The Four Radiotoxicity Groups, and How to Read Them

Who this page is for, and what it answers

The alpha column in table 1 of the instructions in decision 3 of 2007 is split in two. One part is for group one, the other for groups two to four. Where do these groups come from? From article 3 of the instructions, which this page explains.

Three words are needed before the article. Radiotoxicity is the severity of harm a material does per unit of radioactive activity, not the severity of harm done by a quantity. A group is one of four classes into which article 3 divides radioactive materials. And peak energy is the highest energy a beta particle reaches, measured in kilo electron volts, written keV. It is a separate criterion and does not follow the groups.

Radiotoxicity in this place is a property of the material, not of the dose. The opening of the article divides radioactive materials by radiotoxicity per unit of activity into four groups. The criterion is radiotoxicity per unit of activity. There are four groups, and that is stated in terms.

The page is for the protection officer reading a survey report who needs to know which column to compare it against. It is for the trainer explaining the two tables. And it is for whoever keeps the register of radioactive materials in a laboratory.

The most important caution: this page does not transcribe a single nuclide symbol. The lists of article 3 in the transcribed text contain places that are likely transcription errors. We hold them all in reserve until the page image is checked.

What this reservation means in practice: do not take your material's classification from this page. Take it from the decision itself. This page teaches you how to read the classification and its effect, not what the classification of a particular material is.

Radiotoxicity per unit of activity is a criterion that does not follow the quantity of material. At equal activity, a group one material is more severe than a group four one. This is our explanation of what the phrase means; the text says no more than its wording.

The four groups and their headings

The first group is headed as very high radiotoxicity. It is the most radiotoxic of the four. In tables 1 and 2 it has its own column and its own row.

The second group is headed as high radiotoxicity. The third is medium radiotoxicity. The fourth is low radiotoxicity. These three are read together in a single column in table 1.

Why are the three grouped into one column? Because the table gives group one a single limit, and gives everything else a limit ten times higher. The division is practical rather than graded. This describes what the table does; it is not a reason given in the text.

The footnote to table 1 ties the table to this article in terms. It states that the groups of elements follow the degree of toxicity set out in article 3. So the table does not stand apart from the classification, nor the classification from the table.

What falls outside this article

Article 3 is a classification, not a limit. No acceptance or rejection figure is read from its opening or from its group headings. The figures are in tables 1 and 2, each with its own page.

This article is a classification by radiotoxicity. We do not speak about a classification in another instrument, and we do not reason from this one to that.

Neither the opening of article 3 nor the headings of its groups deal with dose limits for workers. What we have not read of its lists, we do not judge.

The opening of article 3 makes the criterion radiotoxicity per unit of radioactive activity. What we have not read of its lists, we do not judge.

Neither the opening of article 3 nor the headings of its groups mention the chemical or physical state of the material. That sits in other clauses of article 1, belonging to a later batch.

The four groups and their effect in the two tables

The table below gathers the four groups and the effect of each in the two tables. Read it once you know your material's group.

The last column in our table is our reading of the effect of the classification in the two tables. The headings are taken from the article itself. The table carries no nuclide symbol at all.

A worked case, and four practical steps

Suppose free, that is loose, alpha contamination on a laboratory floor in a controlled area. Table 3 puts the row for floors, walls and ceilings at 1000 square centimetres for each such area taken on its own. The reading is 2 becquerels per square centimetre. If the material belongs to group one, the limit is 0.37 in both places and the reading is over it. If it belongs to groups two to four, there is a divergence between the two places: clause 1 gives 0.37 and table 1 gives 3.7, a factor of ten. So a reading of 2 is over the clause and under the table. We do not correct the text and we do not reconcile the two places. In training we work to the stricter figure, 0.37, which is our reading, and we think the licence holder should take it up with the competent authority. The laboratory floor also falls within the scope of table 2 as a fixed material, where the alpha exponent is the same exponent. Both headings are read and the stricter is applied, which is our reading.

Step one: know your material by name before reading a column. A figure without a classification cannot be judged.

Step two: check the list in the decision itself, not in a summary. We do not transcribe the nuclide symbols here, and we have said why.

Step three: record the group in your register of radioactive materials. A register without the group forces every reader to classify again.

Step four: if you cannot find your material in the lists, ask the competent authority. Do not reason by analogy to a similar material yourself. We train people to read the classification, and the asking itself stays the licence holder's work. Any exceedance is raised with him and with his protection officer, and they decide the handling under the relevant provisions.

Questions people ask

Notes on transcription and reading

This article contains the third of the transcription points we hold in reserve in this series. The reservation here is wider than the others: the whole symbol lists. The opening of the article and the group headings, however, are transcribed as worded and carry no reservation.

The rule we applied is that what is stated in terms is stated. The number of groups is four, which is stated, so we state it. What would be derived from a doubtful list is not stated. So the number of nuclides is not stated.

One open point in the text: neither the opening of article 3 nor the headings of its groups say how a nuclide absent from the four lists is classified. No view of the competent authority is reported, because we have not put the question to them.

What the institute offers, its limits, and the reference

This page is about the four radiotoxicity groups. The institute trains people to read the classification alongside the two tables and to record it in the materials register.

ALDuha Institute for Training and Environmental Consulting works in training and consulting. Its training is licensed. It does not run a laboratory analysis service for smears. It does not calibrate radiation survey instruments. It does not test equipment or certify it as safe. It does not carry out decontamination in a laboratory or on a site.

Surveying and decontamination are the work of the licence holder and his radiation protection officer. Where outside expertise is needed, it is arranged through specialist partners. We train people to read, measure and document. We do not do the work in place of the licence holder.

Neither our training nor our consulting gives any undertaking that a licence will be issued. There is no undertaking about how long an approval will take. That decision belongs to the competent authority alone.

Reference: decision 3 of 2007 of the chairman of the Supreme Council for the Environment and Natural Reserves, on radioactive decontamination instructions, issued on the recommendation of the radiation protection committee. Location: article 3 of the attached instructions, together with the footnote to table 1. The decision rests on decree law 31 of 2002, in particular its article 17, and on the executive regulation issued by decision 4 of 2003, in particular its article 97.

A note on the names of authorities: the decision was issued by the Supreme Council for the Environment and Natural Reserves. The authority addressed today is the Ministry of Environment and Climate Change, which houses the Radiation Protection Department. The name changed and the duty stands.

This page is an introductory explanation of a published text, and is not a legal opinion. It does not replace reading the decision itself. It does not replace checking with the competent authority.