NUREG-1060

Answers to Questions About
Updated Estimates ofOccupational Radiation Doses
at Three Mile Island, Unit 2

U.S. Nuclear Regulatory
Commission
Office of Nuclear Reactor Regulation

TMI Program Office

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NUREG-1060

Answers to Questions About
Updated Estimates ofOccupational Radiation Doses
at Three Mile Island, Unit 2

Manuscript Completed: December 1983
Date Published: December 1983
TMI Program Office

Office of Nuclear Reactor Regulation
U.S. Nuclear Regulatory Commission
Washington, D.C. 20555

INTRODUCTION
The purpose of this question and answer report is to provide a clear, easy-to­understand explanation of revised radiation dose estimates which workers arelikely to receive over the course of the cleanup at Three Mile Island,
Unit 2, and.of the possible health consequences to workers of these new
estimates. We will focus primarily on occupational dose, although pertinent
questions about public health and safety will also be answered.
The answers to these questions, prepared by the staff of the NRC Three Mile
Island Program Office, are based principally on the detailed examinationof occupational dose in Draft Supplement 1 to the 11Programmatic Environmental
Impact Statement Related to the Decontamination and Disposal of Radioactive
Wastes Resulting from the March 28, 1979, Accident at Three Mile Island, Unit 211(PElS ) , NliREG-0683 issued December 1983. The views expressed in this question
and answer report are those of the NRC staff.
Draft Supplement 1 to the PElS on Occupational Exposure ( N UREG-0683, Supp. 1)
is available for public comment. Copies are available for inspection at the
NRC TMI Program Office, 100 Brown Street, Middletown, Pennsylvania,* the
NRC Public Document Room, 1717 H Street, N.W., Washington, D.C., and at the
TMI-2 local Public Document Rooms at the Government Publications Section, Statel1 brary of Pennsylvania, Education Building, Commonwealth and Walnut Streets,
Harrisburg, Pennsylvania, and at the York College of Pennsylvania, Country Club
Road, York, Pennsylvania.
Requests for single copies of the PElS Supplement should be addressed inwriting to the Director, Division of Technical Information and Document
Control, U.S. Nuclear Regulatory Commission, Washington, D.C. 20555.
Send your comments to Dr. Bernard J. Snyder, Program Director, Three Mile
Island ProQram Office, U.S. Nuclear Regulatory Commission, Washington,
D.C. 20555. They are due to NRC by February 29, 1984.

Dr. Bernard J. Snyder, Program Director
Three Mile Island Program Office
U.S. Nuclear Regulatory Commission
Washington, D.C. 20555*Hours:Tuesdays, Noon to 2 p.m.
Wednesdays, 5 p.m. to 8 p.m.
Thursdays, 3 p.m. to 5 p.m.

iii

Q . 1.

Why has NRC issued Draft Supplement 1 to the Programmatic Environmental
Impact Statement at this time for cleanup operations at Three Mile
Island, Un it 2 ?

A.

For two reasons. First, to revise the estimates of radiation doses
workers are likely to receive during the entire cleanup. Second, toreconsider what these revised estimates could mean to worker health.

Q. 2 .

Is other information in the original Programmatic Environmental Impa ct
Statement out of date because Supplement 1 has been issued?

A.

No. Draft Supplement 1 was issued for the sole purpose of updating
estima tes of radiation exposures and their possible ef fects on
worker health. This information supplements one part of thecleanup discussed in the original Programmatic Environmental
Impact Statement. The original Statement remains the valid
source of information for all other. facets of the cleanup .

Q. 3 .

What are the revised estimates of doses workers could receive?

A.

When the original Programmatic Environmental Impact Statement wasissued in March 1981, the radiation dose to the work force wasestimated to be between 2, 000 and 8, 000 person-rem. According torevised estimates, cleanup workers are likely to receive a total col­lective radiation dose of between 13, 000 and 46, 000 person-rem for theentire cleanup project.

( For an explanation of person-rem, see the answer to Question 15. )Q . 4.

How could this increased dose range af fect worker health?

A.

Statistically, these increased dose estimates slightly raise the cha ncesof cancer for the group as a whole. It is possible that this radiationdose could result in two to six fatal cancers in the worker population.

Q. 5.

The origi-nal Programmatic Environmental Impact Statement estimated tha t
approximately one ad ditional cancer death could occur because of rad ia tion
doses to the cleanup work force. Should this one possible death be ad ded
to the two to six fatal cancers predicted in the Supplement?

A.

No .

Q. 6 .

How does the potential for fatal cancer to cleanup workers compare withri sks of fatal can cer to the entire U.S. population?

A.

Th e average member of the U.S. population has about a 1 -in-5 chance ofdeveloping fatal cancer. That is, for every 1 0, 000 people living in
the U.S . , approximately 2, 000 will die of cancer. For a member of t h ecleanup work force active in decontamination work over the course of
the cleanup, the chances are about 1 in 4.9 , based on statisticalestimates.

-2 Q. 7.

Would nonfatal cancers also result from the level of radiation dose
workers could receive?

A.

Yes.
Statistically, the num ber of nonfatal cancers could be approxi­
mately on e and one-half to two times the num ber of fatal cancers,
according to the best scientific estimates.
That is, in addition to
the possibility of fatal cancers, there could be 3 to 12 nonfatal
cancers.
(The basis for these estimates comes from a 1980 report of
the National Academy of Sciences• Advisory Committee on the Bio­logical E f fects of Ionizing Radiation. )Q. 8.

Would there be other adverse health effects?

A.

There could be from 3 to 12 genetic effects in the of fspringYes.
of the workers.
Should genetic ef fects occur, it is possible thatthey could occur in more than one generation of of fspring.

Q. 9.

Do these new estimates mean that individual workers will be exposedto larger amounts of radiation than was previously thought?

A.

No.
NR C regulations strictly limit the amount of radiation that anindividual worker can receive.
These regulations have been and willcontinue to be strictly enforced.
The additional radiation estimated may be distributed among a larger
num ber of workers, so that an individual worker will still receive no
more than the regulations permit.
(For ad ditional information about these limits, see the answers to
Questions 27 and 35. )Q. lO.

