IAEA-TECDOC-1124 XA On-site disposal

Transcription

1 IAEA-TECDOC-1124 XA On-site disposal

2 The originating Section of this publication in the IAEA was: Waste Technology Section International Atomic Energy Agency Wagramer Strasse

3 On-site disposal FOREWORD

4 In preparing this publication EDITORIAL NOTE

5 CONTENTS 1. INTRODUCTION...! 2. SCOPE OBJECTIVE...^ 4. CONSIDERATIONS INFLUENCING

6 According 1. INTRODUCTION

7 disposal facilities which may give some guidance [7] It is now considered appropriate to collect international experience and views because there could be sound reasons for choosing on-site disposal as the planned decommissioning strategy for a range of nuclear facilities Member States would then have the option of evaluating the extent to which on-site disposal fits their needs and the potential for licensing this approach in their countries It is recognized that radiological safety

8 4. CONSIDERATIONS INFLUENCING THE SELECTION OF ON-SITE DISPOSAL Selection of on-site disposal as a decommissioning strategy is influenced by a number of considerations, which may be either technical or political, and sometimes both. Important technical considerations are discussed in Section 4.1 and the political issues and public concerns

9 external to the primary envelope is done, the expected savings in dose commitment can be rapidly eroded. For example, according to an analysis of the decommissioning of a reference PWR in the USA [11], radiation doses from immediate dismantling and from on-site disposal would

10 Safety and environmental aspects Evaluation of the safety and environmental consequences of using the on-site disposal strategy will generally

11 factors. A safety assessment would also involve an environmental impact study that would be used in the process of gaining acceptance of the strategy by the public. The environmental impact study would also take account

12 treatment

13 to be between 100 and 300 years during which waste with short and medium decay periods will reduce

14 environment

15 Location; geographic, topographical, demographic

16 radioactive material

17 TABLE I SUMMARY OF ADVANTAGES AND DISADVANTAGES OF ON-SITE DISPOSAL Item Reduced cost ADVANTAGES Reduced worker dose Minimal off-site transport of waste Reduced public interaction Continued

18 An environmental impact statement [21, 32] was prepared on alternatives for decommissioning of the original eight shut down plutonium reactors at the Hanford Site in the USA via on-site disposal. These analyses examined costs, radiation doses, and safety considerations for each of the alternatives, one of which was in situ disposal by mound burial. Other alternatives included immediate one piece removal, delayed dismantling and removal, and delayed one-piece removal with transport and disposal to another on-site location. Subsequent analyses [34] have focused on the preferred alternative (delayed one-piece removal). An analysis for estimating decommissioning costs for the major fuel cycle facilities on the Hanford Site [22] examined several possible strategies, including dismantling and removal; dismantling,

19 substances

20 In the Russian Federation, on-site disposal is considered as an option for decommissioning of RBMK, WWER and fast breeder reactors at several sites. The final step of decommissioning is envisaged

21

22 helicopter onto

23 8. CONCLUSIONS AND RECOMMENDATIONS

24 [14] INTERNATIONAL ATOMIC ENERGY AGENCY, Safety Assessment

25 [30] NAQVI, S.J.,

26 Facilities, London, 1992), Mechanical Engineering Publications Ltd, London (1992) [47] IVES, G., Design for Decommissioning, 1992 Summer School on Radioactive Waste Management

27 ANNEXES Eleven annexes have been included based on submissions offered by Member States or have been excerpted from published literature. Some

28 ANNEX

29 R«actor Building No. 4 Rtactor Building No. 1 Reactor Building No. 3 ^300' Typical Burial Pit I

30 Disposal Pit Bed Rock Soil/Sack Ml Sution Substructure Grout Backfill RMctor Package Steam Generators PUT Pumps Preiwnzer Waste Captulet FIG Bruce

31 The studies conclude that on-site disposal offers a technically viable, low cost approach to decommissioning

32 WHITESHELL REACTOR

33 [1-2] RUSSELL, S.B., Preliminary Dose Assessment

34 Annex II FINLAND

35 management plan, because the timetable for interim storage and final disposal of spent fuel covers the same period. It has been shown that decommissioning will not cause any harm to the environment or to the public health, [E-2]. Technical plans for dismantling and waste disposal The Loviisa units The decommissioning plan for the Loviisa units is based on immediate dismantling after the end of the service life of the plant. Radioactive dismantling wastes

36 Prosessirakennus Valvomorakennus Louhintatunneli ExcavaKntrvw HaUi Hal Keskiaktiivinen purkujate kmnneaato MvM decotrvrtsscnng wsst Matala-aktiivinen Lowtctv»«c<«r»nssio ig»«se FIG Final disposal facility of

37 STEAM GENERATOR CONCRETE SLAB CRUSHED ROCK CONCRETE WALL PRESSURE VESSEL CRUSHED ROCK + BENTONITE CONCRETE BACKFILL FIG. II-3, Closed reactor silo for Loviisa plant.

