FR2524316A1 - PHOTODECONTAMINATION PROCESS - Google Patents

Abstract

DECONTAMINATION PROCESS: TO PERFORM DECONTAMINATION, AN ADDITIVE CAPABLE OF ABSORBING RADIATION IN A PREDETERMINED FREQUENCY RANGE IS APPLIED TO A CONTAMINANT; THE CONTAMINANT ADDITIVE SYSTEM OBTAINED CAN BE EXPOSED TO HIGH INTENSITY RADIATION WITHIN A PREDETERMINED RANGE OF FREQUENCIES UNTIL DECONTAMINATION IS COMPLETE; THE METHOD IS PARTICULARLY APPLICABLE TO THE REMOVAL OR NEUTRALIZATION OF CONTAMINANTS WHICH DO NOT STRONGLY ABSORB RADIATION FROM EASILY AVAILABLE SOURCES.

Description

The present invention relates to a decontamination process

  tion and more particularly the photoelimination of agents

  chemical warfare and other contaminants.

  The invention relates to the situation in which sur-

  important surfaces are contaminated with one or more chemical warfare agents Currently, there are no safe and economical ways to decontaminate large surfaces contaminated with a wide variety of chemical warfare agents The term "decontamination" as we use it here

  means removal of toxicity, cleaning and other

  very processes by which a chemical agent is removed

  or its harmful properties are neutralized.

  A process for decontaminating these surfaces includes identifying the composition of the chemical weapon and then applying a second chemical agent to neutralize the material.

  chemical weapon This approach poses several problems.

  One of the problems is the time required to analyze the chemical weapon. The time spent increases the exposure of people.

  in the contaminated environment, especially those

  injecting the materials necessary for analysis and a loss of the contaminated installations, whatever their use This problem is aggravated when several chemical weapons have

  have been used and separate analyzes are required.

  A second problem concerns the perfection of decontamination.

  tion It may not be possible to apply an additive that

  tralize or completely eliminate the contaminant Finally, there is the problem of eliminating the more or less neutralized contaminant / additive system from the affected surface and rejection of the residual product. It must be considered that the product

  waste, even if it is not as toxic as the chemical weapon

  mique of origin, can however be nothing less than trivial.

  Another approach to decontamination includes

  the irradiation of a surface with strong radiation

  density, usually at short wavelength The photo-

  decontamination for several specific applications The bre-

  vet US No. 4,208,135 describes a method for eliminating con-

  surface taminants by prior cleaning of the surface and ambient air Then irradiation of the surface with a

  short wave ultraviolet radiation in the presence of oxygen.

  Short-wave ultraviolet radiation is generally O defined by the wavelength range from 1,700 A to 3,000 A. US Patent No. 4,028,030 describes a similar process used

to clean the optical fibers.

  A problem with some chemical weapons and other chemical agents is that they

  strongly absorb radiation only in the re-

  The ultraviolet region of the vacuum pushed below 2000 A. The ultraviolet radiation of the vacuum is strongly absorbed by the air and consequently the irradiation of surfaces with such radiation requires a vacuum chamber However,

  it is generally not practical to place a surface

  before being decontaminated in a vacuum chamber In addition, the ultraviolet radiation of the high vacuum is not produced by economical sources of very intense radiation If a longer wavelength radiation is used, a major portion of the energy radiant enters the weapon

  chemical and can alter or destroy the surface to be decontaminated

  ner So large-scale decontamination of surfaces contaminated with such chemical weapons is not possible

according to known methods.

  One of the aims of the invention is therefore to provide a pro-

  yielded perfected for decontamination that can be applied

  to contaminants that do not strongly absorb the frequencies

  these optics produced by easy radiation sources-

ment available.

  According to the invention, an improved method of decontamination

  mination uses a chemical additive capable of absorbing a

  radiation of wavelength greater than that of ultra-

  vacuum purple Additive can be mixed with contaminated

  or otherwise deposited on and in contact with the contaminant. The combined chemical system is then exposed to

  high intensity radiation of a strong frequency range

  absorbed by the additive until the contaminant

  either destroyed, altered or eliminated by evaporation, decomposed

  tion or in any other way We can use a laser

  or a flashlight to provide strong radiation

  density. The invention, in particular in its preferred embodiment, has significant advantages over

  known approaches to decontamination Acid para-

  aminobenzoic acid (PABA) which is the preferred additive is inexpensive

  safe and so easy to apply on a large scale PABA can be contained in an aerosol or other spray device to be applied

  convenient way to a contaminated surface ray sources-

  preferred are capable of irradiating large surfaces

  due in a relatively short period of time So humans in the contaminated environment are less exposed to weapons

  chemicals and contaminated devices are found faster

  their use The analysis of the contaminant is not generally

  In addition, the additive protects the surface against the potential risk due to irradiation, just as PABA protects human skin against the harmful effects of the sun. The process generally causes the contaminant to break down into harmless constituents which are then safely evaporated with PABA, so that it does not arise

  no problems with subsequent surface cleaning.

  In the case where a contaminant cannot easily be destroyed, altered or eliminated by irradiation because it does not readily absorb radiation from sources easily

  available, a chemical additive can be added to the contaminant

  that is strongly absorbed by radiation from an easily available source The contaminant / additive chemical system obtained can be irradiated with radiation which is absorbed by the additive until decontamination is complete The contaminant can be a chemical deposit or a

  film on a surface or may be in another form.

  The contaminant can be a chemical weapon or any other substance whose elimination, alteration or destruction is necessary. The additive strongly absorbs the radiation characteristic of a predetermined radiation source.

  radiation source can have a narrow spectrum of the fre

  quences such as a laser or a wide range of frequencies

such as a flashlight.

