ML20062E330

Ack Receipt of Indicating Desire to Work W/Acnw in Resolving Certain Issues on EPA Stds for Disposal of High Level Radwastes in Geologic Repository

ML20062E330
Person / Time
Issue date:	10/10/1990
From:	Moeller D NRC ADVISORY COMMITTEE ON NUCLEAR WASTE (ACNW)
To:	Guimond R ENVIRONMENTAL PROTECTION AGENCY
Shared Package
ML20062E319	List: ML20062E316 ML20062E330
References
NACNUCLE-0024, NACNUCLE-24, NUDOCS 9011200077
Download: ML20062E330 (4)

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NUCLEAR REGULATORY COMMISSION!

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ADVISORY COMMITTEE oN NUCLEAR WASTE -

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WASHINGTON, D.C. 20066 October 10,c1990 1

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L Mr. Richard J.

Guimond l-Assistant Surgeon General, U.S. Public' Health Service-Director, Office of RadiationLPrograms i

U.S. Environmental Protection Agency

'I Washington, D.C.

20460 i

Dear Mr. Guimonds We were pleased.to receive your letter of August 6, 1990,, asLwell' as your telephone call of-the! same : date, sindicating. a' desire to-work with this committee in resolving certain issues related to the Environmental Protection Agency. (EPA) standards for the' disposal' of high-level radioactive - wastes in a, geologic ; repository.

In.

J response to your questions pertaining.to the letter of May 1,.1990, submitted by this - Committee ' to Chairman; Kenneth M..

Carr, ! U. S.'

j Nuclear Regulatory Commission- (NRC)',

we'. offer,;the following!

q comments.

They correspond to the. items o as i enumerated in. your letter.

1.

We believe that the EPA' standards can be' interpreted as-being organized =in a hierarchical structure.

This is based on-the assumption that;the highest' level expression in your hierarchy is a qualitative _ goal, that is, that the risks 1to future generations-

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over the first 10,000- years -due to the disposal _of.high-levele radioactive wastes-in a repository shouldtbeLno greater than #the risks that would have existed it.the; uranium ora had not been mined We note, however, that-thisfstatement is not included in the standards,inor is it'identifiedLas theLhighest. level. goal.

The statement is incisded. only'-in: tho' " Summary" andt.the

" Supplementary Information" that accompanies the original' standards L_

as published in the Federal Registerk '

', i What we interpret as the next level,lwhich is quantitative an'd;is a part of the standards, is the statementLthat there'should be-no-more than 1,000: premature deaths over!the first 10;000fyearsTwhich-

are. attributable'to placement!in.a; repository of the high-level.

o wastes from 100,000 metric tons Af reactor fuel.'.We fail, however, to seetthe. connection or comparabilityibetween this-statement and I

what we' interpret 1as therhighestblevel: goal.

Wafalsoofai1;to see-

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the quantitative relationship between :this# requirement and. the j

limits on the-releases of specific' radionuclides!from aLdisposal K

facility which Lare probabilistic: and' serve as.'what 'we interpret' to be tho' third level in-the hierarchy.

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i Mr. Richard J. Guimond 2

October 10, 1990-Our concern with your apparent hierarchical structure is thatsthe j

lower level quantitative statements - (or standards) appear to be more. stringent than the highest level qualitative statement.

To assist us in better understanding the' approach you have taken,-it 1

would be helpful if. your staff could - (1) state:whether we have z

correctly interpreted the hierarchical _ structure of your standards, i

and (2) provide us with the rationale and, jndeed, the calculations -

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and assessments that served as a basis for developing theflower level quantitative standards.

With respect to the latter request, i

I we note that certain changes have occurred that may impact upon the :

i validity of your earlier calculations..These changes includes (a) analyses of "real" repository sites have-shown-them to be more complicated than your ataff may have-assumed for the hypothetical-site used in your analyses, (b) the potential impact of indoor radon, which was only generally recognized subsequent' to your original assessment,. may need to be factored into - your risk evaluations, and (c) major advances in environmental. modelling techniques over the last few years.

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2.

(a)

We concur with your assumption that a disturbance can occur at any time during.the initial 10,000-year period.-

In recognition of this fact, you have specified the _ radionuclide release limits in your, standards in a manner sorthat it does not-make any difference whether the entire release - occurs _within ~a single year or is spread out over time.

