RADIOACTIVE WASTES FROM FUEL CYCLE OPERATIONS T.N. KRISHNAMURTHI

Chairman C. HAUGHNEY

RADIOACTIVE WASTES FROM FUEL CYCLE OPERATIONS T.N. KRISHNAMURTHI

Atomic Energy Regulatory Board, Bombay, India

Abstract

REGULATORY ASPECTS IN THE TRANSPORT AND DISPOSAL OF LOW AND INTERMEDIATE LEVEL RADIOACTIVE WASTES FROM FUEL CYCLE OPERATIONS

Nuclear Fuel cycle facilities contribute significantly to the generation of radioactive wastes. As per the Atomic Energy Act, 1962, processing and management of radioactive wastes in India is the responsibility of the Department of Atomic Energy , in compliance with the rules, regulations and guidelines prescribed by the competent authority, namely the Atomic Energy Regulatory Board. In the Indian programme of waste management, each nuclear site has its own waste management facilities catering to the needs of the nuclear installations at the site.

By this scheme, the transport of radioactive wastes is avoided in the public domain except for spent fuel shipments to the reprocessing plants. All waste movements take place inside the controlled areas of the nuclear site. Radiation Protection Rules, Radiation Surveillance Procedures for Safe transport of Radioactive materials and the AERB code for Safety in the Transport of Radioactive Materials provide the necessary regulatory controls for safety in transportation. The safety code is further supplemented with technical and administrative procedures, issued in form of regulatory guides. The paper describes in detail the regulatory control aspects in transport.

The type and form of radioactive wastes generated in nuclear fuel cycle operations, their conditioning and the type of packages that are employed for the transport of the waste within the nuclear sites are explained. An adequate and competent infrastructure has been built to cater for the diverse waste management requirements including transport at nuclear installations in India.

l. INTRODUCTION

Nuclear power generation and associated nuclear fuel cycle activities from mining to fuel fabrication and reprocessing of irradiated fuel contribute to radioactive waste generation in significant quantities. Decommissioning of nuclear facilities will also result in considerable amounts of waste materials that are radioactive or contaminated with radionuclides to a widely

varying extent. The facilities and plants connected with the above operations are under the direct control of the Department of Atomic Energy (DAE) of the Government of India. The other installations, not under the control of DAE, such as research institutions, hospitals, industrial radiography companies and other users of radioisotopes also contribute to radioactive waste generation. However, it is the nuclear fuel cycle, which is of major concern from the point of view of protection of the environment and is addressed in this paper. DAE has established waste management facilities at all nuclear sites to cater to the requirements of the nuclear installations at the sites.

2. REGULATORY ASPECTS OF WASTE MANAGEMENT

Radioactive waste management in India must comply with the provisions of the Atomic Energy (Safe Disposal of Radioactive Wastes) Rules, 1987 issued under the Atomic Energy Act, 1962, Environmental (Protection) Act, 1986 and Environmental

(Protection) Rules, 1987. The waste disposal rules cover all aspects ranging from the processes resulting in generation of radioactive wastes to conditioning, storage and disposal of such wastes. Provisions have also been made for hospitals and research laboratories using small quantities of radioisotopes.

Chairman, Atomic Energy Regulatory Board (AERB) has been notified by the Government of India as the Competent Authority for the enforcement of the provisions of Atomic Energy (Safe Disposal of Radioactive Wastes) Rules 1987. An authorisation is to be obtained from the Competent Authority by each person or installation for disposal of radioactive wastes or for their transfer to an authorised waste management agency., It is the responsibility of the authorised person or installation to ensure compliance with the terms and conditions of the authorisation, maintain records of waste disposed, ensure compliance with the Radiation Protection Rules, 1971 and carry out personnel monitoring and environmental surveillance on a continued basis.

He should also appoint with the approval of the Competent Authority a Radiological Safety Officer to carry out radiation safety surveillance. The Competent Authority is authorised to carry out inspection of the installation, to issue directives as deemed necessary in the interests of radiological protection and to suspend or cancel the authorisation given to a person if the latter has failed to comply with the terms and conditions of the authorisation.