  The additive can be mixed with the contaminant, layered on the contaminant, or otherwise placed so that energy transfer can occur between the additive and the

25243-16

  contaminant Transfer can take place by conduction of heat More; in particular, the radiation absorbed by the additive can be transformed into thermal agitation of the additive Molecular collisions between the additive and the contaminant lead to thermal agitation of the contaminant.

  Other energy transfer mechanisms are appro-

  required for specific contaminating systems For example, the radiation can cause a vibratory excitation or an electronic excitation of the additive The stored energy can be transferred by reradiation or by collisions

with the contaminant molecules.

  Depending on the contaminant, the energy transfer can effect

  kill decontamination in various ways thermal energy

  what can cause the evaporation of the contaminant Otherwise, the heat can lead to the decomposition of the contaminant The heat or the electronic excitation can lead to the ionization of the contaminant The molecules of the ionized contaminant can combine with other chemical agents so that

  the harmful properties of the contaminant are neutralized.

  Neutralizing chemicals can be supplied with the additive. In a preferred embodiment of the invention, a PABA solution is applied to a contaminant such as a chemical weapon. PABA solutions strongly absorb radiation in the near ultraviolet region and are therefore sensitive to many sources. high intensity radiation The chemical weapon / PABA system can be irradiated using a high intensity radiation source The

  radiation source can be a laser such as a laser ex-

  dye laser or nitrogen laser Alternatively, a high intensity xenon pulsed flash lamp or other inconsistent flash lamp can be used to irradiate the chemical system. As soon as the radiation is absorbed,

  produces some energy transfer to the chemical weapon

reducing its elimination.

  PABA is particularly well suited for decontamination.

  mination by means of a flash lamp such as a xenon flash lamp PABA which is commonly used in screens

  to protect human skin from ultra-

  purple is readily available in large quan-

  is non-toxic PABA absorbs radiation

  ultraviolet in a large section of the ultra region

  near purple It is therefore a safe and available chemical agent which effectively absorbs radiation in the

  frequency range of a flash lamp.

  PABA is also well suited for the absorption of

  radiation from certain lasers However, special additives

  can be more effective absorbents of energy

  in a narrow spectrum of a particular laser For example, ferrocin can be used as an additive in combination

with an argon-fluoride laser.

  Tests have been performed to assess the effectiveness

  of the present process A mixture was mixed in a test tube.

  lution of PABA and malathion then we applied to glass slides Malathion is analogous to a chemical weapon in that it behaves physically and chemically as much

  chemical agents developed for chemical warfare.

  After evaporation of the solvents, a residual layer remains on the slides. Then slides of this type are irradiated with

  of pulses from a Kr F laser (248 nm) The residue is total-

  eliminated from the irradiated area Elimination is also complete when irradiating similar blades with a blade

  Flashblaster (the Flashblaster lamp is a pulsed flash lamp

  high intensity xenon (developed by Mawxell Laboratories). In a set of control tests, a PABA solution is deposited on a slide PABA is completely eliminated from the irradiated areas of the slides by exposure to laser radiation

  Kr F or Flashblaster lamp In a second group of ess

  know witnesses, we put malathion on glass slides.

  Malathion residue is not removed when irradiated

  by one or the other radiation source These tests established

  feels that the process of the invention allows the photoelimination of contaminants which are not always easy to remove

  with economical sources of radiation.

  The invention therefore relates to a decontamination process

  which allows photoelimination of contaminants from surfaces.

  It is obvious that other chemical agents can be used.

  These chemical agents can absorb in the ultra-

  near violet or in another part of the spectrum in which high intensity radiation sources are economical and practical There are other modes of realization.

  sation within the scope of the invention.

Claims (9)

  1 decontamination process comprising the application of a chemical additive to a contaminant in intimate contact with it, said additive being characterized in that it absorbs radiation in a predetermined range of frequencies; and the irradiation of the contaminant / additive system obtained   with radiation in said predetermined range of frequencies   until decontamination is complete.   2 Method for the removal by cleaning of a contaminant   from a surface comprising: the application of a chemical additive to the contaminant,   said additive being characterized in that it absorbs a ray-   in a predetermined range of frequencies; and irradiating the contaminant / additive system with radiation in said predetermined frequency range until said surface is essentially cleared of said contaminant.   3 Method according to one of claims 1 or 2, charac-   further terized in that said additive absorbs said ray-   in the near ultraviolet region.   4 Method according to one of claims 1 or 2, charac-   further terized in that said additive comprises paraaminobenzoic acid.   5 Method according to any one of claims 1 to   4, further characterized in that said radiation is provided by a laser system.   6 Method according to any one of claims 1 to   4, further characterized in that said radiation is provided by a flash lamp.   7 Method according to claim 6, further characterized in that said radiation is provided by a flash lamp pulsed with xenon.   8 Process for destroying a first chemical agent   taking the mixture of a second chemical agent with said   first chemical agent, said second chemical agent being   characterized in that it absorbs radiation in a predetermined range of frequencies; and exposing the mixture to radiation in said predetermined frequency range so that said first chemical agent is destroyed by the heat produced by the absorption of said radiation by said second chemical agent.   9 Process for destroying a first chemical agent   taking; applying a layer of a second chemical agent to said first chemical agent, said second chemical agent being characterized in that it absorbs radiation in a   predetermined range of frequencies; and the exhibition of the   mixes with radiation in said predetermined frequency range until said first chemical is   destroyed by the heat produced by the absorption of said ray-   by said second chemical agent.