NUREG/CR-4756, Responds to Re Low Level Radwaste Disposal Practices.Info Provided Includes Estimated Porosity of 26% Reported in Table 2.1 of NUREG/CR-4756,five Different Types of Cements & Waste Solidification Processes
| ML20148J761 | |
| Person / Time | |
|---|---|
| Issue date: | 03/11/1988 |
| From: | Greeves J NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Jeffrey Riley AFFILIATION NOT ASSIGNED |
| References | |
| REF-WM-88, RTR-NUREG-CR-4756 NUDOCS 8803300375 | |
| Download: ML20148J761 (15) | |
Text
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/
4 MAR 111988 Mr. Jesse L. Riley 854 Henley Place Charlotte, NC 28207
Dear Mr. Riley:
I recently received your letter of February 22, 1988, and I welcome the opportunity to respond to your questions regarding low-level radioactive waste disposal practices.
The estimated porosity of 26 percent reported on Table 2.1 of NUREG/CR-4756, that is also consonly identified as absorption, was established by drying the test specimen to a constant weight, immersing it in water until saturated and then treasuring the increase in weight as a percentage of the dry weight.
For nomal use of Portland cements in structural concrete, absorption is not typically used as a measure of the quality of the concrete because of the variations in the drying procedures that produce differing results.
In most good concretes that are produced in the construction industry, but not including cement solidification processes where resin beads and boric acid are contained, the concrete will have absorption levels well below 10 percent.
There are five different types of cements that are used in concrete mixes.
Each type has differences in chemical composition and in addition, admixtures such as pozzolans are commonly added to enhance the quality and durability of the concrete. Typically the selection of the type of cement and admixture is governed by specific project conditions and the desired results such as producing sulphate resistant concrete or rapid hardening concrete or a low-permeability concrete.
There are several waste solidification processes that use organic binders such as bituminous materials or monomer / polymeric substances, in these processes the resulting solidified mixture consists of finely dispersed waste particles surrounded by an inert binder that forms a continuous matrix. The NRC staff has reviewed two of thet,e processes and found the solidified products to have acceptable leach resistance characteristics. The results of the staff's technical evaluations on the AZTECH Process and the Waste Chem Process are available in public document rooms.
Plastics are being used in low-level waste disposal to produce polyethylene high integrity containers (HICs). An obvious advantage of the polyethylene HIC is its lower cost in comparison to other construction materials such as concrete or steel.
Polyethylene HICs demonstrate excellent corrosion-resistant characteristics when exposed to groundwater or adverse soil conditions. There are also disadvantages in using polyethylene f
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MAR 11568 Mr. Jesse L. Riley 2
L HICs that require limits to be placed on their use when the disadvantages could cause undesirable results. The disadvantages with polyethylene HICs include their tendency to creep under certain applied loading stresses that could also result in buckling failures or stress cracking and the sensitivity of the polyethylene containers to various organic materials that may be present in the low-level waste.
We are aware of the Westinghouse SUREPAK modules but have not been furnished information with regards to using plastic liners in conjunction with the reinforced concrete containers and grout filling procedures of the SUREPAK system. The staff has not been requested to review the design of the SUREPAK modules that may be requested by a vendor by submittal of a Topical Report to the NRC.
Because we have not evaluated the design and construction of the SUREPAK in detail, we do not wish to express an opinion on the perneability of this unit.
The NRC staff is aware of other vendor products consisting of engineered i
multi-barrier waste containers that are stated to be leak resistant.
Examples of these waste containers include Bechtel's SECURE System (prefabricated concrete canister), LN Technologies Corporation's composite HIC (stainless steel outer casing lined with molded polyethylene), the Nuclear Packaging Inc.
unit (NUPAC) (special stainless steel unit), and Chichibu Cement Company, Ltd.
steel fiber reinforced polymer impregnated concrete (SFPIC) containers. The NRC has reviewed and approved the Topical Reports for the NUPAC and Chichibu designs. A Topical Report has not been submitted for the SECURE syste.n but we have recently received a report for the LN Technologies composite HIC.
