WO2019043732A1

WO2019043732A1 - Radiation shielding composition comprising soft lead

Info

Publication number: WO2019043732A1
Application number: PCT/IN2018/050565
Authority: WO
Inventors: Shreekar MANGESHKAR; Genu PANSARE
Original assignee: Mangeshkar Shreekar
Priority date: 2017-09-04
Filing date: 2018-09-03
Publication date: 2019-03-07
Also published as: GB202003256D0; GB2579956B; GB2579956A

Abstract

Present invention provides a cost effective, low density, less toxic and recyclable radiation shielding composition comprising soft lead, thermo conductive metal foil and insulating material wherein; said thermo conductive metal and insulator is sandwiched between soft lead sheets. Any product such as bag, container, box etc of desired shape and size may be prepared from above composition as radiation shielding product.

Description

Title

Radiation shielding composition comprising soft lead Field of Invention

The present invention relates generally to the field of nuclear radiation shielding compositions.

More specifically the present innovation discloses a low cost radiation shielding composition containing soft lead to attenuate harmful gamma radiations, neutrons or other nuclear radiations in the form of a moldable product of any shape or size capable of acting as a shielding product.

Background of Invention

Today the use of radiation in medicine, agriculture, basic science, industry and military field has reached large proportions. Major sources of radiation are nuclear reactors and associated facilities, medical and industrial x-ray and radioisotope facilities, charged-particle accelerators and cosmic rays. Many of the nations spend large amount of money on the nuclear fuel as well as nuclear waste management. Use of nuclear energy may rise in future in order to fulfill increasing demand of energy.

Another front, ionizing radiation like x-rays and gamma radiation have many applications in fields like medical diagnosis, cancer treatment, radiation treatment of food (preservation) and nuclear (fission) energy. However, exposure to ionizing radiation will cause deterioration in health of the user, depending on the absorbed radiation dose. In order to protect users of such facilities from ionizing radiation, shielding is necessary. Economic and effective means of handling and transporting nuclear materials, nuclear products and nuclear waste are needed in near future. Hence, radiation shielding products or compositions play important role in providing protection against harmful effect of radiations on human beings or animals or plant life.

There are two types of radiations: directly ionizing (charged particles) and indirectly ionizing (neutrons, gamma rays, and x-rays). The most efficient absorbers of gamma radiation are elements of high atomic number, since the gamma absorption cross section of a nucleus varies approximately as the fourth power of its atomic number. For reasons of economy and relative ease of fabrication, the two most commonly used gamma shielding materials are lead and tungsten. These elements are used in the form of blocks, sheets, and in combination with other materials. Lead composite shielding is a mixture of lead and other lighter weight metals. These lead-based composite blends are a proprietary mixture of lead and other heavy metals that attenuate radiation that may include a mixture of lead, tin, rubber, PVC vinyl and other proprietary attenuating metals.

Traditionally lead boxes with cement coatings have been used for transporting or storing highly radioactive material or nuclear waste.

However, the use of a toxic heavy metal like lead (Pb) could cause serious long term effects on health and environment. Also, lead boxes are very heavy to carry from one place to another, costly and toxic in nature, unable to reuse or recycle, not moldable in desirable shape and sizes which is required in different nuclear fields such as medical field , industrial field , energy field and aerospace field etc.

A variety of alternative compositions and methods including wearable material (cloth) made from Lead mixed with binders and additives or lead alloy to form a flexible lead vinyl sheet or a radiation shielding bag capable of shielding radiation made from lead wool etc have been tried in the art to provide a radiation shielding product or composition in order to overcome above mentioned drawbacks. Although these provide flexible, wearable and moldable shielding products in desirable shape and size, they do not provide a non-toxic, recyclable and cost effective shielding material since they still comprises lead as a major component.

There is a need for a suitable radiation shielding material which is cost effective, recyclable, flexible, non toxic and light weight shielding material so that it can shield radiation effectively and environmental friendly manner.

In order to overcome the limitations of current shielding composition options, present invention provides a novel less toxic, less expensive and more effective radiation shielding material that protects against neutron, gamma and X ray radiations comprising a soft lead, a thermo conductive metal foil and an insulating material. Any product such as bag, container, box etc may be prepared from above composition as radiation shielding product.

