ML13330B102

Eia Supporting Proposed Mods Re Sleeving Project

ML13330B102
Person / Time
Site:	San Onofre
Issue date:	11/28/1980
From:	Office of Nuclear Reactor Regulation
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ML13330B101	List: ML13330B100 ML13330B102
References
TAC-42090 NUDOCS 8012160260
Download: ML13330B102 (19)

Text

ENVIRONMENTAL IMPACT APPRAISAL BY THE OFFICE OF NUCLEAR REACTOR REGULATION LICENSE NO. DPR-13 SOUTHERN CALIFORNIA EDISON CO.

SAN ONOFRE NUCLEAR GENERATING STATION UNIT 1 DOCKET NO. 50-206 November 28, 1980 8012160 6

TABLE OF CONTENTS Page 1.0 Proposed Action 1-1

2.0 Background

2-1 3.0 Description of the Sleeving 3-1 4.0 Environmental Impacts of the Sleeving Project 4-1 4.1 Occupational Exposure 4-2 4.2 Public Radiation Exposure 4-4 5.0 Conclusions 5-1 6.0 References 6-1

1.0 PROPOSED ACTION Southern California Edison Company proposes to install sleeves in approximately 7500 steam generator tubes at San Onofre, Unit 1.

Although this action requires no authorization by the Nuclear Regulatory Commission, we have nevertheless evaluated whether or not it involves any significant environmental impact and conclude that it does not.

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2.0 BACKGROUND

In April, 1980, San Onofre I experienced sufficient leakage in the steam generator tubes to require plant shutdown. During testing to locate the leaking tubes, the licensee discovered that many of the tubes were experiencing significant degradation just above the tubesheet on the hot side (inlet side) of the steam generator due to caustic intergranular attack. This condition is extremely difficult to detect by conventional eddy current testing methods.

However, by a combination of several testing methods including removal and lab testing of several sample tubes, the licensee identified the problem and determined the extent of the problem.

The technical specifications of San Onofre Unit 1 require that the licensee report steam generator tube degradation to the Nuclear Regulatory Commission. If the degradation exceeds certain bounds the technical specifications require the licensee to sub mit a plan to restore the integrity of the steam generator tubes.

This plan must be approved by the NRC and completed before the reactor can be restarted. In fulfillment of those technical specifications, SCE submitted a plan on September 1980 to the NRC to install sleeves in the San Onofre I steam generator tubes.

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3.0 DESCRIPTION

OF PROPOSED SLEEVING PROGRAM The repair program proposed by SCE to restore the integrity of the San Onofre I steam generator tubes is sleeving. In simple terms, sleeving is the insertion of tubes within the existing steam generator tubes.

The program involves several steps.

First, to reduce radiation levels inside the steam generator channel head, the channel head is decontaminated using a high pressure water/grit spray.

Second, the inside surface of the bottoms of the tubes will be cleaned to prepare f". sleeve insertion and joining. The surface cleaning process also reduces radiation levels inside the channel head. Then, the sleeves will be manually inserted. The joining area and the bottom of the sleeves will be expanded. Next, the bottom of the sleeve will be hard-rolled into the tubesheet. The sleeve will be joined to the top using a proprietary process.

Finally, ultrasonic testing will be used to ensure that the sleeves have been properly joined.

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4.0 ENVIRONMENTAL IMPACTS OF THE SLEEVING PROJECT After a scoping assessment of the environmental impacts of the proposed sleeving project, the staff concluded that occupational exposure and !

public radiation exposure were the only impacts which had the potential to significantly affect the quality of the human environment. The environmental impacts of occupational exposure and public radiation exposure are discussed in following sections.

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(1 4.1 Occupational Exposure We have reviewed the occupational radiation exposure expected to result from the steam generator tube sleeving planned for San Onofre Nuclear Generating Station, Unit 1, and the steps to be taken to assure that the occupational radiation exposures will meet the requirements of 10 CFR Part 20, Standards for Radiation Protection, and will be as low as is reasonably achievable (ALARA). The major source of the radiation dose rate inside the steam generator channel head is a tenacious layer of "oxide" which includes deposited activated corrosion products. Southern California Edison (SCE) has used a Westinghouse mechanical decontamination process involving grit driven by a high pressure water spray to remove this deposited.activity from the inside of the channel head. Based on Westinghouse experience with grit/high pressure water decontamination, SCE expects to reduce dose rates inside the channel head 4y a factor of 5 (after decontamination, surface cleaning and shielding).

