Import of Metal Scrap - Risks Associated with Radioactivity
KEMAKTA AR 92-22
Import of metal scrap - risks associated with radioactivity
Mark Elert
KEMAKTA Konsult AB
November 1992
KEMAKTA KONSULT AB Box 12655, S-112 93 Stockholm, Sweden Import of metal scrap - risks associated with radioactivity
Mark Elert
KEMAKTA Konsult AB
November 1992
Report prepared for Swedish Radiation Protection Institute (SSI) under contract number P702.92 Abstract
There is a growing concern in Sweden for the possibility that imported metal scrap is radioactive. The recent political and economical changes in eastern Europe and the increased cooperation with the CEC has affected Sweden's import. In the last years, the import of metal scrap from the former USSR has increased considerably. In view of recent incidents, when radioactive materials have been found, the Swedish Radiation Protection Institute has detected a need for identifying the potential risk sources and evaluating the magnitude of the risk associated with the import of metal scrap.
The purpose of this report is to provide some background material concerning import statistics, use of metal scrap in Sweden and to identify potential sources of radioactive metal scrap. In addition, the radionuclides of most concern has been identified and the possibility of detecting them in metal scrap shipments is analyzed. Ill List of contents
1 INTRODUCTION 1
2 IMPORT AND USE OF SCRAP METAL IN SWEDEN 2 2.1 Import statistics 2 2.2 Metal scrap trade 3 2.3 Iron and steel production 3 2.4 Production of other metals 4 2.5 Foundries 4
3 REGULATIONS IN EXPORTING COUNTRIES 10
4 RISK FOR IMPORT OF RADIOACTIVE SCRAP METAL 13 4.1 General 13 4.2 Situation in the former USSR 14 4.2.1 Russian authorities in the nuclear area 14 4.2.2 Potential sources of radioactive material IS 4.3 Discussion 18
5 RADIONUCLIDES AND DETECTION POSSIBILITIES 19 5.1 Radionuclides in metal scrap 19
5.2 Detection of radioactive metal scrap 22
6 SUMMARY AND CONCLUSIONS 25
REFERENCES 26 INTRODUCTION
Background
Presently large changes are occurring in the world trade that affects Sweden'* impon and export. The reasons for these changes are the removal of internal borders within the European Community and the economical and political changes in eastern Europe. Still larger changes can come after the signing of the agreement on the European Economic Area (EEA) between the CEC and the EFTA countries. These changes have lead to an increase in the import of a number of products to Sweden. Particularly large is the increase in the import from the countries in eastern Europe.
In the summer of 1992 a shipment of copper plates with radioactivity was detected in the port of Stockholm. The activity concentration in the shipment was low and it did not give rise to any risk to persons involved with the shipment or to the public. However, this incident together with reports of similar incidents from other sources has lead to some concern at the Swedish authorities. If large amounts of low activity scrap metal are imported into Sweden and remelted for the production of new metal, the general level of activity in metals will increase and thus give rise to an increased societal risk in the form of cancer. An increased activity level may also be caused by small amounts of high activity material that is imported and melted. In addition, high activity material may give rise to an immediate risk to persons coming in direct contact with the material, e.g. truck drivers, customs officers, scrap handlers, and steel mill workers.
The Swedish Radiation Protection Institute has detected a need for identifying the potential risk sources and evaluating the magnitude of the risk associated with impon of scrap metal.
Purpose and scope
This repon intends to give background material for the Swedish Radiation Protection Institute concerning the risk connected to the impon of scrap metal that may contain radioactive material. The repon also treats the risk connected to forgotten, misplaced or stolen radiation sources. Statistics from the last years concerning metal scrap impon are analyzed and the main users of metal scrap are identified. Steel mills, melting plants and scrap dealers have been inquired of their current practicies for scrap impon and monitoring of radioactivity. Furthermore, a study has been made of potential sources of radioactive steel scrap with the focus on the countries of the former USSR. Russian authorities in the area of radiation protection have been contacted with help from the Swedish Technical Attache in Moscow.
The radionuclides of most concern have been identified and the possibility of detecting these radionuclides in metal scrap shipments is analyzed. IMPORT AND USE OF SCRAP METAL IN SWEDEN
2.1 Import statistics
The Swedish custom collects statistical information of imports and exports based on the shipping records. This information is compiled in a database by the Official Swedish Statistics of Sweden, SCB. From this database, excerpts can be obtained concerning amounts, values and origin countries for various intervals.
For this project an excerpt was made for metal scrap imports during the years 1990.1991 and the first half 1992. The type of goods is identified by a category number. Statistics for 24 different metals could be obtained from the SCB database. The division into categories is relatively fine, but depends on how common a certain type of goods is. For example iron and steel scrap is divided into ten subcategories. while for less common metais, raw material, scrap, and powder may be combined into one category. It is therefore not possibie to obtain a complete statistics for metal scrap. The selected categories for metal scrap are given in Table 2.1.
Tables 2.2-2.4 give the import for 1990, 1991 and first half of 1992 in tonnes. The imported quantity is given for total import, and from different parts of the world. In the data for 1990 and 1991, the sum for the different parts of the world does not always add up to the given total. The reason for this is that the origin country is not specified when the total import of a certain category is less than 300000 SEK. There are large fluctuations in the imported amounts among the three periods, depending on demand from Swedish industry, prices, statistical fluctuations, etc. However, in this period a noticeable increase can be seen in the import of scrap metal from the former USSR, especially concerning imports of copper, nickel, aluminum, molybdenum, magnesium, cobalt, titanium, and manganese, see Figure 2.1. During the first half of 1992 more than 40% of the total import of copper (5700 tonnes of 13100 tonnes) came from the former USSR.
The scrap metal import to Sweden may change in the future. For example it is very sensitive to changes in the economy. In 1985,700 000 tonnes of iron and steel scrap were imported while the import in 1991 was 165 000 tonnes. With the signing of the EEA- treaty, the previous ban on expon of iron and steel scrap from Sweden will be removed. It is expected that this will lead to an export of metal scrap from southern Sweden to Germany, and an increased import of scrap metal to the steel mills in Northern Sweden. A large part of this import is likely to come from the east.