The NRC is currently reviewing Topical Report submittals on polyethylene HICs from Chem-Nuclear Services, Inc., Westinghouse-Hittman Huclear, Inc., and TFC Nuclear Associates, Inc.
I am hopeful the above responses to your questions provide you with the background information that you requested and assist you in your efforts on the Technical Committee of the Governors Waste Management Board.
I have also enclosed a May 1983 edition of the staff's Technical Position on Waste Form that is used by vendors and the staff in the review of Topical Reports.
Since issuance of the Technical Position in 1983, a considerable amount of new data and information on cement and bituminous waste solidification processes and on high integrity containers has become available. The new information and the
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MAR 111988 Mr. Jesse L. Riley 3
experiences that have been gained are prompting the NRC to work on the development of a new Regulatory Guide on this important subject. The guide will be made available to other governmental agencies and the public upon its completion.
Sincerely, C/161nr.1 Stows 2v John T. Greeves, Deputy Director Division of low-Level Waste Management and Decomissioning, HMSS
Enclosure:
Tech Position on Waste Form cc:
Dr. Linda Little DISTRIBUTION:
(LLWM88-37)
LLWM/5F NMSS r/f LLTB r/f JKane MTokar JJSurmeier Have discussed this with Steve Salomon end MRKnapp CCantor cardelia Maupin of SLITP on 3/11/88. (MT)
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- 03/7/88
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- 03/ // /88 OFFICIAL RECORD COPY
1 En closer e.,
i May 1983 Rev. O Technical Position on Waste Form A.' Introduction Waste," 10 CFR Part 61, establishes a waste classif on the radionuclide concentrations in the wastes.
Class B and C waste are required to be stabilized.
and may be segregated without stabilization. Class A waste have lower concentration wastes, however, require solidification or absorption liquid requirements.
waste does not degrade and promote slumping, collapse, or of the cap or cover over the disposal trench and thereby lead to water infiltration.
Stability is also a factor in itmiting exposure to an inadvertent intruder since it provides greater assurance that the waste form will be recognizable and nondispersable during its hazardeus lifetime.
Structural stability of a waste fom can be 'provided by the waste fom itself (as with large activated stainless steel components),
by processing the waste to a stable form (e.g., solidification), or by emplacing the waste in a container or structure that provides stability (e.g., high integrity container).
This technical position on waste fom has been developed to provide guidance to both fuel-cy* and non-fuel-cycle waste generators on waste
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fom test methods and resu... acceptable to the NRC staff for implementing the 10 CFR Part 61 waste form r.equirements.
as an acceptable approach for demonstrating compliance with the 10 CFRIt can Part 51 waste stability criterta.
This i
processing of wastes into an. acceptable, position includes guidance on the stable waste form, the design of acceptable hign integrity containers, the packaging of filter cartrid and minimizing the radiation effects on organic ion-exchange resins. ges, i
It is the intent of the NRC staff to add other guidance on waste fonn in i
additional technical positions as is necessary to address other pertinent waste fem issues.
I
2 B.
Backdround Historically, waste form and container properties were considered of secondary importance to good site selection; the combination of a properly operated site having good geologic and hydrologic characteristics were considered the only barriers necessary to isolate low-level radioactive wastes from the environment.
Experience in operating low-level waste disposal sites indicated that the waste form.
should play a major role in the overall plan for managing these wastes.
j The regulation for near-surface disposal of radioactive wastes, 10 CFR l
Part 61, includes requirements which must be met by a waste fem to be acceptable for near-surface disposal.
The regulation includes a waste classification system which divides waste into three general classes:
A, B, and C.
The classification system is based on the overall disposal hazards of the wastes. Certain miniinum requirements must be n,at by all wastes. These minimum requirements are presented in Section 61.56(a) and involve basic packaging critaria, prohibitions against the disposal of pyrophoric, explosive, toxic and infectious materials, and requirements to solidify or aosorb liquids.
