ML19317H348
| ML19317H348 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom, Hope Creek, Sterling, Crane  |
| Issue date: | 04/28/1980 |
| From: | Conner T, Silberg J CONNER, MOORE & CORBER, METROPOLITAN EDISON CO., PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC, Public Service Enterprise Group, SHAW, PITTMAN, POTTS & TROWBRIDGE |
| To: | |
| Shared Package | |
| ML19317H349 | List: |
| References | |
| NUDOCS 8005290318 | |
| Download: ML19317H348 (44) | |
Text
I
()
4 April 28, 1980 p
s
- /
DOCKETED UNITED STATES OF AMERICA USNRG NUCLEAR REGULATORY COMMISSION 62 APR 3 01980 * -3 Othce of me Secretary q
Dockedr.g & Service 9
BEFORE THE ATOMIC SAFETY AND LICENSING APPEAL BOA Eranch b
m In the Matters of
)
)
PHILADELPHIA ELECTRIC COMPANY et al.
)
Docket Nos. 50-277 (Peach Bottom Atomic Power Station,
)
50-278 Units 2 and 3)
)
)
METROPOLITAN EDISON COMPANY et al.
)
Docket No. 50-320 (Three Mile Island Nuclear Station,
)
Unit 2)
)
)
PUBLIC SERVICE ELECTRIC AND GAS CO.
)
Docket Nos. 50-354 (Hope Creek Generating Station,
)
50-355 Units 1 and 2)
)
)
ROCHESTER GAS AND ELECTRIC CORPORATION
)
Docket No. STN 50-485 et al.
)
(Sterling Power Project, Nucle'ar Unit 1)
)
PROPOSED FINDINGS OF FACT SUBMITTED ON BEHALF OF PHILADELPHIA ELECTRIC COMPANY ET AL.,
METROPOLITAN EDISON COMPANY ET AL.,
AND PUBLIC SERVICE ELECTRIC AND GAS CO.
I.
EMISSIONS FROM MILL TAILINGS PILES I-1.
The order which set the generic radon issue for eviden-tiary hearing, Philadelphia Electric Company et al. (Peach Bottom Atomic Power Station, Units 2 and 3), ALAB-562, 10 NRC 437 (1979), noted that the topic of radon emissions from mill tailings piles was the one that involved "by far the largest number of factual questions which need further development."
ALAB-562, supra, 10 NRC at 441.
In keeping with that l
80 05290
e 3
admonition, this area produced the greatest amount of testimony at the hearing, from witnesses Dr. Robert O. Pohl (for intervenors), Mr. Hubert J.
Miller (for Staff) and Dr. Morton I. Goldman (for Licensees).
The issues covered at the hearing can, for convenience, be classified into five categories:
(a) implementation, verification and effectiveness of stabilization guidelines; (b) assurance of regulatory control of mill tailings; (c) de-stabilizing effects of erosion, tails migra-tion and other factors on stabilized piles; (d) emission rates from uncovered tailings piles; (e) survivability of uncovered piles, and radon emission rates from dispersed tailings.
Cf.
ALAB-562, supra, 10 NRC at 441-442.
This classification will be utilized in the discussion that follows.
As will be seen, the testimony at the hearing indicates that continued stability of mill tailings for many thousands of years is to be expected as a result of the programs being implemented by the NRC Staff; stabilized mill tailings piles will release radon at a rate from 1 to 10 Ci/ year per AFR.
If the stabilizing cover is nonetheless lost, the mill tailings piles are likely to retain their physical integrity for long periods of time; an unstabil-ized pile of average depth will emit 75-80 Ci/ year per AFR Rn-222.
Dispersal of a pile after loss of its cover will proceed slowly (0.036% per year on the average for currently existing piles) giving sufficient time to take corrective action to restore the piles to a stabilized condition.
The tailings from a dispersed pile will eventually be carried by surface waters to the bottom of the oceans or will be covered 1
f or deposited upon by other soil materials, so that they will not continue to emit radon to the atmosphere for the full lifetime of the radon progenitors.
A.
Implementation, Verification and Effectiveness of Mill Tailings stabilization Guidelines.
I-2.
The Uranium Mill Tailings Radiation Control Act of 1978 (P.L.95-604, 92 Stat. 3021) ( " the Ac t" ) gave authority to the NRC to license and regulate uranium mill tailings, and required reclamation and state or federal ownership of tailings and their disposal sites.
Sections 201-204 of the Act; NRC Staff Testimony of Hubert J. Miller, foll. Tr. 151
(" Miller") at p.
5.
I-3.
To comply with the reclamation requirements of the Act, the Staff issued proposed regulations for the management and disposal of mill tailings.
Proposed Appendix A to 10 CFR Part 40, " Criteria Relating to the Operation of Uranium Mills and the Disposition of Tailings or Wastes", 44 Fed. Reg.
50020-50022 (August 24, 1979)
(" Criteria"); Miller at pp. 7-8.
The Criteria established " technical, financial, ownership, and long-term site surveillance requirements relating to the 1
siting, operation, decontamination, decommissioning, and reclamation of mills and tailings or waste systems and sites at which such mills and systems are located."
- Criteria, Introduction.
I-4.
The " prime option" for tailings disposal is below grade l
burial in specially excavated pits or in mines.
Criterion 3;. _ - _
f f
9 Miller at p. 12.
Where conditions do not permit below grade burial of tailings, above ground disposal will be permitted subject to the following conditions intended to reduce or eliminate erosion potential:
(a) minimization of upstream rainfall catchment areas; (b) selection of site with topo-graphic features providing gnad wind protection; (c) relatively flat embankment slopes after final stabilization to minimize erosion potential; (d) provision of a full, self-sustaining vegetative cover or a riprap cover to retard wind and water erosion; (e) selection of a site not near a potentially active fault; (f) impoundment design incorporating features which promote deposition to enhance the thickness of cover over time.
Criterion 4; Miller at p. 12.
I-5.
Regardless of disposal methods, sufficient cover is to be placed over the tailings to result in a calculated radon 2
emission rate from the tailings of less than 2 pCi/m -sec.
above background.
Criterion 6; Miller at pp. 9-10.
The reason this emission standard is based on calculated rather than measured radon releases is that any radon exhalation measured for compliance with the guidelines would be the sum of the emanations from the tailings through the cover material, from the cover itself, and to a lesser degree from the soil beneath the tailings.
Therefore, it may not be possible to distinguish by measurement alone the contribution from each of those sources, and in many instances the exhalation rates from the cover material may mask the releases from the piles.
Testimony of Morton I. Goldman, foll. Tr. 441 ("Goldman") at pp. 21-22.
Furthermore, radon concentrations in the air are extremely variable because of the large number of environmental factors that influence the rate at which radon is released, and it would take as long as a year to obtain measurements that would smooth out those factors.
Radon measurements, therefore, could not be used to guide the tailings covering operation.
Miller at p.
10.
2 I-6.
The calculated 2 pC1/m -sec. release limit will be implemented by requiring a mill operator, prior to NRC licens-ing of the mill, to define the kind and thickness of cover he intends to use so that when the tailings pile is reclaimed there is a reasonable expectation that the release limit will not be exceeded.
Tr. 169-170 (Miller).
I-7.
Confirmatory radon release measurements will be made from time to time after the mill tailings pile has been reclaimed to determine compliance with the calculated release limit.
Tr.
171, 188 (Miller).
A mill operator who is not fully in compliance with the release limit may be required to place additional cover on the pile.1 Tr. 188 (Miller).
1 The difficulty in distinguishing between pile radon emissions and natural background and cover releases (wh typically of the same order of magnitude as the 2 pCi/m{ch are
-sec.
limit) may make it impossible to determine exactly whether a licensee is meeting the limit.