Will these new estimates result in increased health or safety risk s tothe public?

A.

Other than the possibility for genetic ef fects discussed in the answer to
Question 8, the dose to workers will not af fect the general public.
Generally, public health and safety will be enhanced because of fuelremoval and cleanup.
(For additional information about public protection, see questions

60, 83, and 91. )Q. ll.

How ca n NR C, the Environmental Protection Agency, and other involved
organizations be conf ident in the accuracy of their estimates of these
health risk s to workers?

A.

These estimates are based on principles developed by internationallyrecognized authorities on the health ef fects of harm ful radiation.
The da ta used to predict health ef fects for cleanup workers are thoserecommen ded by the U. S. National Academy of Sciences• C ommittee .on the
Biological Ef fects of Ionizing Radiation; the United Nation•s ScientificCommittee of the Ef fects of Atomic Radiation; the National Council on
Radiation Protection in the U. S. ; and the International Commission on
Radiological Protection.

-3-

Q . 12 .

To what type of radiation will workers be exposed and why does theradiation have the potential to be harmful?

A.

Cleanup wo rkers will be exposed to ionizing radiation. This ty pe o fr adiation has enough energy to pass through living tissue . A s it
do es, it can displace electrons from the atoms and molecules of theliving tissue. Atom s or molecules with displaced (or missing) electrons
are called io ns. (That's why it's called ionizing radiation . ) Living
tissue exposed to ionizing radiation may be damaged.
(See the a nswer to Question 51 for information abo ut ty pes o f io nizing
radiatio n . )Q . 13 .

What are some sources of ionizing radiation?

A.

Ionizing r adiation can come from both natural and manmade sources.
Io nizing radiation found in nature includesocosmic radiation from outer spaceocertain elements which occur naturally in the human bo dyocertain elements from the soil and rocks that may be containedin the things we eat and smoke

Manmade sources include - omedical and dental X-raysoradioactive materials used to detect and treat diseases

0nuclear po wer plant fuel and its by productsocombustion of fossil fuel (coal-fired po wer plants)ofallout from nuclear weapon testing in the atmosphereoco nsumer products (for example, color television tubes
and some ty pes of smoke detectors)

Q. 14.

What units are used to measure ionizing radiatio n?

A.

Fo r its biological ef fects in people, it is measured in units call ed rems .
To account for small exposures, rems are frequently broken do wn into
thousandths of a rem, or millirems. That is, o ne rem equals 1,000 milli­
rem.

Q.l5.

If radiation doses are measured in rems and millirems, why do es Dra ft
Supplement 1 to the Programmatic Enviro nmental Impact Statement r eferto worker dose in a unit called perso n-rem?

A.

Person-rem refers to the sum of individual radiation doses that ma y
be received by members of a certain group, in this case workers

-4doing the actual cleanup work. Person-rem is calculated by multi­
plying the average dose per person by the number of persons in agroup. For example, 1000 people each exposed to 1 millirem ofradiation would have a collective dose of 1000 millirem, which is
1 person-rem.
Q . l6.

Why were estimates of worker dose in March 1981 lower than the mostrecent estimates?

A.

There are several reasons. The most important reason is that GPU Nuclear
now has actual experience in performing decontamination in the reactor
building at TMI-2 . When the Programmatic Environmental Impact Statement
was written, the reactor building had been entered only five times, andthat was so that workers could collect data about conditions in thebuilding. The actual cleanup of the reactor building had not begun atthat point . Another important reason is that delays have made cleanuptasks more difficult to perform, as noted in the answers to the next
three questions.

Q.17 .

What has experience since March 1981 shown?

A.

GPU Nuclear has learned that draining the highly contaminated water fromthe lower level of the reactor building did not lower radiation levels
because the building surfaces covered by the water were also highly
contaminated. They have also learned that decontaminating thP. surfaces
at the up per levels of the reactor building is much more difficult thanpreviously thought. This is probably because of the long time lapse
between the accident and the start of the cleanup. During that time
contamination penetrated both unpainted concrete surfaces and the rustthat formed on metal surfaces.

Q.l8.

If all the money needed for the cleanup were available, would theincreased risk from worker exposure be necessary?

A.

Although there is a relationship between the availability of funds andradiation doses to workers, that relationship is not a simple one andcannot easily be quantified. Nevertheless, several issues seem clear.
A lack of funds causes delays. Delays, in turn, can increase worker
doses for two reasons. First, workers must enter the reactor building
periodically for routine inspection and maintenance activities and to
take samples required to ensure safety. These entries, however, do notcontribute to the progress of the cleanup. Second, as time passes, theradioactive contamination becomes more difficult to remove because it
seeps further into concrete and becomes part of the layer of corrosionthat forms on metal surfaces.

Q . l9 .

Were delays, whatever their cause, considered in the updated dose
estimates?

A.

Yes, to a limited extent . The lower dose estimates in Draft
Supplement 1 to the Programmatic Environmental Impact Statement ( about
13, 000 person-rem ) assume little ad ditional delay. The higher dose
estimates ( about 46, 000 person-rem ) allow for some delay, but are based on
more or less continuous progress. None of the estimates take into accou nt
the worst case of delay, where wor��rs receive relatively small doses year
after year to keep the reactor safely shut down, but where no real progr ess
in the cleanup is made.

-5-

Q. 2 0.

How do scientists arrive at the upper and lower numbers when they givethe range of person-rem likely for the entire cleanup?

A.

Each cleanup task was analyzed in two ways to arrive at high and low
estimates. For the low estimate, the radiation specialists considered
how long ea ch task would take if the work went very well, and what thedose rate (the rems per hour) in the work area would be if previous
decontamina tion and shielding had reduced dose rates as much as canreasonably be expected, based on current cleanup experience . The numberof worker h ours times the dose rate in units of rem per hour gave them
the low (or optimistic) estimate of dose (in person-rem) for each task .
The low estimates for all future tasks were then summed and added to th edose to date. This total gave them the low estimate of 13, 000 person-rem
for the alternative in which the fuel is removed prior to building decon­tamination .
For the high estimate, they considered how long the task would take ifthings went slowly and if some tasks had to be redone . They estimatedthe dose rate as if previous decontamination and shielding had beenless ef fective than they would hope . These time and dose rate values
were multiplied together and then summed in the same way as for the low
estimate. This total gave them the high (or pessimistic) estimate of46, 000 person-rem for the alternative involving fuel removal followed byreactor building decontamination .

