Mechanical Engineering and Material Handling Aspects of NSDF

Transcription

1 Mechanical Engineering and Material Handling Aspects of NSDF R. K. Gupta and A. K. Singh BARC- IAEA Regional Training Course on Development of Near Surface Disposal Facility February 15-19, 2010 Mumbai, India

2 Index 1) Disposal Modules 2) Engineering Design Aspects a) Design Criteria b) Operational Aspects c) Closure Aspects 3) Waste package integrity 4) Equipment Design Events 5) Material Handling Activities 6) Material Handling equipment 7) Alpha Solid Waste Disposal

3 Introduction Material handling of low level radioactive packages in the form of drums, cartons and polythene bags plays an important role in safe and long term disposal of the waste. All active operations are carried out using mechanical devices such as forklifts, trucks, mobile cranes, gantry cranes, etc. In keeping with the ALARA Principle, automation of handling equipment/tools has been attempted in the design.

4 Disposal Modules - NSDF Based on activity levels of the waste packages following three modules have been adopted under NSDF: 1) Tile Holes 2) RCC Trenches (RCCT) 3) Stone Lined Earth Trenches

5 Tile Hole

6 Elevation View of RCC Trench

7 Plan View of RCC Trench

8 Stone Lined Earth Trench

9 Engineering Design Aspects Civil Engineering Aspects General engineering aspects related to mechanical design, handling and transportation.

10 Mechanical Engineering Design Aspects During the design phase of NSDF all the mechanical engineering inputs are worked out in tandem and in consultation with the civil designers. These inputs may be. 1) Design of structures and supports 2) Design for the safe operation of the facility 3) Logistics of material handling. 4) Top closure arrangement

11 Design Criteria Approach and safe working load for crane Road width and adequate turning radius for mobile crane access. Size standardization of the Trenches & Tile holes Drum/package storage Layout Structural grid work for supporting the stored material Weight of individual waste package and it s activity Floor loading for equipment and material movement such as Goliath Crane, Cask and Mobile Crane 1/2

12 Design Criteria Provision of sump and gutter with proper slope Metallic construction of Tile Holes with centrifugal cement casting Optimization in placement of waste packages in order to minimize disposal volume Provision of decontamination and maintenance aspects of component, equipment, etc. Versatility of handling equipment with respect to different modules. Selection of proper material for the construction of primary barrier with respect to corrosive nature of waste and environment 2/2

13 Operational Aspects Equipment safety Fail Safe mode of equipment operation Low exposure to the operating personnel Weight and size of the shielding plugs and waste packages Ease of operation for the equipment and structures such as mobile cover provided for rain water protection

14 Closure Aspects Suitable engineered barriers of natural or manufactured materials is incorporated in the design of the facility for the purpose of guaranteeing the integrity of the waste under all foreseeable circumstances. Possibility of water infiltrating the disposal structure has to be minimized. Delaying or preventing radionuclide migration, both during operations and after closure of the facility has to be ensured. In addition, the engineered barriers is designed to provide protection in the event of inadvertent manual intrusion into the disposal structure.

15 Waste Package Integrity The integrity of the waste package for NSDF is ensured by: 1. Appropriate Material selection for the barrier 2. Minimizing the release of the radio-nuclides from the package 3. Restricting infiltration of moisture 4. Providing a mechanism for restriction and dispersal of gases generated, if any 5. Providing long term structural stability 1/2

16 Waste Package Integrity 6. Disposal of waste in a manner which so that voids between packages is minimized and such spaces filled to prevent subsidence or settlement. 7. Constructing the base of a disposal structure in accordance with best engineering practice, and to support the weight of the whole system. 2/2

17 Waste Package Design Aspects 1) The storage environment (e.g. the ranges in ambient temperature and humidity) is taken into account in the design of storage containers and these containers should be sufficiently resistant to corrosion over the duration of storage. 2) The placement of storage containers on surfaces where condensation cycles can develop should be avoided. 3) Consideration has been given to the dynamic and static loads resulting from the handling and stacking of the waste packages. 1/3

18 Waste Package Design Aspects 4) During the design stage consideration is accorded to the wall thickness of the containers, their filled weight and the stacking orientation. 5) For certain types of waste (corrosive liquid), special precautions such as the use of double walled containers and/or the lining of storage rooms with stainless steel or other corrosion resistant material is necessary. 2/3

19 Waste Package Design Aspects 6) Liquid waste requires a collection and recovery system below the containers (i.e. a secondary containment) with provision for monitoring for any leakage. In keeping with the principles of passive safety, liquid wastes should be converted to solids as early as practicable. 7) Some waste may have the potential for generating airborne radio-nuclides within the container; many types of storage container vent naturally but some may require a purpose built vent. The need for package venting should be considered as part of the safety assessment. 3/3

20 Equipment Design Events The equipment shall be designed to comply with : 1) Design Events I and II for Operational Requirements and 2) Design Events III and IV for Emergency Requirements as well: A) Operational Events(I) B) Likely Events(II) C) Unlikely Events(III) D) Very unlikely Events (IV) 1/5

21 Equipment Design Events Operational Events(I): These consist of those set of events that are expected to occur regularly or frequently in the course of normal operation of the facilities like transfer, handling, transportation, storage and maintenance activities. 2/5

22 Equipment Design Events Likely Events(II): Consist of such set of events that, although not occurring regularly, can be expected to occur with moderate frequency or on the order of once during a calendar year of operation of the facilities like short operator error, minor failure of mechanical and handling equipment, spurious operation of active components, minor leakage of radioactive waste and repair activities 3/5

