2. Is it contingency or just sensible radiation protection practice?

Source: Ionactive Resource

Is it contingency or just sensible radiation protection practice?

Scenario. HSE attend site and inspect the use of an x-ray machine for screening freight. The machine is larger than your average airport ‘carry on’ baggage machine – it has a roller bed into and out of the enclosure and can take a whole pellet of goods. Most of the unit has fixed radiation shielding, and each end is protected by a leaded curtain. Freight is loaded onto the rollers by a forklift, and then moved via the rollers through the x-ray enclosure. Various radiation safety features are present including active signage (four “x-ray on” warning lights, one on each corner), emergency stops and the ability to lock the unit off so x-rays cannot be generated. Among other documents, local rules, and a radiation risk assessment are present in the area.

The situation

A Notice of Contravention (NoC) and FFI was issued by HSE (see How to use for definition). Three issues were presented. One will be discussed in some detail here, one will be mentioned briefly, and the third can wait until another article.

The basis of point 1 of the NoC was that ‘… Contingency arrangements … the local rules did not include procedures for retrieving stuck items, these should be included in the local rules …’

So – let us look at what was in the contingency section of the local rules.

  1. Procedure for dealing with significant damage to a shielding curtain
  2. Procedure for dealing with damage to the x-ray units fixed shielding
  3. Procedure for dealing with a known or suspect unintended exposure of an employee
  4. Procedure for dealing with fire interaction with the x-ray system
  5. Procedure for dealing with the x-ray unit where x-rays fail to terminate on demand

As you will note – there is not a procedure for retrieving stuck items from inside the x-ray unit.

In the opinion of the Ionactive RPA, retrieving stuck items from inside the X-ray unit should not be a contingency arrangement.

Instead, safely retrieving a stuck item from the x-ray machine should be a specific arrangement within the everyday operation of the unit and specified in the local rules.

In fact, if one looks at the local rules in this scenario then the following will be seen ‘ … Should access to the tunnel be necessary, for example to retrieve trapped freight, the unit must be switched off at the control console, and the x-ray inhibit key removed… ‘

So, perhaps -

  • The regulator did not see this wording in the main body of the local rules; and
  • Did not see a contingency arrangement for retrieval in the contingency section (obviously this is the case)

The NoC asks for retrieval to be placed in the contingency section (i.e. it is missing).

Radiation Protection Adviser comment

We believe this is wrong.

  1. A significant failure of the shielding curtains (for example) is reasonably foreseeable but is not a regular occurrence when screening cargo or freight. Should such a failure occur, the employee should quite rightly look to contingency to control the situation (i.e. switch off and isolate) and then arrange for a repair. They should investigate how the curtain become so badly damaged and look at ways of avoiding such a reoccurrence. This should be recorded in a report and retained for two years (IRR17 – 13). So far so good.
  2. Unlike the shielding curtain example, freight or packages do get stuck in the unit from time to time and this is reasonably foreseeable and does not lead to a radiation accident. It is expected – packages can move, pallets may twist on the rollers etc. The actions taken are those given earlier (shut off, take out inhibit key etc – with one small improvement, see below). Sure, loading the unit correctly will help stop freight getting stuck, but it will happen from time to time. If these actions are included in a contingency plan, then every time they occur will require an investigation, analysis, a report and a record being retained for two years. This does not enhance health and safety – it just adds to paperwork with negligible benefit.

In this scenario the employer accepted the FFI since they decided to agree with the regulator, pay the FFI, and get on with their day job.

[Point 2 of the NoC did suggest that when the x-ray inhibit key is removed it should be placed in a secure location when not in use, and carried by any person who needs to enter the interior of the x-ray system. This is a point well made by the regulator and was accepted].

Further thoughts

We do not believe there is a material breach in Point 1. Suitable wording was in place, and we believe in the right place – not in contingency, but in the specific instructions for operating the x-ray unit correctly and safely. This is a moot point since the NoC was accepted by the employer in this scenario.

A contingency plan is required where a radiation risk assessment (IRR17-8) has determined that a radiation accident is reasonably foreseeable (IRR17-13-1).

A radiation accident is defined as ‘an accident where immediate action would be required to prevent or reduce the exposure to ionising radiation of employees or any other persons’ (IRR-17-2-1).

For the x-ray machine in this scenario, the RPA carried out a dose assessment which is presented in the radiation risk assessment and determined that the dose per pass of an object was about 5 micro Sv (i.e. if an employee were to ride through the machine – clearly a prohibited action). This data is included to present the magnitude of the radiation exposure risk when inside the cabinet. Ionactive believes it is important for all regulators, employers and RPA’s to understand the magnitude of the radiation risk in every specific case. Not all x-ray machines and circumstances are the same.

In considering the above definitions and data, and noting that trapped objects in an x-ray are not unexpected (it happens), then Point 1 of the NoC is not valid and no material breach of IRR17 occurs.

3 years ago the RPA spoke over the phone to a specialist radiation inspector who completely agreed with the above analysis. This was regarding food items getting stuck in food screening x-ray systems in food packing sites. They agreed that there was no radiation accident, and that contingency was in inappropriate. These systems are much smaller than your typical freight screening x-ray unit, but the principle remains the same since it is possible to place hands beyond the curtain (into the Controlled Area) to retrieve stuck objects.

In a future article we will discuss the concept of ‘all singing from the same hymn sheet’.

Mark Ramsay

Radiation Protection Adviser

Physics is really nothing more than a search for ultimate simplicity, but so far all we have is a kind of elegant messiness

– Bill Bryson -