Q. 21.

Given this increased range of worker exposure, why should the cleanup
go forward ?

A.

The TMI site i s not suitable as a permanent repository for radioactive
wastes generated by the accident . (The reactor was designed for a normal
operating life of about 40 years with an adequate margin of safety; 1t
was not designed or built to contain radioactive wastes for an indefinite
number of years, particularly when those wastes include damaged fuel a ndother hazardous byproducts from an accident . ) Given that limitation, thewaste will have to be removed at some time in the future .
Most of the short-lived radioactive material has already decayed toinsignificant levels (that is, has essentially stopped emitting ionizing
radiation) , and the dose rate currently af fecting workers is due almost
entirely to cesium-137, a radioactive material which has a 30-year ha lf­
life. A 3 0-year half-life means that if GPU Nuclear waited 30 years
before cleanup, the dose rate would decrease to one half its present va lue .
However, cleanup workers have already learned that waiting makes clea nup
more difficult because contamination can penetrate building and equip ment
surfaces, as was noted in the answer to Question 17 . Since more ef fort
would be required to remove contamination that had penetrated certa insurfaces, waiting is not expected to reduce worker doses very much .
Another reason for going ahead with the cleanup is that there is apossibility, however slight, that some radioactive materi_ al could esca peto the environment outside the reactor building . The risk of th ishappening, even though small, increases over time.

-6Q.2 2.

What is the risk to the public of leaving the damaged fuel in the core?

A.

The damaged fuel in its present condition, under a boron-water solution,cannot harm anyone outside the reactor building. The borated water, thereactor vessel, and the reactor building all play a part in assuringsafety. But a small probab ility exists that in any given period oftime something could happen to the borated water, to the reactor vessel,
or to the building to impair safety. NRC cannot regulate for a limited
period. They must look at long-term conditions at TMI. The probabilityof something eventually happening to the borated water, the reactor
vessel or the building over a long period of time is too high to leavethem in their present condition. Because of these possib ilities, NRC
has concluded that the building must be cleaned up.
(See the answe r to Question 77 for an explanation of why the chemicalbo ron is added to the water.)

Q.2 3.

What organizations are monitoring the radiation doses workers receive?

A.

Worker doses are monitored by GPU Nuclear. In addition, NRC has a full­time professional staf f of radiation specialists at Three Mile Island.
They conduct ongoing reviews of the GPU Nuclear radiation protection
program and the methods that GPU uses to monitor worker doses.

Q. 24.

What kinds of radiation monitors are being used to measure worker doses ?

A.

GPU Nuclear has a number of op tions as to the kind of radiation-monito ring
instruments they can use. A device called a dosimeter is used to regis ter
the radiation dose a worker receives. GPU Nuclear assigns each radiation
worker a thermoluminescent dosimeter (TLD) . This device registers aworker• s accumulated dose from ionizing radiation. The TLDs are analyzed
or 11read11 every month, and the dose indicated for each worker is added t oprevious readings for that individual.
GPU Nuclear also provides a direct-reading, or self-reading, dosimeterfo r each worker who enters a radiation area. Workers can read thisdosimeter during work to know how much dose they have received fromthe time they enter a radiation area. Workers are required to readthese devices before, during, and after work and report the results o ftheir readings. These devices allow workers to tell immediately if
a dose is larger than expected. If it is, workers can leave the area
at once. These devices also allow GPU Nuclear to keep track of eachworker• s do se between TLD readings and to determine how much dose isbeing received for each job. These doses are then added to theworker• s cumulative exposure record. Both NRC and GPU officials
review these records for their compliance with NRC regulations
governing dose limits.
Other instruments, some in fixed locations and some carried by workers,
are used to locate sources of radiation, to estimate the dose workers could
receive, to determine the concentration of radioactive substances in air,and to do other specific jobs.

-7Filtered ventilation systems, instruments for monitoring airborne radio­
activity and respirators are in use to minimize the possibility thatworkers could inhale, swallow, or otherwise get radioactive materials into
their bod ies. To monitor for such a possibility, GPU Nuclear requires
all workers to be measured for internal radiation before they are
employed and at least once a year thereafter. A worker suspected ofinternal contamination is examined in a special radiation-detection
device for this purpose (a 11Whole-body counter11) and, depending on the
results, may also have urine an d/or fecal samples analyzed.
Q.2 5.

What range of dose will the dosimeters measure?

A.

At TMI, TLDs used by workers are good from about 10 millirem to 200 rem(2 00, 000 millirem) . For self-reading dosimeters, the range is not aslarge, but it is more than suff icient to cover the dose that a worker
could receive during a sing le entry to the reactor building or in
performing work in any other radiation area.
These dosimeters also warn workers of overexposures bec;ause they are
equipped with alarms that sound when radiation readings reach a certain
point. Should the alarm sound, workers would leave the area immediately.

Q.2 6.

W ill a long-term survey of the medical histories of cleanup workers be
conducted by GPU Nuclear?

A.

No such survey is planned at this time. GPU Nuclear keeps medical records
on workers while they are employed by the company, but other than that
there is no 1eng-term survey program. Such a survey waul d not be
statistically meaning ful because of the relatively small number ofhealth ef fects expected when compared to the normal incidence of cancer
and genetic diseases. (See the answer to Question 6 for figures about
the normal incidence of cancer.)
Doses that individual workers have been and will continue to receive
throughout the cleanup are well within the requirements in NRC regula ­tions and are typical of doses for other radiation workers.

Q.27.

Do NRC regulations spell out how much radiation a worker can receive?

A.

