ML19242D516
| ML19242D516 | |
| Person / Time | |
|---|---|
| Site: | Allens Creek File:Houston Lighting and Power Company icon.png |
| Issue date: | 06/05/1979 |
| From: | Gears G NRC OFFICE OF STANDARDS DEVELOPMENT |
| To: | |
| Shared Package | |
| ML19242D509 | List: |
| References | |
| NUDOCS 7908150348 | |
| Download: ML19242D516 (11) | |
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UNITED STATES OF A!! ERICA NUCLEAR REGULATORY C0!?tISSION BEFORE THE ATCMIC SAFETY AND LICENSING BOARD In the Matter of
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HOUSTON LIGHTING a o0WER COMPANY
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Docket No. 50-466
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(Allens Creek Nuclear Generating Station,
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Unit 1)
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NRC STAFF SUPPLEMENTAL TESTIMONY OF GERALD E. GEARS ON CONTiNTION N0. 2 In this proceeding, the.ntervenors have advanced the following contentions:
W. E. Rentfro: The electrical impact of the 345,000 volt transmission lines on human health has not been adequately evaluated.
The Staff has considered the effects of electrostatic field's gradients on humans in the Allens Creek Nuclear Generating Station Final Supplement to The
" Final Environmental Statement (Sections 5.3.4, 5.5.1.2, and 5.11.2).
The purpose of this testimony is to supplement the above document as related to humans, plants and animals.
The Staff is working with EPA, DOE, FEA, and other Federal age.ecies as a member cf the Federsi Interagency Advisory Committee on Electric Field Effects which is funding research on all aspects of electric field effects.
Based upon the review of the latest findings on this matter, the Staff does not believe that changes in the applicant's proposed design are warranted.
To authorize construction of HPL's proposed 345 kV facilities, final decisions concerning acceptable levels of exposure to various effects, and consequent design or operating conditions, may be made at the OL stage except in one 4390'2bb 7 908150 3 9 &
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subject area -- induced current shocks.
Because the only practical ways now to amelicrafe shock effects from induced current on other than fix' objects (e.g.,
tractor-trailer, school buses, etc.) are to increase conductor-to-ground clearances or lower the voltage of the facilities, the Atomic Safety and Licensing Board (the Board') would have to decide now whether HPL's proposed line may be
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built and operated at 345 kV and would also have to determine proper clearances.
It is our position that there are sufficient data on this subject th'at will permit the Eoard to make the necessary final determinations.
In another subject area -- that of long-term electric magnetic field effects --
the Staff realizes that there are uncertainties in this area. The pertinent point for the present is that possible protective measures do not include changes in tower design or conductor size or configur ation.
It is our position tha t 345 kV may be approved as the design voltage with reconsideration of impact data at the OL stage including possible imposition of protective conditions on
. 345 kV operation.
We will now address in g,- iter detail the areas of induced shocks and biological effects of electric and magnetic fields.
I.
INDUCED CURRENT SHOCKS The proposed 345 kV transmission line will induce an electric charge and proportional voltage on insulatod conducting objects on or near the R/W. A person grounded through bare feet, shoes, or a grounded conducting object, 'who touches such an insulated charged object may receive a current flow and experience " shock" effects of two general kinds -- s teady s ta te (o r short GOO'263
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- circuit"} current and transient current (or " spark discharge").1,2 The level of the induced charge will vary with a host of factors, including:
voltage (which affects electric field strength), transmission line conductor-to-ground clearance (which'is affected by line loadine and ambient temperature) (the lower
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the clearance, the greater the charge), size of the insulated conducting object (the larger the object, the greater the induced charge), degree of insulation of the conducting object, and spatial, relationship of the insulated conducting object to the transmission line conductors.
The levets of steady state or transient currents experienced will also be affected By the degree to which the person touching the insulated obiact is effectively grounded.3 For steady state currents, direct physical harm occurs only above the "let-go" level -- where involuntary muscle contraction makes the person unable to release the conducting object.
The minimum "let-go" level for men is about 9 milliamperes
..(mA) and that for women about 6 mA.
