ML19209B515

Occupational Exposure & Alara

ML19209B515
Person / Time
Issue date:	10/04/1979
From:	Hinson C, Murphy T Office of Nuclear Reactor Regulation
To:
References
RTR-REGGD-08.008, RTR-REGGD-8.008 NUDOCS 7910100035
Download: ML19209B515 (14)

Text

PDQ i

• 'i OCCUPATICriAL EXPOSURE AND ALARA T~

_[~__

__Z _; 7 Charles S. Hinson and Thomas D. Murphy. _ __ _ Z _))

Office of Nuclear Reactor Regulation _ _

_g U.S. fluclear Regulatory Commission _ _.

Washington, D. C. 20555 INTRODUCTION

_ ~ f f ~ __ ii- ~

In order to maintain radiation doses to maintenance, contractor and operating parsonnel as low as are reasonably achievable, it is necessary to provide design features and operating procedures to reduce radiation fields around reactor coolant system components, to reduce the time needed for maintenance operations, to reduce the frequency of such operations, and to. reduce the number of people involved in such operations. Plant design features intended to reduce occupational doses during plant operation also serve to lessen personnel doses during the eventual plant decommissioning.

Recent recommendations by the NRC Regulatory staff,2 under consid-T eration by the Commission, may require that industry provide addi tional means to reduce occupational radiation exposure. This paper-~

outlines the regulatory considerations for further controlling

_. doses to personnel at nuclear power plants.

[

CCCUPATI0flAL EXPOSURE DATA AT COMMERCIAL LWRS Thi NRC has requirements for reporting occupational radiation exposure data for licensee power reactors in both 10 CFR Part 20 and in Regulatory Guide 1.16.

The analyses in this section is drawn from data received in response to these NRC requirements and reported annually by the NRC.2 Table 1 shows that the average man-rem per reactor per year has been increasing for reactors since 1969 at a rate roughly equivalent to the inc' ease in the average mega-watt (electric) years generated per reactor per year and the average rated plant capacity. This data is shown graphically in figure 1.

Average exposure per individual has remained relatively even in the ~

same time period while the average number of personnel per reactor 7910100 O J S

~

1125 335

9 g

2

~~ ~

with measurable exposure has increased, as shown in Table 2.

Table 3 provide. a breakdown of the 1977 data reported to the NRC by work and job function. This table clearly shcws that the majority of the dose is received by maintenance workers performing routine and special maintenance activities. Table 4 indicates that these observations have been reasonably consistent cver the four years that the NRC has received data in a format which allows a break-down of exposures by work and job function.

CA'JSES OF INCREASING COPMERCIAL REACTOR PLANT EXPOSURES

~~Z

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The staff has observed that the primary causes of the increasing radiation exposures at power reactors are:

(1) in. _

creasing radiation fields around reactor components, (2) a relatively constant need to perform routine and special maintenance _

activities at reactor plants, and (3) several recent, widespread.

unexpected repair efforts on major reactor components. ____.__ _

(1, Increasing radiation fields - - _..

Several recent studies have documented the increasing radia-~

tion levels associated with reactor coolant components at U.S.

nuclear power plants. Based on extensive surveys of operating plant s:,utdown radiation levels, Sawochka, et. al. have plotted radiation level increases on PWR (Figure 2) and BWR (Figure 3) reactor coolant piping.3 The important corrosion product radionuclides contributing to these increacing radiation levels are shown in Table 5.

The nuclide contributing most to the dose is Co'8 (2) Maintenance activities

~

The reasonably constant forced outage rate over the past

~~

several years for such reasors as steam generator tube leakage and.

pump and valve failure and maintenance lead us to believe that in- _

creasing radiation exposures to plant personnel may be more influenced by increasing radiation levels than by increased size or increased failure rate of equipment. Typical activities for which routine exposures are required by reactor plant personnel are listed in Table 6.

(3) Unexpected major reactor plant repair efforts Although U.S. power reactors have had a rea'sonably constant outage rate in the last several years, there have been several major repair operations in recent years that have caused unexpected high collective radiation dose accumulations at se'veral reactors.