However, the limit is set so low that small deviations from it would be inconsequential in view of the normal fluctuations in natural background. Tr. 170-171 (Miller).
r I
e I-8.
There was uncontested testimony that the technical capability exists for isolating large volumes of tailings so to keep radon releases from the piles within the release limit.
The isolation is carried out by straightforward earth moving operations, for which there is more than sufficient experience in the mining industry.
Miller at pp. 8, 38-39; Goldman at pp.
13-14.
The NRC has ensured that there will be sufficient economic resources to meet the cost of stabilizing mill tailings piles by requiring, as authorized by Section 203 of the Act, that a prospective mill operator provide adequate financial sureties (in the form of a surety bond, letter of credit, or similar device) to guarantee that there will be funds available to cover the cost of mill tailings reclamation and stabilization.
Criterion 9; Miller at p. 5; Tr. 173, 189 (Miller).
B.
Regulatory Control Of Mill Tailings Isolation.
I-9.
To implement the regulatory requirements, the Staff and the applicant work out the specific details of the tailings disposal method during the period preceding the issuance of a 2
Similarly, the costs of providing long-term surveillance and maintenance of the disposal site are paid in advance by the mill opers' by making a one-time payment to the General Treasury c_ v250,000 or such greater amount as may be deemed necessary for a particular site.
Criterion 10; Miller at p.
17; Tr. 181-83, 190 (Miller).
r f
f mill license.3 The Staff then imposes suitable licensing conditions that commit the mill operator to the specific 4
disposal plan agreed upon prior to licensing.
Tr. 292, 318 (Miller).
Such licensing conditions are within the Staff's power to issue and enforce.
Tr. 293 (Miller).
I-10.
Tailings disposal is to be accomplished in a manner that does not require active maintenance to preserve tailings isolation.
Criterion 12; Miller at p. 11; Tr. 192, 194-195, 201 (Miller).
A mill will not be licensed if there is an expectation then that active maintenance of the tailings it generates will be required.
Tr. 195-196, 205 (Miller).
I-ll.
Since the tailings disposal methods are designed to rely on " stable physical barriers" to provide tailings isolation for many thousands of years without resort to institutional con-trols or active maintenance (MilJer at p.
11; Tr. 205 (Miller)), it is important that a suitable quality assurance program be implemented before the tailings are reclaimed.
Mr.
Miller testified that the Regulatory Guides for uranium mill 3
The siting, stabilization method, cover material and other aspects of the disposal of mill tailings are thoroughly discussed through the NEPA process so that the public has an opportunity to participate and influence the decision before a license is issued to the mill operator.
Tr. 241-242, 244 (Miller).
4 The Criteria provide the broad bases for the stabilization requirements; the details of what must be done at each site can i
only be arrived at on a case by case basis.
Tr. 242 (Miller). !
.-~
f r
e operators require that quality assurance be a part of the development of a mill tailings disposal scheme, and specific-ally that quality assurance plans be implemented for key elements in the program such as the design and construction of tailings retention structures and embankment structures.
Tr.
333-336 (Miller).
The mill operator's quality assurance plan is enforced by periodic audits of the tailings disposal program, performance reviews, site inspections during construc-tion, and review of inspection reports, all intended to verify that construction is proceeding in conformity with the tech-nical specifications of the license.
Tr. 316, 328-329, 334-337 (Miller).
I-12.
After the tailings piles are stabilized, there will be at a minimum annual site inspections and visual surveys of the disposal areas, taking of water samples, and a combination of ground and aerial photography to verify that the piles remain in stabilized condition.
Criterion 12; Miller at p.
17; Tr.
176-178, 197 (Miller).
Surveillance at the sites is to be l
perpetual, i.e.
it will continue as long as the institutional controls now existing remain in place.
Tr. 191-192, 199-200, 293 (Miller).
l I-13.
The licensing scheme described by the Staff will provide reasonable assurance of long-term stability or uranium mill tailings piles.
Piles stabilized in accordance with the Criteria and the Staff's licensing requirements should remain l l
f 5
stable for many thousands of years without reliance on institutional controls and without need for active maintenance.
Miller at p.
13; Tr. 205 to 216-a, 276 (Miller); Tr. 468-469 (Goldman).
C.
De-Stabilizing Effects of Erosion, Tails Migration and Other Factors on Stabilized Piles.
I-14.
Staff witness Miller testified that, in view of cli-matological changes and unusual natural phenomena which may occur over very long periods of time, no absolutely certain prediction can be made that a mill tailings pile will remain stabilized for a period of 80,000 years (the half-life of the thorium progenitor of radon-222).6 Indeed, over such periods of time it is just as likely that there will be further covering added to the pile as it is that the pile will experi-ence substantial deterioration. Miller at pp. 15-16; Tr. 210, 215, 216-a, 271-273 (Miller); Tr. 498, 502-503 (Goldman).
This is particularly true since the Staff intends to implement 5
While Staff witness Miller was of the opinion that properly stabilized mill tailings piles would remain isolated for "many" thousands of years, he could not give upper and lower limits on that number because of uncertainty as to the effects of weather phenomena and climate changes over very long periods of time.
Tr. 210, 215, 216-a (Miller).
6 Intervenors' witness Dr. Pohl expressed the opinion that the stability of aboveground piles is " doubtful" over time periods of 80,000 years or more.
Testimony of Robert O.
- Pohl, foll. Tr. 24 ("Pohl") at p. 6; Tr. 49-50 (Pohl).
It should be noted, however, that Dr. Pohl has also expressed a contrary view in a 1976 magazine article.
Tr. 468-469 (Goldman).
l i
disposal schemes which make it likely that the cover thickness will increase over time.
Criterion 4; Miller at p. 12.
I-15.
To explore these issues further, the Staff commissioned 7
a study by the Colorado State University to examine long term scenarios and identify th ase stabilization failure mechanisms that may conceivably occur, the time periods for those failures, an
- possible interactions between them; and to describe wh n siting and design features can be built into the tailings isolation program to eliminate or reduce the probabil-ity of those failures.
Miller at p.
13; Tr. 208-209, 219, 237-238 (Miller).
I-16.
The Staff incorporated the findings and recommendations of the Colorado State University study into the Criteria and in its siting and design reviews.
Tr. 237-238 (Miller).
For instance, the Colorado State University study found that floods would be the greatest potential cause of severe stabilization failure.
Tr. 274-275 (Miller).
Therefore, tailing disposal sites will not be located near streams but will be located on the head end of divides, so that the amount of precipitation and runoff at the sites is minimized.
Tr. 234 (Miller).
In addition, impoundment dams will be designed to contain a probable maximum flood augumented by a number of contingency 7
J.D.
Nelson and T.A.
Shepherd, " Evaluation of Long-Term Stability of Uranium Tailings Disposal Alternatives", Colorado State University, April 1978.
factors.
Tr. 340 (M111er).8 Thus, aside from the possibility of drastic climatological changes, floods should not be a concern at future mill tailing sites.
I-17.
Another potentially significant failure mechanism mentioned in the Colorado State University study is the occurrence of earthquakes which may cause substantial disper-sion of tailings.
Tr. 275-276 (Miller).
Earthquakes, however, are of concern mainly in the period of 30-40 years during which the mill is operational, whereas the dams are designed to withstand a thousand-year earthquake.
Tr. 340 (Miller).
I-18.
Th failure mechanisms likely to occur in a given case are site-1pecific, as are the design requirements to protect against those and other failure modes.
Tr. 240-241 (Miller).
In general, however, failure mechanisms such as cap gullying, cap erosion, wind erosion, flooding and the like are suffi-ciently slow that they can be identified in the yearly site inspections with enough time to remedy the failures.
Tr. 248, 295-297 (Miller).9 Even assuming no site supervision and maintenance, such failures would not be likely to occur for 8
The probable maximum flood is the maximum expected flood at a given site based on climatological records.