Chairman, AERB has been notified as the statutory authority to carry out certain duties envisaged under Environmental (Protection) Act and Rules in respect of the installations set up for the furtherance of the objectives of the Atomic Energy Act, 1962. These duties include (a) power of inspection of the installation and (b) power to take samples of air, water, soil or any other substances from any factory or premises for purposes of analysis. The Ministry of Environment and Forests has recognised the Environmental Survey Laboratories set up by the

Health Physics Division of the Bhabha Atomic Research Centre (BARC) at nuclear sites to carry out environmental protection surveillance for the installations of the Department of Atomic Energy.

3. RADIOACTIVE WASTE TRANSPORT IN INDIA

In the Indian programme of radioactive waste management, waste management facilities are co-located with nuclear installations at each nuclear site. No off-site storage, transport or disposal is practiced as yet. Each nuclear site has a liquid waste treatment plant and a solid waste management facility. A near-surface repository for low and intermediate level solid waste is also set up at each site. In addition, an interim storage facility for high level solid wastes is also planned at each site, where plant for immobilisation of high level liquid wastes is located. In the Tarapur site, where a twin unit BWRs and a reprocessing plant for power reactor fuel are in operation, an interim storage facility based on natural convective air cooling with induced draft is already operational.

In general, siting considerations for locating nuclear power plants and / or reprocessing plants take into account establishment of the required waste management facilities also.

By the above scheme, transport of radioactive wastes are avoided in the public domain, except for irradiated fuel shipments to reprocessing plant. All waste movements take place within the controlled areas inside nuclear sites. The only radioactive waste materials that are transported in the public domain are decayed sealed sources from the users and occasionally contaminated objects sent to BARC for final disposal.

The Indian programme currently envisages investigation of candidate sites for a final repository for the high level vitrified waste products and alpha bearing wastes. This facility is planned to be set up on a centralised basis and will be common for many nuclear sites. When such a facility is established, transport of high level immobilised wastes in the public domain will arise and will be subject to regulatory control.

The type and form of radioactive wastes that are required to be transported within the controlled areas of the nuclear sites depend on the nature of operations that are carried out at the waste management facilities. In the following paragraphs, a brief summary of the principles and processes followed for treatment of low and intermediate level liquid and solid wastes are described. High level waste management is excluded from the scope of this paper as well as that of the seminar.

4. WASTE MANAGEMENT PRINCIPLES

The basic philosophy in the management of all radioactive wastes has been (i) dilution and dispersal of low active wastes,

(ii) delay / decay and dispersal of waste containing short-lived

radionuclides and (iii) concentration and containment of highly active waste containing long lived radionuclides.

The broad outlines of the waste management policy are : (1) Any discharge of radioactive liquid or gaseous wastes to the

environment should be as low as reasonably achievable, economic and social factors being take into consideration;

(2) Solid wastes resulting from conditioning of waste concentrates or liquid wastes generated in the operation of reactors and research facilities are to be stored in near surface repositories, specially engineered for the purpose.

Conditioned low and intermediate level wastes along with trace quantities of alpha contamination from fuel reprocessing facilities are also permitted for storage in such facilities;

(3) High level liquid wastes from reprocessing plants are initially stored for an interim period in high integrity stainless steel tanks underground. These wastes will be vitrified and the solidified products will be provided interim storage in near surface engineered storage facilities with appropriate cooling and surveillance provisions. The interim storage will allow for decay and hence reduction in heat generation;

(4) High level vitrified and cooled waste products and alpha wastes will be disposed off in a suitable deep geological formation, serving as a centralised repository.

5. WASTE CATEGORISATION

For the purpose of waste handling and radioactive wastes are categorised generally as :

treatment, Low Level Waste (LLW)

Intermediate Level Waste (ILW)

High Level Waste (HLW)

Waste because of its low radioactivity content, does not require shielding during normal handling and transportation.

Waste because of its radioactivity content, requires shielding but needs no provision for heat dissipation during handling and and needs cooling due to decay heat.

00O Alpha Waste Waste with high concentration of alpha activity and low decay heat,requires remote handling in air-tight enclosures.

6. TREATMENT OF LOW AND INTERMEDIATE LEVEL WASTES

Present practices in respect of low and intermediate level radioactive waste management are summarised below :

(1) Uranium mining and milling wastes

The barren liquor produced in the uranium recovery process is neutralised with lime and treated with Bacl2 to precipitate radium and other daughter products of uranium. The precipitate is mixed with the tailings slurry and is disposed off into a tailings pond, which is normally a natural depression that ensures settling. The waste transportation from the mill to the tailings pond is by means of pumped transfer.