38 Very low-activity concrete, mainly from the dismantling of the outer layers of the biological shields, is packaged in wooden boxes. The quantities of waste include 2500 tonnes of activated wastes, 5000 tonnes of contaminated wastes

39 08000 \BETONITULPPA 3m CONCRETE BLOCK MURSKE-BENTONlim CRUSHED ROCK

40 [II-l] RYHANEN, REFERENCES TO ANNEX II

41 Annex

42 In

43 TABLE m-1. INVENTORY OF MATERIALS AFTER SHUTDOWN (MAY 1998) Radioactive materials: Activated materials: (l)heat shield and concrete of biological shielding (2) Core construction

44 cavities of horizontal experimental channels with concrete thereby encapsulating the radioactive waste. As a result of the preferred option the real possibility of the useful re-application of the rest part

45 The decommissioning option is quite favourable and acceptable because it is Radiation safe and ecologically clean during construction,

46 Annex IV GERMANY The approach to decommissioning nuclear facilities followed by the utilities and operators in Germany is the conventional method of safe enclosure and dismantling in the combination suitable for the specific plant situation. Also, there is the official resolution on disposal of radioactive wastes which has exclusively been directed towards deep geologic repositories in salt dome

47 is shown that external events do not interfere with the sinking process in any way that could terminate

48 TABLE IV-I. DATA

49

50 working chamber.

51 SEAL CONCRETE JACKET FIG. IV-2 Sinking phase intermediary state -BACKFILL -CONCRETE COVER - COVER SEAL

52 Radiation exposure

53 TABLE IV-IV. TOTAL COLLECTIVE STAFF EXPOSURES DURING DECOMMISSIONING BY SINKING Type

54 insignificance of the radionuclide inventories provide evidence even without discussion that most events cannot occur

55 steel environment Only if the ph value of the groundwater (normally at about 125) fell below

56 concentrations

57 10 10

58 TABLE IV-VI. INDIVIDUAL EFFECTIVE DOSE EQUIVALENT FOR 1 YEAR INTAKE AND 50 YEARS DOSE COMMITMENT IN NSV/YEAR (1 NSV = l.e-9 SV) Scenario Distance (m) 1st maximum (y) 59 Ni 94 Nb "Tc 2nd maximum (y) 59 N, 94 Nb "Tc

59 TABLE IV-VIII. SEQUENCE OF OPERATIONS AND WORK INVOLVED (INCLUDING RADIATION PROTECTION) Time (a) Phase Activities shut down

60 Annex V ITALY

61 Annex VI JAPAN Background Construction

62 body. It will be completed by The one-piece removal method will be applied to dismantling

63 stool Ml frame -. horizontal transportation system roller reactor vertical core boring hori/onlal core taring tcm[x)rary sup>(x)rt

64 FIG. VI-3. Transportation of

65 13 msv. The waste arising from the dismantling activities consisted of 2200 tons for the reactor block, 540 tons for contaminated materials and 110 tons of secondary waste.

66 Annex

67

68

69 [VII-3] VNEPIET, A Concept of Decommissioning of Industrial Uranium-Graphite Reactors Transferred

70 Annex VIII SWITZERLAND In January 1969 an accident occurred to the 10 MW experimental gas cooled reactor at Lucens. This reactor was housed in underground caverns. A fuel channel became blocked, overheated

71 Annex IX UKRAINE The Chernobyl Nuclear Power Plant Unit 4 was a vertical pressure tube graphite moderated, boiling water cooled reactor (RBMK). There were four RBMK units operating

72 most

73 waste, final dismantling

74 (b) Operations

75 [IX-10] URANIUM INSTITUTE INFORMATION SERVICE, Ukraine, US$103 million made available for strengthening the Shelter, NucNet News 64/99, 9 February [IX-11] First contract signed for Chernobyl Sarcophagus Work, Nucleonics Week, 18 February 1999(11). 72

76 Annex

77 ensure that there were no insurmountable problems in terms of making the radiological safety assessment. Study methodology Three specialist consultants were engaged

78 SAND DELIVERED ~BY DREDGER REDUCED HEIGHT MOUND FULL HEIGHT MOUND REACTOR BUILDING INFILLED RETAINED STRUCTURE INFILLED NON-ACTIVE BUILDINGS DEMOLISHED I V BASEMENT INFILLED- FIG. 1. In-situ decommissioning concept. LOSS OF COVER TO BUILDINGS STABILITY OF RETAINED STRUCTURES MATERIALS STABILITY OF MOUND

79 maximized if hypothetical site conditions were chosen which had high dispersion and dilution The site was assumed to be on an estuary but close to the sea with local streams which drained

80 Capenhurst (enrichment plants) strategy is for the following scope of work to be undertaken: removal

81 Annex XI UNITED STATES

82 allowable non-occupational body burden. This criteria is not applicable for elements such

83 exceeding

84 FIG. XI-2.

85 reactor was placed in safe storage and monitored under a maintenance and surveillance programme.

86 On-site disposal of non-reactor nuclear facilities in the USA The nuclear facilities that have been disposed of using the on-site disposal strategy in the USA are owned by the DOE and are located on major DOE sites (e.g. Hanford, Idaho National Engineering and Environmental Laboratory [INEEL], Savannah River). Several examples of these types

87 arising from

88

89 nuclear reactors

90 disposal.

91 Hanford Site, Richland, Washington, DOE/EIS-0119 F, USDOE, Washington, DC (1992). [XI-8] Trojan reactor disposal project gets final regulatory approval, Nucleonics Week, 3 December 1998 (17). [XI-9] SPEER, D.R., Decontamination and Decommissioning of a Fuel Reprocessing Pilot Plant,

92 A selection GLOSSARY

93 provide long term isolation of radionuchdes from the biosphere Usually such a repository would be used for long lived and/or high level wastes repository, near surface.

94 CONTRIBUTORS