The statistical material is associated with some uncertainty. Since the statistics are based on information in the shipping documents many error sources may be present. The importer may willfully or unknowingly declare false information concerning type of goods, amount, or place of origin. Since there is no customs fee on scrap metal it is unlikely that it should be declared as an other type of goods willingly. However, the Swedish customs have experienced several occurrences when the value of the cargo has been falsely declared, e.g. by giving a lower weight. It may therefore be possible that scrap of more valuable metals can have been declared as metals of lower value. It is also possible that erroneous information is given concerning the country of origin. 2.2 Metal scrap trade
The major Swedish steel mills import iron scrap through a jointly owned company, see below. Steel manufactures may import alloyed scrap metal themselves 01 turn to other metal scrap traders. The import of copper, brass and aluminum goes mainly through metal scrap traders.
There are a large number of small and medium size metal scrap traders in Sweden, most of them dealing with domestic scrap. The import of metal scrap is to a large extent handled by a few major scrap traders with established connections in the countries they import from. The metal scrap is transported on boat, rail or trucks in containers or platforms each with a load of roughly 20 tonnes. Usually certificates verifying the quality of the scrap metal are required. The major scrap traders have become aware of the potential risk of receiving radioactive scrap metal and some traders have started to measure radiation on imported metal scrap.
The recent changes in eastern Europe have lead to increased commercial connections. These countries have a lack of hard currency and thereby scrap metal may become pan of a payment. Thus, many traders normally dealing with other types of goods get involved in metal scrap trading. These traders may lack the necessary competence in evaluating the quality of the metal scrap, which increases the risk of importing "unwanted" metal scrap to Sweden. The traders sell the metal scrap to larger scrap dealers or to the manufacturers directly. The contacted purchasing managers at major Swedish steel and metal melters we have reached, claim they are contacted several times a week by this type of traders. However, there is a reluctance among the manufacturers to buy scrap metal without proper quality verification. There is information that large parts of this scrap is re-exported from Sweden. However, it has not been possible to verify this.
2.3 Iron and steel production
As previously mentioned is the iron and non-alloyed steel import to the major Swedish steel mills handled by a jointly owned company, AB Järnbruksförnödenheter. However, foundries may import iron and non-alloyed steel in other ways. Alloyed scrap or alloys are imported individually by each steelwork usually through the major scrap traders.The import is mostly by boat to Sweden and from the harbor to the steelworks by rail or truck. Typical shipments are of the size 500- 2000 tonnes.
The main iron and steel scrap consumers are the two ore based steel mills (SSAB Luleå and SSAB Oxelösund) and the electro steel mills (presently 12). In the ore based steel mills scrap metal is added for cooling during the conversion of the raw iron to steel. The total consumption is variable, but is in the order of 300-400 thousand tonnes per year. In the electro steel mills, scrap metal is the raw material, the annual consumption is in the order of 300 thousand tonnes.
The problem with radioactive metal scrap has been identified. Radiation measurements are either performed regularly or on "suspicious" shipments. One major steel mill is presently considering the installation of a permanent detection system through which all incoming scrap has to pass.
2.4 Production of other metals
There are several major melters for copper, brass and aluminum in Sweden. The scrap metal is bought from metal traders, sometimes part of the same corporation. Many melters perform radiation measurements on all scrap or on "suspicious" shipments such as copper tubes or material of military origin. One company has measured since 1986, but have so far only discovered fire detectors.
2.5 Foundries
There are more than 200 foundries in Sweden for steel, copper/brass, aluminum and zink, of which roughly 140 are major. Most of these use scrap of aluminum, copper or zink. The annual production of the Swedish foundries is in the order of 200 000 tonnes. The raw material is metal scrap and metal ingots. No information has been available on the amount of imported scrap used in Swedish foundries or if any radiation monitoring of metal scrap occurs. Table 2.1 Customs statistics categories for metal scrap.
Metal Description Au Waste and scrap of gold or plated with gold Pt Waste and scrap of platinium or plated with platinum Steel Waste and scrap iron or steel Cu Waste and scrap of copper Ni Waste and scrap of nickel Al Waste and scrap of aluminium Pb Waste and scrap of lead Zn Waste and scrap of zinc Sn Waste and scrap of tin W Wolfram in unprocessed form; including bars obtained from sintering; waste and scrap Mo Molybden in unprocessed form; including bars obtained from sintering; waste and scrap Ta Tantalum in unprocessed form; including bars obtained from sintering; waste and scrap Mg Waste and scrap of magnesium Co Cobolt matte and other products from cobalt manufacturing; unprocessed cobalt; waste scrap and Bi Bismuth and products of bismuth including waste and scrap Cd Cadmium in unprocessed form; waste and scrap; powder Ti Titanium in unprocessed form; waste and scrap; powder Zr Zirconium in unprocessed form; waste and scrap; powder Sb Antimony and products of antimony including waste and scrap Mn Manganese and products of manganese including waste and scrap Cr Chromium and products of chromium including waste and scrap Ge Germanium and products of germaium including waste and scrap V Vandinium in unprocessed form; waste and scrap; powder Others Other metals or products of other metals incluriinn waste and scran Table 2.2 Import of metal scrap during 1990 in tonnes.
