ML19276H128

Applicants' Prepared Testimony Re as Low as Practicable Radioactive Requirement

ML19276H128
Person / Time
Site:	Three Mile Island
Issue date:	10/25/1973
From:	METROPOLITAN EDISON CO.
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ML19276H123	List: ML19276H122 ML19276H124 ML19276H125 ML19276H127 ML19276H128 ML19276H130 ML19276H131 ML19276H132 ML19276H133 ML19276H134 ML19276H135
References
NUDOCS 7910100550
Download: ML19276H128 (12)

Text

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. October 25, 1973 UNITED STATES OF AMERICA ATOMIC ENERGY COMMISSION Before the Atomic Safety and Licensing Board In the Mhtter of )

)

METROPOLITAN EDISON ) Docket No. 50-289 COMPANY, et al. )

)

(Three Mile Island Nuclear )

Station, Unit 1) )

APPLICANTS' PREPARED TESTIMONY RELATED TO AS LOW AS PRACTICABLE ALAP Regulations and Regulatorv Guidelines During the nearly ten years since Three Mile . Island Nuclear Station's ( TMI 's ) initial site studies and subsequent design and construction, the regulations and guidelines governing the release of activity in the liquid and gas effluents from a nuclear power plant have undergone considerable change. The basic regulations governing radioactivity in the liquid and gas effluents through December, 1970, were those contained in 10 CFR Part 20 which is still effective. The bulk of the design and procurement of equipment and components for the TMI-l liquid and gas radwaste systems was completed by September, 1969. Therefore the 10 CFR Part 20 concentrations basically

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set the performance standards for these systems through the design and procurement stages for the TMI-1 radwaste system. At Met Ed's request, however, the liquid and gas systems were designed to achieve small fracticns of the 10 CFR Part 20 concentration limits in the liquid and gas effluents of TMI-1. This necessarily included full flow charccal filters in the exhaust ventilation systems of the auxiliary, fuel handling and reactor buildings.

In April of 1970, the AEC proposed a change to the regulations governing the release of radioactivity in liquid and gas effluents from nuclear power plants. Under the proposed regulation, the designer had to demonstrate that the design of a nuclear plant's radioactive liquid and gas waste treatment systens made them capable of " keeping the levels of radioactive materials in effluents to unrestricted areas as low as practicable" . The proposed regulation qualitatively defined "as low as practicable" as "As low as practicably achievable taking into account the state of technology, and the economics of the improve-ments in relation to benefits to the public health and safety and in relation to the utilization of atomic energy in the public interest" (10 CFR Section 50.34a(a) ) . Thus, the qualitative standard indicated that there was an economic as well as a technical optimum to what had to be provided to achieve "as low as practicable". On December 3, 14i7 093 1970, the AEC incorporated the proposed regulation en "as low as practicable" into 10 CFR Part 50 to beccme effective as of January 2, 1971.

Recognizing that the qualitative definition of "as low as practicable" was open to subjective interpretation and did not provide numerical guidance, the Ccmmission, on June 9, 1971, issued a proposed Appendix I to 10 CFR Part 50, which attempts to quantify "as lcw as practicable" .

This proposed regulation has been the subject of an extensive adjudicatory rulemaking proceeding which now involves consideration of the AEC's Final Environmental 1/

Statement related to Appendix I, WASH-1258,-- issued in July of this year. Propcsed Appendix I quantifies "as low as practicable" by specifying both allowable radioactivity concentration limits and periodic quantity limits in the liquid and gas effluents from nuclear power plants. It also allows variance from these limits provided that the designer can afford reasonable assurance that ef fluent concentrations and quantities different from those specified will result in less than a designated annual exposure to the whole body or any organ of an individual. The generally applicable dose limit in proposed Appendix I is 5 mrem to a hypothetical " worst case" individual. Ecwever, in the case of Iodine 131, AEC's latest guidance in Regulatory Guide 1.42 1417 094 (which is incorporated into WASE-1258 ss Annex 9 A) provides t".at the annual thyroid dose objective due to Iodine 131 exposure is 15 mrem per year.

Present ALAP Doses in Perspective In order to put in perspective the range of doses (5 mrem whole body and 15 mrem thyroid) presently considered to be ALAP, a brief discussion of comparative doses from natural background and other radiation sources is included in this section of this testimony.

We are all exposed to radiation La varying degrees from the ground, sky, and air around us, as well as from the food we eat. The average natural radiation exposure to persons living in the United States is estimated to be about 130 mrem per year, of which 25 mrem results from internal 2/

radiation.-- The average exposure to persons in the Harris-burg area is closer to 112 mrem per year because terrestrial 3/

radiation levels are slightly lower than average.-- The source of this exposure is cosmic rays and naturally occurring radioactive elements in the earth. The exposure to cosmic radiation increases with elevation above sea level, therefore, persons living in mountain areas or who frequently fly in airplanes receive a greater annual exposure than persons at sea level. We receive radiation directly from many minerals containing uranium and thorium isotopes in the ground or in the construction materials in our homes. A

,. - k f ()O,3

radioisotope of potassium is the most significant radio-active substance in our food. An additional small amount of exposure is received through radioactive gases in the air.