We do not concur, however,

.l that this makes it difficult to apply annual risk limits under l

these types of circumstances.

The principal basis for our position is the guidance provided by the International Commission on Radiological Protection-(ICRP) in its Publication 46.

In this report, the ICRP recommends that-the risks from releases from~the undisturbed: performance of a waste repository be controlled through _ the. application of, annual dose limits.

The ICRP further recommends that-the risks from releases accompanying the disturbed state (classifiedo as "probabilistic events") be limited on u similar ' basis, that' 'is, through the application of annual risk limits.

In both cases, the limits would apply to the critical population group.

If you maintain your-position that_ application of an: annual _ risk limit to releases occurring during - the ' disturbed. state is not workable, an alternative approach:would.be'to apply some form of

" accident or event" risk limit -to these types of occurrences. This would be_ comparable.to the; approach being, used in. safety assessments of nuclear power.-plants'where annual dose limits are applied for the. control of radionuclide' releases associatedLwith-routine operations and (single-event) risk' limits are applied to releases occurring as a result of accident situations.

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zi Mr. Richard J.

Guimond

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' October 10, 1990 h

In making these suggestions, we clearly recognize that.therelare definite limitations in comparing the standards and' approaches used in the regulation of a-nuclear. power plant to those needed for-.a-l high-level. radioactive waste: repository.

Nonetheless,.where;the transfer of-knowledge and experience from one. type of nuclear a

facility to another can be beneficial,. such analogies-should be encouraged.

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(b)

We agree that the licensing organization.should have -

the authority for defining the critical population group.

Having stated this, however, we ' also believe that: i t w o u l d.. b e l

l helpful if the EPA-staff could identify and' justify the; critical' population _ group assumed to be-exposed in setting what wen have t

referred to as your intermediate level goal.

If wet interpret the situation correctly, such information would permit estimation of.

the average annual risk (dose) limit that corresponds to this goal.

In a similar manner, we would appreciate. knowing the-critical population group that was assumew in calculating the probabilistic radionuclide release limits specified in Table 1 of'your-standards.

Another item of intornation_that would'be helpful would,be to know l

how the collective doses associated with,the establishment of these l

radionuclide releases were _ calculated.

To be : specific; 'was;a l,

cutoff used, as was suggested by the1ICRP in its Publication'46 i

and as has more recently been suggested by the' National Council on d

Radiation Protection and Measurements in'its' Report No. 91,' or was the full range of dose rates included in making these estimates?

Please note that our interest in:being-able to. define =a critical population group and to estimate'this group's associated permis-sible dose rates is in line with our;, understeding of1 the guidelines recommended by the ICRP 2 and by radiation Orotection authorities in other countries of: the world for high-lee *1 waste l-repositories.

_ e believe the guidance provided by these groups is W

sound and represents a satisfactory basis on which to judge the acceptability of the health risks associated with radioactive vaste disposal facilities.

3.

In recommending that a disposal facility be addressed as a system, we reaffirm our position that' a properly organized system l

requires a consistent hierarchical structure, iThe application'of remedial' actions beyond retrievability of the' emplaced; waste is an

-integral part of such a system.-

4.

(a)

We concur.with your statement;that "what is really.

important is the' total anticipated. impact of repositorya perfor-mance."

The reason that we called for specific-attention: to human 4

l intrusion is that preliminary performance assessments for.the~WIPP facility-have shown that this concern.is the dominant contributor

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to the risks-to-the public.

We have'no data.that-show the same 1

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1 Mr.-Richard J.LGuimond

-4 October 10, 1990 situation is' valid ~for the proposed-Yucca Mountain repository, but I

it is possible that.this will-prove to beitrue.

lIn fact, the EPA-j staff may have foreseen this situation when ' it -included 'in the

'd standards the statement that_"..

it is'possible to conceive of intrusions (involving widespread ~ societal loss. of knowledge i

regarding radioactive wastes) that;could result;in major-disrup-J tions that no reasonable repository selection or design precautions 1

could alleviate." We are aware that.your standards state that "The J

Agency believes ~ that the most productive consideration of inadver-1 tant intrusion concerns those realistic. possibilities that may be usefully mitigated by' repository design,~ site selection,.or use of, but. what - constitutes. realistic; pos-passive controls sibilities is open.to multiple interpretations.

