ML14358A172
| ML14358A172 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 04/03/1978 |
| From: | Case E Office of Nuclear Reactor Regulation |
| To: | Levine S NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| Shared Package | |
| ML14358A173 | List: |
| References | |
| NUDOCS 7904250280 | |
| Download: ML14358A172 (6) | |
Text
UNITED STATES ENCLOSURE 2 NUCLEAR REGULATORY COMMISSION WASHING TON. 0. C. 20555 April 3, 1978 MEMORANDUM FOR:
S. Levine, Director, Office of Nuclear Regulatory Research FROM:
E. guCase, Acting Director, Office of Nuclear Reactor Regulation
SUBJECT:
STUDIES TO DETERMINE CAPABILITY OF EXISTING PERSONNEL NEUTRON DOSIMETRY SYSTEMS AT OPERATING NUCLEAR POWER REACTORS TO MONITOR REACTOR NEUTRON ENVIRONMENTS (RR-NRR-78-8)
S NRR requests RES to fund a program for the purpose of collecting data on the effectiveness of personnel neutron dosinetry proorars at operating nuclear power plants.
To achieve this objective there is a need to identify plant areas in which siqnificant neutron levels occur, and to characterize the nu tron spectral distribution in order to determine the dose equivalent rates at these locations (e.g., containment areas of PWR's), so that occupational dose estimates, provided by the personnel neutron dosimeter, can be compared with the "true" theoretical dose as determined by the neutron spectrum and respec tive dose rateper unit flux for each energy interval at these locations.
Neutron exposures have seldom been observed (reoorted) using curren~t measure ment techniques at operating reactors.
We need to evaluate the adequacy of present neutron monitoring techniques at reactor sites.
Obtainin the data in this manner would appear more efficient than requesting all licensees to performi these surveys independently.
Status of Problem Regulatory Guide 8.14 "Personnel eutron osimeters" requires that licensees supply personnel monitoring equipment to those emoloyees whose exoosure to neutrons is likely to exceed 3CO mrern in a ouarter.
The Guide provides cri teria for acceptable devices and techninties for neutron personnel monitoring.
NTA film, a neutron dosimeter used throunhout the nuclear industry, is not sensitive to neutrons below about 0.7 NIEV.
Therefore, dependinq upon the spectrum, the dose equivalent can be grossly underestimiated.
nln the other hand, al bedo dosi meters, whi ch are not Qui te as wi dely used as NTA among power reactor licensees, are ouite sensitive to low enerqv neutrons and can overestimate the dose equivalent by factors of 20 to 50 (again dependina on the neutron spectrum and calibration technique).
Since most licensees do not routinely measure the neutron spectral distribution at their facilities, the devices worn by the workers, although acceptable by R.G. 8.14, may be provid incq inaccurate dose estimates.
Contact:
S. Block, EEB/DOR 28066'
S. Levine 2 -
April 3, 1978 Accurate measurement of the neutron spectrum requires specialized nuclear instruentation and methods generally not available to the licensee, ex cept through consultants. Therefore, few attempts have been made by li censees to determine spectral distribution.
Several PWR reactors (e.a.,
Calvert Cliffs, St. Lucie, Millstone 2 and Trojan) have neutron streaming problems inside containment and are installing additional neutron shield ing.
This problem is generic, and considerable staff time has been de voted to its resolution. This ignorance of specific neutron spectral distribution in occupied areas of containment is therefore of concern to the staff, because incorrect dose assessments may result.
Information Needs A study is therefore needed which can provide the followina data:
- 1)
The neutron spectral distribution at selected locations inside and outside containment of operating nuclear power plants.
The measure meint technique should be of sufficient sophistication to show any structure that may exist in the spectral distribution curve, par ticularly in the interme t e y region (i.e., fro 10 ev to 100 key) which may contribute an appreciable fraction of the dose equivalent.r The neutron spectrum should also be characterized with respect to geometry and any shielding perturbation that could effect
'the measurement.
- 2) The theoretical ("true") dose equivalent rate, at each location, de termined from the spectral distribution data of (1) and the Neutron Flux Dose Equivalent parameters of 10 CER 20.4(4).
- 3)
The neutron dose equivalent rates made at the locations selected in (1) above, using rem counter devices such as the Andersson-Braun neutron survey meter.
Other dpvices that can measure neutron dose or dose equivalent rates with at least the same accuracy as the rem counter, over the neutron energy region of interest, may'also be used in parallel.
- 4)
The survey meter measurements, compared with the theoretical values, to show the effectiveness of portable survey metcrs to read out "tu"dose equivalent rates of reactor neutron spectrum.
- 5)
Measurements made using personnel monitoring methods described in Regulatory Guide 8.14 at the selected locations in (1), intercom pared with the
""rul dose equivalent to determine the accuracy of each method.
(Personnel roni tori na exrcosure techniques shoul d be at the discretion of the contractor).
Co77-ercial oersonnel neutron dosimeter systens should he used, as available, for each oersonnel
,nonitorinq performance check (e.a., albedo personnel dosinmeters anid NTA film).
S. Levine 3 -
April 3, 1978
- 6)
Conclusions with respect to the accuracy of the various techniques, grouped according to physical geometry and neutron shielding.
Cost and Possible Contractor Battelle Northwest has submitted a draft 189 working paper to performh a study of this type.