In addition to natural radiation, we are also exposed to man-made sources such as medical X-rays, luminous dials on watches, bomb detonations in the atmosphere, and television. It is estimated that an additional exposure of 44 mrem per year may be received on the average from other then natural sources, mostly from medical sources.--1/

One measure of the extent of population exposure is to add all the radiation exposures received by each individual in a population group. This resulting quantity is referred to as man-rem. The natural background population exposure within a 50 mile radius of the TMI side is computed to be about 340,000 man-rem. The thyroid gland also receives this dose.

Application of the ALAP Standard to TMI-l As stated earlier, the TMI-l liquid and gas radwaste systems were designed to meet standards considerably more demanding than those set forth in 10 CFR Part 20 which, at the time of their design, were the basic criteria to be met.

On the basis of calculational results presented in the TMI-l FSAR and the TMI F.nvironmental Report, TMI-l can be operated with the currently installed radwaste systems such chat:

1. The concentrations of radioactivity in its liquid and gas effluents are considerably lower than the limits set for them in 10 CFR Part 20 ;

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2. The concentrations of radioactivity in its liquid and gas effluents meet the intent of the qualitative "as low as practicable" standard in 10 CFR Section 50.34a; and

3. The maximum offsite doses to individuals due to radioactivity in TMI-l's effluents are less than the limiting values specified in the proposed Appendix I and Regulatory Guide 1.42.

Table 1 attached to this testimony shows that with the present design the annual maximum individual whole body and thyroid exposures due to gaseous effluents during routine operation at TMI-l are 0.7 millirem per year and 5.4 millirem per year respectively. These doses are considerably below present ALAP stancards. For purposes of comparison, Column (1) of Table 1 also reflects the whole body and thyroid doses of 112 millirem per year due to back-ground radiation. If a containment kidney system employing charcoal filtration were added to TMI, the thyroid dose would be reduced to that shown in column (5) of Table 1.

Similarly, if the main condenser vacuum pump discharge is charcoal filtered, the individual thyroid dose would be reduced to that given in column (7). If both of these modifications were made, the resultant thyroid dose would be that shown in colu=n (9). The individual doses shown in Table 1 were calculated based on continuous operation viti one quarter of one percent failed fuel in accordance 1417 097

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with current AEC guidelines. The whole body gamma and iodine inhalation doses reflected in Table 1 are those for an individual at the worst site boundary location.

The iodine dose to the thyroid is that of a child who drinks milk from the cows nearest to the site boundary and was calculated using the latest meteorological diffusion and other assumptions of Regulatory Guide 1.42 for computing thyroid dose through the cow-milk pathway. Other pathways to the thyroid are also included but are small in comparison

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to that of the cow-milk pathway. Whole body doses were computed usin- the semi-infinite plume model for gamma radiation as given in Regulatory Guide 1.4. The thyroid gland is assumed to receive the same dose as the whole body from gamma irradiation. The dose , as calculcted above, represent 2he highest potential doses to an individual off-site although it is unlikely that any one actual individual would satisfy the conditions necessary to receive the highest doses from each pathway evaluated.

In the Final Environmental Statement related to proposed Appendix I (WASE-12561, the AEC measures the cost effectiveness of adding environmental radwaste system modifications by comparing the cost of the additional equip-ment in dollars to the benefit to be derived from the additional equipment in terms of reduction in population exposure. We have employed this technique to display the cost effectiveness i4i7 098

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of adding a charcoal filter containment kidney and/or a charcoal filter on the main condenser vacuum pump at TMI-1.

Total population doses, expressed in " man-rem" are shown in Columns (2), (4), (6), (8), and (10) of Table 1.

Adding an 18,000 cfm charcoal kidney system inside containment would reduce the present cotal population thyroid dose of 306 man-rem to a dose of 70 man-rem; there would be no reduction in the whole body dose. The current cost of purchasing and installing this equipment in TMI-l is estimated to be $300,000. Thus, the cost / benefit of this modificatien can be expressed as the ratio of $300,000 to 236 man-rem, or $1271 per thyroid man-rem.

Adding a charcoal filter system in the main condenser vacuum pump discharge would reduce the present total population thyroid dose of 306 man-rem to a dose of 282 man-rem; there would be no reduction in whole body dose. The current cost of purchasing and installing this equipment in the plant is estimated to be $100,000. Thus, the cost / benefit of this modification can be expressed as the ratio of $100,000 to 24 man-rem or $4167 per thyroid man-rem.

