1、EIA TEP181 BO m 3234600 0008511 T m - FROM POWER TUBES NOVEMBER 1980 RECOMMENDED PRACTICE FOR MEASUREMENT OF X-RADIATION FORMULATED BY EIA TUBE ENGINEERING PANEL ADVISORY COUNCIL (TEPAC) TEPAC PUBLICATION No. 181 (Revision of TEPAC Publication No. 81) EIA TEP181 80 = 3234b00 0008532 I m Published by
2、 ELECTRONIC INDUSTRIES ASSOCIATION Engineering Department 2001 Eye Street, N.W., Washington, D.C. 20006 PRICE: $4.00 - a- * - EIA TEP181 80 m 3234b00 0008513 3 m RECOMMENDED PRACTICE FOR MEASUREMENT OF X-RADIATION FROM POWER TUBES TEPAC PUBLICATION NO. 181 This publication was prepared by the JT-32
3、Committee on Electron Tube Safety and approved by the Tube Engineering Panel Advisory Council (TEPAC) 1, Purpose and Scope 1.1 Purpose - To obtain the X-radiation characteristics of power tubes in order to determine the levels emitted by the tubes when they are operated with integral tube shielding
4、in place, but without external shielding. JEDEC Publication No. 81 .) (This pub1 ication replaces and supersedes 1.2 Scope - This test method applies to the measurement of incidental X-radiation emitted from power tubes. CAUTION: SAFETY CONSIDERATIONS Measuring instruments should be properly grounde
5、d. Caution should be taken to auoid shock hazard, par- ticuZmly in the vicinity of the anode connection and the voZtage metering system. Safety gksses should be worn at all times during the measurement procedure. X-ray film badges should be worn in accordance with established plant safety practices
6、for monitoring radiation dosage. 2. . Apparatus 2.1 Search Instruments - For Initial Survey a, Rapid response instruments used for locating the position of maximum i ntensi ty . Example: Texas Nuclear Model 2652 GM Portable Survey Meter b. X-ray Film. For use in initial surveys to determine the X-ra
7、diation pattern and for locating positions of maximum EIA TEP181 80 m 3234600 00085L4 5 = intensity. Examples of X-ray films are as. QOEIS; 1. No Screen Medical X-Ray Film, double coated duplitized 2. Industrial X-Ray Film, double coated Estar Base 2.2 Measuring Instruments - for making defini tive
8、measurements. Measuring instruments shall be calibrated in the range of energies and exposure rates comparable to that of the X-radiation emitted by the tube to be tested. The instruments shall read in units of exposure rate, i.e., R/h, mR/h, and they shall be shielded against RF interference. a. b.
9、 c. Examples are as follows: Victoreen Model 440 RF/C RF Shielded Low-Energy Survey Meter Victoreen Model 440 RF Radiation Exposure Rate Measuring System Victoreen Model 666 F1 uoroscopic Survey Meter complete with background probe Model 666-25 modified with Mylar window and diagnostic probe d, Vict
10、oreen Model 471 RF Survey Meter (RF Shielded) e. Texas Nuclear Model 2652 GM Portable Survey Meter f. Condenser Ionization Chambers: Victoreen Model 208A Victoreen Model 239A Victoreen Model 687C Minometer Charger-Reader g. Harshaw Chemical TLD1 O0 Thermal Luminescent Dosimeter and Reader 2.3 Test E
11、quipment - To provide stable electronic conditions for operation of the power tube under test and to measure voltage and current. 2.3.1 High-Voltage Meter - A meter for measurement of the high-voltage with an accuracy of at least 0.5% for direct current, 1% for alternating current and 2% for pulse v
12、ol tage measurements (*Note). Calibrate using a high-voltage divider with suitable accuracy and *Note: If the recommended accuracy of the measurement system cannot be achieved then the inaccuracy shall be accounted for by reducing the recorded vol tage reading by the maximum possible measurement dev
13、iation. 2.3.2 Current Meter A meter for measurement of current with less than 2% error. -2- P 4 O - EIA TEP381 80 E 3234600 O008535 7 E i- - 2.3.3 2.3.4 Waveform Oscilloscope - A device to measure pulse duration. RF Counter - A device to measure pulse repetition rate. 3. Cal i bration X-radiation me
14、asuring instruments shall be calibrated regularly by exposure to a spatially uniform X-ray field having an exposure rate and energy representative of the fields to be measured. The calibration shall be traceable to the National Bureau of Standards. The stability of calibration of X-radiation measuri
15、ng instruments should be checked prior to use. An internal radioactive check source or one supplied by the instrument manufacturer is a con- venient means of checking the stability of the calibration. 4. Measurement Conditions 4.1 General - Measurement of X-radiation arising from the operation of po
16、wer tubes is general ly separable into two categories. a. Initial or general surveys b. Measurements on power tubes having known X-radiation patterns. In making surveys, especially initial surveys, it is important that no assumptions be made regarding the nature of the field pattern to be expected.