23 Equipment Design Events Unlikely Events(III): Consist of those infrequent events which could reasonably be expected to occur during the lifetime of the facilities like an extended loss of external power supply, major mechanical malfunction during operation, jamming of mechanical equipment, handling and transportation accident with load drop, leakage of radioactive waste, loss of containment, major malfunction of auxiliary system and severe external climatic conditions. 4/5

24 Equipment Design Events Very unlikely Events (IV): Consists of such events which are postulated because their consequences could result in the maximum potential impact on the immediate environs. This consideration establishes a conservative design basis for systems with Important Confinement Features. Typically this set of events will consist of External Events that have lower frequencies of occurrence than considered in Design Events I, II and III. Examples are: Earthquake, Flooding, External Fire and Explosion. 5/5

25 Material Handling Activities Collection of waste from generators Transportation of waste packages to NSDF site Receiving of waste packages at NSDF site Categorization of waste packages Identification & coding of waste packages Maintaining the record of waste package & its characterization Allocation of the module & location for waste package Unloading of the waste packages in appropriate module.

26 Handling Equipment used for NSDF Overhead Crane / Mobile Crane Remote Operated Grapples Heavy Duty Truck Tying Arrangement Remote Positioning Guide Fixtures Standard fork lift for cement cask handling Radio Operated Forklift for drum handling Winches for pulling & lifting

27 Transportation of Waste Packages After meeting the prerequisites such as waste segregation, categorization, identification & coding, packages are loaded on transport vehicle Transportation of waste to the facility shall comply with the legislative requirements for the transport of radioactive materials. Regulatory clearances from Health Physics and industrial safety

28 Remote Operated Drum Grappler Drum grappler is one of the important tools for placing the waste filled drums into RCC Trenches. A scissor type drum grappler has been developed for remote handling of the drums. The design of the grappler emphasizes on positive gripping of the drum in fail safe mode. After placing the drum into trench further lowering of grapple opens the grip and automatically locks the grapple in open condition so that the grappler can be taken out. 1/3

29 Remote Operated Drum Grappler The pneumatic cylinder provided on grappler facilitates unlocking of grappler and gripping the next drum. Since human intervention is not required for picking and placing of the drums in RCC Trenches, considerable amount of man-rem expenditure could be saved as compared to earlier operations. 2/3

30 Drum Grappler A scissor type drum grappler 500 Kg load capacity Positive grip and fail safe of operation Human intervention is not required for operation Reduction in man-rem expenditure 3/3

31 Drum Grappler Operation

32 Gantry / Mobile Cranes Gantry crane of adequate capacity to handle the waste packages Cranes having 30 m span & 10 Te capacity are used For HLW packages, provision of suitable shielding for the crane operator cabin Provision of radiation resistant cables (100 Mrad) Provision of parking bay for maintenance of the crane Periodic preventive maintenance of the crane to assess the health of brake liner, wire ropes, hook and crab

33 Remote Positioning Guide Fixtures A structural frame are used to facilitate the easy loading of waste filled drums into RCC Trenches. A frame provides required guide for drum and the grappler in order to place the drums in predetermined locations. It will take the reference from the RCC Trench top and shall be shifted to next location with the help of crane. The frame is also equipped with CCD Cameras and lamps if required. Operator will be able to operate the loading activity from temporary control room, 20 meters away from the actual loading operation with the help of cameras.

34 Direct loading of drums from Cask In order to minimize the remote handling activities at NSDF sites, the feasibility shall be studied for direct loading of the drums from Cask to the RCC Trench. This will further reduce radiation exposure to the operators.

35 Direct Loading from Cask

36 2 Te & 5Te Capacity Forklift Fork Lift is a versatile material handling equipment for management of LLW Waste Packages They are available in different types such as Rechargeable Battery Operated and Diesel operated The equipment is designed for it s reach to corner points having self loading features The Package placed on the equipment can be easily lifted to a suitable height, transported and unloaded to the required destination

37 Forklift

38 Radio Operated Forklift This is a special equipment developed for handling the standard 250 L capacity drums powered with rechargable batteries. The forks are suitably modified with two semi circular jaws for positive gripping of the drum. This equipment has an unique provision for remote operation from the control station. Additional features such as viewing Cameras, Antenas, etc are provided. This reduces the radiation exposure to plant personnel

39 Radio Operated Forklift

40 Maintenance & Auxiliary services All necessary tools, tackles & necessary accessories for maintaining the material handling equipment are provided Skilled manpower for the maintenance work are deployed Periodic preventive maintenance for crane wire ropes, hoist machinery, lifting hook, brake liners, gear boxes are performed Inventory management for spare part availability such as bearings, bushes, brake liners, cables, batteries & lubricants etc. Testing & certification of all the material handling equipment are being carried out periodically

41 Alpha Solid Waste Disposal Alpha contaminated glove boxes from R&D Laboratories declared as unserviceable units have been handled and disposed at NSDF Glove boxes reading less than 4000 Bq/gm of alpha activity are encased in SS housing and suitably transported to the disposal site. The glove boxes are suitably handled with the help of crane, taken out from SS housing and lowered into the RCC Trench at identified location.

42 Loading / Unloading Unloading Loading & Transportation

43 Disposal in RCC Trench

44 References IAEA-TECDOC-1256, Technical Considerations in the Design of Near Surface Disposal Facilities for Radioactive Waste IAEA Safety Standards, Storage of Radioactive Waste, Safety Guide No. WS-G-6.1

45 THANKS