WO1994029745A1 - Dispositif de mesure de la concentration en radioactivite dans un liquide - Google Patents

Dispositif de mesure de la concentration en radioactivite dans un liquide Download PDF

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Publication number
WO1994029745A1
WO1994029745A1 PCT/SE1994/000553 SE9400553W WO9429745A1 WO 1994029745 A1 WO1994029745 A1 WO 1994029745A1 SE 9400553 W SE9400553 W SE 9400553W WO 9429745 A1 WO9429745 A1 WO 9429745A1
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WO
WIPO (PCT)
Prior art keywords
cylinder
liquid
measuring
column
radioactivity
Prior art date
Application number
PCT/SE1994/000553
Other languages
English (en)
Inventor
Björn BJURMAN
Original Assignee
Forsmarks Kraftgrupp Ab
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Forsmarks Kraftgrupp Ab filed Critical Forsmarks Kraftgrupp Ab
Publication of WO1994029745A1 publication Critical patent/WO1994029745A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/16—Measuring radiation intensity
    • G01T1/17—Circuit arrangements not adapted to a particular type of detector
    • G01T1/178—Circuit arrangements not adapted to a particular type of detector for measuring specific activity in the presence of other radioactive substances, e.g. natural, in the air or in liquids such as rain water
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C17/00—Monitoring; Testing ; Maintaining
    • G21C17/02—Devices or arrangements for monitoring coolant or moderator
    • G21C17/022—Devices or arrangements for monitoring coolant or moderator for monitoring liquid coolants or moderators
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E30/00—Energy generation of nuclear origin
    • Y02E30/30—Nuclear fission reactors