These are feedwater nozzle, pipe crack and control rod drive return line nozzle crack repairs in boiling water reactors and repair of steam generator tube degradation in pressurized water reactors.

E 1125 336

NRC ACTIONS TO CONTROL RISKS ASSOCIATED idITH OCCUPATIONAL

[

RADIATION EXPOSURES Confronted with present uncertainties regarding radiation

~

dose-health effect relationships, some of which are not likely to be resolved for many years, the staff has considered further regula-tory strategy to assure that workers are adequately protected.

In brief, the NRC staff has concluded that (1) a reasonable additional effort should be made to control further the overall risks asso _ _

ciated with occupational radiation doses, and (2) appropriate control of risk can be achieved through regulatory action which places additional emphasis on maintaining occupational doses ALARA by making radiation protection programs inspectable and enforceable. _

It should be noted that such regulatory action has been recommended by the NRC staff irrespective of the question of whether dose limits should be lowered.

~

The NRC staff has considered many alternatives, and combina-tions thereof, for such additional regulatory action that would reduce radiation risk. The principal alternatives are summarized below:

Alternative 1:. Amend 10 CFR Parts 20,30,40,50and70torequire1; licensees to develop and implement occupational ALARA programs, with guidance on the program content to be given in regulatory guides tailored for the various types of licenses activities.

Alternative 2:' Require these licensees to perform cost-benefit analyses for major tasks and to provide all safety procedures, equipment, and facilities that are shown to be cost-effective, using a dollars-per-man-rem criterion.

i Alternative 3: Establish annual design and operational collective cose (man-rem) objectives (goals) for various types of licensees.

Alternative 4: Continue to implement the occupational ALARA concept ~ ~ ~

~

through the license review process and the issuance of regulatory guides that address ALARA in different types of facilities, training ~

of workers, surveys, etc., but without amendment of the regula-

~-

tions requiring licensees to develop and submit ALARA program for NRC evaluation and incorporation into the license.

~

Alternative 5:

Impose additional specific design criteria in

~~

10 CFR Part 50, Appendix A, to reduce occupational radiation doses

-~

at power reactors.

It is the NRC staff's proposal (SECY-78-415 of July 29,1978) that implementation of Alternative 1 will result in centrol of the -

current trend of increasing collective dose in a reasonable and -

effective manner. As mentioned above, this alternative would

~~

1125 337

require licensees to develop and implement individual occupational ALARA programs, with guidance on the program content to be given in ___.

regulatory guides tailored for the various types of licensed acti-vities.

In developing these occupational ALARA: programs, licensee __..

management would have to consider the ALARA aspects of each radia-tion work effort, treating specific factors involved in the effort within the guidance to be provided in regulatory guide format. The ]

_ NRC staff would evaluate the ALARA programs using the regulatory guides and commonly accepted approaches to worker protection to judge _

their acceptability. These regulatory guides will be developed after evaluation of public comments on the proposed rules and wil.1

.1 be available in final form when the amendments are published to be.

