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Revision of IEC 61005Neutron ambient dose equivalent meters

Alfred KlettBerthold Technologies, Bad Wildbad Germany

Neutron Users Club Meeting NPL/Teddington, November 1, 2011

History of Standard IEC 61005

Radiation protection instrumentation – Neutron ambient dose equivalent (rate) meters prepared by

IEC technical committee 45: Nuclear instrumentation

subcommittee 45B: Radiation protection instrumentation

working group B8 Active Electronic Dose Equivalent and Dose Equivalent Rate Meters and Monitors

current project leader: Radoslav Radev / LLNL

IEC 61005 1st edition 1990-09

IEC 61005 2nd edition 2003-02

IEC 61005 3rd edition (CD) 2011-11

Alfred Klett Nov 1, 2011 2

IEC 61005 Revision Documents & Plan

Document ID Title Date

45B/684/RR Review Report (RR) 2011-02-18

45B/685/CD Committee Draft (CD) 2011-02-18

45B/685/CC_MV Comments (CC) 2011-05-16

Schedule

Committee Draft for Vote (CDV) 2013-02

Final Draft International Standard (FDIS) 2014-02

Publication of International Standard 2014-06


Scope

assemblies for the measurement of ambient dose equivalent for neutrons up to 20 MeV, comprising:

detection assembly (for example thermal neutron detector with neutron moderator/absorber)

measuring assembly (display reading)

not applicable to unconventional dose meters as

spectroscopic neutron dose meters (more than 1 probe)

meters based on bubble dosimeter technology

meters based on silicon pillar neutron detectors

electronic personal dose (rate) meters

No requirements for pulsed radiation fields defined Alfred Klett Nov 1, 2011 4

Normative referencesElectromagnetic compatibility (EMC)

IEC 61000-4-2:1995

IEC 61000-4-3:2002

IEC 61000-4-4:1995

IEC 61000-4-5:1995

IEC 61000-4-6:1996

IEC 61000-4-8:1993

IEC 61000-4-12:1995

ISO 8529 Reference neutron radiations

ISO 8529-1:2001 Characteristics and methods of production.

ISO 8529-2:2000 Calibration fundamentals

ISO 8529-3:1998 Calibration and determination of response

ISO 11929:2010 Determination of the characteristic limits Alfred Klett Nov 1, 2011 5

TestsTests for influence quantities of

Type F

Type S

Radiation sources241Am-Be, 252Cf 241Am-Be, 252Cf moderated by D2O sphere ∅ 30cm

accelerator target sources (ISO 8529)

for thermal & epithermal reference fields, accelerator target, reactor beams, 241Am-Be or 252Cf sources with well defined moderator/filter arrangements may be used


Radiation sources for tests241Am-Be, 252Cf bare241Am-Be, 252Cf moderated by D2O sphere ∅ 30cm

accelerator target sources (ISO 8529)

for thermal & epithermal ref. fields, accelerator target, reactor beams, 241Am-Be or 252Cf sources with well defined moderator/filter arrangements

Work place neutron fields

simulated fields specified in ISO 12789

other work place environments whose fields are well defined by spectral calculations and/or measurements traceable to or recognized by a primary standards laboratory


General requirements: effective range

For dose meters with an analogue display: omitted here

for dose meters with a digital display, from an indication in the 2nd least significant digit up to the maximum indication on each range. (example: with max. indication 9 999,9, the effective range can extend from 1,0 to 9 999,9)

for dose meters with digital & scientific display the mantissa shall have 3 digits at least (for instance 1,00 to 9,99). The manufacturer shall define the effective range of measurement (for instance 1,00 E–7 to 9,99 E–2 Sv h–1).

The minimum effective range of measurement ofdose equivalent rate: at least 4 orders of magnitude including 10 µSv h–1

dose equivalent: at least 4 orders of magnitude including 0,1 mSv.


General requirements

Mechanical characteristics

assembly labels shall include

measured quantity

effective range of measurement

the type of radiation the dose meter is suitable for

rated range of particle energy

reference point & orientation (or in the manual)

IP classification shall be stated by the manufacturer according to IEC 60529

Ease of decontamination


General requirements

Interface requirements

output connection for a remote readout is recommended

recommended input and output connections

input connection to the pre-amplifier input for electrical test purposes

output connection from the amplifier

output connection from the discriminator

manufacturer shall deliver the evaluation algorithm of the indicated value


Radiation detection requirements

indication of the assembly shall be in units of ambient dose equivalent (rate), for example in millisieverts (per hour)

variation of relative response due to the non-constancy of the dose rate response shall not exceed –17 % to +25 % over the whole of the effective range of measurement for neutron reference radiations chosen

The statistical fluctuations of the indication measured as coefficient of variation shall fulfill the requirements given in Table 3.


it is permissible to employ an equivalent electrical test in order to determine the intrinsic error at the ambient dose equivalent rates that cannot be provided by the sources of radiation.