It is more infrequent than a thousand-year flood (i.e. one whose level is expected to occur once in a thousand years).
Tr. 230-233 (Miller).
9 Erosion of stabilized tailings would be readily detectable by inspection without instrumentation, since it would take the form of gullying or deterioration of cover material.
Tr. 461 (Goldman).
T thousands of years at sites where rock cover or below grade burial of tailings have been provided.
Tr. 295-296 (Miller).
D.
Radon Emission Rates From Uncovered Piles.
I-19.
The record contains a comprehensive analysis of the rate of radon emissions from uncovered mill tailings piles.
Goldman at pp. 3-12.
The analysis of licensees' witness Dr. Goldman, which was endorsed by other witnesses (see Tr. 31, 54-55 (Pohl)) and was largely uncontested at the hearing,10 indicates that the radon exhalation rate from mill tailings piles is mainly a function of the ore grade, the bulk diffusion coeffi-cient of radon through the mass of tailings, and the area-depth relationship for the tailings pile.
Goldman at pp. 3, 12.
10 There was some question as to whether the mill recovery recovered from fraction ( that is, the percentage of U 0 the ore) could be approximated, as Dr.3 gGoldman did, as a straight line function of the ore grade.
However, Dr. Goldman testified that the straight line approximation gave a good fit for reported industry data and was reasonable for grades down to at least.07% (Tr. 442, 475-479 (Goldman)).
He also stated that, since each point through which the straight line was fitted represented a yearly average of reported industrial recovery rates, it was reasonable to anticipate that as the ore grade being mined decreased the recovery process would be made more efficient.
Further, he stated that he was aware of indi-vidual mills recovering 90% from ores of about 0.1% grade; those mills could not be fitted by a curvilinear relationship.
l Tr. 491-492 (Goldman).
Consequently, it would be impossible to predict whether a curvilinear relationship (such as sketched by Dr. Kepford, see figure foll. Tr. 487) would be more accurate at lower ore grades than the straight line posited by Dr.
Goldman.
Tr. 490-493 (Goldman).
The dispute in any event is largely academic because, according to Dr. Goldman's analysis, the radon exhalation rate is far more strongly dependent on the pile's surface area-to-volume ratio and the radon bulk diffusion coefficient than it is on the ore grade as long as the recovery fraction does not change significantly.
Goldman at p.
- 12. I
I-20.
The U 0 recovery rate is a slowly varying ' function of 38 ore grade for the ore grades currently in use.11 In turn, the tailings surface area per AFR is a very slight function of ore grade; for a given tailings depth, halving the ore grade increases the area by a factor only a bit greater than 2.
Consequently, the milling of lower ore grades would have very little impact on the radon exhalation rates.
Goldman at p. 7 and Fig.
2.
I-21.
Far more significant to the radon release rate is the bulk diffusion coefficient.
The diffusion of radon through tailings is a function of the moisture content of the pile; the higher the moisture, the lower the dif fusion (and hence exhalation) of radon from it.
Goldman at p. 8; Tr. 494 (Goldman).
Dr. Goldman computed in a parametric manner the radon release rate from dry tailings as a function of tailings depth for three bulk diffusion coefficients reported in the literature; two of these coefficients were the result of theoretical analysis and the third (and lower) one was derived from experimental measurements of radon flux from tailings by Argonne National Laboratory.
Goldman at pp. 8-11 and Fig. 3.
Dr. Goldman testified that he expected the measured diffusion coefficient to be more realistic than the analytical values.
l 11 As the ore grade decreases from.2% to.07%, Dr. Goldman computes a decrease in recovery rate just from 92% to 89%.
See Goldman at Fig. 1.
t l
Tr. 480-481 (Goldman).
Dr. Goldman's computations indicate that the radon exhalation rate may vary by as much as a factor of two depending on which diffusion coefficient is used.12 I-22.
The third significant factor in radon exhalation is the depth of the tailings pile.
Goldman at pp. 11-12; Miller at pp.
28-30; Tr. 31, 54-55 (Pohl).
As shown in Fig. 3 of Dr.
Goldman's testimony, the radon release rate is strongly dependent on the depth of the pile; Dr. Pohl testified that the radon mean-free-path through tailings is approximately 1.5 meters, so that if the pile is deeper than six meters there is essentially " perfect protection" against radon emanations from layers below 6m.
Tr. 53-54 (Pohl).13 From a pile 8 meters deep, only 3.7% of the radon generated would be released to the atmosphere.
Tr. 34 (Pohl).
Increasing the pile depth from 3 reters to 12 meters reduces the radon emanations from 200 to 130 Ci/ year per AFR. Tr. 61 (Pohl).
I-23.
It is uncontested that the effective depth of existing active piles is between 12 and 13 m. and could be reasonably expected to go as high as 15 m.
Miller at p. 18; Goldman at p.
12 Figure 3 of Dr. Goldman's testimony shows that, for a 10 l
m.
deep pile and ore grade of 0.07%, use of the measured diffusion coefficient would give a radon release rate of 100 Ci/ year per AFR; use of the theoretical diffusion coefficients j
would give, respectively, 165 and 200 Ci/ year per AFR.
13 A 6 m.
pile would emit anywhere between 165 and 320 Ci/ year per AFR of Rn-222 depending on the diffusion coefficient one assumes.
See Goldman at Fig. 3. l l
l
12; Tr. 31 (Pohl).
The radon release rate for the median of those depths (12.5 m) would be 75-80 Ci/ year per AFR if the most realistic, measured diffusion coefficient is used.
Goldman at p.
12 and Fig. 3.
These values are in line with those testified to by witness Magno in Perkins (110 Ci/ year per AFR) and ratified at the hearing by Mr. Miller. Tr. 212
( Miller ) ; Duke Power Company (Perkins Nuclear Station, Units 1, 2, and 3), LBP-78-25, 8 NRC 87,93 (1978).
E.
Survivability of Uncovered Tailing Piles.
I-24.
Even assuming the stabilizing cover of mill tailings erodes completely at some point in the indefinite future, the tailings piles will retain sufficient integrity so that the radon emissions associated with the erosion and spreading of a pile are not significant.
I-25.
Both Dr. Goldman and Mr. Miller testified that tailings piles, even without stabilizing cover, are likely to remain in place without substantial erosion for long periods of time.
The proposed Criteria would require tailings piles to be shaped with slopes no steeper than Sh (horizontal) to lv (vertical),
and preferably 10h to lv, which is more than sufficient to ensure that the piles will not spread out or slump from their own weight.
Criterion 4; Goldman at p.
14; Miller at p.
- 12. = _,
i
]
l I-26.
Dr. Goldman testified at length about the survival for thousands of years of earth structures (" mounds") built by Pre-Columbian Indians in North America.
Goldman at pp. 15-17.
Several thousand of these mounds remain, largely in the eastern part of the United States, with the oldest dating back about 3,000 years.
Goldman at p.
15; Tr. 446, 482 (Goldman).
These mounds, which were apparently used as burial grounds or for ceremonial purposes, must be regarded as unstabilized piles analogous to mill tailings piles because no particular atten-tion was given by their builders to protect them against erosion; for instance, no rock cover was placed on tcp of the structures.
Tr. 445, 469, 484 (Goldman).14 I-27.
These mounds have survived natural forces for many centuries without substantial erosion.
Goldman at p.
15; Tr.
450-51 (Goldman).
While it is unknown what fraction of the mounds built several thousand years ago has survived to the present time, the large number of mounds still in existence, and the physical condition of those that remain,15 strongly 14 The slopes of many mounds are relatively flat, a practice intended to facilitate transport of materials to the top and, as noted above, one that protects the structure against erosion.
Tr. 445 (Goldman).
15 Some mounds were constructed in the shape of animals (birds, deer, bears).
If there had been a substantial amount of erosion, the shapes of the effigies, including such details as horns, ears and toes, would no longer be visible.