Imoort 9O Total W Europe £ Eurooe ex USSR NAmer. S Amer. Asia Africa Au 0 0 0 0 0 0 0 0 Pt 0 O O O 0 0 0 0 Steel 246872 227562 7062 5783 5353 0 0 0 Cu 15074 10885 100 271 3237 502 22 0 Ni 8492 4775 0 0 3713 0 0 0 Al 6779 5350 342 499 560 0 0 0 Pb 20007 19714 0 0 0 0 0 0 Zn 32 47 0 0 0 0 0 0 Sn 180 153 0 0 31 0 0 0 W 227 102 0 0 0 0 86 0 Mo 177 155 0 0 0 0 14 0 Ta 0 O 0 0 0 0 0 0 Mg 0 0 0 0 0 0 0 0 Co 732 341 0 37 130 0 6 208 Bi 15 10 0 0 0 0 0 0 Cd 252 213 0 0 19 0 20 0 Ti 0 O 0 0 0 0 0 0 Zr 143 114 0 0 19 0 0 0 Sb 59 0 0 0 0 0 43 0 Mn 1254 564 0 0 228 0 462 0 Be 0 0 0 0 0 0 0 0 Cr 315 263 0 49 0 0 0 0 Ge 0 0 0 0 0 0 0 0 V 0 0 0 0 0 0 0 0 Others 1 0 0 0 0 0 0 0 Table 2.3 Import of metal scrap during 1991 in tonnes
Metat Total WEurooe £ Europe exUSSR NAmer SAmer Asia Aus Africa Au 1 1 O 0 0 0 0 0 Pt 100 82 0 0 18 0 0 0 Steel 164666 153734 0 2858 7155 0 0 0 Cu 33060 22167 44 2603 3347 2950 201 1727 Ni 9877 6429 0 165 3244 0 0 0 Al 4593 3532 O 936 0 0 0 0 Pb 29496 29235 0 0 0 0 0 0 Zn 205 0 143 0 0 0 0 0 Sn 170 161 0 0 0 0 0 0 W 144 64 O 42 7 0 26 0 Mo 165 107 0 41 12 0 0 0 Ta 0 0 0 0 0 0 0 0 Mg 0 0 0 0 0 0 0 0 Co 493 304 0 40 32 0 9 101 Bi 13 9 0 0 0 0 0 0 Cd 156 121 0 0 35 0 0 0 Ti 16 0 0 0 0 0 0 0 Zr 45 43 0 0 0 0 0 0 Sb 29 0 0 0 0 0 28 0 Mn 1862 605 0 0 217 0 990 0 Be 0 0 0 0 0 0 0 0 Cr 253 205 0 44 0 0 0 0 Ge 0 0 0 0 0 0 0 0 V 37 37 0 0 0 0 0 0 Others 8 8 0 0 0 0 0 0 8
Table 2.4 Import of metal scrap the first half of 1992 in tonnes.
Metal Total W Europe E Europe ex USSR NAmer SAmer Asia Aus Africa Au 0 0 0 0 0 0 0 0 Pt 196 131 0 0 65 0 0 0 Steel 137844 114949 16540 3558 2778 0 17 0 Cu 13093 5425 0 5674 1833 0 40 121 Ni 8368 4392 0 1972 2003 0 0 0 At 3153 1510 0 1643 0 0 0 0 Pb 17114 16794 57 263 0 0 0 0 Zn 16 4 0 13 0 0 0 0 Sn 35 25 0 11 0 0 0 0 W 71 25 0 26 2 0 18 0 Mo 175 88 0 88 0 0 0 0 Ta 0 0 0 0 0 0 0 0 M? 65 0 0 65 0 0 0 0 Ce 383 148 0 185 15 0 0 35 Bi 7 7 0 0 0 0 0 0 Cd 90 90 0 0 0 0 0 0 Ti 157 40 0 118 0 0 0 0 Zr 48 48 0 0 0 0 0 0 Sb 47 3 0 0 10 0 34 0 Mn 1468 372 0 590 129 9 369 0 Be 0 0 0 0 0 0 0 0 Cr 194 170 1 12 200 0 1 0 Ge 0 0 0 0 0 0 0 0 V 0 0 0 0 0 0 0 0 Others 4 3 0 0 0 0 0 0 6000 -r-
5000 -
• 1990
4000 D 1991 • jan-jun 1992
3000
2000
1000 r
I i 1, I,, Steel Cu Ni Al Pb Zn Sn W Mo Mg Co Ti Mn Cr
Figure 2.1 Import of metal scrap from the countries of the former USSR 10 3 REGULATIONS IN EXPORTING COUNTRIES
The regulators in different countries have made considerable efforts in finding acceptable levels of contamination in metal scrap. The reason is the large amounts of very low-level radioactive steel that will arise from the decommissioning of nuclear power plants. Presently, there are no international rules for the activity levels that can be accepted in various products in order to exempt them from the regulations for radioactive materials. The International Atomic Energy Agency (IAEA) has developed dose based limits regarding practices that can be exempted from notification, registration, etc. These rules state that the annual dose equivalent to the public should not exceed 10 /xSv, and the collective dose equivalent should not exceed 1 manSv per year of the practice [IAEA, 1987]. However, die application of these limits requires that dose estimations are performed. There is ongoing work within the IAEA to define recommended unconditional exempt activity levels for radionuclides in solid materials.
Many countries have adopted national exempt activity levels or guidelines. Exempt activity levels are usually based on risk estimations considering a large range of possible use of products as well as disposal. However, the exempt levels may vary between different countries partly because the conditions in different countries may vary and partly because of different assumptions used in the risk estimations. This section will contain a brief summary of the present exempt levels in a few countries. A direct comparison of the values is sometimes difficult since the exemption may be connected with certain conditions.
Sweden
At present there is no unconditional exempt limit being defined in Sweden. Instead the authorities can exempt material on a case-by-case basis. The exempt limit presently applied for reuse is between 0.1 and 1 kBq/kg.
The import of nuclear material requires special permission of the Swedish Radiation Protection Institute.
The Swedish steel industry has general rules for the composition of steel scrap for melting, where it is said that no radioactivity shall be present in the scrap. However, no activity limits or practical instructions for controlling this are available.
Finland
In Finland exemption limits for unrestricted and restricted exemption of nuclear waste havs been defined [STUK, 1992]. For unrestricted release the total activity concentration averaged over not more than 1000 kg of waste should not exceed 1 kBq/kg of beta or gamma activity, or 100 Bq/kg of alpha activity. In addition no single item weighing less than 100 kg may contain more than 100 kBq of beta and gamma activity or 10 kBq of alpha activity. The total surface contamination of non-fixed radioactive substances may not exceed 4 kBq/m2 (beta - ijamma) or 400 Bq/m2 (alpha), averaged over a maximum 11 area of 0.1 nr. For restricted exemption, activity constraints are applied by the Finnish authorities on a case-by-case basis.