In addition to the minimum requirements Class B and C wastes are required to have stability. As defined in Section 61.56(b) of the rule, stability requires tnat the waste fom maintain its structural integrity under the expected disposal conditions.
Structural stability is necessary to inhibit slumping, collapse, or other failure of the disposal trench resulting from degraded wastes which could lead to water infiltration, radionuclide migration, and costly remedial care programs.
Stability is also considered in the intruder pathways where it is assumed that after the active control period wastes are recognizable and, therefore, continued inadvertent intrusion is unlikely. To the extent practical Class 8 and C waste foms should maintain gross physical properties and identity over a 300 year period.
In order to ensure that Class B and C waste or its container will maintain its stability, the following conditions need to be met:
a.
The waste should be a solid fom or in a container or structure that provides stability after disposal.
2
, b.
The waste should not contain free standing and corrosive liquids. That is, the wastes should contain only trace amour.ts of drainable liquid, and in no case may the volume of free liquid exceed one percent of the' waste volume when wastes are disposed of in containers designed to provide stability, or 0.5 percent of the waste volume for solidified wastes, c.
The waste or container should be resistant to degradation caused by radiation effects, d.
The waste or container should be resistant to biodegradation, e.
The waste or container should remain stable under the compressive loads inherent in the disposal environment.
f.
The waste or container should remain stable if exposed to moisture or water after disposal, g.
The as-generated waste should be compatible with the solidification media or container.
A large portion of the waste produced in the nuclear industry is in a fann which is either liquid or in a wet solid fonn (e.g., resins, filter sludge, etc.) and requires processing to achieve an acceptable solid, monolithic fonn for burial.
The liquid wastes, irregardless of its classification, are required to be either absorbed or solidified.
In order to assure that the solidification process will consistently produce a product which is acceptable for disposal and will meet disposal site license conditions a prodess control program should be used. General requirements for process control programs are provided in the NRC StandardRey)tewPlan11.4,"SolidWasteManagementSysus."
(NUREG-0800 and its accompanying Branch Technical Position ETSB 11-3, "Design Guidance for Solid Waste Management Systems Installed in Light-Water-Cooled Nuclear Power Reactor Plants," (revised in July 1981).
These documents may i.lso be used as the basis for individual solidification process control programs by other fuel-cycle and by non-fuel-cycle waste generators who would solidify wastes. The guidance in this technical position should be the basis for qualifying process control programs for Class B and C wastes.
The use of applicable generic test data (e.g., topical reports) may be u!.ed for process control program qualification. Process control programs for solidified Class A waste products, which are segregated from Class B and C wastes, need only l
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4 de'nonstrade that the product is a free standing monulith with no more than 0.5 percent of the waste volume as free liquid.
An alternative to processing some Cless 8 and C waste streams, particularly ion exchange resins and filter sludges, is the use of a high j
integrity container. The high integrity container would be used to i
provide the long-term stability required to meet the stability requirements in 10 CFR Part 61.
The design of the high integrity container should be based on its specific intended use in order to ensure that the waste contents, as well as interim storage and ultimate disposel env'ronments, will not compromise its integrity over the long-term. As with waste solidification, a process control program for dewatering wet solids should be developed and utilized to ensure that the free liquid requirements in 10 CFR Part 61 are being met, i
l C.
Regulatory position 1.
Solidified Class A Waste Products a.
Solidified Class A waste products which are segregated from Class 8 and C wastes should be free standing monoliths and have no more than 0.5 percent of the waste volume as measured using the method described in ANS 55.1.{ree liquids as b.
Solidified Class A waste products which are not segregated from Class B and C wastes should meet the stability guidance for Class B and C wastes provided below.
2.
Stability Guidance for Processed (i.e., Solidified) Class B and C Wastes a.
The stability guidance in this technical position for processed wastes should be implemented through the qualification of the individual licensee's process control program.
Generic test E
data may be used for qualifying process control programs.