The surface.preparation will.remove deposited radioactivity in the bottom few feet inside-each tube, thereby reducing gammaradiation shine to the workers from the tubes. To further reduce the doses to personnel working in the channel head, lead shielding will be placed on a) the cold leg side of the divider plate to eliminate cold leg streaming to the hot leg plenum, b) over the opening of the hot let inlet pipe, and c) on the bottom of the tube sheet to cover portions of the tube sheet not being worked on. These decontamination and shielding techniques are expected to reduce the dose rates inside the hot leg channel heads from approximately 10 rem/hr to approximately 2 rem/hr. In order to minimize worker time spent inside the steam generator plenum, SCE intends to use remote techniques where they are practicable. Most of the channel head decontamination and preparation of the inside surfaces of the tubes will be done remotely. Most of the joining of the sleeves inside the tubes and the non-destructive examination of the repaired sleeves will be done remotely.

SCE and Westinghouse will provide training to the maintenance crews to minimize the time spent in the radiation fields. As recommended in Regulatory Guide 8.8, "Information Relevant To Ensuring That Occupational Radiation Exposures At Nuclear Power Stations Will Be As Low As Is Reasonably Achievable", this training will include the use of full-scale mockups of the steam generator plenum and surrounding work area. The same tools used to train the workers will be used during the sleeving work. All workers will wear a series of TLD's to measure doses to their chests, heads and extremities.

The methods used by SCE to develop a collective occupational radiation exposure for the entire sleeving project are based on actual experienct and testing.

SCE 1) determined the maintenance activities that will be involved in the sleeving program; 2) estimated the person-hours of work necessary to perform those activities; 3) determined the areas maintenance personnel must occupy to perform those activities and estimated the radiation dose rates in those areas; 4) multiplied the man-hours by the dose rate for each activity; and

5) summed the doses for all the activities.

The dose rate estimates mentioned above are the measured dose rates at San Onofre with adjustments for decontamination and shielding. The resulting 4 -2

estimate for total collective occupational radiation exposure for the project is 1800 person-rem. Based on our review, we conclude that the licensee's estimate-is reasonable.

No individual will be allowed to exceed the dose limits imposed for workers by 10 CFR Part 20, which are established as dose limits appropriate to the health and safety of individuals.

To determine the relative environmental significance of the estimated 1800 person-rem, comparisons were made with 1) the doses expected from normal operation of nuclear plants, and 2) other non-nuclear risks.

Table 4.1 shows the occupational dose history for San Onofre 1.1.3 With the addition of 1800 person-rem for the sleeving project, the average annual dose for the twelve years of dose history at Unit 1 will be less than 500.

person-rem. Occupationag exposure estimates were not specifically considered in the San Onofre 1 FES.

In recent environmental statements for new nuclear power plants we have provided an estimate of 500 person-rem per reagtor unit as the average annual occupational dose (e.g. San Onofre 2, 3 DES).

This estimate is based on reported data from power reactors that are operating with radiation protection programs in accordance with NRC guidn 5e and regulations. A summary of that data is provided in Table 4.2.

-.Those data Tshow that 500 person-rem per reactor unit year is roughly the average of the wide range of doses incurred at all light water cooled reactor units over the last several years. The amount of dose incurred at any single reactor unit in a year is highly dependent on the amount of major maintenance performed that year. Every year several units require some items of major maintenance which result in doses for those units well above the annual average of 500 person-rem.

These doses are included in the average and are considered normal deviations from the average, particularly since such maintenance contributes to effective and safe plant operation and since it is carried out with procedures that maintain exposures ALARA. As Table 4.2 shows, the 1800 person-rem estimate for the sleeving project is within the historical range of doses about the average for one unit in a year. -This collective exposure would represent about 10% of the anticipated 40 year collective exposure of approximately 18,000 person-rem, based on the average annual exposure at San Onofre, Unit 1 so far, and less than that for the plant life average for all plants.

wecalculate that 1800 person-rem, the occupational dose estimate for the

-sleeving project, corresponds to a risk of less than one prepnature fatal cancer in the exposed work force population. We also calculate that

-1800 person-rem corresponds to a risk of less than one genetic effect to

.te ensuing five generations. These risks 1ire based on riskestimators

-derived in the BEIR Report and WASH-1400 from dfta for the population

-4s a whole.

New information in the BEIR III Report would lead to an even lower

-estimated risk for premature fatal cancers-. These risks are incremental risks; risks in addition to the norma1 risks of fatal cancer and genetic

.effects we all face continuously. For a population of 1000 these normal

.risks would be expected to result in about 190 cancer deaths and about 14 1 genetic effects (genetic effects are genetic diseases or malformations),

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-plus about 300 more genetic effects among their descendents.