These regulations apply to nuclear waste and not general metal scrap. It is also stated that unrestricted exemption is not applicable to waste of significant practical value. There exists another guideline [STUK, 1991] for exemption other types of radioactive materials for disposal or incineration. The maximum activity allowed in solid waste is in this case based on ALI-values. So far the Finnish authorities has had no case with imported radioactive metal scrap and it is thus not clear what rules should be applied.
Germany
The Federal German Republic rules for recycling and reuse of low-level radioactive steel from nuclear power plants [SSK, 1987] presently operates with exempt limits for unrestricted recycling or reuse, for release of scrap for general remelting, and one for controlled reuse. Exempt limits are given both for surface contamination and as a mass based specific activity. For unrestricted reuse the limits are 0.37 Bq/cm2 and 0.1 kBq/kg, respectively. Release of scrap for melting together with inactive scrap is possible if the specific total activity of each single item not exceeds 1 kBq/kg. Controlled recycling can be performed if the specific activity is above 1 kBq/kg provided that the product that is made will have a mean specific activity that in no case exceeds 1 kBq/kg. Controlled recycling requires a special license.
United States
Exemption levels for nuclear waste and other radioactive products are presently being revised in the United States. In the mean time, exemption is performed on a case-by-case basis.
In the United States Regulations (10 CFR §30.70) exempt limits have been defined for a number of radionuclides. Typical limits are in the order of 10-50 kBq/kg, e.g. Co-60 18.5 kBq/kg, Zn-65 37 kBq/kg and Ir-192 15 kBq/kg. Byproducts or products with activity concentrations below these limits may be handled or possessed without license. However, the import of radioactive products or byproducts is not covered by this regulation. These exemption limits have not been applied to waste from nuclear installations. The US Nuclear Regulatory Commission would not apply them to radioactive metal scrap from other or unknown origin. Acceptable residual concentrations in metal scrap are presently being looked at in a research project sponsored by the Department of Energy.
There exist requirements for decontamination of waste from nuclear reactors (NRC Regulatory Guide 1.86) given as acceptable surface contamination levels (average, maximum and removable) for four categories of radionuclides. The limits for beta-gamma emitters (except Sr-90), natural uranium, U-235 and U-238 is 0.83 Bq/cm2 as an average value. For alpha emitters the average value is 0.017 Bq/cm2. 12 Canada
Canadian authorities have issued exempt limits for isotopes that can be contained in products available to the public or for export are in the same range as the values in the United States 10 CFR 30. Co-60 10 kBq/kg, Cs-137 30 kBq/kg and Ir-192 30 kBq/kg. We have no information if these limits are being applied at present. Exemption of nuclear waste is being performed on a basis of "de minimis" with 50 /iSv/a and person.
Commonwealth of Independent States
No information on exempt limits for nuclear waste has been available. The regulation of metal scrap export is governed by the license requirements developed for different types of products. According to the Russian authorities export of radioactive material outside their control is forbidden. However, radiation monitoring is normally not being performed. If this is done, it is as a part of the quality certificate required by the user.
The Baltic States
The Baltic States, Estland, Latvia and Lithuania did not have any radiation protection authority at the time for their independence. The organization of such authorities are now underway with assistance from Sweden and Finland. A large problem in these contries is the lack of measuring equipment. 13
4 RISK FOR IMPORT OF RADIOACTIVE SCRAP METAL
4.1 General
Metal scrap can become radioactive in several ways:
- the metal has previously been exposed to neutrons or other heavy particles which have induced activity in the material, i.e. the original isotopes of the metal have participated in a nuclear reaction and become radioactive
- the metal has been exposed to radioactive powders, solutions or gases that have contaminated the surfaces of the metal or penetrated into fine cracks
- the metal scrap includes a device or instrument containing radioactivity, e. g. radiation sources in level gauges
The first type of metal scrap are mostly likely to come from nuclear reactors used for research, power production, in ships and submarines, or for nuclear weapon fabrication. In addition, this type of rnetal scrap may come from particle accelerators. The second type of metal scrap may come from nuclear reactors, but also from other nuclear installations, e.g. reprocessing plants, or any other facility where radioactive solutions or ga.;es are used. Metal scrap may also be contaminated by material released from nuclear accidents. In the third case the most likely source is industrial scrap, but lost radiation sources may of course come into any type of metal scrap.
It should also be noted that the radioactive scrap may have been contaminated in an earlier melting process and may thus not necessarily be identified as scrap coming from a facility handling radioactive materials.
The reported accidents with radioactive metal scrap are connected with the accidental melting of radiation sources. No such accidents were reported before 1983, but since then a number of accidents have been reported. In a recent IAEA report 8 accidents between 1983 and 1986 are reported involving the melting of up to IS TBq. In some cases the radiation source was detected before melting, in other cases the radioactivity was detected in products or by-products after the melting [IAEA, 1991b]. In a US compilation for the years 1985 - 1989, 92 incidents were reported of radioactive materials found in steel scrap, melted in a steel-making facility, or contained in slag or other byproducts of steel or aluminum smelting or foundry operations [Bex, 1991].
The large number of incidents reported are mainly due to the large number of radiation sources in use. Radiation sources are used for a number of different purposes, therapy, radiography, sterilization, moisture and density measuring, level gauges, etc. The activities may range from a few MBq to up to several hundred PBq in large irradiators. The most numerous sources are branchytherapy sources with an estimated world wide number of 100 000 and industrial gauges with an estimated world wide number of 500 000 [IAEA, 1991b]. No accidents or incidents have been reported in Sweden, most 14 likely due to the limited amount of radiation sources, roughly 4000 industrial sources, and the requirement for individual licenses.
The meltng of radiation sources is only in one case kncwn to have caused high individual exposure (Mexico, 1983), but several accidents have lead to substantial economical costs. The decontamination and disposal costs after the accident in Auburn, NY, in 1983 has been estimated to exceed $2.2 million. The accidents with radiation sources have lead to an awareness among steel producers. In Canada a majority of the steel mills have installed radiation monitors [Walke-, 1988]. The increased monitoring in Canada has also lead to the detection of increased levels of natural radionuclides such as thorium and uranium at some occasions [Walker, 1988]. Increased levels of natural occurring radionuclides have also been found in scales that attach to crude oil transmission pipes and oil drilling pipes [Bex, 1991].