Yes. A radiation worker may receive no more than 3 rem of radiationdose in any three-month period. No worker may average more than ·5 rem
per year for each year past a� e 18 . There is also another more limiting
guideline in NRC regulations {Code of Federal Regulations, Title 10,
Part 20, 11Standards for Radiation Protection11 ) requiring that all
NRC-licensed facilities
make every reasonable ef fort to maintain radiation ex­
posures as low as is reasonably achievable. The term
11as low as is reasonably achievable.. means as low as isreasonably achievable taking into account the state oftechnolog y, and the economics of improvement in relation
to benefits to the public health and safety, and othersocietal and socioeconomic considerations
•

•

•

•

-8Q.2 8.

Does GPU Nuclear have a program to comply with these guidelines?

A.

Yes. GPU Nuclear has a dose-reduction program to comply with the ALARA(As Low As is Reasonably Achievable) princip les. This program is the
responsibility of upper-level management with the authority to carryout the program. As part of the program, all workers receive training in·
how to limit radiation doses. GPU Nuclear of ficials review equipment
modifications and work procedures and control who may enter radiation
zones. Shielding and protective equipment and clothing are also used, as
ap propriate.
(The types of training workers receive are explained in the answer to
Question 44.)

Q.29.

What step s does the dose reduction program involve?

A.

First, GPU Nuclear identifies significant sources of worker radiation
doses. Then they evaluate the various alternatives for removing,
decontaminating and/ or shielding workers from these sources. They thenselect a method for reducing the radiation and carry out an evaluation
to detennine whether the cleanup work can be perfonned under existingprocedures. Then GPU Nuclear gives the method an extensive review
to consider the benefit in worker dose reduction that can be expected.
NRC also reviews all such procedures for how well they comply with ALARA
guidelines.

Q.3 0.

What controls does NRC use to ensure that worker doses are limited?

A.

Special procedures are in place at TMI for reviewing GPU Nuclear's work.
Before GPU Nuclear begins any part of the cleanup involving radioactivity ,they must submit plans, procedures, and safety analyses to NRC radiation
specialists for approval.

Q.31.

Has NRC rejected any of GPU Nuclear's cleanup proposals?

A.

Yes. NRC has rejected approximately 10% of the proposals reviewed
and required GPU Nuclear officials to modify or further justify them.

Q.3 2.

What dose reductions have been achieved so far as a result of thedose reduction program?

A.

The so..;called "transit dose" (that is, the dose to a worker who
enters the reactor building, goes upstairs to the main work area, andthen leaves the reactor building) has been reduced from an average of
40 millirem per entry to an average of 18 millirem. The program has
also reduced radiation in particular work areas. For example, the average
dose rate on the first floor was 430 millirem per hour when entries werefirst made in the fall of 1980. By late 1982 , but before the dose
reduction program began, the rate was 350 millirem per hour. In thesummer of 1983, it was down to about 140 millirem per hour.

Q.33.

What are the goals of the dose reduction program?

-9A.

The goals of the dose reduction program are specific radiation
reductions in various areas of the building at specified stages of
the cleanup. The dose reduction goals become lower for the laterstages of cleanup. Ultimately, the goal is to reduce the dose rate
in most of the building work areas to 1 0 millirem per hour and reduce
airborne concentrations so that workers no longer have to wear respira­tors. (A detailed description of the licensee's dose rate reduction
goals is given in Table 2.1 of Draft Supplement 1 to the Programmatic
Environmental Impact Statement.)

Q.34.

How does 10 millirem per hour compare with the dose rate inside thereactor building of a normally operating plant?

A.

This dose rate is comparable to that in a very clean operating
plant, or to one that has operated for only a short period of time.

Q.35.

Does GPU Nuclear also have radiation dose limits for workers?
what are they?

A.

Yes. GPU Nuclear has established limits to ensure that NRC regulations
will not be violated. Al most all workers are limited to 1 rem every
three months, a dose rate below the NRC limit. Those workers whose jobs
require doses of 1 to 2 rem in any three-month period must receive special
prior authorization from GPU,Nuclear•s Radiological Engineering Manager
after the need for these dose levels have been reviewed. If a worker's
job were to require 2 to 3 rem in a three-month period, the approval ofboth the Radiological Engineering Manager and the Radiological Controls
Director would be required. These approvals are very difficult to obtain.

Q.36.

How many person-rem have workers received since the accident in March
1979?

A.

As of August 22, 1983, workers had received approximately 1, 700
person-rem since March 28, 1979.

Q.37.

What level of doses have cleanup workers received during the cleanup
at TMI on an annual basis, and how do these compare with the doselevels permitted in NRC regulations?

A.

We show a breakdown of this information on page 1 .9 of Draf t Supplement 1
to the Programmatic Environmental Impact Statemnt. The information,
combined for TMI Units 1 and 2, shows that 9, 91 5 workers have received
less than 1 rem per year since 1 979. Another 509 workers have received
1 to 2 rem per year ; 1 1 1 workers have received 2 to 3"refl} per year;
2 0 workers have received 3 to 4 rem per year; and only 7 workers havereceived 4 to 5 rem in any one year. No workers have received more than
5 rem per year. More of the total dose received was incurred at Unit 1
than at Unit 2. Furthermore, the doses at TMI-2 are lower than the doses
received by workers at the majority of NRC-licensed reactors.

Q.38.

How many rem could the average worker expect to receive during thecleanup?

If so,

-1 0A.

There is pr obably no average worker because the majority of those
involved in cleanup are involved in design, engineering, planning, andsupport functions; these workers do not enter radiation areas very
often and generally average less than � rem per year . The workers
who do clea nup work in the reactor building will receive a larger dos e,
but cleanup experience to date indicates that they receive much lessthan the ma ximum allowable dose. permitted by NRC regulations.

Q . 39 .

What adverse health ef fects are possible from this level of dose?

A.

The health effects will depend, of course, on a number of factors,
including the age and health of the worker, the actual amount of dose
received (at TMI and elsewhere) , and the time period over which thedose is received . For example, consider a 30-year old person who wo r k snine years and receives 1 rem per quarter for each year worked (that is,
9 x 4 = 36 rem) . Statistically, that person has a 1 in 2 10 chance o fpremature death from cancer. This is in addition to the 1-in-5 probabilityof death from cancer from other causes, which is the average for the entire
U . S. population .

Q . 40.

