765
Fig. 7. Anchorage components in tendon system.
Table 4 Roles of anchorage components in tendon system. Designation
Description
Bearing plate Anchorhead Shim plate
Protecting the exterior concrete surfaces Anchoring the tendon-strands Adjusting & buffing plate between bearing plate & anchorhead Preventing the anchored wedges from ejecting out Element for fixing & anchoring the tendon-strands Seven-wire twisted prestress element Tunnel for tendon-strands & prevention from leaking of grease Storage and protection for grease & anchorage ends Access tunnel for injection of grease Venting of inside air/gas and draining of inside water
Retainer plate Wedge Strand Sheathing duct Grease cap Grease injection access Vent & drain
during inservice inspection were predesignated for prestress force measurement and material test separately. Especially for material test of tendon-strand, tendon anchorage should be designed that at least one tendon-strand could be detensioned and removed. In the 4th stage containments, tendon anchorages were designed so that all tendons could be available for both prestress force measurement and material test during inservice inspection (Fig. 11).
4. Inservice inspections All of the nuclear power plants should be inspected periodically according to the ‘‘Regulation on Inservice Inspection of Nuclear Reactor Facilities’’ by Notice of the Ministry of Science and Technology (MOST), Korea government (MOST, 2004). This Notice stipulate technical regulations such as standards, codes, inspection periods, and others. Because of various types of nuclear containments, several appropriate codes, standards and procedures are applied differently depending on the specific nuclear containment types. ‘‘Long Term Inservice Inspection Plan of Containment
Building’’ (KHNP, 1985–2004) and ‘‘Technical Specification and Inspection Procedure for Inservice Inspection of Containment Building’’ (KOPEC, 1978–2006) were issued and approved by the utility (KHNP) and enforcement authority (MOST) respectively. And fundamentally all the required technical regulations were contained in those documentations. Main technical requirements and inspection items were summarized briefly in Table 5. The main performing body for inservice inspection (ISI) in nuclear containments is ‘‘Korea Hydro & Nuclear Power Company (KHNP)’’ cooperated with several industries. And all of these inservice inspection plans, performances, procedures and documentations should be reviewed, witnessed and supervised by Korea Institute of Nuclear Safety (KINS) and Korea Institute of Materials Science (KIMS) as entrusted regulatory agency and authorized nuclear inspection agency respectively. Finally all of the records and results of inservice inspections should be reported and approved by the Atomic Energy Bureau, Ministry of Science and Technology. The examination categories, contents and frequency of inservice inspections in KSNP nuclear containments were summarized briefly in Table 6. 5. Discussions With evolution of nuclear power plants in Korea from 1970s to present year, there have been remarkable changes of containment systems and inservice inspections. First, the noticeable change with transition from the 1st stage (metal containments) to the 2nd stage containments (prestressed concretes with grouted tendons) was conversion of traditional concrete to prestressed concrete system. Consequently it could overcome traditional concrete’s natural weakness in tension. Second, with transition from the 2nd stage (grouted tendon systems) to the 3rd stage containments (ungrouted tendon systems), real tendon prestress force measurement (in situ) during inservice inspection could be available. In the 2nd stage containments, real prestress force measurement of grouted tendon system was not available even
Fig. 8. Seven-wire strand.
766
J. Park, J. Hong / Progress in Nuclear Energy 51 (2009) 761–768
Fig. 9. Tendon anchorage for prestress force measurement only.
though simulated test beam methods (indirect prestress force measurement) were used. In the grouted tendon system of the 2nd stage containments, adjustment of tendon force and replacement of tendon in need were not available. In the meantime, adjustment of tendon force and replacement of tendon in need were available in the 3rd stage containments (ungrouted tendon system). Third, with transition from the 3rd stage to the 4th stage containments (KSNP), perfect random selection of tendons (representative tendon sampling) for inservice inspection (ISI) could be available. In the 3rd stage containments, inspection tendons were already predesignated for prestress force measurement and material test separately. On the contrary in the 4th stage KSNP containments, any tendon could be selected for tendon prestress force measurement and material test during ISI. The assurance of perfect random selection of tendons is basic concept of inservice inspection and also strongly required by Korea regulatory authority. And in the 3rd stage containments, new tendonstrand should be replaced after removal of 1 tendon-strand for
Fig. 11. 4th Stage tendon anchorage.
material test. However in the 4th stage containments, replacement of new tendon-strand is not necessary because the containment was designed to ensure safety margin of prestress force with sufficient number of tendon-strands. In many cases, the technical requirements of ISI in KSNP containments are similar with those of ASME, US NRC Regulatory Guide, CAN/CSA, RCC-G & etc. However, more severe and strictly conservative concepts were applied and contained in the
Fig. 10. Tendon anchorage for material test.