Again, what we are suggesting ' is : directly comparable L to. the -

approach being used-in the regulation'and: assessment of the public-

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health risks from' nuclear power. plants.

For-a waste facility, the undisturbed state would correspond to a nuclear power-plant during normal operations,?and theidisturbed state'would. correspond'to a plant in which an; accidents has occurred.

Innthe. case of= risk assessments for nuclear plants, it was found that tho' difficulties and uncertainties in addressing certains types of accidents were'so j

large that the approach that.has been adopted-is to analyse their contributions separately.

?In-these. cases, estimates of the l

associated risks are based on the best judgments of. expert groups.

l We believe a similar approach (i.e.,.using expert judgment) is almost essential and twould. be ~ appropriate - for ' assessing the

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potential impact of human, intrusion on the performance.of a waste y

repository.

.t (b)

The basis for our comments on borehole sealing was that, if we. assume (as you indicate-in the: guidance'provided;in Appendix B of your standards):that' exploratory procedures willJbe

" adequate for:the intruders;to soon detect,'or be warned.of,1the incompatibility of the area with their activities," then the need R

i for a carefully. sealed borehole would be ' recognized quickly : and action would be taken to ensure that-proper corrective measures.

were taken.. Your consideration of removing this: requirement from 1

the standards is welcomed.

We concur.-

R (c)

Our r,tatement ; calling _ for

>"nore-realistic-assessments" of the potential ' impacts of _ human intrusion at the proposed Yucca Mountain site was' based -in part - on the guidance

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provided in : Appendix.B of the current ~ EPAf standards,. which states that a borehole will_ create "a ground _. water, flow path with a j

permeability' typical of a' borehole filled by soil'or~ gravel that would normally settle into an - open hole over'. time -- E not the

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permeability of a ' carefully sealed.jborehole."~ to demonstrate

Under-these H

constraints, we believe it' might be difficult compliance of any facility'with the EPA standards._ We are. pleased to learn that the licensing authority?"(NRC) :Will make the

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Mr. Richard J..Guimond 5

' October-10, 1990-i determination as to the_ appropriate-realism for assessments regarding human intrucion.

At the same time, however, we remain. concerned with this approach. -

The guidance in Appendix B to the EPA standards includes' detailed =

discussions of borehole seals and human intrusion.

As a result, we believe - that your < Agency _- has preempted -the definition of reasonable approaches in assessing '5ese-matters.

Any deviation by the licensing authority from yor juidance will almost certainly be viewed by the public'as an exc gion to the standards.

(d)

We appreciate the comments provided.in your letter 1

related to the role of passive controls, such as markers-- and records, in reducing the likelihood of human intrusion.-

We also concur wit's the statement in Appendix B of the EPA standards that-passive institutional-controls can never be, assumed 2 to

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eliminate the chance of inadvertent and-intermittent = human intrusion into.

" waste disposal, sites.' Wa concur that it is-the role of the implementing agency,to determine ~ the degree to

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which these factors should 'be considered to control human intrusion.

5.

The - ACNW understands the need to include 1 probabilistic.

_ e believe'it'is important to W

requirements in,the EPA standards.

recognize that (a) the probabilistic requirements in your standards apply only to the lowest set of L goals in your hierarchy, and (b) contrary to what is practiced in comparable situations-(e.g., the NRC safety goals for nuclear power plants), your requirements include a risk aversion factor.

What we believe needs to be

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explicitly stated is that the.probabilistic approach can be an l

important factor.in regulating a:wasterdisposal facility, but it should not be the sole basis for decisionmaking.. ' Equal or greater i

weight can and should be placed.on the: development and application:

of deterministic requirements and, when-necessary, the use of expert judgment.- We are pleased to note that your staff is.using_

a deterministic approach in developing requirements for the control of doses to the public due to the contamination of drinking water-as a result of radionuclide releaces from a waste'. facility.

We thank you for your thoughtful and cc structive letter. !As soon as you. and your staff have had an opportunity to review our responses to your questions, we would welcome your reply and.an-L opportunity to ' meet and discuss 'these matters with -you in additional' detail, i

Sincerol

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Dade W.'Moeller Chairman 3

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