When Is the Contamination Limit Zero? Table 2 Explained

Who this page is for, and what it answers

A glove contaminated with alpha has no permitted level. Its limit is nil, in other words zero. This is the strictest entry in the tables of decision 3 of 2007. This page explains the table that this zero comes from.

Four words are needed on this page. A material capable of transfer is one that is carried and moved, such as a glove, a shoe or furniture. A fixed material is one that stays where it is, such as a floor or a bolted bench. The becquerel is a unit of radioactive activity, and a microcurie is a millionth of a curie, so a table cell gives the figure in microcuries and then its becquerel equivalent. There are four radiotoxicity groups; they are a precondition for reading the two alpha rows for fixed materials, and they are explained on a separate page in this batch.

The table is table 2 in article 10 of the instructions. Its title names the upper contamination limits allowed according to the nature of the materials. It does not divide by place as the first table does. It divides by the nature of the material: transferable or fixed.

The scope of the table is stated at its head: laboratory floors, tools, equipment, and things that can be carried and moved. Furniture, gloves, shoes and clothing are given as examples.

The most important caution: zero here does not mean an impossible reading. It means that any alpha contamination on something that transfers is not permitted. A small reading is not accepted under this row, and what follows from that is not in this place.

The difference between this table and the first is a difference of question. The first asks where the reading was taken. This one asks what it was taken on. A reading may fall under both headings at once. Then both rows are read and the stricter is applied.

Applying the stricter rule where both headings meet is our reading, not a provision of the decision. The text does not say what happens when they meet. We regard it as what caution requires, and we attribute it to ourselves.

The rows of the table as the decision states them

The first row covers materials capable of transfer with alpha contamination, and sets the limit at nil, in other words zero. The wording is explicit in its negation. This row is read only against alpha contamination.

The second row covers fixed materials with group one alpha contamination. Its limit is the same exponent that table 1 gives for group one alpha, with a written equivalent of 0.37 becquerels per square centimetre.

The third row covers fixed materials with alpha contamination from groups two to four. Its written equivalent is 3.7 becquerels per square centimetre. The last three groups are less radiotoxic than the first, so their limit is higher. Clause 1 of article 1 gives alpha 0.37 with no split by group, so this row is a place of divergence from the clause, just as in table 1. We do not settle it on one figure, and it is set out on the controlled-area limits page in this batch.

The fourth and last row covers all materials with beta and gamma contamination. The exponent written for it is ten to the minus four microcuries per square centimetre, the same exponent as the row above.

Here is a transcription point that we hold in reserve and build nothing on. The transcribed text writes a becquerel equivalent beside this exponent. That written equivalent conflicts with the arithmetic of the other tables in the same decision. We choose neither figure and we do not correct the text. The exponent is what we transcribe.

What falls outside this table

Table 2 does not deal with skin. Skin is a row in table 1, not in this one. We do not move a figure from one table into the other.

It does not deal with calculating the rate by area. That is table 3 in article 11, which has its own page. The limit is one thing; the area it is calculated over is another.

This table gives nothing but the limit. What follows an exceedance is not in this place. And we do not say what the places we have not read contain.

The table does not deal with the method of removal. The methods of removal sit in other clauses of article 1, belonging to a later batch in this series. We neither impose them here nor explain them.

The table does not deal with what to do when an incident occurs in a laboratory. That sits in another article of the instructions, in a later batch. Anyone looking to this page for an emergency plan will not find one.

Table 2 restated, with its values transcribed

The table below gathers the four rows of table 2, and its first row is where the zero sits. Take it up when you classify, not on a first reading.

The alpha row for groups two to four sits above the clause 1 figure, which is the divergence set out in the rows section, so compliance is not declared on a table figure alone. The cell in the last row carries the exponent alone, together with a note that the written equivalent conflicts with the arithmetic of the other tables. That is the reservation itself, written where it belongs.

A worked case, and four practical steps

Suppose a glove that has been used in a laboratory. The survey shows alpha contamination on it at 0.05 becquerels per square centimetre. Table 3 gives no row for gloves, so the area to calculate over is a point we see as open. A glove is a transferable item, so its limit is zero. The reading is therefore over the limit however small. Had the contamination been on a bolted bench and from group one, the limit would have been 0.37 in both places and the reading would be below it. For groups two to four the limit is a place of divergence between the clause and the table, 0.37 in the clause and 3.7 in the table, and the reading is below both figures. In training we work to the stricter figure, 0.37, which is our reading and not a provision of the decision.

Step one: classify the item first, transferable or fixed. The classification is what selects the row you read.

Step two: establish the type of emitter, alpha or beta and gamma. If it is alpha, establish its group.

Step three: first satisfy yourself that the reading is a real reading and not instrument noise; that is a technical caution of ours, not a condition in the text. Then do not accept a small alpha reading on something that transfers, because the limit is zero. The reading is an exceedance to be raised with the licence holder and his protection officer, and they decide the handling under the relevant provisions.

Step four: document the classification, not the reading alone. Whoever reads your report a year later needs to know why that row was applied. We train people to record that classification, and the classification itself stays the licence holder's work.

Questions people ask

Notes on transcription and reading

This table contains the first of the transcription points we hold in reserve in this series. The reason is arithmetic, not linguistic: the same exponent is matched with a different figure in table 1. Either the equivalent is a transcription error, or the exponent is. We do not decide.

Our rule in such a case is to transcribe what is beyond doubt, and to declare what is doubtful as doubtful. The doubtful figure does not enter a table and no rule is built on it.

Something the table leaves open: the table does not define what is capable of transfer. It states no test for distinguishing it. This has not been put to the competent authority, and we report no view of theirs on it.

What the institute offers, its limits, and the reference

This page is about contamination limits by the nature of the material. The institute trains people to classify items and to read the right row.

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. Location: table 2 in article 10 of the attached instructions. 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.