Variation of the response due to neutron radiation energy and angle of incidence

Combination of requirements for angular and energy response was intended (like for instance IEC 60841-1:2009)

But it was unclear if any existing instrument could meet these requirements they are now independent in the CD


Variation of response due to neutron energy

“it would be desirable for the variation of the response with the neutron energy over the whole energy range from thermal to the maximum energy specified by the manufacturer not to exceed 50%. However, at the time of publication, such requirement is not practically achievable” (6.4.1)

appropriate response calculations, the results of these calculations shall be made available for the entire energy range with data at least at two energy points per decade of radiation energy.


Alfred Klett Nov 1, 2011

Neutron Survey Instruments

International Atomic Energy Agency IAEA, Technical Reports Series No. 403, Compendium of Neutron Spectra and Detector Responses for Radiation Protection Purposes, Supplement to Technical Report Series No. 318, Vienna, 2001, Table 3.II. p. 27

15

16

Energy Dependent Dose Response Rem-Counters

Calculated from the data of IAEA TRS 418

Alfred Klett Nov 1, 2011

Variation of response due to neutron energy

Energy Range Requirements

thermal - 50 keV manufacturer shall specify variation of ambient dose equivalent with neutron energy. The recommended variation should not be more than 20%-800%

50 keV - 10 MeV within 50%-150% of response for 0°incident radiation and reference energy

10 MeV – max. Energy manufacturer shall specify variation of ambient dose equivalent with neutron energy. The recommended variation should not be more than 20%-100%


Method of test of energy response

at least at two neutron energies below 50 keVor with a moderated source

at least at three neutron energies in the energy range between 50 keV and 10 MeV

at least with 1 broad source (e.g. 252Cf or 241Am-Be)

at least at one neutron energy exceeding 10 MeV

only tests at energies within the manufacturer’s specified energy range are required

In addition, it is recommended to state response to standardized simulated work place neutron fields


Dose & dose rate alarm requirements

when the dose equivalent (rate) meter is subjected to a dose equivalent (rate) of 0,8 of the dose equivalent (rate) alarm set point for 10 min, the alarm shall not be activated

Similarly, at a dose equivalent (rate) of 1,2 times the alarm level set, the alarm shall be activated

the alarm shall actuate within 5 s or within a time such that the product of this time and the dose equivalent rate of the alarm point is less than 10 µSv


Additivity of indicated value requirements

The indicated value shall be additive

with respect to simultaneous irradiation with different types of radiation (for example, photon and neutron)

and with different neutron energies

and with different angles of radiation incidence


Test additivity of indicated value

Perform subsequently two irradiations under the two different irradiation conditions K and L (different energies, different angles of incidence or even different types of radiations) with the conventional quantity values HK and HLDetermine the indicated values GK and GL for the two irradiations.

Then perform a third simultaneous irradiation under the two irradiation conditions K and L with the conventional quantity value HK+L = HK + HLand determine the indicated value GK+L


Test additivity of indicated value

shall be determined for any value of HK and HL and any simultaneous combination of radiation fields SK and SLAs simultaneous irradiations are very difficult to perform, the use of calculations as a replacement for the simultaneous irradiations is permitted and recommended for this test

∆gmix shall be lower than 0.1


Variation of angular response

The response values shall be measured

for polar angles of incidence of α = 0°, ±45°, ±90°

for azimuth angles β of 0°, 90°, 180°, 270°, 360°while keeping α = 0°

measurements shall be performed at one monoenergetic or one broad neutron spectrum.

Test distance should be at least 3 times the sum of the largest linear dimension of source & detector

The scatter contribution to the indicated value of the device shall not exceed 20 % (ISO 8529-2).


Overload characteristics

The dose equivalent meter shall read off-scale on the high side or shall indicate overload when exposed to doses greater than the maximum of its measuring range

When subjected to dose rates high enough to cause wrong dose indication, there shall be indication that the equipment is not able to provide correct dose indication


Overload chracteristics test ?!? CHECK

Subject the dosemeter to a dose in excess of 10 times the maximum dose that can be indicated, at most 50 Sv, at least 1 Sv.

Dose rate during exposure shall be less than the maximum dose rate capability as specified by the manufacturer. The equipment shall not be reset or switched off for at least 30 min after the equipment has been subjected to the test dose.

Subject the dose equivalent meter to a dose rate 10 % in excess of that specified as the dose rate limit by the manufacturer for a period of 100 s. In case, no error of the doseAlfred Klett Nov 1, 2011 25

Response time

30 s for the increases or decreases of the ambient dose equivalent rate less than 0,1 mSv⋅h–1

10 s for the increases or decreases of the ambient dose equivalent rate between 0,1 mSv⋅h1and 1 mSv⋅h–1;

4 s for the increases or decreases of the ambient dose equivalent rate greater than 1 mSv⋅h–1.

The manufacturer shall state the response time.


Response time

for the increases or decreases of the ambient dose equivalent rate

30 s for less than 0,1 mSv⋅h–1

10 s between 0,1 mSv⋅h1and 1 mSv⋅h–1;

4 s for greater than 1 mSv⋅h–1.