(2) Low and Intermediate Level Liquid Waste

The low level liquid radioactive wastes are treated by chemical, ion-exchange or evaporation methods. The sludge containing most of the radioactivity is separated and sent for solidification, storage and disposal. The treated effluent is discharged after further dilution and monitored to meet the specified regulatory discharge limits. With the continuing trend to restrict the discharges of radioactivity to the environment to as low as possible, a solar evaporation facility is being operated at the Rajasthan Atomic Power Station. The concentrate reduced in volume several fold, is solidified in suitable matrices for long term storage. Cement-concrete is found to be a suitable matrix for incorporation of waste concentrates with low activity. Bitumen is used for incorporation of concentrates from evaporation with intermediate levels of activity. Polymer matrices have also been used to immobilise spent ion exchange resins and higher level active waste concentrates.

(3) Low and intermediate Level Solid Waste

Radioactive solid wastes are generated in nuclear fuel cycle operations in a wide variety. Primary solid wastes consist of contaminated articles and products resulting from active chemical processes, viz., tissue materials, glassware, plastics and protective rubber wares in the contaminated category and ion exchange resins, filter sludge, incinerator ash etc. in the latter category. While low level wastes are produced in large volumes in the front end of the fuel cycle, intermediate levels of activity in solid waste are mainly from reactors and fuel reprocessing plants and isotope production laboratories.

Low active and combustible waste which constitute a major portion of the solid waste, are sent for incineration in

specially designed incinerators, provided with gas cleaning systems for volume reduction. Other wastes are baled to reduce the volume prior to disposal.

Permanent storage or disposal of radioactive solid wastes is carried out only at controlled sites, evaluated for the purpose.

In India, as a matter of policy, each nuclear site is planned to have a near-surface repository for low and intermediate level solid waste. The facilities in the repository include earthen trenches, RCC trenches, tile holes, RCC vaults etc. The reinforced concrete trenches located underground with waterproofing on the external surface and bitumen based painting on the inner surface provide good containment for low level solid wastes. For storage or disposal of higher level active wastes, deep circular underground tile holes are used. These are steel lined RCC pipes extending to 4-5 metres down and having water proofed external surface.

7. REGULATORY ASPECTS OF RADIOACTIVE WASTE TRANSPORT

Transport of radioactive waste is regulated under the same provisions that are applied to the movement of radioactive materials in the public domain for use in industry, hospitals and research laboratories. Radioactive material transportation in India is regulated under the provisions of the Atomic Energy Act, 1962, which empowers the Central Government to frame rules and lay down safety standards for ensuring an acceptable level of safety for transport workers and members of the public.

Radiation Protection Rules, 1971 issued under the Atomic Energy Act, the Radiation Surveillance Procedures for Safe Transport of Radioactive Materials issued under the above Rules and the AERB code for Safety in Transport of Radioactive Materials provide detailed regulatory control for safety during transportation. For the purpose of enforcement of the transport regulations. Chairman, AERB is notified as the Competent Authority by the Central Government. The regulatory provisions in the code are essentially based on the IAEA Regulations for Safe Transport of Radioactive Materials, Safety Series No.6 (1985 edition, as amended in 1990). IAEA has also issued supplementary information relevant to the interpretation of the regulations viz. ,

(1) An explanatory material - Safety Series 7 [1]

(2) An advisory material - Safety Series 37 [2]

(3) Schedules of requirements - Safety Series 80 [3]

(4) Guidance to Competent Authorities - TECDOC 413 [4]

The IAEA regulations serve as the basis for shipments of radioactive materials in most countries, thus ensuring complete harmony among various national and international regulations.

The AERB safety code on transport of radioactive materials prescribe safety standards governing the package design and

operational aspects. These standards are supplemented with technical and administrative procedures in a number of documents issued by AERB as guides. These are listed below with a brief description of their scope :

(1) Safety Guide on Compliance Assurance Programme for the Safe Transport of Radioactive Materials (1991)

The guide outlines the procedures for review and assessment of package designs, special form of radioactive materials, shipments and inspection activities.