In fact, such details are still visible from aerial inspection, indicating that erosion has not been significant.
Tr. 482-483 (Goldman).
indicate that most mounds have retained their stability over extensive periods of time without specifically being designed to withstand the long term effect of environmental forces.
Tr.
482-483 (Goldman).
I-28.
The climatic conditions in the regions of the United States where most of the mounds are found are significantly wetter and less windy than in the areas in the West where the mill tailings will be located.
Goldman at p. 16.16 On the other hand, the mounds have been subjected to erosive forces of rainfall and flooding to a greater extent than mill tailings
,could be.
Id.
Therefore, while the mounds experience is not directly applicable to mill tailings, it provides a good indication that unstabilized piles are likely to retain their integrity for long periods of time and will erode at a suffi-ciently slow rate to permit corrective action to be taken.
Goldman at pp. 16-17.
i I-29.
Evidence of the erosior mad migration that has taken place on existing uncovered aings piles over the last twenty years and the radon emissions resulting from such migration confirms the slow erosion indication provided by the mounds.
Goldman at pp. 17-20.
Dr. Goldman analyzed survey reports of radioactive contamination in the vicinity of 13 inactive mill 16 The mounds may also have benefited from the presence of vegetative cover, which is unlikely to be available to the same extent in the more arid areas in which the tallings will be located.
Tr. 251 (Miller). m
sites in western United States and computed the Ra-226 disper-sed at various distances from the tailings piles.
He cal-culated that a total of 56.1 Ci of Ra-226 had been dispersed from the piles, or 0.55% of the total pile inventory of about 10,140 Ci.
The dispersed 56.1 Ci of Ra-226 were calculated to release 743 Ci Rn-222 per year, which would be about 1.9% of the radon released by the piles themselves.
Goldman at pp.
18-19 and Table 1.
The mean dispersion period for the 13 facilities was calculated as 15.3 years, giving a mean disper-sion rate per year of 0.036%.
Assuming the piles dispersed at 17 this uniform rate complete dispersal would occur in about 2700 years.
Goldman at p.
20.
After the first 200 years of dispersal, the total radon emissions from all existing uns-tabili ed tailings piles would have increased only by 25%, at an annual. ate of increase of 750 Ci/ year.
Goldman at pp.
19-20; Tr. 455-58 (Goldman).
Such a modest rate of increase should provide sufficient time for taking remedial action to correct the effects of erosion and tails migration.
Goldman at 20.18 p.
17 Dr. Goldman testified that the erosion rate of mill tailings piles is likely to decrease with time since the morc readily eroded material (finer particles, stopper slopes) is removed first.
Goldman at p. 20.
18 Dr. Pohl would assume that future generations would take no remedial action to restore tailinga piles to a stabilized condition.
Pohl at pp.
2-3.
His reason, however, was that future generations will not have the economic means required for surveillance and maintenance of the piles.
Id.
Dr. Pohl offered no basis for this speculation.
I-30.
There was testimony by Dr. Pohl that a number of existing tailings sites have been categorized as having "high priority" for remedial action and that there are 22 additional
" inactive uranium processing sites where mill tailings need remedial action."
Pohl at p. 4.
However, none of the sites was used in connection with the production of uranium for the commercial fuel cycle, and none of them was licensed by the NRC or subjected to any of the current mill tailings disposal regulatory requirements.
Tr. 503-505 (Goldman).
Moreover, the processes utilized at those sites and the nature of the resulting waste piles are completely unlike those resulting from milling of uranium ores to produce reactor fuel, Tr.
509-510 (Goldman).
These examples are thus of no relevance to the present proceeding.
I-31.
Mr. Miller testified that none of the Staff estimates of radon releases af ter reclamation considered the possibility of complete dispersal of mill tailings.
Tr. 280 (Miller).
He explained that he did not consider such a " worst case" scenario because the regulatory system of tailings licensing and the management programs developed for mill licensing provide enough conservatism to account for a reasonable range of conditions.
He therefore did not believe it was appropriate to go beyond the Perkins testimony, i.e. to assume complete uncovering of the tailings piles leading to average releases of 110 Ci/ year per AFR.
Tr. 293-294 (Miller-).19 I-32.
Dr. Pohl would postular s the complete dispersal of the mill tailings piles into a uniform, very thin layer above ground, leading to radon releases in the order of about 1000 O
Ci/ year per AFR.
Tr. 57-58 (Pohl).
He expressed no basis for predicting that such a dispersal would take place; in fact, he stated that he had not studied the question of the eventual dispocition of mill tailings piles, but only sought to analyze a " worst case" situation regardless of its likelihood.
Tr.
36-37 (Pohl).
I-33.
On the other hand, Dr. Goldman testified that it was quite unlikely that a mill tailings pile would experience complete dispersal and noted that, if it did, the tailings materials would either be carried by surface waters towards major water bodies and deposited on the bottom of the oceans or would remain on the land and be eventually covered or deposited upon by other soil materials.
Therefore, even completely 19 The Staff's radon release estimates in Forkins incorporated an additional measure of conservatism in that they were " inflated" by a factor of 10, from 1 to 10 Ci/ year per AFR, in the case of stabilized tailings.
This extra conservatism was intended to account for the uncertainty about survival of the stabilizing cover over very long periods of time.
Tr. 210-213, 294 (Miller).
20 There appears to be no dispute that the radon releases for a " worst case" situation of perfect dispersal of a mill tailings pile would be about 1000 C1/ year per AFR. Pohl at p.
2; Tr. 497 (Goldman).
dispersed callings would not continue to emit radon to the atmosphere for the full lifetime of the radon progenitors.
Tr.
502-503 (Goldman).21 It appears, therefore, that the " worst case" assumption of complete dispersal of a mill tailings pile followed by uninterrupted maximum release of radon for thou -
sands of years lacks any factual basis or other support.
Such an assumption is therefore unnecessary and unwarranted.
I-34.
Two more radon release mechanisms associated with milling of uranium merit brief mention.
One is the dispersal of tailings dust containing radium-226 which takes place during milling operation.
Mr. Miller testified that about.056% by volume or mass of the tailings generated would be lost by dust migration during the period of mill operation and subsequent drying out of tailings.
Tr. 301, 436 (Miller).
The upper limit of radon releases produced by this mechanism, assuming (contrary to existing regulations) no control of dusting during operation and no cleanup and decontamination of the site at the end of mill operations, would be about 1.4 Ci/ year per AFR.
f 21 Mr. Miller testified that radium-226 dispersed from tailings dust has an " environmental half-life" of 50 years, i.e.,
within that period of time half of the radium dispersed on the surface of the ground will become chemically bound with the soil and leach into it so that a shielding effect takes place which inhibits the escape of radon to the atmosphere.
Miller at p.
25; Tr. 299-300, 322-325 (Miller).
The environmental half-life of radium could in fact be shorter than 50 years (Tr. 260-261, 330-332, 342-344 (Miller)), but assuming a fifty year half-life, all the contamination by dis-persal of tailings dust containing radium would be eliminated in less than 500 years.
Miller at p.
- 25.,-
This release rate falls within the 1-10 Ci range testified to by Mr. Magno in Perkins and therefore need not be considered as an additional source term.
Miller at pp. 25-26.
The worst case releases from dusting would be about 1.3% of the radon released during the period of mill operation and drying-out from an uncovered pile.
Tr. 436-437 (Miller).
I-35.
The other potential release mechanisms would be those associated with local phenomena such as failure of mill tailings impoundments, or the intrusion of individuals into mill tailing piles and the removal of tailings to be used as building materials.
Pohl at pp. 4-5.
Such occurrences, however, are at most isolated, localized events that can not be fairly identified with industry-wide radon releases.