How many workers will be involved in the cleanup?

A.

NRC cannot say for certain at this time because of things like normal
turnover among workers and the need for specialists in various disci­plines. In Draft Supplement 1 to the Programmatic Environmental Impact
Statement, NRC estimated that about 1 0, 000 workers would eventually
be involved.

Q . 41 .

Is the work force made up only of GPU Nuclear people?

A.

GPU Nuclear, its contractors, and other GPU utility personnel inake up
the cleanup work force . Some NRC and Department of Energy personnel a ndsome of their contractors will also receive some dose .

Q. 42.

What• s the age range of cleanup workers?

A.

They range between 18 and 70 and are primarily male.
at present is 42 .

Q . 43.

You in dicate that there are some women in the work force . Could a womanof childbearing age work in areas contaminated by radioactivity ?

A.

Yes . All women radiation workers receive training for work in radia t io nzones when they are first hired and annually thereafter . A t these tra in­ing courses they are provided with NRC • s guidance on exposure of the
fetus. In addition, the doses received by women em plo yees are mainta ined
separately on a special computer code and are reviewed weekly by theRadiological Engineering Department . When any woman• s dose approaches·� rem, which is the NRC-recommended limit for a fetus, the woman is
contacted and again reminded of the guideline and the reason for it .
When a woman radiation worker becomes pregnant she is given theopportunity to limit her dose, whenever possible, without her job being
put in jeopardy .

The average age

-11Q. 44.

Are all radiation workers informed about the possible risks they face?

A.

Yes . In accordance with NRC regulations, all radiation workers receive
training in the subject. Workers receive three types of training. New
employees are given both classroom and on-the-job training . All employees
are also g iven annual refresher courses, both in class and on the job .
Finally, all workers about to enter a radiation area are given a prejob briefing that informs them about the nature of the task, theradiation levels anticipated, and the types of protective clothing
and respirators they will have to wear. In addition, women who work inradiation zones are given special instructions and a copy of NRC's
recom men ded guidelines on the protection of the fetus .

Q . 45.

Have discussions been held with unions representing cleanup workers
about the nature of the work and about the potential risks?

A.

Yes . Some meetings have been held and NRC plans to hold additional
meetings in the future.

Q.46.

Have outside workers been brought in because regular workers might use
up their quarterly or annual dose limits?

A.

No, they have not.

Q . 47 .

What kind of protective clothing do workers wear i n contaminated areas?

A.

Protective clothing is selected for the conditions in the work area andalso for the job the worker will be doing. At a minimum, workers are
required to wear one pair of coveralls, a hood, and a respirator (an air
filter for breathing) for all work in the reactor building. For work in
wet areas, plastic outer clothing is also used .

A . 48 .

Isn't it hard for the workers to get their work done in all that pro­tective clothing?

A.

Yes . It is a problem because the clothing is both bulky and hot towear. Workers in areas with high temperatures may wear ice vests tocool them selves.

Q . 49 .

Do protective clothing and respirators protect workers from receiving aradiation dose?

A.

Yes and no . Protective clothing and respirators help to protect workers
from becoming contaminated by radioactive material, but they do not keepthem from receiving a radiation dose from sources of penetrating gamma
radiation. (The answer to Question 51 explains why protective clothing
will not shield against some radiation.) Even though respirators are
not ef fective against some types of airborne radioactive materials,
these types of contamination are not present in the reactor building
atmosphere at TMI-2 in concentrations high enough to be hazardous toworkers.

Q . SO.

Why

is it important to cover workers with protective clothing?

-1 2 A.

A worker's skin must be protected for two reasons. First, if radio­
active material gets on the skin, the material continues to give of fradiation until it is removed. Second, radioactive material on theskin has a chance of being taken inside the body if the skin is broken.
Finally, workers must avoid swallowing or inhaling radioactive material
because the material will continue to give of f radiation until it iseliminated from the body, a process which could take from several hours toseveral years.

Q.51 .

What kind of radiation will protective clothing stop?

A.

There are three types of ionizing radiation: alpha, beta, and gamma.
The one that gives workers at TMI a whole-body radiation dose is pre­dominantly gamma radiation. ( "Whole-body" refers to radiation exposurein which the entire body rather than an isolated part -- an arm or leg -­is exposed. ) Gamma radiation is like the X-rays used in medicine anddentistry in that it will penetrate clothing and other lightweightmaterials. It takes something heavy, like lead or a lot of water, tostop it.
l pha and beta radiation are responsible for much less of theradiation ose.

s

Alpha radiation is stopped by almost anything ( a piece of paper, humanskin, clothing, etc. ) and is therefore only a health problem if it gets
inside the body. Beta radiation is more penetrating than alpha radia­
tion. Although some beta radiation can penetrate protective clothing,its ef fects are greatly weakened as a result. It can affect the lens of
the eye and other soft tissues, but it is easily shielded by the plastic
eye cover of the respirator or by ordinary safety g lasses.
Q.52.

Were alternat ive cleanup plans considered in Draft Supplement 1 to theProgrammatic Environmental Impact Statement that might result in lower
occupational doses?

A.

Yes. Three alternatives were considered, but only one of these wasfound to result in signif icantly lower worker doses.

Q.53.

What was the first alternative for cleanup discussed in Draft Supplement 1 ?

A.

The first alternative considered was to clean the reactor building thoroughly
before removing the damaged fuel from the reactor.

Q.54.

Does the present cleanup plan dif fer from this plan?

A.

Yes. The current plan calls for removal of the fuel as. soon as po ssible( while implementing a plan to reduce worker exposure ) and completion of
the building cleanup later.

Q.55.

Why isn't the original plan going to be followed?

-13A.

The cleanup of the reactor building and equipment will require moretime and involve more radiation dose to workers than was originally
anticipated. Removing the fuel is considered too important to leave
until after the building cleanup is completed. Also, removing the fuelis likely to cause some additional contamination, necessitating thatsome areas in the reactor building be cleaned again.

Q.5 6.

Why is removing the fuel so important?

A.

