How can you tell if a package has
undergone irradiation?

Every package that undergoes irradiation at Sor-Van is affixed with a sticker and a chemical indicator that changes color from yellow to orange/red (depending on the dose) following irradiation. The chemical indicator's color change does not indicate the actual dose, but serves as a basic indication that the package has been irradiated.
 

What effect does split irradiation has on sterilization quality?

When irradiation does not occur in a single process, for example, when an additional session is required in order to complete or double the dose. According to radiation guidelines (ISO 11137, paragraph A.10.10), manufacturers should distinguish between products that support microbial growth from those who does not support microbial growth. Products based on polymers or metals do not support microbial growth, whereas products containing organic material provide nutrients that might support microorganisms' growth. With regard to the first group, there is no significance to stopping the irradiation sequence, and no special activity is required besides documenting the matter. With regard to the second group, the maximum time interval between irradiations, as well as the products' storage conditions while waiting for the supplementary irradiation, must be defined. When preparing irradiation that is supplementary to the first dose, it is necessary to ensure that the maximum accumulated dose does not exceed the maximum permitted dose to product.

Do products which were processed by gamma radiation emit radiation afterwards?
 

Products that have been irradiated with gamma or beta rays become radioactive only under the following conditions: 

Use of particles with an activation level over 10 MeV or the insertion of active radioactive material into a neutral substance.

During gamma irradiation, the energy of the particles does not exceed 1.33 MeV, which is significantly lower than the activation level. It is therefore impossible that the irradiated product will become radioactive and emit radiation. During the process, the product's packaging does not come into contact with the radiation source, so there is no risk that any of the radiation source will enter the product making it radioactive itself. Gamma irradiation technology is the leading method of sterilization for medical products, and is a process that is carried out according to international ISO 11137 standards.

 

How are dosimeters in the
gamma radiation facility calibrated?

The radiation doses for gamma radiation are determined by the Harwell's Red Perspex 4034 dosimeter. Every new batch of dosimeters is being calibrated separately, in cooperation with RISO, a certified Denmark laboratory. The calibration process is based on very sensitive radiation master dosimeters, which are irradiated together with the new batch of perspex dosimeters requiring calibration in at least five different radiation doses throughout the expected dosage range. Following irradiation, perspex dosimeters respond with opacity change, which is calibrated to the laboratory measured dose. A conversion table is then constructed based on these findings that determines radiation doses as a function of dosimeter color change response. The conversion table is then recorded along with the dosimeter information for ongoing use. It becomes the basis for determining radiation doses until this batch of dosimeters is no longer used.

How does exposure time of products or process cycle time is determined [cobalt-60 facility]?
 

Facility's cycle time is directly linked to facility's radioactive material activity. Radioactivity of materials decreases at a regular rate over time (this process is called radioactive decay). The radioactive material used in the facility has a decay rate of 1% per month. Whenever new radioactive material is introduced to the facility (which generally occurs approximately once a year), Nordion, the world's sole supplier of Cobalt-60, provides an updated table for determining the exposure time required for different products. This table is calculated according to a minimum absorbable dose of 25 KGy. The table determines cycle times based on the following data: product density, calendar date, and the radioactive material's exact activity for that date. 

The greater the density, the longer exposure time required for the same dose level. The exposure time for radiation in the 25-40 KGy category is determined by the calendar date and a density of 0.24 [g/cm2], which is considered the maximum density for irradiating products in this category. Updated lifecycles are determined based on the table at approximately one-month intervals.

How sterilization expiry date is determined?
 

According to ISO standards, products are considered sterile at the level of SAL 10-6 if in a sample of a million items, a maximum of one bacterium is found. The validation of a product sterility is determined by many factors, including: the initial bioburden, the quality of packaging and whether it is sealed against bacteria, the nature of products with regard to microbial growth, and so on. The customer is responsible for validating the required dose range for his products sterility and function.

 

Bear in mind that after all the germs have been eradicated and it has been established that the packaging has not been damaged in any way, there is no possibility that germs will be found in the packaging, as nothing can come from nothing. 

 

Sor-Van's responsibility is to provide irradiation within the predefined dose range, and SorVan is not in any way responsible for the variety of factors that may affect the validity of the sterilization.