In addition, they are expected to be quite improbable in view of the new licensing requirements imposed by the Staff.22 I-36.
In summary, mill tailings piles constitute a potential source of radon releases over long periods of time.23
- However, 22 The dam that failed at the Church Rock mill in Gallup, N.M.,
was licensed and built before the new NRC regulatory requirements went into effect.
Tr. 253-260 (Miller).
The intrusion into tailings piles in search for construction materials has apparently stopped and should not resume in the future, given the access control measures that will be implemented at the sites, the Federal or State ownership of the sites, and the posting of signs warning of the danger in disturbing the piles. Tr. 174-75 (Miller); Tr. 467-468 (Goldman).
23 There was testimony regarding the " toxicity index" of mill tailings, which was characterized as the same as of 1,000 (continued next page) _.
the record indicates that adequate measures are being taken and will continue to be taken by the Staf f and the mill operators to provide disposal methods providing assurance of tailings isolation over many thousands of years.
Under stabilized conditions, the radon releases estimated in Perkins (1-10 Ci/ year per AFR En-222) appear to be conservatively high.
Assuming complete erosion of the stabilizing cover, the typical mill tailings pile is expected to release at most 75-80 Ci/ year per AFR Rn-222, an even less significant estimate than the 110 Ci/ year per AFR estimated in Perkins.
Assuming the complete failure of the stabilizing cover, tailings piles could be expected to disperse slowly; annual radon releases from an unstabilized pile will not have increased by more than 25% two hundred years after the pile becomes uncovered, therefore allowing sufficient time for taking remedial action to restore stabilization.
There is no basis in the record to find that any necessary remedial action will be unavailable during a two-hundred year period; even if complete dispersal should nonetheless occur, the dispersed tailings could be covered on (continued) year-old spent nuclear fuel.
Pohl at pp. 5-7.
The toxicity index of a substance is a measure of the quantity of water required to dilute the toxic constituents of the substance to their maximum permissible concentrations in water under drinking water standards (Tr. 88-89 (Pohl)).
The toxicity index may be a useful concept in some applications, but it appears to be irrelevant to the determination of the radon source term.
Tr. 472-474 (Goldman).
For instance, uranium ore in the ground has the same " toxicity index" as mill tailings.
Tr. 109-110 (Pohl).
o land or submerged under water in a relatively short period of time (compared to the thorium-230 half-life).
Therefore, a scenario in which the tailings piles become completely disper-sed and emit maximum amounts of radon into the environment for thousands of years is unrealistic.
II.
ABANDONED UNDERGROUND MINES II-1.
ALAB-562 asked for further testimony on emissions from abandoned underground mines because the record did not indicate "the extent to which abandoned underground mines both can and will actually be ' sealed'...[nor] the extent to which an unsealed mine could continue to emit radon through, for example, natural convection." ALAB-562, supra, 10 NRC at 442, footnotes omitted.
A.
Releases from Sealed Underground Mines.
II-2.
There was unchallenged testimony that abandoned under-ground mines can be sealed in ways which are simple and effective in minimizing radon releases.
The hoisting and ventilation shaf ts of the mines can be sealed by filling them with overburden, waste rock or soil; additional sealing may be provided by placing a concrete plug in the collar of the.__ -
)
i shafts.24 NRC Staff Testimony of Ralph M. Wilde, foll. Tr. 355
("Wilde") at pp. 5-6; Goldman at p.
24; Tr. 415-417, 428 (Wilde).
Assuming proper sealing,25 the radon emission rates from the mine shaf ts will be negligible, and the only measura-ble radon releases associated with sealed underground mines will come from waste rock remaining on the surface af ter the mine is abandoned.
The waste rock pile is estimated to release approximately 10 Ci/ year per AFR Rn-222.
Wilde at pp.
8-9, 15.
B.
Releases From Unsealed Underground Mines.
II-3.
The principal mechanism for the discharge of radon to the atmosphere from an abandoned, unsealed underground mine is natural circulation air flow.
Wilde at p. 11; Goldman at p.
25.
The driving forces for this flow are the temperature difference between the air inside and outside the mine and the difference in elevation between the openings of the mine.
Id.
Natural circulation air flow is quite variable in magnitude and direction, and may reverse direction as frequently as twice a 24 Mr. Wilde testified that all that is required to seal an abandoned mine effectively against radon releases is to intercept the gross air flow through the mine shafts.
This can be done simply by dropping a sufficient amount of rock and dirt down the vent holes.
Tr. 416, 428 (Wilde).
25 The responsibility for the promulgation and enforcement of recla.aation regulations for uranium mines rests primarily with the State in which the mines are located, and the regulations and enforcement thereof vary considerably from State to State.
Wilde at p.
6.
Some mine operators have committed to Pheir State agencies to seal underground mine shafts, or plan to do so in the future.
Goldman at p. 24; Tr. 428 (Wilde)..
day in a mine having several openings.
Wilde at p.
11; Tr.
361-362 (Wilde).
II-4.
Because of the fluctuations in air flow volume and direction and the physical dif ferences among mines in terms of 26 size, interconnections, and obstacles to flow it is not possible to model a " typical" unsealed underground mine to obtain a representative prediction of the radon releases from such mines.
Wilde at p.
11.
II-5.
In the absence of a model, witnesses Goldman and Wilde suggested that a conservatively high upper limit to the radon releases associated with abandoned unsealed underground mines could be calculated by assuming that the radon emitted by an abandoned mine equals that released by an active mine under conditions of forced ventilation, i.e. with the ventilation fans in operation.
Wilde at p.
12; Goldman at pp. 25-26.
II-6.
Mr. Wilde computed the long term radon releases for this upper limit condition based on radon emissions measured by 26 A number of factors may contribute to minimize the flow of air out of abandoned underground mines.
Most of those mines are located below the water table, so that when the mine is abandoned and pumping stops the mine floods and radon is unable to escape.
Tr. 357-358 (Wilde); Wilde at p.
14; Goldman at pp.
25-26.
Also, bulk-heading and sandfilling of worked-out areas to reduce worker exposure to radon daughters are common practices which also reduce radon flow.
Tr. 426-427 (Wilde).
Caving and collapse of workings and shafts in abandoned mines may also restrict or preclude air flow through the mine.
Wilde at p. 14; Goldman at p.
- 25.
Battelle Pacific Northwest Laboratory ("PNL") at 27 active mines accounting for over 63% of the total U.S.
uranium production from underground mines.27 PNL reported total radon releases of 150,000 Ci/ year and a combined annual production of 5760 short tons U 0 At 271 metric tons per AFR, this 38 emission rate results in approximately 7970 Ci per AFR; with an effective mine life of 30 years, the radon emission rate would be roughly 260 Ci/ year per AFR.
Tr. 394 (Wilde).
An addi-tional 10 Ci/ year per AFR would be added, as in the case of sealed mines, to account for emanations from waste rock remaining on the surface when the mine was abandoned.
Wilde at pp. 12, 16.
The upper limit radon release from unsealed underground mines would therefore be approximately 270 Ci/ year per AFR.
Wilde at pp. 14-15.
II-7.
Mr. Wilde testified that this upper limit estimate of 270 Ci/ year per AFR was reliable and conservatively high and that actual radon releases from abandoned mines would be considerably lower.
Wilde at pp. 14, 16; Tr. 395-396, 429 (Wilde).
His opinion is consistent with measured releases at abandoned underground mines; he testified that measurements taken at a " worst case" abandoned mine in McKinley County, New Mexico, showed radon emissions in the order of 70-80 Ci/ year 27 "An investigation of Radon-222 Emissions from Underground Uranium Mines", Pacific Northwest Laboratory, NUREG/CR-1273, PNL-3262 (Progress Report 2), February 1980.
per AFR.
Tr. 361 (Wilde).28 Another, more typical abandoned mine in the same area released radon at a rate of 1,2 Ci/ year per AFR.