effective. Six months after the effective date of the new regula

~~~

tions, IE inspectors would begin to.deterniine that the licensee has ]

developed an adequate ALARA program and is implementing the program.

The NRC staff proposes that these amendments be applied to all 7

licensees who are required by the regulations, technical specifica _

tions, or license conditions to perform personnel monitoring, ___ L bicassays, or air sampling.

In addition to whatever alternative or combination of alterZ

~

natives is selected, the NRC staff has proposed certain related -

amendments. These amendments would eliminate the Form NRC-4 exposure history and impose annual dose-limiting standards while retaining quarterly standards, including 5 rems per year, 3 rems per quarter to the whole body. Related amendments would conform other sections of the regulations to express, in terms of the new annual standards, the standard for dose.to minors, the require-ments for the provisions of personnel monitoring equipment, and the requirements for control of total dose to transient and moon-

~

lighting workers.

REGULATORY GUIDE 8.8 AND REACTOR DECONTAMINATION / DECOMMISSIONING

[

The document presenting ALARA design guidance is Regulatory

=

. Guide 8.8, Information Relevant to Ensuring that Occupational Radiation Exposures at Nuclear Power Stations Will be As Low As

[

-7 Is Reasonably Achievaote, Revision 3, 1978. For reactors, the NRC W11.1 use this guide as the primary basis of acceptability of

~

licensee's ALARA programs. For reactors undergoing construction permit and operating license review, the NRC staff concentrates

~

on the design considerations for reducing 1;adiation exposures and ~'

radiation fields. The guidance provided in Regulatory Guide 8.8 for the control of activated corrosion products (crud) is of parti-cular interest:

Design features of the primary coolant system, the selection of construction materials that will be in

~~

contact with the primary coolant, and features of equipment that treat primary coolant should reflect 1125 338

5 considerationsthatwillreducetheproduckionand

[

accumulation of activated corrosion products (crud) in areas where it can cause high exposure. levels The following items should be considered in'the crud control effort:

(1) Production of Co-58 and Co-60, which constitute

_.__..._ substantial radiation sources in crud, can be reduced _

by specifying, to the extent practicable, low-nickel

.._:__ and low-cobalt bearing materials for primary coolant pipe, tubing, vessel internal surfaces, heat exchangers, _. __

wear materials, and other components that are in contact with primary coolant. Alternative materials for hard facings of wear materials of high-cobalt content should._._.._

be considered where it is shown that these high-cobalt i

materials contribute to the overall exposure levels. ___

l Such consideration should also take into account potential increased service / repair requirements and over- _. _ _

all reliability of the new material in relation to the old.

(2) Loss of material by erosion of load-bearing hard

[

facings can be reduced by using favorable geometrics and lubricants, where practicable, and by using controlled

~

leakage purge across journal sleeves to avoid entry of particles into the primary coolant.

(3) Loss of material by corrosion can be reduced by

~

continuously monitoring and adjusting oxygen concen-

~

tration and pH in primary coolant above 250 F and by using bright hydrogen-annealed tubing and piping in the primary coolant and feedwater systems.

]

(4j Consideration should be given to cleanup systems

[

(e.g., using graphite or magnetic filters) for removal of crud from the primary coolant during cperation.

[_L (5, Deposition of crud within the primary coolant

~[

system can be reduced by providing laminar flow and smooth surfaces for coolant and by minimizing crud traps in the system to the extent practicable.

In addition, Regulatory Guide 8.3 addresses 'the removal of activated corrosion products (decontamination).

rotential doses to station personnel who must service equipment containing radioactive sources can be reduced by removing such sources frcm the equipment (decontami-nation), to the extent practicable, prior tu servicing.

~

Serviceable systems and components that constitute a n_

~~

l125 339

..e 6

substantial radiation source should be designed, co the extent practicable, with features that permit isolation and decontamination. Station design features should consider, to the extent practicable, the ultimate decom-missioning of the facility and the following concerns:

(1) The necessity for decontamination can be reduced by limiting, to the extent practicable, the deposition of radioactive material within the processing equipment-. _.