Through the use of a well designed and implemented process control program, frequent requalification to demonstrate stability is expected to be unnecessary.
However, process control programs should include provisions to periodically j
demonstrate that the solidification system is functioning properly and waste products continue to meet the 10 CFR Part 61 stability requirements. Waste specimens should be prepared
S r
b4 sed ori the proposed waste streams to be solidified and based on the range of waste stream.chemi.stries expected. The tests identified may be performed on radioactive or non-radioactive sainples.
l b.
Solidifiedwastespecimensshouldhavecompressivestreggthsof i
at least 50 psi when tested in accordance with ASTM C39.
Compressive strength tests for bitumino products sliould be performed in accordance with ASTM 01074 Hany solidification agents will be easily capable of meeting the 50 psi limit for properly solidified wastes.
For these cases, process control parameters should be developed to achieve the maximum practical compressive strengths, not simply to as;.ieve the minimum deceptable compressive strength.
The specimens for each proposed waste stream formulation should c.
remain stable after being exposed in a radiation field equivalent to the maximum level of exposure expected from the -
proposed wastes to b2 solidified.
Specimens for each proposeg waste stream formulation should be exposed to a minimum of 10 Rads in a gasuna irradiator or equivajent.
If the maximum level of exposure is expected to exceed 10 Rads, testing should be perfonned at the expected maximum accumulated dose. The irradiated specimens should have a minimum compressive strength j
of 50 psi following irradiation as tested in accordance with ASTM C39 or ASTM 01074.
d.
Specimens for each proposed waste stream formulation should be tested fgr resistance go biodegradation in accordance with both ASTM G21 and ASTM G22. No indication of culture growth snould be visible.
Specimens should be suitable for compression testing in accordance with ASTM C39 or ASTM 01074. Following the biodegradation testing, specimens should have compressive strengths greater than 50 psi as tested using ASTM C39 or ASTM 1
01074.
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For polymeric or bitumen products, some visible culture growth i
from contamination, additives or biodegradable components on the specimen surface which do not relate to overall substrate
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integrity may be present.
For these cases, additional testing should be perfonned. If culture growth is observed upon l
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i completion of the biodegradation test for polymeric or bitunen products, remove the test specimens from the culture, wash them free of all culture and growth with water and only light
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scrubbing. An organic solvent compatible with the substrate may be used to extract surface contaminants. Air dry the specimen at room temperature and repeat the test. Specimens should have observed culture growths rated no greater than 1 in the repeated ASTM G21 test, and compressive strengths greater than 50 psi.
The specimens should have no observed growth in the repeated AF'M G22 test, and a compressive strength greater than 50 psi. Ce ?ression testing should be performed in
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accordance with ASTM C39 or ASTM 01074.
If growth is observed following the extraction procedure, longer term testing of at least six months should be perform 9d to determine biudegradation rates.
The Bartha-pramer Method is acceptable for this testing. Soils used should be representative of those at burial grounds. Biodegradation i
extrapolated for full-size waste forms to 300 years should I
produce less than a 10 percent loss of the total carbon in the waste form, Leach testing should be performed for a mfnimum of 90 days in e.
accordance with the proceoure in ANS 16.1.
Specimen sizes should be consistent with the samples prepared for the ASTM C39 or ASTM D1074 compressive strength tests.
In addition to the demineralized water test specified in ANS 16.1, additional testing using other leachants specified in ANS 16.1 should also be performed to confirm the solidificatien agents leach resistance in other leachant media.
It is preferred that the synthesized sea water leachant also be tested. In addition, it is preferable that radioactive tracers be utilized in performing the leach tests. The leachability index, as calculated in accordance with ANS 16.1, should be greater than
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f.
Waste specimens should maintain a minimum compressive strength of 50 psi as tested using ASTM C39 or ASTM D1074, following immersion for a minimum period of 90 days.
Immersion testing may he performed in conjunction with the leach testing.
g.
Waste specimens should be resistant to therral degradition.
The heating and cooling chambers used for the therral 1
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degradation testing should conform to the description given in ASTM 8553, Section 3.