While these measurements point to a wide range of radon releases from abandoned underground mines, the 270 Ci/ year per AFR upper bound given by Mr. Wilde appears to be well above the anticipated releases of even the " worst case" abandoned mines and therefore constitutes an appropriate radon source term for this activity.
28 The " worst case" mine in question, the " Mesa Top" mine, is a vertical shaft mine dug on the surface of a mesa and interconnected underground with several other mines, some of which are still active.
The entries for the other mines are horizontal tunnels driven into the side of the mesa
(" adits").
These adits are at elevations of 150 feet or more below the entry for the Mesa Top shaft, providing a large " head" for air flow.
All the air ways are open, and the ventilation fans are kept running during the week since some of the other mires are in operation.
Tr. 359-362 (Wilde).
Under those circumstances, the Mesa Top shaft operates as an intake or exhaust air conduit, resulting in appreciable air circulation between the Mesa Top shaf t and the mine adits Tr. 360 (Wilde).
The direction and magnitude of air flow at any given time depend on the temperature difference between the two levels, and on whether the ventilation fans are in operation.
Tr. 361-362, 401-403 (Wilde).
In Mr. Wilde's opinion, the 70-80 Ci/ year per AFR Rn-222 measured at Mesa Top is representative of " worst case" emissions from abandoned underground mines.
Tr. 363 (Wilde).
29 This other mine, known as the " Barbara J" mine, is a vertical shaft mine, without underground interconnections that would provide a flow path for air and radon to escape.
The mine is flooded, and the elevation differences between the various mine opening are small.
The low air flow rates and the radon release in the order of 1.2 Ci/ year per AFR measured at the Barbara J mine are, in Mr. Wilde's opinion, "in the right order of magnitude" for a typical vertical shaft underground m ine.
Tr. 362-363 (Wilde).
III.
OPEN PIT MINES III-1.
Although the Perkins record (See LBP-78-25, supra, 8 NRC at 90-91) contains estimates of the radon releases associated with abandoned open-pit mines, ALAB-562 noted that some degree of uncertainty remained regarding radon emissions from both reclaimed and unreclaimed open-pit mines.
"In particular, releases from reclaimed mines may be higher than expected, due to the physical rearrangement of the overburden as it is replaced in the pit."
ALAB-562, supra, 10 NRC at 442, 443, footnote omitted.
III-2.
Staff witness Wilde testified that the data base for radon releases from reclaimed open-pit mines had become "much improved" since the Perkins proceeding, and was now adequate "to predict the long term radon release during the post-mining period of reclaimed open pit and underground mines."30 Wilde at pp.
8, 9.
He assumed a model open-pit mine which, at the end of its active mining period, is a compromise between complete reclamation (anticipated for present and future mining 30 In particular, Mr. Wilde referred to another in te r im report published by Battelle Pacific Northwest Laboratory entitled " Prediction of Net Radon Emission From a Model Open Pit Mine", NUREG/CR-0628 (PNL-2889 REV), September 1979.
This report " provide [s] recent information on radon exhalation rates and also analyses of current and projected mining methods and practices which were used to develop mine models and radon releases both for th'e period of active mining and for the period after the mine are shutdown."
Wilde at pp.
7-8.
operations) and no reclamation (as was the case in the past in many mining operations).
For such a mine, 85% of the mine volume would be refilled with overburden containing 20 ppm U0 The balance of the overburden, approximately 15%, would 38 remain as a pile on the surface.
Another surface pile con-taining 150 ppm U 0 w uld remain as a as a sub-ore pile 38 awaiting possible commercial use in the future. Wilde at p.
8.
III-3.
For this partially-reclaimed model open-pit mine, radon emanations would result from overburden fill in six pits, sub-ore and overburden exposed in the last unfilled pit, and sub-ore and overburden dump piles.
The combined long-term radon releases from these sources were computed at about 40 Ci/ year per AFR.
Wilde at p. 8; Goldman at p.
28.
III-4.
Mr. Wilde also prepared an estimate of long-term radon releases from the same model open-pit mine, now assuming no reclamation whatsoever (i.e.,
no refilling of the worked-out mine pits).
This model of an unreclaimed open-pit mine would release radon from the overburden and sub-ore exposed in seven unfilled pits, seven overburden piles, and a sub-ore pile.
Mr.
Wilde calculated that such an unreclaimed open-pit mine would release approximately 80 Ci/ year per AFR Rn-222.
Wilde at pp.
9-11, 15.
III-5.
Dr. Gcidman also made a calculation of the radon releases from unreclaimed open-pit mines.
His estimate was based on a model mine established by EPA as an average of more than 900 abandoned open-pit mines.
For the EPA model mine, the 0
total waste and ore removed from the pit would be 1.18 x 10 MT 5
and 4.75 x 10 MT, respectively.
The sub-ore was assumed to be placed in a uniform layer on top of the overburden pile, thus maximizing radon emissions.
The pit and waste pile were calculated to emit about 54 Ci/yr.
Assuming an average ore grade of 0.29% and 95% recovery rate, the long-term Rn-222 emissions for that model unreclaimed mine would equal 100 Ci/ year per AFR.
Goldman at pp. 20-29.
III-6.
The radon release estimates provided by witnesses Goldman and Wilde for reclaimed and unreclaimed open-pit mines approximated each other and the values testified to in Perkins.31 No evidence was offered at the hearing to contro-vert these estimates and they appear reasonable.
Therefore, appropriate upper bounds for open -it mine radon releases are 40 Ci/ year per AFR from reclaimed open-pit mines and 100 Ci/ year per AFR from abandoned, unreclaimed open-pit mines.
Wilde at p.
15; Goldman at p.
29.
31 Mr. Wilde had given in Perkins an estimated release of 100 Ci/ year per AFR Rn-222 for abandoned unreclaimed open-pit mines.
Perkins Tr. 2609-2613 (Wilde); Dr. Goldman independently arrived at the same estimate, which he expressed in the form of a 100-200 Ci/ year per AFR range.
Perkins Tr. 2639-2640 (Gold-man).
There was, however, no estimate in Perkins of the releases from reclaimed open-pit mines.
IV.
WATER PATHWAYS IV-1.
ALAB-562 noted that there appeared to be no complete assessment of potential exposure to radon reaching humans through water pathways.
In particular, the possibility was raised that groundwater ma.y " enter abandoned mines or mill tailings piles, absorb radon or its progenitors and then transport them to points which could ultimately lead to their inhalation or ingestion by humans."
ALAB-562, supra, 10 NRC at 443, footnote omitted.
A.
Groundwater contamination from abandoned mines or mill tailings piles.
IV-2.
Most of the testimony at the hearing in the area of groundwater transport of radon or its progenitors addressed the possibility that mill tailings buried below grade may acci-dentally come in contact with groundwater.
Dr. Pohl identified two circumstances under which this phenomenon could occur:
(1)
A rise (over geologic periods of time) of the 32 The technical criteria proposed by the Staff for disposing of mill tailings would consider permitting deliberate (as opposed to accidental) tailings disposal into the groundwater "provided supporting tests and analysis are presented demonstrating that the proposed disposal and treatment methods will preserve quality of groundwater." Proposed Appendix A to 10 CFR Part 40, Criterion 5, 44 Fed. Reg. 50012, 50021 (August 24, 1979).
At the hearing, Mr. Miller explained that a heavy burden of proof on the safety of such a disposal method would be placed on any party proposing it.
Tr. 235 (Miller). _.
groundwater table bringing it to the level where mill tailings are buried.
Pohl at 5-6.
This scenario assumes failure of the liner used for isolating the tailings from the surrounding soil.33 Tr. 99 (Pohl).