Table 5 Main inspection items & technical requirements for ISI. Containment system
Main inspection items
1st stage Kori 1–2
Main technical requirements
Metal containment Concrete Surface Integrated leak rate test Local leak rate test
Notice of the Ministry of Science & Technology Long term ISI plan of containment building Technical specification & inspection procedure - ASME Sec. XI, Div.1 IWE (ASME, 1989–2004a) - FSAR (KHNP, 1978–2005)
2nd Stage Wolsong 1w4
Concrete surface Indirect prestress force test (test beam method) Integrated leak rate test Local leak rate test
Notice of the Ministry of Science & Technology Long term ISI plan of containment building Technical specification & inspection procedure - CAN/CSA-N287.7 (CSA, 1980) - U.S. NRC Regulatory guide 1.90 (U.S. NRC, 1977) - FSAR
2nd Stage Ulchin 1–2
Liner plate Leak resistance test Strength test
Notice of the Ministry of Science & Technology Long term ISI plan of containment building Technical specification & inspection procedure - RCC-G Part 3 (AFCEN, 1981) - ASME Sec. XI, Div.1 IWE - FSAR
3rd Stage Kori 3–4
Yonggwang 1–2 4th Stage Yonggwang 3–6 Ulchin 3–6 New Kori 1–4 New Wolsong 1–2
Concrete surface Liner plate Integrated leak rate test Local leak rate test Tendon Anchorage Prestress force test Material test:
Notice of the Ministry of Science & Technology Long term ISI plan of containment building Technical specification & inspection procedure -
- Strand - Grease - Free water
US NRC Regulatory guide 1.35 (U.S. NRC, 1990) ASME Sec. XI, Div.1 IWE ASME Sec. XI, Div.1 IWL (ASME, 1989–2004b) ACI 201 (ACI, 1992) FSAR ASTM & APHA
Table 6 ISI examination categories, contents and frequency. Categories
Contents
Liner plate Shell/dome/embedment Pressure retaining welds Penetrations/hatch Seals/moisture barriers Dissimilar metal welds Pressure retaining bolting
-
Degradation Corrosion Crack Abrasion/Erosion Loss of coating Material loss. Leak tightness Peeling Blistering Strikes Discontinuity Localized leak rate test Integrated leak rate test Cracks Degradation Grease leakage Abnormal behavior Compressive strength Reinforcing steel corrosion Differential settlement
-
-
Corrosion Damage Deformation Dent Slippage
-
Crack Fracture Balance Scratch Grease leakage
-
Prestress force measurement Color Smell Crack Chemical analysis Elongation
-
Viscosity Corrosion Physical damage Yield strength Tensile strength
LLRT ILRT Concrete Exterior concrete surface (dome, shell & buttress) Tendon anchorage area
Anchorage hardwares Bearing plate Shim plate Wedge Gasket ring Retainer plate Grease injection access Tendon Material test Grease Free water Strand/wire
Anchorhead Strand/wire Grease cap Vent cock
Frequency Aging Pitting Wear Bolt tightness Deformation Flaw Flaking Discoloration Distress Gouges Dents
w7 Times per 10 years
Every 3~5 years - Chemical analysis - Distress - Damage
1, 3, 5 & every 5 years following SIT
1st unit: 1, 5, 10 & every 10 years following SIT 2nd unit: 1, 5 & every 10 years following SIT
768
J. Park, J. Hong / Progress in Nuclear Energy 51 (2009) 761–768
‘‘Technical Specification and Inspection Procedure for ISI of Containment Building’’ (KOPEC, 1978–2006). Overall inservice inspection results of most Korea nuclear containments did not show any serious evidence of damage, degradation, corrosion, grease leakage and loss of prestressing force even though 20 units have been operated since 1978. In minor cases, the presence of free water and grease degradation in the tendon cap might be presumed due to the grease injection during installation in rainy season. The first nuclear power plant, Kori unit 1 was designed with 30 year lifetime, and it has been operated since 1978. Now the extension for further use of Kori unit 1 is hot issue and under review by the utility (KHNP) and government (MOST). Several years ago, ‘‘Korea Electric Power Industry Code (KEPIC)’’ (KEA, 2005a, b) corresponding with ASME was issued, and it is under plan to be adopted as main technical standard and code for inservice inspection of nuclear power plants in Korea.