For three reasons. First, the fuel is the source of the majority ofradioactivity in the reactor building at TMI-2. Second, the presence ofthe fuel in the reactor represents a potential hazard to workers and the
public because there is a small chance that the fuel could begin a sel f­sustaining chain reaction and give of f unwanted heat and radiation.
Third, scientists and engineers expect to learn a lot about preventing andcontrolling nuclear accidents from examining the damaged fuel from
TMI-2 .

Q.57.

After the fuel is removed, why don't workers seal the building shutfor 30 years rather than take the risks associated with decontami­
nating the rest of the building?

A.

The main reason for not accepting this ap proach is concern for thesafety of the public. As long as there are potentially harmful levelsof radiation in the reactor building, workers will need to make periodic
inspections, take samples, change filters, and do other work to protect
the public. All these activities will expose workers to radiation
without contributing toward permanent removal of the radioactivity.
In addition, as was discussed in the answer to Question 2 1, the radio­
active chem ical cesium-137 has a 30-year half-life, so the amount ofradioactivity it emits would decrease only by one-half in 30 years.
More time and therefore more exposure would be required to clean thebuilding, even after a 30-year wait. Waiting also increases thedif ficulty of decontamination. However, if there were reason to expect
breakthroughs in useful robotic technology to save workers fromsignificant radiation doses, there could be merit to this approach.
(For information about the potential use of robots, see Questions 59
through 68.)

Q.58.

Would decontaminating the entire reactor building before removing thefuel lower the radiation dose to workers?

A.

Probably not. The current cleanup will likely result in from 1 3, 000 to
46, 000 person-rem. Decontaminating the reactor building first will
likely result in from 1 2, 000 to 42, 000 person-rem. This is really nota significant dif ference in view of the large degree of uncertainty inthese estimates.

-14-

Q. 59.

What were the other alternatives considered, and would they reduce
worker exposure?

A.

A second alternative would be to design and build equipment tovacuum the fine fuel pa rticles out of the reactor vessel through oneof the small openings in the reactor top (or head) where a small
TV camera has already been inserted for a visual inspection of the core.
Unfortunately, this alternative would result in just as much radiationdose to the workers as the current plan.
The third alternative considered was to remove the fuel, just as pro­
posed in the current plan, but then wait until robots were ava ilable
to finish the reactor building cleanup.
This alternative would
lower worker radiation doses and it would get the fuel out as soon a s
possible, but no one ca n be sure that this alternative is technicallyfeasible.

Q. 60.

Aside from risk s to cleanup workers, is one cleanup alternative sa fer
for the public than the others?

A.

Although the alternative cleanup methods were all selected to meetthe objective of protecting the public, there are slight dif ferencesin how weJl they do so.
The current cleanup plan provides for the
earltest possible removal of the damaged fuel, and we believe that
Because1ts �emoval is important to public sa fety and peace of mind.
·the other alternatives put certain other ta sk s before fuel removal,
they are slightly less desirable from the standpoint of public healthIn the third alternative, the fuel would be removed
and w ell-being.
first, but there would be a significant delay in cleaning the rest of
the facility while robot technology is being developed.
The ef fects on
public safety of such a delay have not been evaluated, but they are notexpected to be as beneficial as proceeding with the cleanup .

Q. 61.

What do you mean by 11 technically feasible11 in connection with robots?

A.

Cleaning the building by robotics could not begin in earnest until
robotic technolog y has ad vanced beyond its present stage of develop­
ment.
No one can at this time say how long such developments wouldtake.

Q. 62.

What is the di f ference between 11 robots11 and 11robotics11?

A.

To most of us, robots conjure up the devices we see in science fiction
movies.
They are mobile, self-contained, and able to perform a wide
variety of tasks -- and sometimes they have personalities.
The current
state of robotic technology is a long way from producing such ver­satile devices, however.
The term robotics, as used here and in Draf t
Sup plement 1, refers to the technolog y of remotely controlled devices
which can do one or perhap s two job s well.
These are the ty pes ofdevices that would have to be used at TMI.

-15Q. 63 .

How much could the radiation dose to workers be reduced by using robotic
technology ?

A.

This alternative would reduce worker dose by about 40% -- to between
6,900 to 28, 000 person-rem .

Q . 64.

If this alternative is not feasible now, could it eventually be
us ed?

A.

Yes, i f developments in robotics are rapid .

Q. 65 .

As suming that developments in robotic technology permitted their us ein the cleanup, would the robots become contaminated?

A.

Yes. Workers would probably have to take special precaution to pre­vent vital parts, such as electronic circuits, from becoming contami­
nated, but any part that came in contact with contaminated building
surfaces or equipment would become contaminated .

Q. 66 .

Would workers decontaminating the robots be exposed to contamination
and radiation?

A.

Workers would be protected from contamination by the same ty pe of pro­tective clothing and respiratory protection that they now wear in thereactor building . They would, however, be exposed to .some radiation,and they would receive some radiation dose .

Q . 67.

How much?

A.

Current estimates are that they would receive between 5% and 1 5% of thedos e they would receive if the work being done by robots were done
manually .

Q . 68 .

If robotic technology was advancing fast enough so that its us e wasfeas ible, would workers at TMI-2 still be expos ed to radiation during
the period while the robotics technology was being developed?

A.

Yes. There are certain tasks that would be required whether or notcleanup work was going on . Estimates are that these tas ks could
result in worker exposure of between about 2 and 31 person-rem per year .

Q . 69 .

What are the most up-to-date estimates of doses workers could· receiv efrom each cleanup tas k?

A.

Disass embling the reactor and removing the fuel is expected to require
between 2, 600 and 1 5, 000 person-rem; cleaning the reactor building a nd
equipment, 5, 900 to 2 1, 000 person-rem; and all other activities , includ­ing work to date, between 4, 500 and 9 , 900 person-rem.

-16Q.70.

That seem s 1 ike quite a large dose for the 110ther activities...
are they?

What

A.

They include the dose reduction program, decontaminating the reactor's
primary cooling system, cleaning the auxiliary and fuel-handling building,managing and transporting radioactive wastes, routine inspection andmaintenance activities, and those cleanup activit ies completed so far.
(Details about the dose reduction program are discussed in Questions 28
and 2 9.)Q.71.