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11 To make the health risk associated with radiation dose more understandable, risk comparisons can be made with non-nuclear activities commonly partici pated in by many individuals. One rem of rdiation is numerically comparable to a lifetime mortality risk of about 10-4.

Table 4.3 presents the equivalent risk of 10-4 for several common activities - risks which many people take routinely and consider to be insignificant.16 The average dose to a worker for the sleeving project will be roughly 1.8 rems. As Table 4.3 shows, the lifetime risk from radiation dose for the average sleeving project worker is smaller than the lifetime risk associated with many common activites.

Another perspective of an occupational risk comes from comparison of occupational mortality risks in the U. S. One such comparison is shown in Table 4.4. It indicates that radiation exposure in the work place, as experienced at an average radiation worker exposure rate, results in a relatively low occupational risk.

Some have cri icized occupationally related cancer estimates as being overly conservative.

However, most experts feel the risk estimates in Table 4.4 relating to occupational exposure to low-LET radiation are overestimates.

In our opinion, the comparisons just presented are reasonable ones.

The risks of occupational exposures in the range of 0.5 rem per year to 5.-.

i per year do not significantly affect a a typical worker's total risk of mortality.

In summary, the staff has drawn the following conclusions regarding occupa tional radiation dose. SCE's estimate of 1800 person-rem for the sleeving project at San Onofre 1 is reasonable. This dose falls within the normal range of annual occupational doses which have been observed in recent years at operating reactors. This dose will not increase the annual average dose at San Onofre 1 above 500 person-rem per year, the overall power reactor average. SCE has taken appropriate steps to ensure that occupational doses will be maintained within the limits of 10 CFR 20 and ALARA. The additional health risks due to these doses over normal risks are quite small, less than one percent of normal risk to the project work force as a whole.

The risk to an average individual in the work force will be lower than the risk incurred from participation in many commonplace activities. The individual risks associated with exposures involved in the repair program will be controlled and limited so as not to exceed the limits set forth in 10 CFR Part 20 for occupational exposure. For the foregoing reasons, the Staff concludes that the environmental impact due to occupational exposure will not significantly affect the quality of the human environment.

4.2 Public Radiation Exposure SCE has estimated the amount of radioactivity which will be releajed in liquid and gaseous effluents as a result of the sleeving project.

Those estimates are presented in Table 4.5. The estimates are based on past effluent experience at San Onofre 1 during steam gl erator majitenance.

Table 4.5 also presents effluent releases for 1978 and 1979 from San Onofre 1 and the FES annual average effluent release estimates.

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12 SCE will take several steps to minimize releases.4 To minimize airborne releases the channel head decontamination process and the surface prepara tion process will be wet processes, entraining removed material in water.

Also, an enclosure tent will be erected around the steam generator channel head manway to prevent the release of contamination from the steam generator.

Air from the enclosure will be exhausted through a high efficiency particu late filter. The water from the decontamination process will be treated by filters and demineralizers to minimize liquid releases. The main source of liquid releases, laundry waste water, will be treated by demineralizers.

We have reviewed SCE's estimates of effluent releases for the sleeving project.

Those estimates are based on estimating methods acceptable to the Staff and actual releases from similar operations at San Onofre 1 and elsewhere.

Based on our review, we conclude that SCE's estimates are reasonable.

As Table 4.5 shows, the expected releases from the sleeving project are small compared to both the FES estimates and San Onofre's actual annual releases.

Our estimates of doses to individual members of the public as well as the population as a whole in the area surrounding San Onofre are based on the radioactive effluents which SCE estimated for the sleeving project (summarized in Tab32 4.5) 15d on the caliulational methods presented in Regulatory Guides 1.109, 1.111, and 1.113.

The doses to individuals offsite from the sleeving project will be less than 10% of the limits of 40 CFR Part 190.

The annual limits of 40 CFR Part 190 are 25 millirem to the total body or any organ except the thyroid and 75 millirem to the thyroid. The doses to the population within 50 miles will be less than I person-rem to the thyroid or total body from liquid effluents, and less than I person-rem to the thyroid or total body from airborne effluents. Every year the same population of about 7 million will receive a cumulative total body dose of more than 700,000 person-rem from the natural background radiation (about 0.1 rem per year) in the vicinity of San Onofre.

Thus, the population total body dose from the sleeving project is less than 0.0001 percent of the annual dose due to natural background. On these bases, we conclude that the doses to individuals in unrestricted areas and to the population within 50 miles due to gaseous and liquid effluents from the.sleeving project will not be environmentally significant.

SCE has estimated that the sleeving project will generate about 300 4cubic meters of solid waste containing about 100 curies of radioactivity.