6. Conclusions At present, 20 unit nuclear power plants have been operated and maintained in Korea since the first nuclear power plant ‘‘Kori unit 1’’ was started in commercial service in 1978. And most recently, 8 units were started to be constructed and planned. From 1970s to present year, nuclear containment systems have been evolved mainly as following 4 stages. 1st stage (metal containment), 2nd stage (prestressed concrete containment with grouted tendons), 3rd stage (prestressed concrete containment with ungrouted tendons), and finally 4th stage (KSNP containment) was settled down. With evolution of nuclear containment systems, structural integrity, reliability of inspection, and estimation of lifetime extension could be much improved even though the shortcomings of high cost of installation, extended inspection items & technical requirements, and high cost of inspection remained. All of the nuclear containments should be inspected periodically according to the ‘‘Regulation on Inservice Inspection of Nuclear Reactor Facilities’’ by the Notice of the Ministry of Science and Technology (MOST), Korea. For periodic inservice inspection, technical requirements, inspection items, frequencies, and procedures are applied differently depending on the specific nuclear containment types. Even though various mixed codes and standards have been used for inservice inspection (ISI) of nuclear containments until now, ‘‘Korea Electric Power Industry Code (KEPIC)’’ is under progress as main technical code for inservice inspection of nuclear power plants in Korea. Since 1978, overall inservice inspection results of most Korea nuclear containments did not show any serious degradation evidence. The first nuclear power
plant, ‘‘Kori unit 1’’ which was designed with 30 year lifetime is under approval for lifetime extension. Acknowledgements The authors would like to express thanks to all the colleagues in Korea Authorized Nuclear Inspection Center, Korea Institute of Materials Science (KIMS) for the encouragement and excellent guidance during research. And we must express deep appreciation to the president and staffs of KHNP Co., Ltd. for support and assistance for a long time. References American Concrete Institute (ACI), 1992. Guide for Making a Condition Survey of Concrete in Service ACI 201. American Society of Mechanical Engineers (ASME), 1989–2004a. Requirements for Class MC and Metallic Liners of Class CC Components of Light Water Cooled Power Plants ASME Sec. XI, Div.1 IWE, New York, USA. American Society of Mechanical Engineers (ASME), 1989–2004b. Requirements for Class CC Concrete Components of Light Water Cooled Power Plants ASME Sec. XI, Div.1 IWL, New York, USA. Canadian Standards Association (CSA), 1980. Inservice Testing and Examination Requirements for Concrete Containment Structures for CANDU Nuclear Power Plants CAN/CSA-N287.7, Mississauga, Canada. French Society for Design and Construction Rules for Nuclear Island Components (AFCEN), 1981. Design and Construction Rules for Civil Works of 900 MWe PWR Power Plants, RCC-G Part 3, France. Jihong, P., Jaekeun, H., Byunghoon, L., Youngho, S., 2007a. Present status of nuclear containments in Korea. In: Proceedings of 15th International Conference on Nuclear Engineering, April 22–26, Nagoya, Japan. Jihong, P., Jaekeun, H., Banuk, P., 2007b. Nuclear Containment Systems and Inservice Inspection Status of Korea Nuclear Power Plants. In: Proceedings of International Congress on Advances in Nuclear Power Plants, May 13–18, Nice, France. Korea Hydro & Nuclear Power Company (KHNP), 1978–2005. Final Safety Analysis Report Korea. Korea Hydro & Nuclear Power Company (KHNP), 1985–2004. Long Term Inservice Inspection Plan of Containment Building Korea. Korea Hydro & Nuclear Power Company (KHNP), 2007. Homepage. www.khnp.co.kr Korea. Korea Power Engineering Company (KOPEC), 1978–2006. Technical Specification and Inspection Procedure for Inservice Inspection of Containment Building Korea. Korea Electric Association (KEA), 2005a. Inservice Inspections of MC and Metallic Liner, Korea Electric Power Industry Code (KEPIC) MIE Korea. Korea Electric Association (KEA), 2005b. Inservice Inspections of Containment Structures, Korea Electric Power Industry Code (KEPIC) MIL Korea. Ministry of Science and Technology (MOST), 1958. Atomic Energy Act Korea. Ministry of Science and Technology Korea (MOST), 2004. Regulation on Inservice Inspection of Nuclear Reactor Facilities, Notice No. 2004-13 Korea. United States Nuclear Regulatory Commission (U.S. NRC), 1977. Inservice Inspections of Prestressed Concrete Containment Structures with Grouted Tendons, U.S. NRC Regulatory Guide 1.90 USA. United States Nuclear Regulatory Commission (U.S. NRC), 1990. Inservice Inspections of Ungrouted Tendons in Prestressed Concrete Containments, U.S. NRC Regulatory Guide 1.35 USA.