Based on these data, 5 mA is being used as t'.e allowable maximum "let go" current in Part 2 of the National Electrical Safety Code.4 At some point above the let-go level, respiratory arrest and consequent suffocation may occur if tb. current flows through certain parts of 1
United States Department of Interior.
Electric Effects of Transmission Lines, Bonneville Power Administration, September 15, 1975.
2 United States Department of Agriculture.
Electrostatic and Electromagnetic Effects of Overhead Transmission Lines, Rural Electrification Administration, May 1976.
3 T. D. Bracken.
1976. Field Measurements and Calculations of Electrostatic Effects of Overhead Transmission Lines, IEEE Trans on Power Apparatus and Sys tems, Vol. PAS-95(2 ): 494-504.
4 National Electrical Safety Code.
Institute of Electrical and Electronics Engineering, Inc., National Bureau of Standards. ANSI C2.
1977 GdO270
. a the body for a sufficient time.
Below the let-go level but above the thr eshold of perception, steady state current flow may cause anything from mild suri rise to a sudden, involuntary " startle" reaction of part or all of the body.
While about 1% of children and small adults can perceive steady state currents of,
about 0.1 mA, the threshold of perception for 50% of the population is about 1.0 mA.s,s For transient currents, spark discharges at the maximum levels predicted for the proposed 345 kV tran[ mission line will not cause any direct permanent physical harm.
To protect oeople not only against direct permanent physical harm but also against possible u, direct or secondary injury that might occur from an involuntary reaction to a shock current -- such as from jerking a hand back and catching it in moving cachine parts, a program of grouading -- or grounding and bonding of stationary, fixed conducting objects on or near the R/W (like
_. metal buildings, roofs, or fences), without any change in voltage or facility design will be initiated by the applicant (FES Suppl. Sect. S.11.2).
Vehi cles which may use or cross the R/W, howe ter, present a more difficult problem, since they may not be equipped with grounding straps or chains.
The National Electrical Safety Code covers this problem in Section 23-Clearances.
5 C. F. Dalziel and W. R. Lee.
1969, Lethal Electric Currents, IEEE Spectrum, February, pp. 44-50.
6 J. C. Keesey and F. S. Letcher.
1970, Human Thresholds of Electric Shock at Power Transmission Frequencies, Arch. Environ. Health, Vol. 21: 547-552.
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The applicant has indicated to the Staff that proposed clearances will not result in a maximum induced current of 5.0 m.1 (res), when ti.e largest anticipated truck, vehicle, or equipment under the line were short-circuited to ground based upon the National Electrical Safety Code (Sect. 232,B.I.c).
The Staff believes there is no evidence to warrant rejection of the proposed 345 kV facilities, merely to protect against the possibility of improbable indirect injuries caused by involuntary reaction to shocks.
It is practical to design the 345 kV line for 5.0 mA steady state limit and the applicant has indicated that this will be done.
If additional data from research and other sources determine the necessity of additional protection against indirect injury, operating conditions providing some type of public educational program may be warranted.
That question need not be decided now.
Minimal clearances that will meet the 5.0 mA steady state current limit for all vehicles reasonably anticipated to travel on or across any part of the R/W will be provided by the applicant. No currents _ above that limit would be experienced from touching a school bus, a milk tanker, a bucket truck or a combine operating on the R/W away from roads.
In conclusion, we believe that HPL's present design clearances that maintain a maximum induced current of 5.0 mA rms when the largest anticipated truck, vehicle or equipment under the line is short-circuited to ground for the proposed 345 kVline provide adequate protection from induced shock currents.
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II.
BIOLOGICAL EFFECTS OF ELECTRIC AND MAGNETIC FIELDS The passage of an electric current through any unshielded conductor produces both electric and magnetic fields in the surrounding medium.
The effect of electric fields on humans has been and presently still is being studied extensively throughout the world. As transmission designs result in larger and larger voltages, more intense fields that cover wider areas may result.