These estimates are based on SCE's experience with solid wastes during steam generator maintenance at San Onofre 1 and on Westinghouse experience with the wastes generated during steam generator channel head decontamination.

We have reviewed SCE's estimates of solid radwaste for the sleeving project.

Those estimates are based on acceptable-estimating methods and on solid radwaste experience with similar operations at San Onofre 1 and elsewhere.

Based on our review, we conclude that SCE's estimates are reasonable.

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During 1978 and 1979, San Onofre 1 generated an annual average of 108 cubic meters of solid waste per year containing 129 curies of radioactivity.

Therefore, the estimated volume and radioactive content of the solid wastes from the sleeving project are of the same order.of magnitude as the solid waste normally generated annually at San Onofre. This amount of waste is a very small part of the amount of solid waste handled each year by the nuclear industry; therefore, this waste does not represent a siqnificant affect on the quality of the human environmentl The sleeving project will not change the plant in any way which might increase effluent releases. Therefore, we conclude that the impact from routine releases of radioactivity after the sleeving project will be no greater than the impact before the project. In fact, the sleeving operation should result in decreased steam generator tube leakage thereby reducing future radioactive effluents when compared to past facility operation.

Since we expect no larger radioactive effluents from San Onofre after sleeving (over presleeving operation), we conclude that the impact on biota other than man will also be no larger after sleeving.

In summary, the radioactive releases resulting from the sleeving project will be less than those due to normal plant operation. These releases are also much less than the estimates presented in the FES. The doses due to these releases are small compared to the limits of 40 CFR Part 190 and to the annual doses from natural background radiation. SCE plans to take the necessary steps to minimize releases. The estimated amount of solid wastes for the sleeving project is not greatly different than normal.

Therefore, the radiological impact of the sleeving project will not significantly affect the qualitynof the human environment.

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5.0 CONCLUSION

S Based on our review of the proposed steam generator sleeving project, we have reached the following conclusions which are discussed in greater detail above.

(1) Including the dose from sleeving, the annual average dose at San Onofre I over the life of the plant to date will still be less than 500 person-rem, the annual average dose for all light water reactor units.

(2) The estimated dose of 1800 person-rem for the sleeving project is within the expected range of doses incurred at light water power reactors in a year.

(3) The risks to the workers involved in the sleeving project from radiation exposure are no larger than the risks incurred by:

(a) workers in other industrial businesses and (b) most people, working or not, from commonplace activities such as driving a car.

(4) SCE has taken aDprODriate Steps.to ensure that occupational dose will be maintained as low as is reasonably achievable and within the limits of 10 CFR Part 20.

(5) Offsite doses resulting from the sleeving project will be (a) no larger than those incurred during normal operation of San Onofre 1 and (b) small in comparison to the doses members of the public in the vicinity of San Onofre 1 receive from natural background radiation.

On the basis of the foregoing statements, the staff concludes that the proposed sleeving project at San Onofre Nuclear Generating Station, Unit No. 1 will not significantly affect the quality of the human environment.

We have reviewed this proposed facility modification relative to the require ments set forth in 10 CFR Part 51 and the Council of Environmental Quality's Regulations 40 CFR Part 1500 et seq.

We have determined that the prolosed action will not significantly affect the quality of-the human environment.

Attached:

Tables (5) 5 -1

6.0.

REFERENCES

1.

NUREG-0594,"0ccupational Radiation Exposure at Commercial Nuclear Power Reactors 1978," U.S.N.R.C., Novemiber 1979.

2.

The Effects on Populations of Exposure to Low Levels of Ionizing Radiation, "BEIR Report," report of the Advisory Committee on the Biological Effects of Ionizing Radiations, National Academy of Sciences - National,'Research Council, November 1972.

3. Annual Report by Southern California Edison in compliance with 10 CFR Part 20.407, San Onofre Nuclear Generating.Station, submitted to U.S.N.R.C., 1980.

4. Letter dated November 26, 1980, from K. P. Baskin, Southern California Edison Company, to 0. M. Crutchfield, U.S.N.R.C.

5.

NUREG-0490, "Draft Environmental Statement - San Onofre Nuclear Generating Station, Units 2&3", USNRC, November 1978.

6.

Final Environmental Statement related to operation of San Onofre Nuclear Generating Station Unit 1, United States Atomic Energy Coumission, October 1973.

7.

The Effects on Population of Exposures to Low Levels of Ionizing Radiation "BEIR III Report", report of the committee on the Biological Effects of Ionizing Radiation's Natural Academy of Sciences - National Research Council, 1930.

8.