Why do estimates of doses workers could receive vary so widely foreach task ? For example, the range for cleaning the reactor building
and equipment varies from 5, 900 to 2 1, 000 person-rem.

A.

Even though the engineers and radiation specialists have a good idea ofthe cleanup required for most of the reactor building and equipment, there
are still unknowns. One big unknown is the condition of the basement of
the reactor building, because it was under contaminated water for so long.
Some decontamination is being done from above this level, but radiation
specialists can only estimate what the dose rates will be when hands-on
decontamination has begun. They also must estimate the amount of time
workers will spend on each task. Given these unknowns, it really is not
surprising that there is such a dif ference between the high and low
estimates.
For the low estimate, the assumption was made that the work would be donein the shortest time at the lowest dose rates. For the high estimate, theassumption was made that everything would take the maximum amount of timeat the highest dose rate that might be estimated.

Q.72.

How are workers being protected from contamination at the present
time?

A.

Cleanup workers wear the protective clothing and respiratory protection discussed in Question 47. After each entry to the reactor
building, each worker is examined for contamination after the protective
clothing is removed. Only a few workers have been contaminated. In eachcase, simple decontamination methods, such as washing the af fected area,
eliminated the contamination.
(See the answer to Question 2 4 about radiation-detection devices.)

Q.73

What type of radioactive material accounts for the major source of con­tamination?

A.

Cesium-137 is the major contributor to worker dose because it emits gamma
radiation. Strontium-90 is also a problem, but because it emits beta
radiation, protective clothing reduces worker exposure.
(See the answers to Questions 49, 50, and 51.)

Q.74.

Where did these radioactive materials come from?
in normally operating reactors as well?

Aren't they present

-17A.

Yes. They are present in all reactors, but they are usually trappedin the fuel. The accident at TMI-2 damaged much of the fuel, resulting
in the release of these radioactive materials.

Q.75.

When workers remove the top {or head) of the reactor vessel, will thefuel expose workers to large doses of radioactivity?

A.

No. When the head i s removed, the fuel will be under a t least 10 feetof water, which will shield the workers {as noted in the answer to
Question 51) . Head removal, however, will entail some radiation dosefrom contamination on structures on the underside of the head. Radiation­
protection measures will be implemented to reduce this dose.

Q.76.

When the damaged fuel in the core is removed, will it·be exposed to the
air or will it be moved under water?

A.

The fuel will be kept un der water at all times to shield the workers
from radiation. The canisters into which the fuel will be placed will
also be kept under water, not only while they are filled, but continuously
until they are placed in shielded, crash-resistent casks for shipment.

Q.77.

Would worker exposure be reduced if the fuel was not removed and theentire reactor vessel was flooded with water?

A.

Workers are exposed to radiation only when they are in a radiationarea, so in that sense you could reduce worker doses substantially{2, 600 to 15, 000 person-rem) by leaving the fuel in place forever--ifthat were acceptable from a safety standpoint. NRC, however, believes
that the risk of leaving the fuel in place is unacceptable in the longterm. According ly, the fuel will have to be removed.
The fuel is currently flooded with a boron-water solution and willcontinue to be throughout defueling. Boron is added to the water
because it absorbs the neutrons {atomic particles) necessary for theuranium fuel to sustain a chain reaction. Without a chain reaction,
the fuel will not achieve criticality and hence will not produce
additional radiation or heat. In a normally operating reactor, thischain reaction is carefully controlled to produce the steam that rotates
turbines to generate electricity.

Q.78.

Has any sampling been done to measure radiation levels under thereactor vessel head?

A.

Yes. Radiation detection devices provide this information. In
ad dition, samples of reactor coolant water are taken regularly, andthere is an ongoing program to sample both the particulate material
inside the reactor and the damaged fuel itself.

Q.79 .

What are current radiation levels?

A.

Radiation levels below the reactor vessel head are about 2 00 to 1, 000
rem per hour. Remember that these are radiation levels inside thereactor vessel. They do not represent readings in areas where workers
will be positioned to remove the head and fuel. These tasks will be
performed in areas with lower radiation levels.

-18-

Q.80.

What would happen if radiation levels are higher than expected when thereactor head is lifted?

A.

The sampling procedures detailed in Question 78 will ensure that thisEven so, there will be procedures intype of surprise doesn't occur.
effect should something like this happen.
For instance, if radiationlevels at a particular point reach a certain level as the head is lifted,
then the head could be replaced immediately.
Further, workers will be
instructed to leave the building if radiation reaches levels that could
result in worker doses exceeding permissible levels.
Even though all
the data have not been accumulated at this writing, GPU Nuclear and NRC
will have sufficient data to kn ow what to expect before the head is lifted.

Q.81.

What would the risk be for a worker who received an overexposure?

A.

The risk to a worker from an overexposure would depend on the levelof dose rece ived.
An overexposure usually means receiving moreradiation dose than was planned.
For example, an overexposure may mean
exceeding GPU Nuclear's 1-rem-per-three-month-period limit without
having the special authorization required or it may mean exceeding NRC's
3-rem-per-three-month-period limit.
The response to Ouestion 39 notesthat a worker who receives 36 rem during the entire cleanup has a 1 in
210 chance of premature death from cancer induced by the dose.
If thedose due to overexposure were 36 rem, the risk would be about the sam e.

0.8 2.

Would flooding the area around the reactor vessel cut down on theradiation level that workers could be exposed to when the head islifted?

A.

Flooding the area around the reactor vessel could potentially reduce
worker doses.
Prior to flooding, several time-consuming modifications
would be required.
As one example, a high-volume water decontamination
system would have to be installed to prevent the flood water from itself
becoming a major source of radiation.
The potential reduction in doses
to workers would be· too small to .iustify flooding the area for a "wet"head 1 ift.

Q.83.

Can radiation trapped inside the reactor building penetrate the walls
to the outside environment?

A.