17、When the X-radiation pattern is known, the power tube being meas- ured shall be positioned relative to the measurement equipment so that measurements are made at the point where maximum X-radiation is observed. beginning measurements so that measurement equipment and the tube being measured are oper
18、ating at stable specified conditions. Shunt Regulators - The tube being measured shallbe operated at the maximum rated dc anode (not supply) voltage and current, which shall not vary (including ripple) or drift more than, rr0.5% in voltage and +2% in current the entire measurement period. If the com
19、bination of maximum rated dc anode voltage and current produces a dissipation value in excess of the tubes maximum A suitable warm-up period shall be provided before 4.2 EIA TEP383 80 m 3234b00 0008536 9 m 5. rated anode dissipation, the current shall be reduced so that this dissipation value is acq
20、uired without reduction of the rated dc anode voltage. 4.3 High Vol tage Rectifi,ers - The measurement procedure described in sub-paragraph 4.3.1 is required only if the anode emits in the inverse vol tage phase. When this does not occur, the measurement procedure described in sub-paragraph 4.3.2 ma
21、y be used. 4.3.1 Operational Measurements - An ac potential corresponding to the limiting value of the peak inverse voltage shall be applied to the cathode or filament relative to the anode. tage regulation shall be within the stated limits. supply and load impedance shall be chosen to result in ope
22、ration at: Peak-to-peak vol- The power a. b. c. Both, Maximum rated peak current, or Maximum rated anode dissipation, or 4.3.2 Inverse Measurements - A positive dc potential, corresponding to the maximum rated peak inverse voltage (total dc and peak), shall be applied to the cathode or filament rela
23、tive to the anode. voltage, including ripple, shall not vary or drift more than +0,5% during the entire measurement period. to apply heater or filament voltage during this measurement. This It is not necessary 4.4 Gridded Power Tubes, Hi gh-Vol tage Switch Tubes , Microwave Tubes , & Thyratrons The
24、tube being measured shall be operated at typical operating conditions and within the tubes maximum ratings. should also be measured under other than normal operating on- ditions within the maximum ratings to increase the likelihood of emission of X-radiation without causing damage to the tube. The t
25、ubes Measurement Procedures General - Prior to making measurements the location of maximum radiation intensity should be determined by use of film or by use of a search instrument, 5.1 The surface of the tube outline (see -4- O definitions) may be scanned with the rapid response search instrument, o
26、r the surface may be covered with X-ray film. Measurements Using X-Ray Film - X-ray film covering the entire tube outline may be used to define the X-radiation source, to evaluate the relative intensity and to determine the X-radia- tion pattern. initial surveys to determine the point of greatest ex
27、posure rate for later measurement with portable exposure rate instruments. Measurements Using Portable Exposure Rate Instruments - Explore the tube outline with the measuring instrument and proceed slowly to allow the instrument to respond to sharp beams of X-radiation. The X-radiation measurement s
28、hall be made at the location of maximum exposure rate and at a distance such that the effective center of the instrument is 12 in. (30.48 cm) from the basic tube surface unless otherwise specified for a particular power tube design At least three successive readings shall be taken for each expo- sur
29、e rate instrument position, and the average value of the read- ings is recorded. 5.1.1 It is recommended that X-ray films be used on 5.1.2 Background radiation shall be measured at the measurement point before and after the exposure period and corrections applied to observed data as required. 6. 6.1
30、 6.2 6.3 I-. Precautions X-radiation emitted by power tubes may have significant exposure rates. The survey techniques used must avoid excessive exposure to measurement personnel. When operating a power tube with integral tube shielding in place but without external shielding, precautions must be ta
31、ken to pro- tect measurement personnel. Precautions should be taken to prevent exposure of measurement personnel to non-ioni zing electromagnetic radiation. - 5- 6.4 6.5 6.6 7. 7.1 7.2 7.3 7.4 7.5 7.6 7.7 8, EIA TEP181 80 323i4b00 0008518 2 The presence of radio-frequency energy may cause irregular
32、read- ings or apparently high background. Precautions must be taken to assure that the X-radiation masuring instrument is shielded from RF interference, Measuring instruments and equipment shall be thoroughly grounded to prevent operating voltage shocks to measurement personnel. Film badges and/or d
33、osimeters shall be used by measurement per- sonnel to monitor their X-radiation exposure, Def i ni ti ons Dosimeter - A personal X-radiation meter intended to measure the absorbed X-radiation dose. Exposure Rate - Energy flowing through unit area perpendicular to the beam per unit of time and usuall
34、y expressed in milli-Roentgen per hour (mR/h). Film Badge - A type of dosimeter consisting of a badge containing a sensitized film which, when developed, gives an indication of the total dose of X-radiation to which the badge has been subjected. Portable Exposure Rate Instrument - An instrument , pr
35、operly shielded against electromagnetic radiation other than X-radia- tion, for probing, surveying, and measurement of X-radiation. Target - An electrode or portion of an electrode on which accelera- ting electrons bombard and, hence from which X-rays are emitted. Tube Outline - The accessible outer
36、 surface of the power tube or an arbitrary but stated surface used for reference in the survey and measurement of X-radiation. X-Ray Film - Comercial industrial or medical sensitized film used to record spatial distribution of X-radiation, to locate leaks and to determine profiles of X-radiation. References - International Electrochemical Commission Pub1 ica- tion 562, IEC Standard for “Measurements of Incidental Ionizing Radiation from Electronic Tubes“. - 6-
