Replies to LegCo questions
LCQ7: Tritium exit sign
Following is a question by the Hon Albert Ho and a written reply by the
Secretary for Food and Health, Dr Ko Wing-man, in the Legislative Council today
(June 1):
Question:
Under the Radiation Ordinance (Cap 303), possession or use of tritium
self-luminous exit signs (TES) requires a licence issued by the Radiation Board
of Hong Kong (RBHK) unless an exemption has been granted. In reply to my
question at the Council meeting of March 27, 2013, the Government advised that
the United States Environmental Protection Agency (USEPA) had stated that TES
were potentially hazardous and RBHK's licensing policy on "the justified use of
tritium exit signs where the use of electrical power is not possible or feasible
is well echoed by the USEPA". Nevertheless, I have learnt that there are other
views that the Government should pay attention to. For instance, the
International Atomic Energy Agency (IAEA) has classified TES containing up to
740 GBq. of gaseous tritium as category 5 (i.e. "most unlikely to be dangerous
to the person"). Also, IAEA’s guidelines on "Exemption from Regulatory Control
of Goods Containing Small Amounts of Radioactive Material" have stated that (i)
regarding TES, "the regulatory body should only concern itself with the risk
from the tritium in normal use, in accidental conditions and following disposal"
and it is "not within its competence to assess the more conventional risks such
as those arising from broken glass following an accident or to take decisions on
the basis of these risks", (ii) the justification relating to the use being a
net benefit from the device concerned is "normally applied to a type of practice
and therefore need not be applied to each and every application for
authorisation or candidate for exemption... [and] the existence of a technical
standard for a particular type of practice may often be taken to indicate that
the type of practice is justified", (iii) "[t]he benefits from a practice could
therefore be of many different types, not just possible saving of life or
prevention of injury or illness, but also technical benefits, prevention of
property damage, improvements in security or simply improvement in the quality
of life", and (iv) the requirement for justification relates to there “being a
net benefit from the particular type of device [while] to search for the best of
all the available alternatives is a task that is beyond the responsibility of
the regulatory body". Besides, the United States Nuclear Regulatory Commission
(USNRC) has stated that (i) TES "serve an important safety function by marking
exits to be used during power outages and emergencies", (ii) TES "pose little or
no threat to public health and safety or security", and (iii) TES "are designed
to be inherently safe so they can be used without the need for radiation
training" and facilities do not need a specific licence to use TES. In this
connection, will the Government inform this Council:
(1) whether RBHK has considered the aforesaid views and practices of IAEA and
USNRC; if so, of the details; if not, the reasons for that;
(2) as I have been told that since there is hardly any building requiring exit
signs for emergency evacuation of its occupants is not supplied with electrical
power, RBHK's current licensing policy on the justified use of TES where the use
of electrical power is not possible or feasible is tantamount to a total ban on
TES, of the types of buildings or premises that would be allowed to install TES
under such policy; and
(3) of the buildings in Hong Kong in respect of which RBHK has issued licences
for the installation of TES therein and the relevant details; if there is no
such building, of the reasons for that?
Reply:
President,
(1) Tritium gas is a radioactive substance. Tritium exit sign is a self-luminous
product illuminated by gaseous tritium light sources for the indication of the
location of fire emergency exit. Currently, the Radiation Board (the Board)
requires the use of tritium exit signs to be justified by the potential benefit
of saving life and where the use of electrical power is not possible or
feasible.
In formulating the policy on use of tritium exit signs, the Board considered
that while the potential benefit of tritium signs is saving of life by providing
illuminated indication of emergency egress routes in indoor premises, there
exist the potential harm of increased risk of internal radiation exposure of the
uninformed public by the leakage of tritium during their normal use, and
potential internal radiation exposure of the public on breaking of signs because
of accidents, acts of vandalism and losses or improper disposals. Another
consideration is the availability of other types of luminaries that do not
contain radioactive substances such as light-emitting diode and compact
fluorescent lamp type luminaries. As the licensing authority with the duty to
protect public health from the potential deleterious effects of ionising
radiations, the Board has properly considered the availability of these
alternatives in the overall balance between the risks and benefits of using
tritium luminaries. Among other considerations, the Board's policy has also made
reference to the regulatory practices in different countries and views from
international organisations.