Definitions

  • the present invention relates to an apparatus and a process for measuring radioactivity in circulating water contaminated by radioactivity, for example, in a nuclear power plant.
  • An apparatus of the type mentioned in the preamble is known, i.a. from JP-C-55581/77 and JP-C-137595/77.
  • JP-C-55581/77 discloses, for example, an apparatus having a vertically arranged water-relear g pipe through which the radioactive liquid to be measured flows.
  • a measuring cylinder having a diameter which is greater than that of the water- releasing pipe is arranged coaxially with the water-releasing pipe, allowing the radioactive liquid to flow down into the measuring cylinder along its vertical longitudinal axis.
  • the end of the water-releasing pipe extends into the measuring cylinder so that the radioactive water is not brought into direct contact with the inner surface of the measuring cylinder. As a result, the risk of radioactivity accumulating on the measuring cylin ⁇ der's surface is reduced.
  • a detector for measuring radioactivity is arranged on the outside of the measuring cylinder and measures the concentration of the radioactivity in the radioactive liquid without being in contact with the measuring cylinder.
  • the water passing through the measuring cylinder is discharged through a discharge opening via a water outlet pipe arranged on the measuring cylinder's outlet side, and then via a check or stopvalve, to a tank.
  • JP-C-137595/77 discloses an apparatus of mainly the same basic structure as the last mentioned apparatus, but with the additio ⁇ nal characteristic that in the upper part of the measuring cylinder there is a twin-tube structure, whereby the inner tube or pipe element, i.e. the discharge pipe, directs the water to be measured for radioactivity and causes a vertical flow down through the measuring cylinder. Furthermore, clean water is supplied to the outer measuring cylinder in such a way that the clean water runs along the inner surface of the measuring cylinder and thus forms a protective film of clean water which reduces the risk of contamination on the inner wall of the measuring cylinder.
  • the latter apparatus is impaired by the disadvantage of the great amounts of flushing liquid which are needed in order to ensure a homogeneous cleaning film on the inner surface of the measuring cylinder, without formation of "tracks" i.e. breaks in the continuous film which are quickly transmitted to the inlet pipe's opening. Due to the large amounts of cleaning liquid required there are problems handling the waste, i.e. the radioactive contaminated test liquid mixed with cleaning liquid.
  • EP-B-0 053 364 discloses an apparatus comprising a vertically arranged outer cylinder, means for measuring radioactivity, means for supplying a radioactive liquid to the inner part of the outer cylinder, and means for supplying cleaning liquid along the inner surface of the outer cylinder.
  • this apparatus one has tried to solve the problem of the large amounts of contaminated waste by returning the liquid to the enclosed system.
  • this system requires that the analysing equipment is pressurized to the prevailing pressure in the primary cooling circuit or cooling water, which may amount to up to 70 bar. For obvious reasons this requires complex equipment, resulting in high costs.
  • EP-B-0143 162 discloses a further development of the technique from the last mentioned patent.
  • the detector for the radioac ⁇ tivity is arranged inside an inner cylinder, and the test flow is arranged in a ring-formed flow around the inner cylinder. To avoid contamination two flushing flows are produced, one along the inner cylinders exterior and one along the outer cylinder's interior surface.
  • the object of the present invention is, thus, to solve the problem which still exists with the known arrangements for measuring radioactivity in water from, for example, the cooling system of a nuclear power plant, i.e. to make it possible to measure radioactivity in such water, whereby only small amounts of sample water need be taken. Furthermore, only very small amounts of cleaning fluid should be required, and the measuring should be undertaken without the measuring equipment being contaminated accumulatively when measuring.
  • the system should be able to be maintained with mainly normal pressure.
  • the waste water should be able to be handled in the same way as ordinary low active waste.
  • the advantage with this device is, thus, that one does not risk the build-up of (radio)activity in the measuring chamber, and that the amount of waste may be kept low.
  • Figure 1 illustrates a device according to the state o f the art
  • FIG. 2 illustrates schematically the device according to the invention
  • FIGS 3a-c illustrate the construction of the inlet of the measuring apparatus, with means for producing the flushing flow
  • Figure 4 illustrates in detail an alternative embodiment of a buffer arrangment in the measuring cylinder.
  • the device illustrated in Figure 1 shows a measuring cylinder which consists of the outer casing of the device.
  • the measuring cyclinder's upper art there is a twin pipe structure, whereby the inner cylinder element, or the discharge pipe, leads the water the content of radioactivity of which is to be measured, and produces a vertical stream down through the measuring cylinder. Further ⁇ more, clean water is supplied to the outer measuring cyclinder in such a way that it runs along the inside surface of the iraasuring cylinder, thereby forming a protective film of clean water, thus reducing the risk of contamination of the inner wall of the measuring cylinder.
  • FIG. 2 illustrates schematically an embodiment of the device according to the invention, generally denoted 1.
  • This device has an outer cylinder 2, on which at the upper end there is arranged a means 3 for producing a thin flushing film 4 along the inner surface of the cylinder 2, and means 5, for producing a down- flowing stream 6 of radioactive water to be tested for radioac ⁇ tivity.
  • the dimension of the cylinder 2 is not critical, but test cylinders having an outer diameter of 50 mm have been used with good results. Means 3 and 5 will be described in more detail hereinbelow.
  • a detector 7 for measuring the radioactivity (for example a Germanium detector 25% relative effectiveness) is arranged further down on the outside of the cylinder.
  • the choice of detector is, obviously, completely dependent upon the measuring- conditions and it is within the field of competence of one skilled in the art to select the appropriate detector, therefor detectors will not be discussed here.
  • the detector is placed in a casing 8 made of, for example, lead and copper, to minimize both outer as well as inner radiation fields.
  • a lead screen 9 On the opposite side of the cylinder 2 is a lead screen 9, provided with a copper lining 10 to further svield or screen off the system against exterior interference.
  • honeycomb structure 11 is arranged over the cross section of the cylinder. Said honeycomb structure 11 prevents splashing which occurs when the test-stream 6 falls down on the bottom of the device and reaches up to the area of the detector 7 and contaminates the inner surface of the cylinder 2 with radioactivity.
  • the honeycomb structure 11 is suitably built of a thin material, for example, a metal sheet, having a thickness of about 0.1 mm, which thickness, however, is not critical, and should have an extension (the thickness of the honeycomb) in the longitudinal direction of the cylinder 2 (i.e.the honeycomb's thickness) which amounts to about 15-20 mm.
  • honeycomb structure 11 an 0-ring 12 is arranged. Its function will be described in conjunction with means 3 and 5.
  • Figures 3a-c illustrate in detail an embodiment of a construction in the upper end of the cylinder 2.
  • This insert consists of an upper part 14 and a lower part 15 which are connected by means of a web or waist 16.
  • the insert 13 may, preferably, be made in one piece from turned steel.
  • the upper part's diameter is adjusted to fit in the cylinder 2 by means of press fitting and for the purpose of achieving an additional caulking against the inner surface of the cylinder 2, there is an 0-ring 17 inserted in a groove 18 in the upper part 14.
  • the diameter of the lower part is somewhat less than the inner diameter of the cylinder 2 so that a column or slot 16a of at most 0.3mm, preferably at most O.lmm is provided between the lower part 15 of the insert 13 and the cylinder 2.
  • a measuring-stream pipe 19 passed through a central bore in the insert.
  • the pipe extends downward ⁇ ly about 10 mm from the lower part of the insert into the cylinder 2.
  • the liquid the radioactivity of which is to be determined is pumped with a flow of about 50-100 ml/s.
  • Two further pipes 20a and 20b are passed through bores in the insert 13. These pipes may be necessary for leading away gases which have been dissolved in the water, for example radioactive inert gases which have degassed in the measuring chamber during the process .
  • the rib 16 forms a ring shaped chamber between the upper part 14 and the lower part 15 of the insert 13.
  • This chamber is a fundamental characteristic of the invention, which will be disclosed by the description which follows.
  • cleaning liquid for example, clean water
  • An altern ive method of achieving that the distribution of the cleaning water forms a homogeneous film without turbulence is to supply the cleaning liquid in a plurality of thin pipes, distributed along the inner perifery of the cylinder 2 and opening immediately above the column (not illustrated).
  • a further method of achieving the distribution of the cleaning liquid is to supply the cleaning liquid tangentially by means of one or several pipes immediately above the column (not illustra ⁇ ted).
  • Such a buffer volume may be easily provided by means of, for example an O-ring 12 in the cylinder above the "honeycomb"-structure.
  • a wedge-shaped space is formed between the O-ring and the inside of cylinder 2, around the perifery. This space acts so that small fluctuations in the liquid flow, caused by irregularities in the "honeycomb"-structure 11, are damped or accomodated in said buffer volume, so that the fluctuations cannot affect the flow above the buffer volume at said O-ring 12.
  • the necessary buffer volume can be achieved in other ways, for example, by constructing the cylinder 2 so as to be provided with a strip 22 on its inside whereby the strip has an upwardly extending rim 23 which forms the necessary ring shaped space 24.
  • This is, obviously associated with higher costs, and said solution with an O-ring should be the simplest possible alternative.
  • the detection level of analysis With the aid of the apparatus according to the in ⁇ vention, lies in the range of 200-500 Bq/kg. With previous methods the detection limits lie in the range of ten power higher. The detection limit depends, obviously, on the number, type and concentration of other nuclides in the sample water, but the tests show a clear improvement of the level of detectable nuclides.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Plasma & Fusion (AREA)
  • General Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Molecular Biology (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Measurement Of Radiation (AREA)