(2)
A change in weather in the semi-arid areas where the tailings will be buried, so that precipitation greatly exceeds evaporation (Tr. 74, 103-104 (Pohl)), followed by overflow of the " catch basin" formed by the liner and the buried tailings or percolation of precipita-tion and tailings into the groundwater through a failed liner.
Tr. 74,99-104 (Pohl).34 33 Clay or synthetic impermeable liners are to be implaced on the bottom and sidewalls of tailings impoundments as a measure of protection against seepage of tailings into the groundwater.
Tr. 302 (Miller).
Liners are relied upon only to hold the mill tailings slurry during the active milling period and until the solutions evaporate.
Tr. 248-249, 302-303 (Miller).
After the tailings dry out, there is no additional significant source of water infiltration besides precipitation; in the area where tailings are found, evaporation rates far exceed precipitation rates.
Tr. 249, 303, 325 (Miller).
34 Dr. Pohl postulated a third scenario in which groundwater '
carrying radionuclides rises by capillary action through the soil, across a unstabilized tailings pile lying above ground, and to the atmosphere from the tailings surface.
Tr. 44-46, 91-99 (Pohl). There is not need to dwell on this scenario, because it would operate only if the tailings pile were uncovered, Tr. 95 (Pohl) and is therefore undistinguishable from the tailings cover erosion scenario discussed above.
Moreover, the unpublished study in which this process is described only reports the upwards migration of non-radioactive substances such as mineral sulphates, and offers no indication of the rate (if any) of migration of radioactive salts through the soil and across the tailings pile.
Tr. 97-98 (Pohl).
- And, in any event, the mean-free-path of any radon generated by the radium will be considerably reduced as it moves in the ground-water, diminishing the radon releases to the atmosphere that would be associated with the phenomenon.
Tr. 98-99 (Pohl).
l 1 I l
1
IV-3.
Both scenarios described by Dr. Pohl are improbable.
While it is possible that the water table will rise (over geologic periods of time) to the tailings level, the reasonable likelihood that this may happen at a given location is a factor taken into consideration by the Staff in licensing a site and selecting a mill tailings disposal method.
Tr. 325-327 (Miller).
Also, there would have to be a significant excess of precipitation over evaporation before the " catch basin" effect would operate.
Tr. 101-104 (Pohl).
Not only would this require a dramatic change in weather conditions in the areas considered for tailings disposal, but the presence of moisture in the buried tailings would reduce the mean free path of any radon that is generated in the process.
Tr. 98-99 (Pohl).
IV-4.
Assuming, nevertheless, that buried tailings do come into contact with the groundwater, any increase in the concen-tration of the radium naturally present in groundwater would be a local effect confined to a relatively short distance from the tailings area.
Tr. 513-514 (Goldman).
The reasons for this 35 36 are the low solubility and low mobility of dissolved radium 35 Data from radium concentration in mine drainage water from underground mines in Wyoming, Utah, Colorado and New Mexico indicate that radium is present in concentrations of less than 0.4% of those which would be in equilibrium with the measured concentration of uranium in the same samples.
Goldman at p.
31.
36 While dissolved uranium moves with the velocity of the groundwater until it precipitates, radium moves at 1/215 of the speed of the seepage water, and thorium essentially becomes
" fixed" on soil particles and does not move.
Tr. 250 (Miller).
and thorium, and the fact that radium tends to coprecipitate or ion-exchange with other salts and is readily sorbed onto soil materials such as clay.37 Tr. 516 (Goldman); Tr. 70-71 (Pohl);
Miller at pp. 18, 40.
IV-5.
Dr. Pohl cited the reported rate of movement of thorium and radium in the groundwater at West Chicago, Illinois of "less than 2 m. per year" as reported in NUREG-0511 at p.
E-21.38 Based on that statement, Dr. Pohl hypothesized that, over a period of ten thousand years, the dissolved radium and thorium from the buried mill tailings "could travel a distance of the order of 10 km."
Pohl at p.
6.
Dr. Pohl did not offer any scientific basis for extrapolating the rate of movement for radium and thorium experienced at West Chicago over thousands of years; in fact, Dr. Pohl explained at the hearing that he was not attempting to predict migration rates for thorium and 37 Dr. Pohl agreed that radionuclides, such as radium, dissolved in the groundwater would move at lesser speed in clay as opposed to substances such as sand, and that the rate of motion of radionuclides through clay soils is not likely to change over time.
Tr. 83-87 (Pohl).
At West Chicago, Ill.,
radionuclides from a waste thorium pile were transported by the groundwater, over a fifty year period, through sandy soil over a distance of less than 100 m. and then " held up at the top of a clayey unit."
Tr. 69 (Pohl).
38 It should be noted that the West Chicago facility on which the measurements reported in NUREG-0511 were taken was used for thorium and rare earth processing and manufacturing.
The wastes and disposal methods at West Chicago were entirely different from those contemplated for uranium mill tailings.
Tr. 507 (Goldman). -
o 39 radium but merely to demonstrate the appropriateness of considering groundwater contamination problems over geologic periods of time.
Tr.
67-70 (Pohl).
IV-6.
There is no evidence on the record (other than Dr.
Pohl's admittedly unfounded extrapolation) for expecting that there will be significant movement of radon precursors in the groundwater; in fact, the very reference from which Dr. Pohl drew his extrapolation concludes that, based on the experience at West Chicago and elsewhere, " thorium and radium concen-trations typically drop off to background within a meter below the tailings piles."
NUREG-0511 at pp. E-20, E-21.
Nor did Dr. Pohl contradict the testimony of Mr. Miller and Dr. Goldman that the low mobility and sorbtion tendencies of dissolved radium and thorium would inhibit greatly their movement in groundwater.
IV-7.
Since increased concentrations of thorium and radium appear to be highly localized phenomena, and therefore have at most only local effects,40 the migration of dissolved thorium 39 Since the half life of Ra-226 is 1600 years, the only radionuclide whose migration over a 10,000 year period might be of interest is thorium-230.
Thorium, however, is the least mobile of the radionuclides.
Goldman at p.
31.
40 Dr. Pohl posed as a " worst case" threat of exposure to the public the possibility that people may drill water wells into groundwater highly contaminated with radionuclides.
Pohl at p.
6; Tr. 117 (Pohl).
Given the low mobility of radium and thorium, the persons diggi i such wells would have to be directly above the buried.ailings, a very unlikely (continued next page) _
O I
and radium from mill tailings is analogous to the naturally occurring transport of those substances by the groundwater.41 This natural migration occurs because the ores from which mill tailings result are normally found below the groundwater table.
Tr. 358 (Wilde); Tr. 505-507 (Goldman); Miller at p. 41.
Therefore, the concentration of radium and thorium from mill tailings in the groundwater should not be measurably greater than what would occur in the absence of uranium mining and milling and, owing to mill licensing requirements to isolate tailings, may be even less.
Tr. 505-506 (Goldman); Miller at 41.42 p.
IV-8.
To summarize, the distance that thorium and radium from mill tailings would travel in the groundwater af ter dissolving is a highly complex and site-specific question, which depends among other things on the characteristics of the aquifer, the composition of the soil, and the nature of the milling process (continued) circumstance in view of the remoteness of the tailings burial sites and the access limitations that will be maintained as long as institutional controls exist.
41 The surface area of the uranium ores is substantially increased by the milling process, which tends to facilitate somewhat the transport of radium from the mill tailings by the groundwater.
Tr. 511, 518 (Goldman).
However, this effect is of little significance since it is confined to a distance in the order of feet from the tailings area.
Tr. 513-514 (Goldman).
42 In fact, far greater concentrations of radionuclides than those produced by mill tailings exist nahurally in groundwater without significant contamination ef fects.
Tr. 114 (Pohl); Tr.
506-507 (Goldman).._-
used.
However, that distance appears to be short in any case, the speed of migration of dit ;olved radium and thorium very low, and the radon emissions ultimately released by those substances insignificant.
