ML20041D965
| ML20041D965 | |
| Person / Time | |
|---|---|
| Issue date: | 02/22/1982 |
| From: | Knapp M NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Martin J NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| References | |
| REF-WM-6 WMHL:3402.1, NUDOCS 8203090679 | |
| Download: ML20041D965 (4) | |
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4, MEMORANDUM FOR: John B. Martin, Director Division of Waste fianagement JOBuntin '
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FROM:
Malcolm R. Knapp
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High-level Waste Licensing u ts m mra T fianagement Branch c,
Division of Waste Management "E"
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SUBJECT:
APPLICATION OF SAFETY G0ALS TO WASTE DISPOSAL 7 n; N
In your note of January 22, you asked what release limits would be necessary to satisfy the Commission's proposed safety goal if it were applied to high-level waste disposal. We have concluded that depending on how the safety goal is adapted to waste disposal, the release limit would be from about 12 to about 36 times the release limit set forth in the draft EPA standard.
Described below are two ways of adapting the proposed reactor accident safety goal to waste disposal as well as how these interpretations imply Jitferent release limits.
These two adaptations represent two ends of the philosophical spectrum on the way risk from waste disposal should be measured.
_ Interpretation 1: Limit Cumulative Societal Risk Under this adaptation of the safety goal, we assume that the acceptable number of cancer deaths from reactor accidents occurring in the production of a given amount of energy would also be acceptable in the disposal of the fuel which produced that amount of energy.
In other words, since the Ccmmission's proposed safety goal allows 3.2 cancer deaths / reactor-yr from reactor accidents, we will allow 3.2 deaths / reactor-yr for waste disposal over 10,000 years.
(An alternative risk limit for waste disposal might be some fraction of the proposed reactor accident risk limit, such as 10%.) The period of 10,000 years is used here because EPA believes that that is the longest period of time over wi:ich regulatory action ncw can be effective.
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- *i 3402.1/SAS/82/02/11/0 FEB 2 21982 Noting that an average LWR produces 25.4 MTHM of waste per year, we conclude that the risk limit per unit waste is 3.2 deaths / reactor-yr = 0.126/MTHM 25.4 MTHM/ reactor-yr This risk limit is 12.6 times the risk which EPA estimates would result over 10,000 years from application of its release limits.
Interpretation 2:
Limit Individual Risk Another way of applying the safety goal to waste disposal is to require that the disposal facility, like a reactor, not significantly increase the risk of cancer death to an average individual living near the site.
The policy statement in effect defines a "significant" increase in risk as 0.1% of the background cancer risk.
An average individual experiences a background risk of cancer death of about 0.16 per lifetime.
The 0.1% of this figure allowed by the safety goal is 1.6 x 10~ per lifetime.
An average individual risk under the EPA standard may be deduced from EPA's analysis by making an assumption about the size of the area over which the risk is present. Although different pathways affect different populations, for purposes of a simple calculation we assume that the affected area is the region within 50 miles of the repository. The choice of a 50 mile radius is conservative in the sense that it restricts to a small area the assumed size of the exposed population, thus tending to predict larger individual risks for a given societal risk.
Including a larger population, such as the entire population of the United States, would result in an unreasonably small figure for individual risk since it would include many people who experience no risk at all.
It should be l
noted that the Commission's proposed safety goal for individual risk l
refers to an average individual, not the maximally exposed individual.
2 Using the EPA's assumed population density of 200 people /mi, and assuming that thg average lifespan is 70 years, we find that over 10,000 years, 2.24 x 10 people are exposed to the risk. Again taking EPA's estimate of 1000 deaths over 10,000 years, we find that the individual risk under the EPA standard is 1000/2.24 x 10 = 4.46 x 10-6 8
per lifetime.
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The figurg found above for individual risk under the safety goal, 1.6 x 10 per lifetime, is 36 times greater than this figure for individual risk under the EPA standard.
Comparison of the Two Interpretations The first interpretation, limitation of cumulative societal risk, would limit total societal danage, regardless of the projected size or lifetire of that society. This interpretation could be excessively restrictive because large projections of societal size and lifetime would force very strict release limits.
Thus, the low level, long duration releases anticipated for a HLW repository could be restricted to limits well below any that would affect a future society in any epidemiological sense.
The second interpretation, limitation of individual risk, permits total societal risk to increase without bound, since, as time increases, more and more generations are exposed to the same individual risk.
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flalcolm R. Knapp High-level Waste Licensing Management Branch Division of Wasic fianaoa s t DIST:
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- See previous concurrence OFC WMHL*
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NAME :SASilling:lme MRKnapp : MJB R 3
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/82 : 2/2432
D 3402.1/SAS/82/02/11/0 The figurg found above for individual risk under the safety goal, 1.6 x 10- per lifetime, is 36 times greater than this figure for individual risk under the EPA standard.
Comparison of the Two Interpretations The first adaptation described above, limiting the umulative societal risk over 10,000 years, has the advantage of 1 ting the total amount of damage that can occur in the future because man's nuclear activities now. However, this adaptation may be exc sively restrictive because it does not allow credit for the huge tim eriod over which the risk is distributed. flike Greismeyer, an AJC Fellow who is an authority on safety goals, has pointed out to j that the individual risk from u
high-level waste disposal will b! so small that no future society will ever be able to feel its effect in an epidemiological sense.
The second adaptation, the l it on individual risk, takes as its figure j
of merit the risk that a society " feels" at any given time in the future.
However, this interpretation has the conceptual disadvantage of theoretically allowin /an unlinited number of deaths, fialcolm R. Knapp High-Level Waste Licensing fianagement Branch Division of Waste flanagement DIST:
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_ _ _ _ _ : _K_. _ _W_f 1H L NAME :SASilling:lme f1RKnapp
- MJBell DATE :. 2/ i0/82 2/l}/82 2/
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