Object of the Invention

Principal object of the present invention is to provide a radiation shield containing soft lead in order to attenuate harmful radioactive material and nuclear waste.

Another object of the present invention is to provide a radiation shielding composition containing minimum amount of soft lead which provides less toxicity and more molding ability for the product.

Yet another object of the present invention is to provide a cost effective, recyclable and easily moldable radiation shielding composition. Summary of the invention

The present invention relates to a nuclear radiation shielding composition comprising soft lead. Said composition further comprising; a thermo conductive metal and insulating material sandwiched between soft lead foils.

Brief description of drawings

Fig. 1 relates to schematic representation of different layers of radiation shielding composition of the present invention.

Fig. 2 depicts gamma radiation spectroscopic analysis of shielding capacity of conventional lead and novel shielding composition of present invention (SM-7) for the Ba-123 radiation source for the time interval of 20 min

Fig. 3 illustrates gamma radiation spectroscopy results for effects observed on traditional shielding composition (lead material) of Co-60 gamma radiation source for different irradiation time intervals using scintillation spectroscopy technique

Fig. 4 illustrates gamma radiation spectroscopy results for effects observed on novel shielding composition of present invention(SM-7) of Co-60 gamma radiation source for different irradiation time intervals using scintillation spectroscopy technique

Detailed description of invention

The present invention is described herein below with reference to the nuclear radiation shielding composition to provide a shielding product for transportation of radioactive materials or nuclear waste or for medical applications; however any description and drawings herein after should not be construed to limit the scope of present invention in any manner. Present invention relates to a novel radiation shielding composition to provide a shielding product for transporting radioactive material or nuclear waste or for medical purpose, comprising a thermo conductive metal layer and an insulating material layer sandwiched between soft lead layers and the process for preparation thereof. Said novel radiation shielding composition has radiation shielding properties similar to conventional lead based shielding materials and provides a cost effective, less-toxic, light weight solution.

As shown in Fig. 1, layer no 1 is a soft lead sheet layer which forms the top and bottom portion of the radiation shielding composition of the present invention. The thermo conductive metal forms a second layer no.2 followed by a layer a third layer no.3 of insulating material layer. Said thermo conductive metal layer and insulating material layer are alternatively placed between two layers of soft lead at the top and bottom in the form of a sandwich.

In one embodiment, the invention relates to radiation shielding composition comprising soft lead for transporting radioactive material or nuclear waste or for medical uses wherein; said thermo conductive metal is selected from the group consisting of Aluminum, Brass, Tungsten or metal alloy or any other thermally conductive metal having density greater than or equal to 2.5 g/cm . Said metal foils are selected in such a way that they can be easily moldable so as to form a final product of any shape and size.

In another embodiment the thickness of said thermo conductive metal layer is in the range of 0.1cm -0.5cm.

In one embodiment, the invention relates to radiation shielding composition comprising soft lead for transporting radioactive material or nuclear waste or for medical uses wherein; said insulating material is selected from the group consisting of Teflon, Light Density Polyethylene (LDP), High Density Polyethylene (HDP) or may selected from a synthetic polymer or any other combination thereof wherein; the minimum density of insulating material is greater than or equal to 2 g/cm .

The selection of insulating material is decided by density, molding ability and recyclability of the material.

In one embodiment, the invention relates to radiation shielding composition comprising soft lead for transporting radioactive material or nuclear waste or for medical uses wherein; said soft lead is in the form of sheet having thickness ranging from 0.5cm- lcm.

In another embodiment, the invention relates to radiation shielding composition comprising soft lead for transporting radioactive material or nuclear waste or for medical uses wherein; said soft lead sheets are prepared from commercially available soft lead material (bricks) by pressing with industrial hammer.

In another embodiment, the invention relates to radiation shielding composition comprising soft lead for transporting radioactive material or nuclear waste or for medical uses wherein; said thermo conductive metal sheets and insulating material sheets are commercially available metal sheets and insulators respectively.

In yet another embodiment of present invention, said radiation shielding composition optionally comprises of cement coatings for more protection.