particularly in the " dead spaces" or " traps" in components __

where substantial accumulations can occur.

The deposition of radioactive material in piping can be reduced and decontamination efforts enhanced by avoiding stacnant legs, by locating connections above the pipe centerline, ____ __

by using sloping rather than horizontal runs, and by _

providing drains at low points.in the system.

(2) The need to decontaminate equipment and station-_

a areas can be reduced by taking measures that will reduce the probability of release, reduce the amount released, and reduce the spread of the contaminant from the source (i.e., from systems or components that must be opened for service or replacement). Such measures can include auxiliary ventilation systems, treatment of the exhaust from vents and overflows, drainage control such as curbing and floors sloping to local drains, or sumps to limit the spread of contamination from leakage of liquid systems.

(3) Accumulations of crud or other radioactive material that cannot be avoided within components or systems can be reduced by providing features that will permit the recirculation or flushing of fluids with the capacity to remove the radioactive material through chemical or physical action. The fluids containing the contaminants

}-

will require treatment, and this source should be con-sidered in sizing station radwaste treatment systems.

j_,

Aspowerreactorsincreaseinage,thebuildupofcrudwithin-[]

the primary system leads to increasing radiation fields. The sub-sequent increase in occupational exposures is a problem which can impede operational maintenance and inspection functions. High plant radiation levels can also have a negative impact on end-of- ~~

plant-life decommissioning operations.

The Commission is continuing its studies on plant design features to control exposure and facilitate plant decccmissioning.

The decontamination cperations at Dresden 1, the Surry and Turkey Point steam generators replacement programs, and the Indian Point I-~

secondary side steam generator chemical decontamination will all yield valuable information that can be used to' complement existing 1125 340

7 exposure reduction and decommissioning techniques. 'In FY 1975 and _

FY 1976, the Commission initiated studies of the decommissioning safety and costs of nuclear fuel cycle facilities and of light-water-cooled reactors." Battelle Pacific Northwest Laboratories was selected to perform the greatest part of these studies.

Initial findings from these studies suggest that the following general criteria be considered in the selection of plant design

. features:5

• Decreasing decommissioning cost

__. _ __ 2 Improving occupational or public safety _

_m Reducing total decommissioning time Creating less volume of radioactive wastes Z

Improved ease of performing the decommissioning

SUMMARY

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As discussed above, the NRC has under consideration certain additional actions to be taken to control the collective dose to NRC licensee's radiation workers to levels as low as is reasonably achievable. The actions that are being considered will be subjected to significant public scrutiny after publication in the FEDERAL REGISTER, including a hearing.

In the meantime, we are coacerned. _ _

that the trend of increasing radiation fields and increasing collective doses at reactor plants may lead to unacceptal:e risks to radiation workers at nuclear power plants. For this reason, it is necessary that the industry and licensees continue to imple-ment the ALARA concept with the utmost vigor.

Oneapproachthatmaybeeffectiveinreducingriskstoradia-1 tion workers is to reduce radiation fields in areas where sicnifi-

_ cant reactor plant maintenance work is required.

In addition, continued review of the technology associated with design and

~

layout of nuclear plants is required to assure that the latest, cost effective and exposure reducing approaches are used. Finally, ~

in the operation of nuclear power plants, consideration of dose

~

reducing activities must constantly be a priority of plant personnel _.~

REFEREN.CES

[

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'U.S.N.R.C. Commission Paper, SECY 78-415, Further Actions to

~~

Control Risks Associated with Occuoational Radiation Excosures in NRC-Licensed Activities, R. B. MINOGUE, July 31, 1978.

~

. 2 NUREG-0482, LINDA JOHNSON PECK, Occupational Radiation Excosure at Light Water Cooled Power Reactors, 1977, U.S.N.R.C., May 1979.

'SAWCCHKA, S. G.,

N. e. JACUS,

d. L. PEARL, Primary System Shut-down Radiation Levels at Nuclear Power Generating Station, EPRI-404-2, December 1975.

"NUREG-0436, Plan for Reevaluation of NRC Policy on Decoreissioning of Nuclear Facilities, U.S.N.R.C., December 1978.