If, as suggested in the next section of this testimony, deses were estimated on the basis of .1% fuel failure instead of .25%, the cost to benefit ratio would be increased by a f actor of two and one half. Thus, the cost / benefit ratio for the charcoal kidney system would be 53177 per thyroid man-rem, and for the charcoal filter for the vacuum pump discharge would be $10,416 per thyroid man-rem.

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A numbe" ,f cost values (see NASH-1250, p. 1-28) for a whole body an-rem have been auggested by various authors ,

ranging from S100 to $600 per man-rem. While no values ha.ve been suggested for dose to single organs such as the thyroid (which is the only dose affected 'cy either of the modifications considered in this testimony) , the relative risk of the dose to the thyroid compared to whole body dose suggests a lower value for population thyroid dose than those referred to above for population whole body dose. This would be consistent with present Part 20 limitations which establish limits for individual organ doses at three times the level for whole body doses. Even ignoring the whole body /

individual organ consideration, the cost effectiveness of 'he two modificaticns are far in excess of the range of values which have been suggested.

Failed Fuel Assumption As stated above, in the foregoing dose calculations we used 0.25% failed fuel as a source term. This was the approach used by the AEC Staff. They averaged the percentage of maximum amount of failed fuel associated with presently operating PWRs that have Pircaloy clad fuel, and found it to

-Y be 0.23%. Then 0.25% failed fuel was used to calculate the activity release from and the environmental impact of the TMI Nuclear Station. This is ecuivalent to saying thac

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the activity release from TMI-l will be consistent with the average maximum percent failed fuel derived from operating experience. This is conservative, since the referenced operating data reflects the relatively high fuel failure rate experienced by the early, unpressurized Zircaloy clad fuels. New, improved Zircaloy clad fuels are expected to exhibit a significantly lower failure rate. Thus, a 0.1% failed fuel was censidered to be the maximum rate for the average amount of failed fuel and was used by Metropolitan Edison in evaluating the environmental impact of TMI-l over its year design life. However, since short term operation with higher amounts of f ailed fuel is possible, 1% failed fuel was used in Chapters 11 and 14 of the TMI-l FSAR as a conservative basis for evaluating tAe consequences of accidents and for the design of the radioa:tive waste disposal system and the shielding of auxiliary system components.

The operating limits (Technical Specification Limits) for IMI-l are based on the measured amount of activity in the plant systems or on the measured amount of activity actually releaned from the unit and are not based on the percentage of failed fuel used as the expected design value.

This approach assures that the dose values used during the design phase to assess the effects of activity releases on the health and safety of the public and on the environment 1417 l0i

will not be exceeded during the operating phase. Thus, regardless of the amount of failed fuel assumed in the design phase and regardless of the amount of f ailed fuel actually experienced, if TMI-l's actual activity levels become greater than the Technical Specification limits, an equipment or operating change will be made to keep the activity levels and activity releases within the accepted limits.

While power transients may affect the radioactive nuclide inventory in the reactor coolant, the radwar.te system has been designed to treat radionuclides asscciated with up to 1% failed fuel and can accommcdate such transients.

REFERENCES:

--1/ Final Environmental Statement Concerning Proposed Rule Making Action: Numerical Guides for Design Objectives and Limiting Coditions for Operation to Meet the Criterion "As Low As Practicable" for Radioactive Material in Light-Water-Cooled Nuclear Power Reactor Ef fluents , WASE-12 5 8.

--2/ Estimates of Ionizing Radiation Doses in the United States 1960-2000, USEPA, ORP/CSD 72-1, 1972.

_3/ Natural Radiation Exposure in the United States, USEPA, ORP/SID 72-1, 1972.

J/ WASH-1258, Volume 2 (page 3-3).

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h T A lli.E 1 - I t3 D I V I D U A I. A tJ D POPULATION DOSES

• Natural iksckground THI 1 Gaseous Effluent / THI 1 Gaseous Effluent / THI 1 Gaseous Effluent / TMI 1 Gaseous Effluent /

Present Design Present Design Plus Present Design Plus Present Design Plus Containment Kidney Vacuum Pump Treatment Vacutun Ptwop and Contain-Treatment ment Kidney Treatseent (1) (2) ( 3) (4) (5) (6) (7) (8) (9) (10)

Individual Population Individual Population Individual Population Individual Population Individual Population 933 (mrem /yr) (man-rem) (mrem /yr) (man-rem) (mrem /yr) (man-rem) (mrem /yr) (man-rem) (arem/yr) (man-rem)

Whole Body

• 112 340,000 0.7 7 0.7 7 0.7 7 0.7 7 Thyroid 112 340,000 5.4 306 1.7 '70 5.0 202 1.3 46 (e x t e r na l ganuna ,

inhalation, and i nge t.t ion )

• Plant doses are f rom plume ganana doue.

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