Yes, to a very limited extent.
Radiation is reduced in intensity as it
passes through heavy materials.
( This is why you get a good image ofdense tissues like bone on an X-ray film, but less dense tissues, like theheart, do not show up well. )The strongest sources of radiation at TMI-2
are in areas of the building below ground level.
The.Y are shielded not
only by the building itself, which is made of reinforced concrete several
feet thick, but also by the ground.
In addition, the inside of the entire
building is lined with a 3/R-inch thick steel liner.
Radioactive materials
in the upper part of the building do emit some radiation that passes throughthe approximately 3-l/2 feet of concrete and steel that form the reactor dome.

- 19If cesium-1 37, for exampl e, gives a dose rate of 1 00 mil l irem per hour
inside th e dome, this rate is reduced 10, 000 times to l/ 100 of a millirem
per hour on the outside surface of the dome. This level of radiation would
be virtuall y impossible to measure a t the pl ant property boundary.
Q.84.

Can radioactive material s contaminate the reactor building• s steel
1iner?

A.

Yes. There is some radioactive contamination on the steel l iner,
especial ly at the l ower el evations of the building.

Q.85.. Will this contamination be difficul t to remove from the steel 1iner?
A.

The l iner is one of the easier surfaces to decontaminate. It has apainted surface, and workers do not expect to find much contamination
beneath the paint.

Q.86.

Can radioactive contamination penetrate concrete surfaces inside thereactor buil ding?

A.

Unpainted concrete surfaces within the buil ding are expected to be highly
contaminated since concrete is a porous material .

Q.87.

How can you tel l how far the contamination has penetrated the unpai nted
concrete surfaces?

A.

Sampl es of concrete from structures in the upper areas inside the reactor
building are stil l being taken and anal yzed, but workers expect contami­
nation may have penetrated only the first few tenths of an inch. For
sampl es of concrete that were un derwater, they expect that contamination
may have penetrated up to a few inches.

Q.88.

What methods can be used to remove contamination from unpainted con­crete surfaces?

A.

The most ef fective methods are those that chip away the surface of theconcrete. Machines that do this have been used successfully to cl ean
concrete surfaces in the auxiliary buil ding.

Q.89.

Does the sandblasting method of scrubbing surfaces rel ease contaminatedparticles into the atmosphere?

A.

Dry sandblasting is seldom used for decontamination without a vacuum
attachment to col l ect particl es that woul d otherwise spread contamination .
The so-called vacuum bl asting and various wet-bl asting techniques hav ebeen used successful ly where contamination is not too deep. ( Wet bla s t­
i ng in vol ves the use of jets of high pressure water.)

-2 0Q.9 0.

Have contaminated materials in the reactor building since the accident
lessened the building • s capacity to prevent these materials from leaking
to the outside environment?

A.

No. The building materials at TMI and other reactors were selected,
designed, and fabricated to be resistant to radiation. Norm al p hysicalprocesses, such as rust caused by high humidity and degradation caused
by caustic cleaning materials, may over an exten ded period of time wea ken
the capability of the reactor building to contain the accident-generated
material. This is one incentive to decontaminate the building so that it
is not lef t in its present condition. GPU Nuclear conducts a continuou senvironmental-monitoring program to evaluate building conditions.

Q.9 1

Does any radioactive material escape to the outside environment when
workers enter and leave the reactor building? If so, how much?

A.

Now that the krypton gas has been vented and the reactor building i s con­tinually being ventilated to the outside through high-efficiency air
filters, there is little radioactive contamination, except for particul a tematerial. These particles are trapped by f ilters in the ventilation systemand cannot reach the outside environment. Some contaminated particles cling
to the protective clothing that workers wear, and this leaves the reactor
building on the clothing. Even so, virtually none of this material reaches
the environment outside the building because of stringent controls on h ow
this clothing is handled in the changing area where workers remove thei r
protective garments.

Q.9 2 .

Are explosions possible d uring any part of the cleanup?

A.

There is virtually no possibility of an explosion associated withthe cleanup. Of course, the potential always exists that a hose underhigh pressure could burst, something that would be hazardous to worker s
in the immediate vicinity. Also, there has been concern about the pos­sibility of a pyrophoric explosion.

Q.9 3 .

What are pyrop horic explosions?

A.

Pyrophoric explosions result from the extr emely rapid burning of very
reactive metals. For example, metallic sodium undergoes pyrophoric
burning (or explosion) in air or if wet. less-reactive metals, such a s
aluminum, magnesium, and zirconium, will undergo pyrophoric reactions if
they are finely powdered.
The zirconium tubes that surround the uranium fuel could undergo pyrop h oric
reactions if exposed to air, although the tubes are now under water and willremain there throughout the cleanup. (Wet particles may undergo pyrop horic
reactions when exposed to air, but such reactions do not take place underwater.) However, this possibility was investigated. Tests were also madeon samples of reactive metals taken from the structures near the top of thereactor vessel. Based on the results of these investigations and tests,
such explosions are considered highly unlikely. Nevertheless, workers wil lperform fuel removal tasks very carefully to avoid even the small chance ofsuch an explosion.

-2 1 Q.94.

What r adiation dose is received by truckers who haul radioactive wastefrom TMI to waste disposal locations?

A.

Truck drivers who haul radioactive waste are radiation workers andare subject to the same NRC dose lim itations as other radiation worke rs(see Que stion 27) . In addition, the U .S. Department of Transportation(DOT) limits the dose rate in th e driver•s seat of any vehicle haulingradioactive material to 2 m illirem per hour. For a tr ip of 2300
m iles from TMI to Richland, Washington, the driver m ight spend up to
60 hours in the truck cab, thereby receiving 1 2 0 m illirem on the trip .
The return trip most lik ely would not involve the transportation ofradioactive material .
For an extre me case, consider a truck driver who spe nds 2000 hours pe r
year dr iving, half of that hauling radioactive material , with them aximum allowable dose rate of 2 millirem per hour in the cab. The
dr ive r would receive at most 2, 000 m illirem (2 rem) pe r year, a dosewell below the NRC guideline of 5 rem .

Q.95.

What are t he potential adverse health ef fects these doses coul d re sultin?

A.

The risk to a truck driver receiving 2 rem per year for 9 years would beapproximately � the risk to the worker we discussed in Question 39, or
about a 1 in 420 chance of premature death from cancer.

·tr u . s .

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