In the accidents reported above the radiation sources have unintentionally been included in the scrap. However, many sources have encapsulations made of precious materials, e.g. platinum, gold, or silver, and may therefore be attractive for theft. Accidents have been reported where gold encapsulation from spent medical sources have been used for the fabrication of jewelry [IAEA, 1991b].
4.2 Situation in the former USSR
This section contains information on the various sources of radioactive material in the former USSR. In the present situation is it very difficult to obtain accurate information of the current conditions. This rection is partly based on material collected and interviews made by the Swedish Technical Attache in Moscow. The main emphasis is on the conditions in Russia.
4.2.1 Russian authorities in the nuclear area
In January 1992 the Ministry of Atomic Power of the Russian Federation (MinAtom) was founded as a successor to the former Ministry of Atomic Power and Industry of the USSR. The MinAtom is responsible for:
• ensuring the nuclear and radiation safety of the nuclear complex, handling of radioactive waste and rehabilitation of land
• the organization and implementation of regulations related to the enterprises and organizations of nuclear complexes
• the implementation of scientific, technical, investment and structural policy in the field of nuclear power development
• forming and realizing nuclear weapons programs, taking into account the reduction of the nuclear arsenal of Russia
The MinAtom is responsible for 151 enterprises covering the mining for raw material. 15 material, reprocessing of nuclear fuel and subsequent storage and burial of radioactive wastes. The total work force is around one million.
There is also an independent inspectorate directly under the Russian president. The State Committee for the Supervision of Nuclear and Radiation Safety under the President of Russia (Gosatomnadzor). The Gosatomnadzor performs inspection within the entire nuclear fuel cycle and has the legal right to prosecute violations of safety regulations. The inspection also issues licenses for different types of activities within the nuclear energy area. As an example, radioactive waste comes from many sources, the ministry of defense, the ministry of industry (the commercial fleet e.g. with nuclear powered icebreakers), individual companies and research institutions. For the latter, the local authorities have the responsibility for the handling of the radioactive wastes, in the former the ministries themselves. In connection with the privatization more and more of the responsibility is taken over by private companies.
The supervision of these activities is performed by Gosatomnadzor. Occasionally also the Ministry of the Environment Minekologiji) or the Ministry of Health may be responsible for questions concerning environmental protection and occupational safety. The different organizations have a close cooperation and divide the responsibility in bordering cases.
Changes in the ministry structure will occur during the autumn and winter of 1992, but so far the consequences for this are not clear as regarding the Gosatomnadzor. Representatives for the organization have apprehensions that they may loose their independent status. A couple of decrees from president Jeltsin have indicated a wish to return to the old system, in which case the Gosatomnadzor would be placed under Minatom. However, the latest signals from the president indicates that this has been reconsidered and that Gosatomnadzor will remain independent.
4.2.2 Potential sources of radioactive material
Nuclear reactors
In November 1991 the former USSR had 45 nuclear power plants in operation and 25 under construction [IAEA, 1991a], Sixteen of the plants were of the type RMBK (the same type as the reactor in Chernobyl), one a fast neutron reactor of type BN-600, and most of the remaining where pressure water reactors (type V VER-440).
Of the former USSR reactors the main part is now in Russia (28) and in Ukraine (15), while there are two in Lithuania. Since 1991, one plant has been taken into operation while several small older plants have been taken out of commission. Armenian has two nuclear reactors of type VVER-440 that are put out of operation because of risks for earthquakes.
The 28 reactors in Russia have a total effect of 20 GW and are producing 11 percent of the total energy. Furthermore, there are 130 research reactors in Russia. In 1992, the Gosatomnadzor decided to shut down two of the reactors at the Kurchatov institute and two industrial reactors at the Krasnoyarsk-26 chemical combinat. The decision was taken as a consequence of lacking safety and in the later case as a consequence of environmental pollution. 16 Nuclear reactors are also used in ships and submarines. Several used submarine reactors have been dumped outside of the arctic coast.
Enrichment and reprocessing facilities
Little information is available concerning the enrichment and reprocessing facilities in the former USSR, since these facilities also are a part of the military program. Most of the facilities are likely to be located in Russia.
Enrichment of the uranium, i.e. increasing the content of the isotope U-23S, is essential for most of its use. High enriched uranium (more than 90% U-235) is used for fuel in research reactors and submarine reactors. The production of high enriched uranium for weapons ceased in 1989. Low enriched uranium is used in light water nuclear power plants.
Uranium enrichment has been made since the early fifties by the gas diffusion method. The number of plants is unknown, but is expected to be one to three. There is also information of a centrifuge enrichment plant, but the localization of this plant is unknown. The capacity of these installations have never been published, but it is estimated that the total production of high enriched uranium is in the order of 500-600 tonnes [FOA, 1992a).
There are several reprocessing facilities (Kyshtym/Chelyabinsk, Seversk/Tomsk). These are located in connection with reactors producing plutonium for nuclear weapons. Therefore, very little information is available concerning the amount of reprocessed fuel and the treatment of the waste, etc. In Kyshtym an accident with reprocessing waste occurred in the late 1950s giving rise to severe contamination of the surrounding area. Even today the area is reported to have a high level of contamination.
Nuclear weapons
The nuclear weapons are fabricated at ten locations, in "closed towns" because of secrecy and safety. Of the previous 13 plutonium production reactors only four were running in May 1992. According to the minister of atomic energy, Dr. Mikhailov [FOA, 1992b] two more reactors should be closed down in 1992 and the other two in 1993. According to other information given by Dr. Mikhailov, the closing of the four remaining reactors will occur later; two reactors will be closed down in 1996 and two by year 2000. The total amount of weapon plutonium produced in the former USSR has been estimated to 120 tonnes [FOA, 1992a]. The total production of plutonium from nuclear power reactors has been estimated to be 40 to 90 tonnes, but the degree of reprocessing is not known. Also, the composition of this plutonium and how well it is suited for weapons fabrication is unknown.
