DE3523873A1 - ANALYTICAL MATERIAL FOR DOSIMETRY IONIZING RAYS - Google Patents

Description

Analytical material for the measurement of ionizing rays

The invention relates to an analytical material on the basis of polyaer foils for dosimetry of systems for Generation of ionizing rays.

In the last few drives there has been a clear increase in the development and use of electron accelerators, X-ray and radiation equipment. These systems are used in various application forums in production and research. The radiation-like treatment of products of different species offers, due to the clear quality gains, which are often achieved without harmful waste products, enormous advantages, which, moreover, are usually only possible using this method can be achieved. The development of the advantageous properties and their constant reproducible setting sets the knowledge of the absorbed dose and its distribution, or, in addition to this information, its constant control ahead of continuous production processes. You can today determine that the structural requirements of powerful irradiation systems were created, so the procedure of a modern radiation technology lies, so is the important field of the measuring problems, so reliable radiation dosing is only inadequate developed.

In the few analytical materials known for this purpose, a wide variety of polyacrylic foils are used, which are also used May contain dyes (Keindl, K. and Graul, E. H. "Strahlencheaie basic technology and application" Hfithig- Verlag Heidelberg 1967; Boag. O.W. Radiation Res. 9 (1958), 559). The dye molecule is destroyed by the action of e.g. electron beams, so that the loss of dye dense statements about the radiation dose allowed. (CH-PS 491 394, DD-PS 124 082). Such materials have been e.g.

using the dye Dlnethoxydiphenyl-bls-ezo-8-aaino-l-naphthol-5,7-disulfosiure and the polyaeren cellulose

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acetate produced (Feterpaker, SA, Patnie SP «r ^ o o 7 q Angew, Makroaol. Che». 90 (1980), 69-81). The non-uniformity of the distribution of colorants in polymers and the inadequate physical properties of these films did not allow them to be used widely. Higher doses of radiation could not be measured because the damage to the film that occurred in this way led to it being unusable.

Furthermore, cellulose acetate follies have been described which do not contain any dyes. Their properties are such that they are unsatisfactory for higher radiation doses, for example when used with high-performance accelerators. These foils change their geometry significantly, and the radiation exposure destroys the polymer structure, which results in easily brittle and therefore unusable foils. This significant embrittlement should be avoided by using polyethylene films (Grünewald, Th. Rumpf, G. Atompraxis IjL (1965) 2, 95-98; Kügler, I. et al. Atomenergie 4 (1959) 1. 23).
But these foils cannot be used for very high radiation doses either. In addition, these foils have insufficient surface hardness, as a result of which mechanical damage can occur during the measuring process. Other oosineter foils cannot be used in daylight, as this would result in premature destruction or activation of the detection aden, a handling requirement that opposes universal use. On this basis, for example, polyamide disimeter foils are produced which contain radiochromic aeinotriphenyl derivatives as the coloring substance (DD-PS 125 045). In addition to the disadvantages already described, it can only be used in the range from 0 to 300 kGy. Another disadvantage of most of the foils known to date is their excessive sensitivity to moisture, which results in changes in the geometry and thus in the measurement accuracy due to the swelling processes taking place.

In U3-PS 3 450 878 a dosimetry method is described, in which the dose measurement by determining changes in viscosity of irradiated polyester films and comparing them with a

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Calibration curve takes place. "Disadvantageous with this jib analytical» **: »EIW O ' • The bit entails a considerable amount of work associated with the viscosity determination and the bit entails a relatively large error contaminated viscosity measurement of irradiated polyether filaments; there Under the influence of high-energy radiation, in addition to the chain structure, the polymer base body is formed into more functional ones Groups takes place that lead to inter- or «intra-molecular Interactions are capable and can thus influence the Viekositfitewert ^ undefined At the moment, the world has reached a level with significant rates of increase in the construction and use of high-performance radiation systems for higher radiation dosing devices Little usable foil diameters due to lack of suitable ones analytical staff are available.

The aim of the invention is to create suitable analytical materials for the dosimetry of electron and beta as well as X-ray and gamma radiation up to energy doses of 2,500 kGy. The object of the invention is the manufacture and type Use of OosiBeter foils for dosing irradiation systems, whereby these foils can be used over the broad field of the most varied of energy needs and in the measurement processes their geometry, their visual transparency and their Maintain good physical and mechanical properties should.