Although their scope does not directly address sev eral issues of interest to NRR, it does contain the essence of these in terests.
Other laboratories that could perform this study include Lawrence Livermore Laboratory, which has developed a portable neutron spectrometer used to study the neutron energy spectral distribution at one nuclear power reactor; Savannah River Laboratory which has done considerable work in albedo personnel dosimetry; Brookhaven National Laboratory with experience in LET dosimetry; and the University of Wis consin which has TLD expertise to perform these studies. We anticipate that the required information can be obtained at a cost of about $100,000 for a one year study at 6 to 12 reactors.
Selection of reactors would be made in conjunction with NRC.
Value Impact We feel that this study is important in confirming that adequate personnel neutron dosimetry isbeing performed by nuclear power reactor licensees, consistent with Regulatory Guide 8.14. if it is determined that the spec tral distribution is heavily weighted with neutrons of energies less than 0.7 mev, those licensees using NTA film may be grossly underestimating personnel exposures.
Appropriate actions could then be taken to change deficient personnel monitoring practices.
Conversely, those licensees us ing albedo dosimetry might have to re-evaluate their calibration procedures if they are grossly overestimating their personnel neutron exposures.
The requested study will provide NRR the technical basis for developing any needed additional guidelines or revising existing guidelines.
Sources of Information on Neutron Radiation at Power Plants Several nuclear power plants have made neutron measurements in containment in conjunction with shield reviews because of their neutron streaming prob lems.
These include Millstone II, Rancho Seco, Calvert Cliffs, Farley, Trojan and St. Lucie. These data can be made available by licensees.
Other data have been reported at ANS meetings or have been developed by A&E firms (e.g.,
- Bechtel, Ebasco, and Sargent and Lundy) for utilities in conjunction with shield reviews.
Edson G. Case, cting Director Office of Nuclear Reactor Requlation cc:
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tron radiation_.Its victims would suiffer was pcertible %!thin a few days, even.
ianufacturczrs not only are producing
..violent nause--a diaurrhea and ot.hot' un-w.hours. fie repoft his findinpgs to Bat-dosimeters but ar-e. supplying ~~
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.not identihy the site ol the te-:t.'Our cnrcoswt hm iticeil powerplant in tht; country.. An inter-own sources have identified tlhe ruyute--.
few of time 68 opcraing-nuclear pla-nts cual mnem.o circulating insids the Nu-
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ulainry Conantssion,. warns two power rea3ctrs are locat'4......NTIC regulaitiors do not require thciu.
".that the workers at nuciear plants are
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Met neutron rad:iton. In a mcaio dnted
'Teeexpos.ures have gone anno-March 6, 1978, o'fficials de-lared:
W Torture hr Mail-43oviet commnissals tiect" states the me.mo,.Tecause of-have no rezson to b~elieve tLat a prob---are callously. !-,(;ingc thc mais-now 2 a.
the inadeotiacy of the ncutrnn Ina eis-ts as long, as radlistion.
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lethal as neuc-ba bombs. No one has think atornic wo-zkes are in any Pinen-
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yet computed the neutron radation In-diate daner IndenDcndert. scicotista We have obtained evitlence fromb a side nuclear plants. The eaact cx-o-dLsagree. chaz7.ng th-at the rue21ods.
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May 8, 1978 The Washington Post 1150 15th Street, NW Washington, D. C. 20071 Sirst The Jack Anderson Column of May 8, 1978, titled "Neutron Radiation at Nuclear Plants" contains three factual errors and other items of misleading information. The errors are as followsi
- 1. "No one has yet computed the neutron radiation inside nuclear plants". This statement is totally untrue as calculations have been made of' the neutron radiation to be expected inside every proposed nuclear plant.The calculations are measureably accurate; as has been confirmed by measurements required by the Nuclear Regulatory Commission as part of the shield performance test that are part of the plant start up tests.
- 2. "scientists have been unable so far to prevent it,"(Neutron scattering, around corners, undetected). Neutron shielding can bffectively'prevent scattering. Scattering around corners can be detected and measured, accurately, when proper measurement techniques are employed. Such techniques are the subject of guidance supplied both by the Nuclear Regulatory Commission and by Industry promul gated consensus standards.
- 3. "regulatory officials don't really know the extent of the neutron radiation problem at nuclear reactors." It is known that very few workers are being exposed to very inconsequential amounts of neutron radiation, in compliance with the regulations imposed on licensees of the Nuclear Regulatory Commission.
The very worst part of the article is the fact that the Jacc Anderson Staff member who compiled the informa:tion fo.
th-article.
was clearly informed of these factua.l error72 well before the publication date and he chose to ignore the true facts, as presented by.
the same individuals he quotes for other facts in the article. This is irresponsible report ing, at the very least.
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~43
The major point that should be made is that workers in the nuclear industry are better protected and subject to less occupational risk, radiation included, than workers in many other parts of the industfial community. Their risks are better calculated,.
better monitored and measured, and of concern to more people, regulators and otherwise, than most other industrial risks. Jack Anderson would be more effective if he turned his atten-.
tion elsewhere.
Sincerely,
-v)
William E. Krege?'
U. S. Nuclear Regulatory Commision r3 William E Kreger 2900 A-scott Lane Olney, MarYl3nd 20832 1....