Said radiation shielding composition optionally further comprises of a binding material such as industrial glue. The experimental work includes a Nal (Tl) gamma ray spectrometer used for measuring gamma radiations transmitted intensities through absorber sample. A sample of each material under study is placed between detector and source. The distance between source and detector window is kept 3.7 cm throughout the experiment.

In yet another embodiment the invention relates to radiation shielding composition comprising soft lead for transporting radioactive material or nuclear waste or for medical uses wherein; the thickness of radiation shielding product comprising soft lead is in the range of 1.5 cm to 2.5 cm and density more than 11.50 gm/cm³

Said thickness of radiation shielding product prepared from novel radiation shielding composition of present invention may increase or decrease depending upon radiation intensity absorption requirement by increasing the number of sheets stacked together.

In another embodiment the invention relates to radiation shielding composition comprising soft lead for transporting radioactive material or nuclear waste or for medical uses wherein; the said radiation shielding composition is in the form of sheet comprising thermo conductive metal sheet and insulator material sheet sandwiched between top and bottom layers of soft lead sheets.

In another embodiment the invention relates to radiation shielding composition comprising soft lead for transporting radioactive material or nuclear waste or for medical uses wherein; each 100 g sheet of radiation shielding composition of present invention comprises 10-20% soft lead, 40-50% thermo conductive metal and 35 - 45% insulating material. In one preferred embodiment the invention relates to radiation shielding composition comprising soft lead for transporting radioactive material or nuclear waste or for medical uses wherein; said radiation shielding product may comprises of storage container or a box or a bag for storage or transportation of nuclear waste or other radiation emitting sources.

In another embodiment the invention relates to radiation shielding composition comprising soft lead for transporting radioactive material or nuclear waste or for medical uses wherein; said radiation shielding sheets stack together to acquire required thickness for the final product.

Fig.2 & Fig.3 illustrates the comparison between conventional lead shielding material and radiation shielding composition comprising soft lead of present invention with the help of time dependant counts.

Fig 2 shows a comparison between conventional Lead as a radiation shielding material and the radiation shielding composition of present invention after 20 minutes of exposure to radiation source Barium- 133 by scintillation spectroscopy technique.

The radiation passes through the rate is denoted as count.

From the Fig. 2 it is clear that both shielding materials show nearly equal counts. This means that shielding composition of present invention is as effective as conventional lead material but the density of shielding material of present invention is very low as compared to existing Lead shield which reduces the cost of material, decreases its side effects as well as toxicity and increases recyclability. The thickness of radiation shielding composition of present invention is in the range of 1.5 cm to 2.5 cm which is half of the conventional radiation shielding products and hence increases flexibility, mold ability, portability and recyclability of product.

The radiation shielding composition of present invention comprising soft lead, which is the purest form of Lead (Pb) metal (lead that has been put through the process of softening) containing virtually no impurities other than the precious metals and hence increases the recyclability of the product.

Fig. 3 and Fig.4 gives the comparison between conventional Lead shield and shielding composition of present invention after irradiation exposure at different time intervals to Co-60 source by scintillation spectroscopy technique.

Fig. 3 explains the results obtained for conventional Lead shield by scintillation spectroscopy technique. The radiation source used is Co-60 and the counts at the time interval of 5, 10, 15 & 20 are observed.

Fig. 4 explains the results obtained for shielding material of present invention (SM-7) by scintillation spectroscopy technique. The radiation source used is Co- 60 and the counts at the time interval of 5, 10, 15 & 20 are observed.

Both shielding materials show nearly equal counts. This means that shielding composition of present invention is as effective as conventional Lead material but the density of shielding material of present invention is very low as compared to existing Lead shield which reduces the cost of material, decreases its side effects/toxicity and increases recyclability. The used radiation sources are the type of LLW (low level radiation waste) and ILW (intermediate level radiation waste). For HLW (high level radiation waste) need to incorporate rubber cement and or concrete for additional protection.

In yet another embodiment, the invention relates to radiation shielding composition comprising soft lead for transporting radioactive material or nuclear waste or for medical uses wherein; the process of preparation of said radiation shielding composition is also disclosed.