Apart from the United States Environmental Protection Agency (USEPA), the Board
is also aware and has duly considered the discussion and views on the safety of
tritium signs by the International Atomic Energy Agency (IAEA) and the United
States Nuclear Regulatory Commission (USNRC) mentioned in the question. A
consolidated summary is as follows:
(a) The classification of tritium signs as "most unlikely to be dangerous to the
person" (i.e. Category 5) is based on the Safety Guide on "Categorisation of
Radioactive Sources" (Safety Guide) issued by IAEA in 2005. However, the Safety
Guide also pointed out that even if the radioactive sources (including tritium)
are at the lower end of the categorisation system, these sources could give rise
to doses in excess of the dose limits if not properly controlled, and therefore
it is still recommended to be kept under appropriate regulatory control.
Besides, the categorisation is only based on the immediate injuries that could
be caused by a radioactive source when effective control on the source cannot be
exercised. Possible delayed health effects on human body, for example, radiation
induced cancers which is a secondary consideration, are not taken into account
(Note). In this respect, the Board has considered that it is not adequate to
solely base its consideration on the above categorisation system of IAEA for
regulating the use of tritium signs.
(b) Besides, although there are opinions from USNRC that the tritium signs pose
little or no threat to public health and safety of security and they are
designed to be inherently safe, past incidents in the United States (US) have
shown that the safety of the signs could be compromised without much difficulty
by tampering leading to the breakage of the tritium tubes inside the signs.
These incidents of damaged signs had resulted in contamination of areas and risk
of radiation exposures to the public.
(c) As for the publication "Exemption from Regulatory Control of Goods
Containing Small Amounts of Radioactive Material", it is a technical document of
IAEA issued in 2012, which aimed to initiate discussion on the issues needed to
be considered in relation to exemption from regulatory control and thus should
not be taken as a guiding principle. In fact, IAEA had issued in 2014 the
General Safety Guide no. GSG-5 "Justification of Practices, Including
Non-Medical Human Imaging" which stated that "alternative methods, not involving
the use of radiation, of achieving the same or similar objectives may exist and
should be taken into account when reaching a decision on justification."
In view of the aforesaid, the Board's policy has indeed taken into account the
international guidelines promulgated by IAEA and the practice on the use of
tritium signs in US including the relevant views of USNRC and USEPA, which are
both legitimate regulatory bodies in US. The present policy of the Board on
controlling the use of tritium signs is consistent with the relevant
international guidelines of IAEA and is commensurate to the potential harms of
tritium signs.
(2) The Board has provided specific guidelines about its policy on the use of
tritium signs including the requirement that "supply of electricity is not
possible or feasible". The guidelines are available in the website of the Board.
It provides that the Board will carefully consider all factors based on the
Principle of Justification, among which the possibility or feasibility of
electrical power supply is one of the considerations. In doing so, the Board
will consider relevant factors such as building structural constraints on
installing electrical wiring around the emergency exit; difficulty in using
electricity due to special circumstances in places like tunnels, mines and
quarries or locations where inflammable or explosive gas is present.
(3) Persons applying for use of tritium signs should provide reasons and
necessary information, with supporting documentation to the Board, of the use of
tritium signs for the proposed location of installation. The Board will consider
each application based on the information provided against the Board's policy on
use of tritium exit signs. Some approved applications in the past include the
installation of tritium signs at premises with the possible presence of
inflammable vapour and the installation of tritium signs at moveable partitions.
These cases had provided sufficient evidence on substantiating the difficulty in
the supply of electricity because of the risk of ignition of the inflammable
vapour or of the structural constraint on installing electrical wiring
respectively.
Note: Please refer to Appendix II, in pages 30 and 33 of the IAEA Safety Guide
No. RS-G-1.9 on "Categorisation of Radioactive Sources".
Ends/Wednesday, June 1, 2016
Issued at HKT 16:39
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