1125 341

NUREG/CR-0130, R. I. SMITH, G. J. K0rlZEK70.~s~.~f(EilNEDY, JR.,

5 Technology, Safety and Cost of Decommissioning a Reference Pressurized Water Reactor Power Station, Report for U.S.N.R.C. by Pacific Northwest Laboratory, June 1978.

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SUMMARY

- LIGHT WATER REACTORS Average Yearly Number Rated

.. Average Average __. Man-Rem /.

Average.

of Capacity

• MW-Yr Man-Rem /

Reactors (MWe)

Generated Reactor MW-Year 1969 7

247

--184

-178 -- -- - 1.0 ---

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-- 311

- 3 64 - ---- -1. 2 -- --

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- - 299

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1974 34 575

-- 319

- 404

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- - 413

- --- 499

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1977 57 682 464 570 1.2 1978 64 702

. 494 497 - -----1.0 b.

PRESSURIZED WATER REACTORS i969 4

349 274 165 0.6 1970 4

349 245 684 2.8 1971 1972 8

446 318 463 1.5 1973 12 533 314 783 2.5 1974 20 619 341 331 1.0 1975 26 643 461 318 0.7 1976 30 684 444 460 1.0 1977 34 707 510 396 0.8 1978 39 723 509 428 0.8 c.

BOILING WATER REACTORS 1969 3

112 64 195 3.0 1970 6

267 152 127 0.8 1971 1972 10 434 306 286 0.9 1973 12 459 283 380 1.3 1974 14 513 290 507 1.7 1975 18 611 321 701 2.2 1976 23 647 373 549 1.5 1977 23 645 396 828 2.1 1978 25 668 471 604 1.3

• Maximum Dependacle Capacity (Net) - the cepenaabie gross electrical output as measured at the output terminals of the turbine generator during the most restrictive seasonal conditions (usually summer) less the normal station service loads.

1125 343

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TABLE 2 1T

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AVERAGE OCCUPATIONAL RADIATION EXPOSURE,PER INDIVIDUAL Average Exposure Average Number of Personnel With Year Per Individual (Rems)

Measurable Excesure Per Reactor

_ 149 1969 0.9

._ 380 _.. _. _

1970 0.6 1971 0.7

__ __ _._ _. 3 09 1973

. __ _ _ _ 3 4 5 1972

_ 0.9 607 l.0 1974 0.7 543 1975

. 0.7 625 1976

.0.7 669

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1977 0.8 742

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PERSONNEL DOSE BY WORK FUNCTION (1977)

PER DATA SUPPLIED BY LICENSEE IN ACCORDANCE WITH R.G. 1.16 __

a.

TABULATION OF MAN-REM BY WORK FUNCTION Contract Work Station Utility Workers Function Ecoloyees Employees and Others Total Reactor Operations 2626 224 427 3277 Routine Maintenance 3470 1544 3708 8722

~

Inservice Inspection 205 245 1536 1986

.. Special Maintenance 1700 2123 6398 13221

~-

Waste Processing 1207 36 554 1797

~~

Refueling 852 390 829 2071 Totals 10060 4562 16452 TTD75

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e 1125 344

TABLE 4 PERCENTAGES OF PERSL1NEL 00SE BY WORK FUNCTION

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Percent of Dose Work Function 1974 1975 1976 1977

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Reactor Operations and

. _. 10.4

_._10.5 Surveillance 14.0

_10.8 Routine Maintenance 45.4 __.

52.5

. 31.7._._ 28.1 _

In-Service Inspection 2.7 2.9 5.7 6.4 Special Maintenance 20.4 19.0 39.5 42.5 Waste Processing 3.5 _. _6.9

_ _ 4.8._. _ _5. 8 _ _._ 1 1 Refueling

._14.0 7.7

____7.9_

6. 7_._

TABLE 5

~

IMPORTANT CORROSION PRODUCT ISOTOPES _ _.___ _ _ ___ _.

Nuclides Half Life Production Reaction to 60 5.2 Years Co 59 (n,y) Co 60 Co 58 72 Days Ni 58 (n,p) Co 58 Cr 51 28 Days Cr 50 (n,y) Cr 51 Fe 59 45 Days Fe 53 (n,y) Fe 59 Mn 54 310 Days Fe 54 (n p) Mn 54 m_

m e

1125 345

12 TABLE 6 TYPICAL ACTIVITIES CAUSING EXPOSURE

[

Valve Repair, Maintenance and Repacking Eddy Current Testing of Steam Generator Tubes Repairs to Spent Fuel Pool, Liner and Upender Steam Generator Tube Plugging

_ _ _ _ _ -. = _

Solid Waste Drumming Reactor Internals Inspection __

__. __ [ ~~_T_~___ ___ _ _C

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Fuel Sipping and Inspection Pump Maintenance, Repair and Seal Replacement Feedwater Sparger Replacement

' ~ ~ ~ ~ ~ - '

~ ~ ~ ~ - -

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Steam Leak Inspections

~~

Reactor By-Pass Line Replacement Control Rod Drive Mechanism Repairs.and Overhaul Inservice Inspection Routine Instrument Maintenance

~~_~

Demineralizer Element Replacement and Resin Removal

~ _]

Piping Modifications Incore Instrumentation Replacement

_ ~ ~ ~

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Refueling, Including Head Removal and Reinstallation Condensate Demineralizer Work Cleanup of Spills

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. = - = -.

e 1125 346

f/SuG t AVERAGE MAN-REM / REACTOR YEAR BWR * ' ' ' ' '.

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