NCRP No. 45, "Natural Background Radiation in the United States," National Council on Radiation Protection and Measurements, 1975.

9.

R. Peto, "Distorting the Epidemiology of Cancer, the Need for a More Balanced Overview," Nature 284, 297-298 (Mlarch 27, 1980).

10. "1978 Effluent Report, San Onofre 1."

11.

"1979 Effluent Report, San Onofre 1,"

12. Regulatory Guide 1.109. "Calculation of Annual Doses to Man from Routine Releases of Reactor Effluents for the Purpose of Evaluating Compliance with 10 CFR Part 50, Appendix " (Revision 1), U.S.N.R.C., October 1977.

13. Regulatory Guide 1.111, "Methods of Estimating Atmospheric Transport and Dispersion of Gaseous Effluents in Routine Releases from Light-Water-Cooled Reactos" (Revision 1), U.S.N.R.C., July 1977.

14. Regulatory Guide 1.113, "Estim~ating Aquatic Dispersion of Effluents from Accidental and Routine Reactor Releases for the Purpose of Implementing Appendix I, U.S.N.R.C.

15. 1979 Cancer Facts and Statistics, American Cancer Society.

16. WASH-1400, "Reactor Safety Study - An Assessment of Accibnt Risks in U.S.

Commercial Nuclear PoVwr Plants." U.S.N.R.C.,

October 1975.

17. E. Pochin, "The Accetance if Risk," British Medical Bulletin 31(3),

1975.

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18.

SE-SP-58(80),

"Steam Generator Repair Report for Southern California Edison San Onofre Unit 1, Westinghouse Electric Corporati6n, September, 1980.

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ANNUAL COLLECTIVE 1'3 OCCUPATIONAL DOSE AT SAN ON0FRfEl TABLE 4.1 Collective Occupational Dose Year myan-rems) 1969 42 1970 155 1971 50 1972 256 1973 353 1974 71 1975 292 1976 880 1977 S47 1978 401 1979 139

TABLE 4.2 Occupational Dose at U.-S. Light Water Reactors1 (man-rems per reactor unit)

Year Average Low High 1975 475 21 2022 1976 499 74 2648 1977 570 87 3142 1978 497 158 1621 1979 593 30 1793

TABLE 4.3 Lifetime Mortality Risks Numerically Equi ialent to One Rem 7 Type of Activity Equivalent Risk to One Rem Smoking cigarettes I carton Drinking wine 66 bottles Automobile driving 6,600 miles Commercial flying 33,000 miles Canoeing 1.6 days*

Being a man aged 60 1.8 days

• Eight hours per day

TABLE 4.4 OCCUPATIONAL RISKS (Events per year per 100,000 workers)

M-ining &

All U.S.

Radiation Quarrying Industries Trade Exposure Fatal Accidents(1) 63

. 14 6

Delayed Effects k-tual readily Occasionally not not Observable Observable Observable Observable Estimated Includes 115-219 4-6 s

lethal cancers( 2) 7 lethal cancers 1976 data, from "Accident Facts, 1977 Edition,' National Safety Council.

(2Estimates from "-!Toxic. Chemicals and Public Protection, A Report to the President by the Toxic Substances Strategy Comnittee," Council on Environmental Quality,.

Gpvernent Printing Office, May 1980.

Assumes 20-38% of all cancers are associated with occupation.

(3)Estimates from BEIR-III, 1980, assuming an average radiation worker exposure rate of 0.5 rem/yr; exposure at the limit, 5 rems/yr, would yield an estimate of from 37 to 63 lethal cancers per year per 100,000 workers.

TABLE 4.5 RADIOACTIVE EFFLUENTS FROM SAN ONOFRE 1 Type of Radioactive SCE Estimates4 for San Onofre 1.10 San Onofre I FES Estimates of.Annual Ef t Slese (i)g (eases 1979 Releases Average Releases (Ci/yr)

Gaseous Noble Gases Negligible 1.8-(+3)*

6.3(+2) 4.4(+3)

Iodine Negligible-2.1(-4) 1.2(a4) 5.5(-2)

• iculates l.2(-5) 2.5(-3) 2.1(-5)

Tritium 4.7 2.7(+1) 2.8(+1)

Liquid Mixed fission and activation products 4.3(-1) 1.2(+l) 1.1(+1) 1.8(+1)

Tritium 1.1 2.4(+3) 2.3(+3) 8.8(+3)

• No estimate was given in FES, but FES stated that there would be particulates and tritium in the gaseous releases.

• I.8(+3) means 1.8 x 10-3.

+Below lower limits of detectability for plant instrumentation.