The process of preparation of said radiation shielding composition comprising the steps of; heating the raw metal sheets of soft lead and a thermo conductive metal and an insulating material to produce thin metal foil by using industrial hammer so as to achieve desire shape; combining thermo conductive metal foil of desired density and thickness and insulating material with desired density and thickness with soft lead sheet in such a way that both thermo conductive metal foil and insulator foil are sandwiched between top and bottom layer of soft lead sheets; applying industrial glue for structural stability and molding the material into a product with desired shape and size.

In one preferred embodiment of the present invention, the radiation shielding composition is in the form of container for storing materials that emit radiation such as gamma rays and neutrons.

The selection of desired thermo conductive metals and insulators is depend upon basic parameters such as weight, density, molding ability, recyclability, availability and cost effectiveness.

In one embodiment the invention relates to radiation shielding composition comprising soft lead for transporting radioactive material or nuclear waste or for medical uses wherein; said radiation shielding composition of present invention is capable of shielding high intensity radiations such as Gamma radiation upto 1330 KeV where conventional shielding materials are unable to shield.

In yet another embodiment the invention relates to radiation shielding composition comprising soft lead for transporting radioactive material or nuclear waste or for medical uses wherein; the radiation shielding composition of present invention is used in the field of transportation of radioactive material or nuclear waste or medical use or storage.

The advantages of present invention are;

Present radiation shielding composition is light weight

Effective for shielding high intensity radiations where conventional shielding materials are unable to shield

Cost effective since the composition comprises soft lead

Can be mold into product of desired size or shape as per requirement Less toxic

Recyclable

Claims

Claims I claim

1. A radiation shielding composition for shielding harmful radiations from nuclear waste or radioactive material comprising; a soft lead in 10-20 wt%, a thermo conductive metal in 40-50 wt% and an insulating material in 35-45 wt%,

wherein, said thermo conductive metal sheet and said insulating material sheet are arranged alternatively and sandwiched between soft lead sheets from both the ends to form a stacked sheet structure.

2. The radiation shielding composition for shielding harmful radiations from nuclear waste or radioactive material as claimed in claim 1, further comprising a binding material or a cement coating or a combination thereof for more efficiency.

3. The radiation shielding composition for shielding harmful radiations from nuclear waste or radioactive material as claimed in claim 1; wherein, said thermo conductive metal is selected from the group consisting of Aluminum, Brass, Tungsten or metal alloy or other thermally conductive metal having density greater than or equal to 2.5 g/cm3.

4. The radiation shielding composition for shielding harmful radiations from nuclear waste or radioactive material as claimed in claim 1; wherein, said insulating material is a synthetic polymer or a combination thereof wherein; the minimum density is greater than or equal to 2 g/cm .

5. The radiation shielding composition for shielding harmful radiations from nuclear waste or radioactive material as claimed in claim 1; wherein, the density of the composition is greater than or equal to 11.5 g/cm .

6. The radiation shielding composition for shielding harmful radiations from nuclear waste or radioactive material as claimed in claim 1; wherein, said composition is flexible to form a product of any shape and size, recyclable and less toxic.

7. The radiation shielding composition for shielding harmful radiations from nuclear waste or radioactive material as claimed in claim 1; said composition is in the form of sheets stacked together to form a radiation shielding product of desired shape and size.

8. A radiation shielding article for storing or transporting radioactive material or nuclear waste comprising,

a thermo conductive metal sheets of thermally conductive metal having density greater than or equal to 2.5 g/cm3,

an insulating material sheets of synthetic polymer or a combination thereof having minimum density 2 g/cm ,

and a soft lead sheets,

wherein; said thermo conductive metal sheets and insulating material sheets are arranged alternatively with each other and sandwiched between soft lead sheets from both the ends so as to form a stacked layer of sheets in the article.

9. A process for making a composition for shielding harmful radiations from nuclear waste or radioactive material as claimed in claim 1, wherein; said process comprising the steps of;

heating the raw sheets of soft lead, a thermo conductive metal and an insulating material to produce thin metal foil by using industrial hammer so as to achieve desire shape;

combining thermo conductive metal foil of desired density and thickness and insulating material with desired density and thickness with soft lead sheet in such a way that both thermo conductive metal foil and insulator foil are sandwiched between top and bottom layer of soft lead sheets; dapplying industrial glue for structural stability and molding the material into a product with desired shape and size.