For an overhead AC transmission line,lthe three separate phases create an interference pattern so that the strongest field exists in the area below the outer phases, approximately 20 to 60 feet from the centerline.
The field drops off moderately as >ne poves closer to the centerline, and falls off rapidly as one moves further awav from the facility. A 345 kV facility may produce a peak electric field of 5 to 6 kilovolts per meter (kV/m) at ground level, dependent upon conductor configurations, and the field drops off to about 1.6 (V/m at the edge of right-of-way.
The magnetic field produced by a high voltage transmission line has similar characteristics.
The maximum calculated magnetic profile at 1.5 m above the ground is about.6 G (gauss).
Safety standards for whole body exposure to magnetic fields for long periods have been recommended at 200 to 3007 G.
No harmful biological effects are expec+ed from magnetic fields "nder transmiss;on lines because magnetic field levels at which biological effects occur are generally much higher than levels under powerlines.
7 U. S. Department of Interior (Bonneville Power Authority). p p. 17-19.
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Precautionary electric field guidelines have been established by the Russians 8
for substation and transmission line workers.
More recently the Russians established general exposure guidelines for the local population and agri-cultural workers.
Using the Russian general population guidelines, HPL's 9
345 kV lines would be permitted *.
I e " Rules and Regulations on Labor Protection at 400, 500, and 750kV AC Substations and Overhead Lines of Industrial Frequency (in USSR)",1972.
Translated by G. G. Knickerbocker in Special Publication No.10, Power Engineering Society (IEEE),1975.
9 Y. I. Lyskov, Y. S. Enna, and M. D. Stolyarov,1975.
Electric field as a parameter considered in designing electric power transmission of 750-ll50kV; the measuring methods, the design practices and direction of further research'.
Trans. by G. G. Knickerbocker in Special Publication No.10, Power Engineerin Society (IEEE), 1975.
These guidelines established higher acceptable gradient standards of transmission lines in accordance with these direct quotations (from Lyskov, et al.1975):
"In dcsigning the 0. H. 750-1150 kV line, considering that cumulative effect of the field due to an infrequent and non-systematic exposure of the local population and the agricultural workers cac practically be disregarded, as permissible magnitudes of the field intensity the following higher standards were accepted:
20 kV/m for difficult terrain, 15-20 kV/m for non-populated regions, 10-12 kV/m for road crossings.
"The permissible field strength must not be exceeded at the center of the span at the height of 1.8 meters above ground and at the lowest sag (at the maximum 15 year temperature).
"The permissible values of field intensity were chosen with consideration of favorable operating experience in over 150,000 km/ years in 0. H. 500 kV lines, for which the designed field intensity is for similar conditions from 10 to 14 kV/m."
However, a Russian paper by V. D. Dumanskiy, et al. enti tled " Hygienic Evalua-tion of Electromagnetic Field Generated by High-Voltage Power Lines" (in Gi giyena I Sani tariya-No. 8 !9-23, 1976), obtained by the Staff, states that la ioratory test animals (albino rats) undergo changes in behavioral reactions when subjected to fields in the range of only 1 to 5 kV/ meter.
These field gradient levels are considerably below the general population standards quoted above.
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Current research is being funded and guided by the Federal Interagency Advisory Committee on Electric Field Effects on which NRC Staff actively serves.
Preliminary findings for 30 day exposures have produced some positive results in the areas of immunology, neurophysiology and behavior in +ests on mice and ra tslC.
These effects were found at field strengths scaled to man of about 4-15 kV/m.
A 4-12 kV/m field strength is typical for the maximum values measured near the ground under 345-765 kV transmission lines near the center of the R/W.
Maximum field strengths at the edge of the R/W, as stated earlier, fall off rapidly and would be about 1.6 kV/m for a 345 kV line.
Since field strengths outside the R/W are still below the range of test field strengths, the Staff finds no compelling argument to recommend halting of construction of HPL's 345 kV lines.
The Staff has also followed the recently completed New York State Public Service Commission (NYPSC) hearings on the health and safety of 765 kV overhead trans-mission systems.