The manufacturer shall state the response time

Definition


Response time tests

The test may be carried out either with a suitable neutron source or by the injection of a suitable electrical signal

The initial and final ambient dose equivalent rates shall differ by a factor of at least 10 and measurements shall be carried out for both an increase and a decrease in the ambient dose equivalent rate by this factor


Variation of the dose response due to dose rate dependence - Requirements

The variation of the relative dose response due to dose rate dependence shall not exceed the range from –13 % to +18 %

In addition, the variation of the rel. response due to low dose rates down to natural environmental radiation shall be stated by the manufacturer


Test of variation of the dose response due to dose rate dependenceDetermine dose responses at 80 % of each order of magnitude of the effective dose range when meter is exposed to a source

Perform the test for each dose at one dose rate of each order of magnitude of the rated range of use for dose rate

Since at lower dose values, the exposure times are too short, whilst at high dose values, the exposure times are too long for the lower rates, these tests shall exclude any exposure in-volving measurement times less than 10 s or in excess of 10 h

The variation of the relative dose response due to dose rate dependence shall not exceed the range from –13 % to +18 %

If integration is done digitally a test of ≈100 s per dose rate is sufficient.


Dose equivalent rate alarm requirements

when the dose meter is subjected to 0,8 of the dose equivalent rate alarm set point for 10 min the alarm shall not be activated for more than 10% of the period of test

Similarly, at a dose equivalent rate of 1,2 times the alarm level set, the alarm shall be activated for 90% of the test period.

alarm shall actuate within 5 s or within a time such that the product of this time and the dose equi-valent rate of the alarm point is less than 10 µSv


Dose equivalent alarm requirements

when the dose equivalent meter is subjected to a dose equivalent of 0,8 times the dose equivalent alarm set, no alarm shall be given

when the dose equivalent meter is subject to a dose equivalent rate of 1,2 times the dose equivalent alarm set point, the alarm shall be actuated.


Response to photon radiation Requirements

Photon response shall be quoted in terms of units of the photon ambient dose equivalent rate

Photons may not only cause the assembly to give an indication, but it may also modify the response to neutron radiation. Therefore, there are two separate requirements

Indication to 137Cs photons at 10 mSv⋅h–1 shall not exceed indication of 0,1 mSv⋅h–1 neutron

high-energy photon radiation (6 MeV) response shall, by agreement between the manufacturer and the purchaser, be checked at higher energies


Test of response to photon radiation

assembly shall be exposed to a 137Cs source in a field having an ambient dose equivalent rate of 10 mSv⋅h–1

indicated value shall not exceed 0,1 mSv⋅h–1

Radiation sources used shall conform with the ISO 4037 series

indication produced by a 137Cs and higher energy (> 1.5 MeV) photon dose rate of 10 mSv⋅h–1 is less

than the indicated value due to a neutron ambient dose equivalent rate of 0,1 mSv⋅h–1


Additivity of indicated value

The indicated value shall be additive with respect to simultaneous irradiation with

different types of radiation (f. e. photon and neutron)

different neutron energies and angles of incidence

If dosemeter uses

only one signal (measured with one detector) for evaluation, then this is fulfilled

more than one signal (measured either with several detectors or with one detector using for example pulse height analysis), then this is not automatically fulfilled


Additivity of indicated value

In that case, it shall be assured that the relative change in indication,mixg∆, caused by the mix of radiation shall not exceed ± 0,1

NOTE If the algorithm used to evaluate the indicated value, (see 5.5) is either a linear combination of the signals or a linear optimization of them, then this requirement is fulfilled or no tests are required


Other Requirements

Environmental

Temperature

Temperature shock

Humidity

Mechanical Requirements

Mechanical shock

Drop Test

Vibration Test

Electromagnetic Requirements

Documentation


References

ICRU The International Commission on Radiation Units andMeasurements, Fundamental Quantities and Units for IonizingRadiation, ICRU Report 60, ICRU Publications, Bethesda, MD, 1998

ICRU The International Commission on Radiation Units andMeasurements, Determination of Operational Dose EquivalentQuantities for Neutrons, ICRU Report 66, Journal of the ICRU, Vol. 1 No. 3, 2001

IAEA Compendium of Neutron Spectra and Detector Responses forRadiation Protection Purposes, Technical Reports Series No. 318, International Atomic Energy Agency, Vienna, 1990

IAEA Compendium of Neutron Spectra and Detector Responses forRadiation Protection Purposes, Supplement to Technical Reports Series No. 318, Technical Reports Series No. 403, International Atomic Energy Agency, Vienna, 2001


References

R.J. Tanner, C. Molinos, N.J. Roberts, D.T. Bartlett, L.G. Hager, L.N. Jones, G.C. Taylor, D.J. Thomas, Practical Implications of Neutron Survey Instrument Performance Report HPA-RPD-016 , Nov. 2006, Health Protection Agency, Chilton, Didcot, United Kingdom

ICRP The International Commission on Radiological Protection, Conversion Coefficients for use in Radiological Protection againstExternal Radiation Publication 74, Annals of the ICRP, Vol. 26, No. 3-4, 1996