Tr. 516-519 (Goldman); Miller at p.
41.
IV-9.
The solubility and transport of radium and thorium from abandoned mines would not be significantly different than those for mill tailings.
Goldman at p. 33.
Measured concentrations of naturally-occurring radon-222 in the groundwater are much higher than the expected equilibrium concentrations between radon-222 and radium-226, leading to the conclusion that a main source of radon-222 in groundwater is radioactive decay of radium fixed in the rock materials through which the groundwater flows.
Goldman at p.
31.
Based on measured concentrations of Rn-222 and Ra-226 in public groundwater supplies and assuming a maximum concentration ratio between these substances, Dr. Goldman computed an upper bound radon source term of 3.45 Ci/yr for all the dissolved radium produced by mining activities.
This quantity is insignificant compared to the uranium mining source term.
Go;dman at pp 31-31.
B.
Surface Water Transport IV-10.
Surface water transport of radium or thorium from mine wastes or mill tailings should, in general, not contribute to the source terms for radon.
In uranium mining and milling areas, evaporation exceeds precipitation and most surface streams are dry except for periods during and af ter precipita-tion. Goldman at p.33.
IV-11.
Short period phenomena, such as high intensity rainfall, local floods, or dam failures can increase the transport of radionuclides by surface water in a very localized and ephemeral manner.43 Dr. Goldman estimated the maximum radon releases associated with complete erosion through surface water action of a sub-ore pile for the EPA model inactive mine, and obtained an increase in radon releases from 100 to 113 C1/ year per AFR Rn-222.
A similar computation for the large mine PNL model yielded an increase in the emission per AFR-year from 39 to 169 Ci Rn-222.
Goldman at pp. 33-34.
These values are still within the range of 100-200 Ci/yr per AFR given in Perkins for abandoned open-pit mines.
Goldman at p.
35.
V.
EMISSIONS ASSOCIATED WITH THE RECOVERY OF URANIUM AS A BY-PRODUCT OF PHOSPHATE FERTILIZER PRODUCTION V-1.
ALAB-562 asked for quantification of those radon releases which could result from the processing of phosphate fertilizer 43 For instance, in July, 1979 an impoundment dam in a tailings pond broke at the Church Rock, New Mexico nill, spilling 1,100 tons of tailings solids and about 300 million tons of tailings solutions into the Puerco river; the solutions traveled about 10 or 15 miles downstream and then, through a process of evaporation and infiltration, vanished.
Very low levels of radionuclides (30 picacuries per gram of thorium and 10 picocuries per gram of radium) were measured in the affected area.
Tr. 254-256 (Miller).
residue de recover uranium; the relevant releases would be those "beyond those attendant upon the phosphate production itself." ALAB-562, supra, 10 NRC at 443. The amount of such releases (if any) should be "sufficiently quantified to ;11ow comparison with the amount of radon released from the direct mining and milling of an equivalent amount of uranium."
Id.
V-2.
Phosphate ores from which fertilizer is manufactured are extracted from the ground by mining, just like any other mineral ores.
Phosphate ores contain small amounts of uranium and radium.
About half of the uranium and radium content of phosphate ores remains in the mining waste piles; the other half goes with the mined ores through the fertilizer-making process.
Tr. 128, 137-38 (Lowenberg).
V-3.
The waste piles resulting from the mining of phosphate ores have uranium concentrations ten times lower than those in ores from which uranium is normally obtained.
Tr. 127,137 (Lowenberg).
These waste piles are not pulverized and remain to a large extent in the same physical form they were before mining.
Consequently, such piles emit less radon than uranium mill tailings piles.
Tr. 132-33 (Lowenberg).
V-4.
For economic reasons, it is very unlikely that attempts will be made in the foreseeable future to recover the low-grade uranium found in the phosphate mining waste piles.
Tr. 135-36 (Lowenberg).
Therefore, radon emissions from such piles (which...
in any event are negligible in magnitude) need not be consid-ered as significant sources of radon.44 V-5.
The mined phosphate ores are taken to beneficiary plants, where they are pulverized and dissolved in acid
(" phosphoric acid liquor") and subsequently processed to become fertilizer.
Tr.
127-29 (Lowenberg).
The phosphoric acid liquor contains largely all the uranium that came in with the phosphate ores, but less than one percent (1%) of the amount of radium-226 that was originally in equilibrium with its parent uranium.
The remainder of the radium is removed by precipitation during the production of the phosphoric acid liquor.
Goldman at p.
35.
V-6.
The ultimate wastes from fertilizer production are primarily gypsum, and contain very little uranium but contain most of the radon-generating radium which accompanied the phosphate ores and which was precipitated during the phosphoric acid liquor formation process.
Tr. 137 (Lowenberg).
V-7.
The bulk of the precipitated radium goes into the gypsum wastes, regardless of whether or not uranium is recovered from the phosphoric acid liquor, from which radium is therefore effectively absent.
NRC Staff Testimony of Homer Lowenberg, 44 If and when phosphate mining residues are processed for uranium extraction, the NRC (or the State, if an agreement State) will have jurisdiction over the process and will super-vise the disposal of any resulting tailings.
Tr. 304-305 (Miller). _.
foll. Tr. 126 ("Lowenberg") at p. 4; Tr. 134 (Lowenberg).
Thus, any radon released from those wastes is not attributable to the production of uranium.
V-8.
When uranium is recovered from phosphate ore processing, it is separated from the phosphoric acid liquor by an extrac-tion process.
Lowenberg at p. 4.
The uranium contained in the ore, if not recovered, ends up in the fertilizer produced at the end of the process.
Tr. 137 (Lowenberg).
V-9.
The effective absence of the Ra-226 parent of radon precludes formation of significant quantities of radon during extraction of uranium from the phosphoric acid liquor. Goldman at p. 35.
V-10.
The upper limit of the radon that would be teleased from the radium-226 left in the phosphoric acid liquor during the uranium extraction process is calculated to be.52 Ci of Rn-222 per AFR of uranium produced.
Goldman at 36.
However, this radon would be produced whether or not uranium is recovered and is therefore attributable to the phosphate production process and not to the uranium recovery process.
Goldman at p.
36.
V-11.
The extraction of uranium as a byproduct of fertilizer production does not change the radon emission rate from fer-tilizer production.
Lowenberg at pp 3-4.
Therefore, no radon releases can be attributed to the recovery of byproduct uranium from phosphate cre mining and processing beyond those attendant l
~
e.,
upon the phosphate production itself.
Lowenberg at p.
4; Goldman at p.
35.
V-12.
Any amount of uranium recovered as a byproduct of fertilizer production will have practically no associated radon emissions and thus would result in a decrease of the potential radon effluents attributable to the uranium fuel cycle.
Lowenberg at pp.
4,5.
Since the radon release computations by the Staf f in Perkins assumed that all uranium for the nuclear fuel cycle comes from conventional uranium mining and milling activities, those computations are, if anything, conservatively high in not taking into consideration the production of uranium as a byproduct of fertilizer manufacture.
Lowenberg at pp.
2, 4-5.
Respectfully submitted, SHAW, PITTMAN, POTTS & TROWBRIDGE O
.r % {
(L0M fayJE. Gilberg" j
Matias F. Travieso-Diaz
/
V I
Counsel for Metropolitan Edison Company et al.
1800 M Street, N.
W.
Washington, D.
C.
20036 (202) 331-4100 _
_ _ =
i, eeo CONNER, MOORE & CORBER
/24>f Troy @.ner, Jr.
Robert M.
Rader Counsel for Philadelphia Electric Company et al.
and Public Service Electric and Gas Co.
L Suite 1050 1747 Pennsylvania Avenue, N.W.
Washington, D.
C.
20006 (202) 833-3500 Dated:
April 28, 1980.
e l
l l l s
y
._y-
-