Upon completion of these hearings, the NYPSC connissioners ordered that " risks, if any, of long-term exposure to 765 kV transmission in the areas traversed by PASNY's'line and any future 765 kV lines will be no greater than those, now widely accepted, of long-term exposure to the 345 kV lines operating throughout the State."
(State of New York Public Service Commission.
Opinion No. 78-13.
Cases 26529 and 26559.
June 19, 1978. p. 41).
10 Effects of Electric Fields on Small Laboratory Animals.
R. D. Phillips and W. T. Kaune; Battelle Memorial Institute-PNL; Richland, Washington.
DOE Environmental Control Symposium; November 27-30, 1978. Washington, D. C.
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a The staff, therefore, recommends that construction of the HPL's 345 kV lines be permitted and that at the OL review stage when additional experi-mental data has been gathered, the Staff will again review this issue.
If experimental data were to warrant protective measures, a variety of actions could be considered including, but not limited to: increasing the width of right-of-way to limit the field Etrengths to whith: the public would be exposed at the edge cf the right-of 'way; potential rights-of-way users be given specific warnings of possible risks; use of shield wires or other types of retrofit +ing techniques which could reduce field gradients to a prescribed level, Thus, protective measures that might have to be taken if, in fact, electric and magnetic fields represent a real hazard may take the form of educational programs, wider right-of-way, possible restrictions on the use of the right-of-way, reduction of operating voltages, and possible engineering techniques to reduce electrostatic fields at ground levels, The Staff had not addressed the question of field gradient ef fects on olant or animal life along the transmission line in the FES for two distinct reasons:
(1) It is our position that any effects attributed to the electric field on humans would generally include animals, since most animals would have a territorial range extending beyond the right-of-way and therefore would not be exposed for long periods to field gradients; those animals which exhibited a more limited range would most likely be shielded extensively from gradients at ground level by surrounding shrubs, grasses,
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etc., and therefore would not receive a high cumulative exposure dose.
(2) Fie1d tests and studies of biological ill effects of field
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gradients conducted on plants and animals have been generally-inconclusive. For field tests and studies which' fall within the range of worst case field gradients b'elow' transmission lines (20 kV/m or less), no significant effects haye b'eer attributed to elec, -ic fields, A maximum field gradient predicted for 345 kV systems 1s about 5 to 6 kV/m; thus no significant effects are expected.
The Staff did not address the question of electric field effects on agriculturally related plant life in the FES. The Staff has reviewed
- the latest data on this subje:t as well as animal la5 oratory and field studies and summarizes the findings b~elow, Results of ongoing researchil on electrit field effects on growth and development of plants and animals indicate that neither gross injuries nor gross abnormalities were apparent from a 50 kV/m~ field.
11The Effects of High /oltage Electric Lines on the Growth and Development of Plants and Animals.
J.W. Bankoski, H. B. Graves, and G.W. McKee.
Proceedings of the First National Symposium on Environmental Concerns In Right-Of-Way Management. Mississippi State University.
1976.
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_11 Some minor physical damage, barely perceivable along corn, bluegrass, and alfalfa leaf tips was indicated in ficids from voltage gradients of 25 kV/m and above. The same series of studies investigating electric field effedts on small animals indicate that no major abnormalities in behavior, activity, or outward apperance have Been demonstrated frcm higfc fields of 50 kV/m. The preliminary results further substantiate published data which to date have n t indicated any hazardoos. effects to laEeratory-and agricultural animals from present levels of field generated from existing transmission powerline technology 12, Based on these findings, the Staff does not believe that changes in the applicant's proposed design are warranted. As in the case of human ill effects, additional extensive studies are currently being conducted.
The Staff is keeping abreast of these studies and of any guidelines
__ resulting frc::, them, and will reconsider the impacts of the transmissior, line operation prior to or at the time of the operating stage review, taking into consideration any new information, 12Biological Effects of High Voltage Electric fields:
State-of-the-Art Review and P,*ogram Plan.
IIT Research Institute, Chicago, Illinois.
November 1975.
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