The production of tritium for thermonuclear devices is continuing. The production is believed to be located at the same facilities as the plutonium production. The total inventory of tritium is estimated to be 55 kg [FOA, 1992a]. 17
The large arsenal of nuclear weapons (40 000 weapons) requires regular maintenance, every year 2000 to 3000 weapons are eliminated or reworked. Previously, the regained plutonium was used for new weapons, but with the new arms limitation treaties the plutonium is stored. Two new plutonium storage complexes are planned, but until then temporary storage is used. Already several dozen of tonnes of plutonium are in storage [FOA, 1992b].
Radiation sources
Russian authorities estimate that 130 000 companies and organizations use radiation sources or handle radioactive waste. Presently, there is an inventory' being made of radiation sources in Russia. This is far from complete but the estimated number of sources in Russia is around 200 000.
Other types of radioactive materials
Other sources of radioactive material are waste storage facilities and the vast areas that have been contaminated either by nuclear weapons tests or nuclear accidents. Padioactive materials have had a much wider use in the eastern countries than in the west. For example strong sources with Co-60 have been reported to be put in wells for sterilization of the water. The potential use for military purposes is to a large extent unknown.
Comments from Russian authorities
According to Russian authorities is the control over radioactive materials from the nuclear power production and the military production extremely strict. It is excluded that any radioactive metal scrap or other radioactive material may go astray. The civilian nuclear power production is controlled by Gosatomnadzor.
In total more than ten research and plutonium production reactors have been stopped since Gosatomnadzor started its activities in the spring of 1992. Decommissioning of the shut down reactors has not yet commenced.
The documentation and control of all radiation sources used in research, education or within industry not connected to the nuclear power industry is ongoing. The Gosatomnadzor believes that this may be the source of contaminated metal scrap or lost radiation sources. Radioactive material may have come into contact with metal, which against better knowledge has been reused. There are cases where radioactive metal scrap has been used to build children cradles.
There are large deficiencies in safety at the companies and organizations that handle radioactive materials. Dosimeters and other measuring equipment are often missing. Radioactive materials or waste are often forgotten. There are also a large number of cases where radioactive materials have been stolen. 18 4.3 Discussion
There have been articles both in international and Russian press dealing with the smuggling of materials for nuclear weapons fabrication and different types of contaminated materials. The majority of these are the result of sensation makers, e.g. the stories of red mercury. However, several documented incidents prove that radioactive materials are leaking out of the former USSR.
The official Russian policy is that the control of the nuclear energy sector and the military sector is strict. However, the country is presently in an organizational chaos and it is likely that not only contaminated metal scrap, but also other types of radioactive materials may come astray. Not the least the harsh economical situation in the country may lead scientists or other persons to attempt to get extra incomes. The many years of controlled economy and limited access to certain types of goods has lead to an appreciation of the value of certain materials that may differ substantially from that of the western countries. Thus, it may also be hard to envisage what materials are believed to be of value, and therefore may be smuggled out of the country. 19 5 RADIONUCLIDES AND DETECTION POSSIBILITIES
5.1 Radionuclides in metal scrap
A number of different radionuclides can be expected in metal scrap. The type of radionuclides will to a large degree depend on how the metal scrap became radioactive. Many radionuclides are very short-lived and will thus not constitute a radiological risk in the metal scrap.
Radionuclides are often divided into the following categories according to how they are produced:
- Activation products. Radioactive isotopes formed when the nucleus of a stable isotope is exposed to neutrons or other heavy particles, e.g. in a reactor or an accelerator.
- Fission products. Radioactive isotopes formed when the nucleus of a heavier isotope is split in parts, e.g. in reactor fuel or in a nuclear bomb.
- Actinides. Heavy radioactive isotopes formed in the reactor fuel through the absorption of neutrons.
- Natural radionuclides. Members of decay chains of uranium or radionuclides with very long half-life, which exist naturally in the environment.
Metal scrap originating from nuclear installations may be contaminated with a combination of radionuclides from these categories.
Activated metal scrap
Metals scrap (and other materials) from a reactor or an accelerator that has been exposed to neutrons or other heavy particles will become radioactive, activation products are formed. The radionuclide inventory will depend on the type of metal and the type of radiation it has been exposed to. The amount of activity will depend on the exposure time and the panicle flux the material has been exposed to. Scrap from materials close to the reactor core may have very high levels of activity, and are normally treated as high level waste. Materials at some distance from the core may have low levels of activity. There is a considerable experience of the radioactive inventory produced when different materials are exposed to radiation of heavy particles. There is also a good theoretical knowledge of the various reactions and computer programs are available that can estimate the radionuclide inventory. However, one problem is that trace elements present in the metal can contribute considerably to the induced activity. Thus, an accurate specification of the initial composition of the material is needed.
Steel is a major construction material in nuclear reactors. The major radionuclides formed due to neutron exposure of carbon steel are Mn-54, Co-60, and Fe-55. Stainless steel have a high nickel content which may give rise to the radioactive isotopes Ni-59, Ni-63. Large amounts of Cr-51 may also be formed, but it has a short radioactive half-life (28 days). Depending on the composition of the steel also other radionuclides may be present, 20 e.g. Zn-65. Mo-93 and Eu-152. The induced activity is usually fixed in the metal and will not be released when handled or treated.
Contaminated metal scrap
Metal scrap from nuclear installations have often come in contact with radioactive solutions, sprays or gases and can therefore be contaminated on the surface. The surface contamination usually consists of a mixture of activations products from corroding metals, and fission products or actinides from leaking fuel elements. The activity in different systems of a reactor is highly varying. It may also vary considerably between different reactors depending on the amount of leakage that has occurred. In reprocessing facilities the fuel is dissolved and the fission products are chemically separated from the actinides. Thus, scrap from reprocessing facilities may have a high content of fission products and actinides. The type of radionuclides formed by fission is determined by the type of reactor. Usually two groups are formed with mass number around 90 and 140, respectively. Fission product* of interest in metal scrap are: Sr-90, Tc-99, Cs-134, Cs- 137, Ce-144 and Pm-147. All of these have half-lives greater than 2 years, except Ce- 144. For material contaminated with actinides the most interesting radionuclides are: Pu- 238, Pu-239, Pu-240, Pu-241, Am-241, Cm-242 and Cm-244.