According to the invention, the object is achieved in that analytical material for oosiaetry of ionizing rays euf the Basis of polyeer foils made from polyethylene terephthalate foils bit a density of 1.393 to 1.397 g / cB, a film fiber of 99 t IM *, a tensile strength of 200 ί 10 N / bb, an elongation of 100 £ 10 %, a crystal initiation of 55 * 1.5 % and a Theraoachruapfung ί 1.5 % accessible measuring range from O to 2 500 kGy. In doing so, these foils lose not their visual transparency, and their geoetry remains unchanged «This advantage of the good geoetry stability remains also get different humidity and tea temperatures "

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O ₀ Since there are no essential restrictive conditions for use in β ©. Further advantages are the very good surface strength, which prevents entanglement due to mechanical influences. Even in the range from 300 to 2,500 kGy, which was previously not evaluable with dosimeter foils, the advantages described are retained. It is also surprising that the films produced according to the strict technological and chemical regime largely retain their good physical and mechanical characteristics and do not become brittle as a result of the radiation exposure. The films can be evaluated by changing their permeability, which is advantageously measured at 340 nm.

It is also unexpected that the changes obtained in the permeability of the films, as a result of the irradiation, occur different climatic conditions remain constant and no time-dependent shift of the measured values occurs. This enables problem-free evaluation even after the most varied of times. These foils can be archived without any problems and show unchanged measured values even after months, a considerable one Advantage in production processes and measurements that take place over longer periods of time. There are other advantages in the fact that no degradation products are formed even with the high doses of radiation that could, for example, contaminate the film and de; it influence the evaluation. Another An important advantage of the films according to the invention is their universal evaluability on a wide variety of photometers, due to the measuring wavelength and the problem-free Preparation of the test samples, e.g. by cutting.

The invention is explained in more detail below with the aid of examples.

Examples of execution example 1

A polyethylene terephthalate film is produced, the physical parameters of which are given in Table 1.

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Thermal shrinkage % ' in both directions

Γ ^ parameter Who t

eo density g / c »1.395

£ J Thick Aim 99

¹ ^ tensile strength N / mm ² 204.5

Elongation % 108

Crystallinity % 55.8

i 0.8 in both

x) determined after 30 minutes at 150 ⁰ C.

Example 2

A polyethylene terephthalate produced according to Example 1 is cut according to the irradiation zone of an electron accelerator, stationary in the radiation field arranged and during an irradiation time of 10 sec.

¹ ^ at a dose rate in the measuring plane of 8.3 kGy / sec, irradiated. The exact dose rate distribution in the entire radiation field of the electron accelerator is determined by simply measuring the transmission value differences point by point. For the determination, test pieces are punched or cut out of the film. Table 2 shows the dose rate distribution of a radiation field of 2.0 · 0.5 m. The numerical values document the relative dose at the measuring point.
The high uniformity of the film allows larger radiation fields to be analyzed without any problems with just one film of the appropriate size.

Example 3

Pieces of 2 × 2 cm are cut from the dosimeter film according to the invention according to Example 1 and a package of 120 film pieces lying on top of one another is formed from them. After the brief irradiation (irradiation time 4 sec., Dose rate in the measuring plane of 8.3 kGy / sec.) Of this film package, the electron energy-dependent deep dose distribution is determined from the transmission value differences of the individual films.

Table 3 and Fig. Ι contain the results of an irradiation system at 3 MeV.

Example 4

Measurement samples are cut from a polyethylene terephthalate film produced and irradiated according to Example 2 and exposed to different humidities and temperatures. In the range of up to 95 % relative humidity and 100 ^° C., no changes in the measurement results are observed. Further film samples are measured within 6 months at intervals of 10 days. These results also show no deviation from the words determined in Example 2. This confirms the excellent properties of the dosimeter film.

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Table 3 '^;

Determined deep endo ice distribution at 3 MeV

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I g / - ² relative depths 0 ⁰ T * 1000 60.14 2000 72.78 3000 83.93 4000 92.61 5000 98.11 6000 100.00 7000 98.65 8000 94.11 9000 87.07 10,000 78.07 11,000 67.40 12000 55.13 13000 41.58 14000 27.87 15000 15.82 16000 6.98 17,000 1.91 0.80

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Claims (1)

Claim Analytical material for dosimetry of ionizing
Rays on the basis of polymer films «characterized in that it consists of polyethylene terephthalate films with a density of 1.393 to
1.397 g / cm, a film thickness of 99 ί lyUm, a tensile strength of 200 1 10 N / mm * ", an elongation of 100 * 10, a crystallinity of 55 t 1.5% and a thereo shrinkage <1.5 % .