ML19224B133
| ML19224B133 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 04/06/1977 |
| From: | Metropolitan Edison Co |
| To: | Mullinix W NRC/IE |
| References | |
| 1604, TM-0073, TM-73, NUDOCS 7906140088 | |
| Download: ML19224B133 (8) | |
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Wilda R. Mullinix, NRC 5:
7906140088 188 216 O
1604 Revision 6
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THREE MILE ISLAND NUCLE AR STATION
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ALPHA SURVEYS
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Table of Ef fective Pages Pace Date R evision Page Date Revision Pace Date R evision 1.0 01/19/76 3
26.0 51.0 2.0 01/15/75 2
27.0 52.0 3.0 04/06/77 6
28.0 53.0 4.0 04/06/77 6
29.0 54.0 5.0 01/15/75 2
30.0 55.0 6.0 01/15/75 2
31.0 56.0 7.0 01/15/75 2
32.0 57.0 8.0 33.0 58.0 9.0 34.0 59.0 10.0 35.0 60.0 11.0 36.0 61.0 12.0 37.0 62.0 13.0 38.0 63.0 14.0 39.0 64.0 15.0 40.0 65.0 16.0 41.0 66.0 17.0 42.0 67.0 18.0 43.0 68.0 19.0 44.0 69.0 20.0 45.0 70.0 21.0 46.0 71.0 22.0 47.0 72.0 23.0 48.0 73.0 24.0 49.0 74.0 25.0 50.0 75.0 Unit 1 Staff Recom ends Ap9roval Unit 2 Staff Recom.nds Ap coval Approval i
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, Date Approval 1
- Date Cogniz/ot b/pt. feab Cogniz[t bedt/le/d Unit 1 PORC Recomruends Apor > val Unit 2 PORC Recommends Approval Date Y'l-S^
Date Y 5' ' 7
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Chairrnan of PORC V/C E ' Chairman of PORC j
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1604 Revision 3 01/19/76 THREE MILE ISLAND NUCLEAR STATION
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STATION HEALTH PHYSICS PROCEDURES 1604 - Alpha Surveys 1.0 PURPOSE The purpose of this procedure is to insure that a proper method is followed in the process of conducting an alpha survey.
2.0 DISCUSSION An alpha particle is a helium nucleus consisting of two protons and two neutrons, with a double positive charge. The alpha particle is a strongly ionizing and weekly penetrating particle. An alpha particle can be stopped by a few thin sheets of paper. The range of the alpha particle is apprcximately three centimeters in air.
Because of their relatively large mass and double positive charge, alpha particles ~1ose their energy very rapidly in the medium through which they pass.
The range of the alpha particle is therefore very short.
Accordingly, alpha particles do not present an external radiation hazard.
However, alpha emitters do present one of the greatest internal hazards when deposited throughout a vital organ. They can cause great damage because of their relatively high energies (4-9 MEV) and high specific ionization, and because their relative damage (REE) ft: tor to tissue is about 20 times greater than that for Beta-Gamma radiation.
239 Different isotopes tend to deposit in different parts of the body.
p deposits predominatly in the skeleton where, many years later, it may j
produce bone disease.
The three ways radiation may enter the body are (1) Inhalation (2) Ingestion (3) Throuch the skin (abrasions, cuts, punctures, etc.).
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Revision 2 2.1 Alpha surveys provide assurance of up to date exposures, regarding radiation hazards (internal) and insure adeauate precautions are appropriately outlined on RWP's.
2.2 Alpha surveys will be conducted according to the area survey schedule board in the H.P. Lab.
3.0 REFEREt1CES 3.1 Basic Radiological Healtn Book 3.2 Health Physics Handbook 3.3 PAC-45 Eberline Technical Manual 3.4 Rad Protection Manual Administrative Procedure 1003 3.5 Health Physics Procedure 1613 4.0 EQUIPMEtiT 4.1 PAC-4S Eberline portable alpha detector 4.2 Area survey maps (in filing cabinet in health physics lab, filed under " flew Forms.")
4.3 Filter papers (in Health Physics Lab.)
4.4 Small coin envelopes 4.5 Portable air sampler 4.6 Air Filters (in Health Physics Lab.)
4.7 Stop watch (in dealth Physics Lab.)
4.8 Wide Beta II/P.C.C.-IIT 4.9 Alpha Scintillation 5.0 OPERATING INSTRUCTIONS 5.1 Portable Alpha Survey:
Survey the specified area with the PAC-4S, portable alpha detector.
Before entering an area, check to see that the instrument is in operating condition.
The PAC-45 has three positions on the switch, OFF, ON and 188 219
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i 1604
$$)'b5)?? 6 BATTERY check.
When the switch is at the Battery position, the black needle should read in the green area.
If it does not, change batteries per the PAC-4S Technical Manual.
Release the switch and it returns to the ON position.
5.1.1 The probe on the PAC-4S, which is a ZnS(Ag) activated scintillation detector, should be held one quarter inch from the object being surveyed.
Touching the objec '.
would give better results; but there is a chance of contaminating the probe or damaging it by puncturing the detector face.
5.1.2 The PAC-4S reads out in counts per minute (CPM) representing the total 2n emission rate from either a one inch diameter 2
239 239Pu source or 59 cm of 3 uniformly distributed Pu source.
To determine the DPM value, use the following formula:
CPM UPM = Eff.
The efficiency of the PAC-4S is 28%, so if an area were surveyed and counts per minute were found to be 44, to obtain the DPM value, put the 44 CPM into the 44 formula as DPM =.28 = 157 DPM.
To calculate the DPM 2
value for 100 cm of area, multiply the resulting number by 100/59 or 1.7.
2 Rule of_ Thumb formula to use for calculation of DPM/100cm is as follows:
DPM/100cm2 = CPM (6.07) 4 2
where 6.07 = 1.7(DPM/100cm Factor) 5
.28(Efficiency) j 5.1.3 The surface contamination limits are:
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2 Contaminated Area:
>100 DPM/100cm alpha; 3o 188 220
1604 Revision 6 04/06/77 2
Clean Area:
<100 DPM/l)0cm alpha (Ref:
Radiation Protection Manual) 5.1.4 Mark all readings.obtained on a survey map (See Figure 1604-1) 5.2 Swice or Smear Survey: To de a swipe or smear survey, number the small envelopes to correspond with the survey points.
5.2.1 Hold the smear papers with a gloved finger and wipe over an area of 100 cm2 (i.e. a 4 inch squara).
5.2.2 Place smear papers in numbered envelopes.
5.2.3 Mark smear numbers on survey map corresponding to points of survey (Figure 1604-2).
5.2.4 After the smears are obtained, they are counted in an appropriate alpha counting instrument.
5.2.5 Calculate the disintegrations per mir ite (DPM) by using the following formula:
DFM = counts per minute (less backaround)
Effic ency i
Bac'. ground as per H.P.P. #1703 Efficiency as per H.P.P. #1706
- 5. 2. 6 The latest background t ;d efficiency for the alpha counting instrument are recorded in the H.P. Lab.
5.2.7 If the activity in counts per minute on the smears (CPM minus background) is less than the value computed by using the following formula 2V Background + Background then 3
(cpm)
(cpm) there is no detectable loose surface contamination present.
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5.2.8 Record all data on Form 1609-1 (attached).
4.0 188 221 e
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1604 01/15/75 Revisicn 2
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5.2.9 Return completed form to tha H.P. Foreman for review and approval.
5.3 Air Samoling NOTE:
Refer to H.P.P.1605 " Portable Air Sampling for Radioactive Particulate.
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