Abstract

L'invention concerne un dispositif servant à mesurer la concentration radioactive d'un liquide et comprenant un cylindre extérieur orienté verticalement (2) et pourvu de moyens (5, 6) servant à l'alimenter en liquide. Le liquide s'écoule à travers le cylindre (2) le long de son axe vertical sans se trouver en contact avec la surface intérieure dudit cylindre (2). Le dispositif est pourvu d'un détecteur (7) servant à mesurer la radioactivité dans ledit liquide. Des moyens (3) servent à alimenter la partie intérieure du cylindre (2) en liquide de rinçage, de telle façon que celui-ci s'écoule vers le bas et forme une pellicule liquide sur la surface intérieure du cylindre (2). L'invention est caractérisée par le fait que des moyens (3) comprennent au moins un raccord ou un tuyau d'alimentation (21a, 21b) servant à effectuer une alimentation en liquide de rinçage qui se décharge au-dessus d'une colonne (16a) s'étendant le long de la surface intérieure du cylindre (2), de façon à former ladite pellicule liquide.
PCT/SE1994/000553 1993-06-10 1994-06-08 Dispositif de mesure de la concentration en radioactivite dans un liquide WO1994029745A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE9301997A SE9301997L (sv) 1993-06-10 1993-06-10 Anordning för mätning av koncentrationen av radioaktivitet i en vätska
SE9301997-4 1993-06-10

Publications (1)

Publication Number Publication Date
WO1994029745A1 true WO1994029745A1 (fr) 1994-12-22

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PCT/SE1994/000553 WO1994029745A1 (fr) 1993-06-10 1994-06-08 Dispositif de mesure de la concentration en radioactivite dans un liquide

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WO (1) WO1994029745A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998047023A1 (fr) * 1997-04-16 1998-10-22 Abb Atom Ab Dispositif de determination des nuclides contenus dans des gaz inertes radioactifs
US7151262B1 (en) 2000-02-23 2006-12-19 Hitachi, Ltd. Radioactive gas measurement apparatus and failed fuel detection system

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0053364A1 (fr) * 1980-12-01 1982-06-09 Hitachi, Ltd. Appareil pour mesurer la concentration de radioactivité
EP0143162A1 (fr) * 1983-07-08 1985-06-05 Hitachi, Ltd. Appareil de mesure de concentration de radioactivité

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0053364A1 (fr) * 1980-12-01 1982-06-09 Hitachi, Ltd. Appareil pour mesurer la concentration de radioactivité
EP0143162A1 (fr) * 1983-07-08 1985-06-05 Hitachi, Ltd. Appareil de mesure de concentration de radioactivité

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN, Vol. 2, No. 21, M-77; & JP,A,52 137 595 (HITACHI SEISAKUSHO K.K.), 17 November 1977. *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998047023A1 (fr) * 1997-04-16 1998-10-22 Abb Atom Ab Dispositif de determination des nuclides contenus dans des gaz inertes radioactifs
US6495835B1 (en) 1997-04-16 2002-12-17 Abb Atom Ab Device for determining nuclide contents of radioactive inert gases
US7151262B1 (en) 2000-02-23 2006-12-19 Hitachi, Ltd. Radioactive gas measurement apparatus and failed fuel detection system

Also Published As

Publication number Publication date
SE500593C2 (sv) 1994-07-18
SE9301997L (sv) 1994-07-18
SE9301997D0 (sv) 1993-06-10

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