These radionuclides are isotopes of different elements with completely different chemical properties, thus inventory of different types of metal scrap may vary strongly. The surface contamination can either be strongly fixed to the scrap or can easily come loose as dust when handled or treated.
Metal scrap containing radiation sourcts
Several accident and incidents where radiation sources have been melted together with metal scrap have occurred, see Chapter 4. Industrial gauges with radiation sources are often used on pipes or in tanks and may not have been removed when the part is scrapped. Other types of sources are often small and difficult to detect in large shipments of scrap. Especially if the shielding is lost, the actual source, in the form of small cylinders or spheres is virtually impossible to identify for an unexperienced person.
Many different radionuclides can be used in radiation sources. The most common radionuclides are: Co-60, Sr-90, Cs-137, Ir-192, Am-241. A summary of equipment containing sealed radiation sources used in industry, research and medicine [IAEA, 1991b] is given in Table 5.1. 21
Table 5.1 The most frequently used types of equipment and the corresponding radionuciides [IAEA, 1991].
Radio- Half- Source Other Application nudide life strength Comments nuclides
I. Industrial application
Belt gauge Cs-137 30 y 0.1- 40 GBq Fixed installations
Density gauge Cs-137 30 y 1 - 20 GBq Fixed installations Sr-90 Am-241 433 y 1 • 10 GBq
Industnal lr-192 74 d 0.1-5 TBq Often portable Cs-l37,Tm-170 radiography Co-60 5.3 y 0.1-1 TBq units Yb-169
Level gauge Cs-137 30 y 0.1- 20 GBq Fixed installations Am-241 Co-60 5.3 y 0.1-10 GBq
Moisture detector Am-241/Be 433 y 0.1-10 GBq Portable units Cf-252, Ra-226/Be
Roentgen fluores- Fe-55 2.6 y 0.1-5 GBq Often portable Pu-238 cence analyser (XRF) units Am-241
Sterilization and Co-60 5.3 y 0.1-400 PSq Fixed installations food preservation Cs-137 30 y 0.1-400 PBq
Thickness gauge Kr-85 10.8 y 0.1- 50 GBq Fixed installations C-14, P32, Sr-90 28.1 y 0.1- 2 GBq Pm-147, Amtt
Well logging Am-241/Be 433 y 1-500 GBq Portable units Cs-137 30 y 1-100 GBq
II. Research applications
Calibration sources Many different < 0.1 GBq Small portable sources
Electron capture H-3 12.3 y 1 - 50 GBq Can be used in Ni-63 detector portable units
Irradiator Co-60 5.3 y 1 -1000 TBq Fixed installations
Tritium targets H-3 12.3 y 1 -10 TBq Fixed installations for neutron production
III. Medical applications
Bone densitometer Am-241 433 y 1 -10 GBq Mobile units 1-125 60 d 1 -10 GBq
Brachytherapy Cs-137 30 y 50 - 500 MBq Small portable Co-60, Sr-90, Ra-226 1600 y 30 - 300 MBq sources lr-192 5.2 Detection of radioactive metal scrap
In general, radioactive materials can relatively easily be detected by the emitted gamma radiation. The exception is some radionuclides which emit little or no gamma radiation and are therefore difficult to detect. The problem is how to obtain a measurement which is distinguishable from the background radiation. The monitoring of metal scrap is complicated by a number of factors:
- the shipments are large thus the distance between the source and the detector may become great - the radioactive parts may be shielded by non-active metal scrap - the time available for measuring are for practical reasons short
Studies have been performed on the monitoring of metal scrap at steel plants. The result of these are to a large extent also applicable to other cases, e.g. the monitoring at customs or at scrap yards. The studies have focussed on permanent monitor installations.
Type of detectors
There are several types of detector designs. In the studies Geiger-Muller tubes, plastic scintillators, and Nal detectors have been considered. The efficiency is greatest for the Nal detectors and lowest for the Geiger-Muller tubes. AECL advocates the use of Geiger- Muller tubes [Walker, 1988] because they are insensitive to moisture, temperature changes and vibrations. Their low efficiency can be compensated by having several detectors since the price is low. Others recommend the use of plastic scintillators [Harvey, 1990; Bex, 1991].
Location of detectors
The most suitable location of the monitors for the incoming scrap may depend on the layout of the plant and how the scrap is handled. Consideration must be taken to measuring distance and time, as well as the general environment for the detector. However, all studies concluded that an installation in connection with the weighing station is favorable. The Canadian study [Walker, 1988] recommends that monitoring is installed at five key locations: the receiving area, the weigh scale, the charge bucket, the metallurgic laboratory and the off-gas system. At smaller plants fewer locations may be needed. The reason for having several monitoring points is that properly shielded sources are unlikely to be detected as received, but may be detected as they are subjected to further processes within the plant.
In a CEC study, [Harvey, 1990] experiments were performed with radiation sources. It was found that the most favorable position for the detector was above the vehicle with the scrap. The Canadian study recommends two detectors one above and one below the vehicle. 23 Shielding by non-contaminated scrap
If only a pan of the load is contaminated, the other scrap in the shipment may shield the radiation and thus making it more difficult to detect. The efficiency of the shielding will depend on the type of scrap, the filling density (the percentage of the total volume filled with scrap), the amount of scrap between the source and the monitor, and the energy of the gamma radiation emitted by the radionuclide. One meter of steel scrap with a filling density of 15% would reduce the radiation level from Co-60 by a factor 100, Cs-137 by a factor of 500 and for Ir-192 by a factor of more than a thousand. Copper scrap would give a slightly higher reduction. The amount of scrap and the filling density is very important. The reduction of radiation from Co-60 would be a factor of 10 with only 0.5 meters of steel scrap between the source and the monitor.