(2) Safety Guide on Standards of Safety in Transport of Radioactive Material (1991)

The guide outlines the basic radiation safety standards governing the transport safety requirements stipulated in the code. It must be noted that the new ICRP recommendations with lower dose limits and introduction of the concept of dose constraints will have an impact on the transport regulations. In India, the effective dose limit for radiation workers is being reduced in a phased manner from 1991 onwards and the dose limit for the year 1993 was set at 30 mSv by AERB. For members of the public, the dose limit is l msv / year from exposure from all radiation sources.

(3) Safety Guide on Procedure for Forwarding, Transport, Handling and Storage of Radioactive Consignments (1991).

The procedures to be followed by consignors of radioactive material of various descriptions for different modes of transport are detailed in this guide. compliance with the procedures stipulated in the guide will help in avoiding transport incidents and improve safety in transportation in the public domain.

(4) Safety Guide on Quality Assurance in Transport of Radioactive Materials (under issue)

Essential features of quality assurance programme in the design, manufacture, use, maintenance, transport, documentation and storage-in-transit are explained in this guide for compliance. The guide is based on IAEA safety Series No. 37 (as amended 1990) and the experience of AERB in regulating the safe transport of radioactive materials in the country.

(5) Safety Code on Emergency Response Planning and Preparedness for Transport Accidents involving Radioactive Material

(1990)

The code specifies the requirements for establishment of emergency provisions, identifies emergency response organisations and prescribes response measures. The code is

intended to be the basis for emergency response action plans to be drawn up by organisations / individual consignors of radioactive materials.

8. TRANSPORT PACKAGES FOR RADIOACTIVE WASTE

Four types of packaging are specified in the transport regulations viz., Excepted, Industrial, Type A and Type B.

Excepted packages are permitted to contain only relatively small amounts of radioactivity. Hence, other types of packages are being used for the transport of radioactive waste. Industrial and Type A packages are being used to transport low level and intermediate level waste and the regulatory requirements in respect of radiation levels, specific activity and total radioactivity content are satisfied. Type B packages are used for the transport of intermediate and high level waste and irradiated fuel. Type B packages are designed to retain adequate shielding and containment under severe accident conditions. Prior approval of the Competent Authority i.e.. Chairman, AERB is required for the design of Type B packages and their shipment. All Type A packages are required to be actually subjected to the prescribed tests. For Type B packages, theoretical assessments of package response to test conditions are examined prior to approval.

Radioactive waste classification is usually linked to safety aspects of their management. A quantitative approach to classification, recommended by IAEA, is adopted by AERB, and is given below. This classification is used for purposes of obtaining regulatory clearance from AERB by waste generating / management facilities.

9. TRANSPORT OF LIQUID WASTE

Low level liquid wastes are normally transported from the place of generation to the treatment plant in the site by engineered pipelines or by tankering under special cases.

(1) Transport by pipelines :

Design and operation of transfer pipelines should take into account quality assurance aspects during design, erection and operation, secondary containment, in-service inspection and maintenance, detection of line failure and management and provisions for cleaning and decontamination. Low level effluent pipelines could be above ground for purposes of inspection and prompt corrective actions. For transport of medium level liquid waste, underground pipelines with necessary shielding is a better option. The pipeline should have double containment to prevent release of activity into the ground in the event of pipe failure.

Concrete trenches, if employed, should be given waterproofing to prevent ingress of subsoil water.

(2) Transport by Tankering

Transport by tanker within the establishment, where the liquid waste is generated, stored and treated does not fall under the purview of the provisions contained in the transport code.

However, the design and operation of the tanker should take into account quality assurance in design, fabrication and operation, adequate shielding, safe containment of leaks, provision for decontamination, in-service inspection for assessment of integrity and safe anchorage to vehicles. The tank should not be filled to capacity and filling level depends on the gradient of the route to be followed. Tankers should preferably be free of contamination on external surface. If levels are in excess of 0.4 Bq/sq.cm for beta-gamma and 0.04 Bq/sq.cm for alpha, the tanker is treated as contaminated. The tankers are periodically decontaminated to minimise the residual radiation field to less than 2 mGy/h on the surfaces. At BARC, Trombay the maximum activity that can be transported in a tanker is at present

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