Test of detectors at steel plants
Tests have also been performed to determine the levels of activity that can be detected in steel scrap. In the CEC study [Harvey, 1990] radiation sources were placed in six locations in scrap vehicle, near the top and at the bottom of the scrap load at three distances from the side were the detector was. The filling density of the scrap load was around 10%. Radioactive sources with Co-60 (37 MBq and 740 MBq) and Cs-137 (185 MBq and 7.4 GBq) were used. The source was considered detected if the obtained count was more than 3 standard deviations above the count without the radioactive source. Readings were taken for 2 periods of 1 minute. The sources were always detected in the case were the detector was placed above the scrap load, but missed in 6 to 20% of the cases when the detector was placed at the side of the scrap load. The test thus gave a detection limit of at least 37 MBq for Co-60 and 185 MBq for Cs-137. The detection of Co-60 was deemed satisfactory, but that of Cs-137 could result in unacceptably high activity levels in dust from the furnaces.
A permeanent installation was later built with a radiation monitor placed above the load. In the permanent installation a microprocessor checks the readings from the detector and automatically updates the value tor the background radiation.
In the Canadian study [Walker, 1988] both theoretical and experimental detection limits have been evaluated. The theoretical detection limits were estimated as the activity which gives a radiation level two times a background of 0.1 jtSv/h. The filling density of the scrap load was assumed to be 20%. For monitoring below a vehicle, detection should be possible of 100 MBq for Co-60 or 2180 MBq for Cs-137. These values are higher than those obtained in the CEC study, largely due to a different criteria for detection and the the somewhat higher filling density. The practical experiments showed that it was possible to detect as little as 3.7 MBq if the filling density of the load was 6%.
Shielded radiation sources
Radiation sources are shielded when not in use, usually in a lead container. Stronger aisn have snecial containers for transoort. The radiation levels from radiation 24 radiation level at 1 meter from the source should not exceed 7.5 /xSv/h. The later limit is shortly going to be lowered to 2.5 /xSv/h.
The radiation level from transport packages is limited by the transportation regulations. The IAEA Transport Regulations [IAEA, 1985] require that the radiation level at 1 meter from a package category III-Yellow should not exceed 100 jtSv/h and that the maximum radiation level at any point of the external surface should be less than 2 mSv/h. If shipped in a package category II-Yellow, the maximum radiation level at 1 meter should not exceed 10 /zSv/h. In practice radiation levels from transport packages may be lower.
The low radiation levels from shielded radiation sources makes it likely that a source in a transport container may remain undetected if placed within a load of metal scrap. However, it should be noted that a visual inspection of the scrap is normaly performed to ensure that no materials that may cause danger during the melting is included, for example closed vessels.
Uniformly contaminated scrap
If the scrap is more uniformly contaminated the placement of the monitor is not so critical. However, the self-shielding by the scrap may reduce the radiation that can be monitored. An estimate has been made of the activity concentration in a 20 tonne load that gives a radiation level equal to a background of 0.1 fiSv/h. The results presented in Table 5.2 are based on a half-cylinder source with a radius of 0.6 meters, a length of 9 meters and a measuring distance of 2 meters [IAEA, 1990]. This would correspond to measuring from the short side of a container.
Table 5.2 Activity concentrations in a 20-tonne load of steel scrap giving a radiation level at 2 meters of 0.1
Radionuclide Activity concentration [Bq/g] Mn-54 28 Co-60 8 Zn-65 44 Cs-137 38 Am-241 3850 25 SUMMARY AND CONCLUSIONS
There is a growing concern in Sweden of the possibility of receiving radioactive metal scrap. Such scrap may consitute a risk for persons handling and inspecting the shipment and if melted also for persons who come in contact with products made of the metal scrap. The political and economical changes in eastern Europe and in the former USSR has lead to an increased expon of metals and metal scrap to the western countries. During the first half year of 1992 a major part of the import of copper, nickel, aluminium and a number of strategic metals comes from the former USSR. In several incidents, radioactive metal scrap and other radioactive materials have been imported. This has lead to an increased alertness among importers, the customs, and metal scrap users. Monitoring of metal scrap for radioactivity is being performed at many places.
The risk for melting of radioactive scrap was first highlighted in the early eigthies when several accidents occured in the United States where radiation sources where melted. These accidents have lead to an awareness amongst the steel producers in the US and Canada. In many places permanent monitoring systems were installed. In Sweden the probability for accidental melting of radiation sources have been considered very small. The relatively small amount of radiation sources has been kept track of. However, with a growing amount of imported metal scrap the probability for an accident may increase.
Radioactive metal scrap may also originate from nuclear facilities. This may be parts that are replaced or parts from facilities that are being disassembled, e.g. from nuclear power or research reactors, reprocessing facilities, or nuclear weapon fabrication facilities. In many of the incidents where radioactive materials have been discovered, the origin is the former USSR. The newly independent countries have large economical and organizational problems. Furthermore, many facilities with radioactive materials are being put out of operation and being disassembled. It is therefore not unlikely that not only radioactive metal scrap, but also other types of radioactive materials may come astray. The Russian authorities declare that the control over radioactive materials from nuclear power production facilities and military production is very strict, but admit that there is a problem with radiation sources and radioactive materials from industry. There are large deficiencies in the safety, measuring equipment are often missing and radioactive materials are often "forgotten". Considering the large amounts of materials handled at many locations it is likely that radioactive materials may become mixed with metal scrap.
Presently, monitoring is being performed on shipments of metal scrap by the customs, the scrap dealers, and at the melting plants. So far the monitoring is not complete in all stages, but the incentive for monitoring is likely to increase. The detection of radioactive materials in metal scrap shipments is difficult since the volumes are large, the sources may be shielded by non-active materials, and since the time for measuring usually is short. Radionuclidei emitting high energy gamma, such as Co-60, are likely to be detected if present in a considerable amount. However, radiation with less energy is more efficiently shielded and larger activities may thus escape without detection. In a CEC study it was concluded that the detection limit for Cs-137 was so high that melting of steel with that amount of activity would generate unacceptably high activity concentrations in the dust. Shielded radiation sources may pass undetected if unfavourably placed in a shipment of metal scrap. The difficulties in detecting radioactivity in scrap loads makes 26
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