Samples suitable for performing
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compressive strength tests in accordance with ASTM C39 or ASTM 01074 shoulo be used.
Samples should be placed in the test charter and a series of 30 thermal cycles carried out in accordance with Section 5.4.1 through 5.4.4 of ASTM B553.
The high temperature limit should be 60C and the low temperature limi t -40C.
Following testing the waste specimens should have compressive strengths greater than 50 psi as tested using ASTM C39 or ASTM 01074.
h.
Waste specimens should have less than 0.5 percent by volume of the waste specimen as free liquids as measured using the method described in ANS 55.1.
Free liquids should have a pH between 4 and 11.
i.
If small, simuleted laboratory size specimens are used for the above testing, test data from sections or cores of the anticipated full-scale products should be obtained to correlate.
the characteristics of actual size products with those of simulatad laboratory size specimens. This testing may be performed on non-radioactive specimens. The full-scale specimens should be fabricated using actual or comparable solidification equipment.
j.
Waste samples from full-scale specimens should be destructively analyzed to ensure that the product produced is homogeneous to the extent that all regions in the product can expect to have compressive strengths of at seast 50 psi. Full-scale specimens may be fabricated using simulated non-radioactive products, but should be fabricated using actual solidification equipment.
3.
Radiation Stability of Organic Ion-Exchange Resins In order to ensure that organic ion exchange resins will not produce adverseradiationdegradationeffects,resinsshouldgotbegenerated that have loadings which will produce greater than 10 Rads total accumulated dose.
For Cs-137 and Sr-90 a total accumulated dose of 10g 3
Rads is approximately equivalent to an 10 Ci/ft concentration.
This position is applicable to resins in the unsolidified, as-generated fonn.
In the event that the waste cinerator considers it necessary to load g
resins higher than 10 Rads, it should be demonstrated that the specific 4
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8 resin will not undergo radiation degradation at the proposed higher loading. The test method should adequately simulate the chemical and radiologic conditions expected. A gamma irradiator or equivalent should be utilized for these tests. There should be no adverse swelling, acid formation or gas generation which will be detrirrental to the proposed final waste product.
4.
High Integrity Containers a.
The maximum allowable free liquid in a high integrity contaP'r Should be less than one percent of the waste volume as menu d j
using the method described in ANS 55.1. A process cratrol '
program should be developed and qualified to ensure uat the free liquid requirements in 10 CFR Part 61 will be met upon f
delivery of the wet solid material to the disposal facility, This process control program qualification should consider the effects of transportation on the amount of drainable liquid which might ce present.
b.
High integrity containers should have as a design goal a minimum lifetime of 300 years.
The high integrity container should be designed to maintain its structural integrity over this period.
c.
The high integrity container design should consider the corrosive and chemical effects of both the waste contents and the disposal trench environment.
Corrosion and chemical tests should be performed to cor.fim the suitability of the proposed container materials to meet the design lifetime goal.
d.
The high integrity container should be designeo to have sufficient mechanical strength to withstand horizontal and vertical loads on the container equivalent tn the depth of proposgd burial assuming a cover material density of 120 lbs/ft. The high integrity container should also be designed to withstand the routine loads and effects from the waste contents, waste preparation, transportation, handling snd disposal site operations, such as trench compaction procedures.
This mechanical design strength should be justified by conservative design analyses.
e.
For polymeric material, design mechanical strengths should be conservatively extrapolated from creep test data.
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The design should consider the thermal loads from processing, storage, transportation and burial.
Proposed container materials should be tested in accordance with ASTM B553 in the manner described in Section C2(g) of this technical position.
No significant changes in material design properties should result from this thermal cycling, g.
The h!gh integrity container design should consider the radiation stability cf the pr' posed container materials as well as the radiation degradation effects of the wastes.
Radiation degradation testing should be performed on proposed container materials using a gamma irradiator or equivalent.
No significant changes in material design properties shgald result followir.g exposure to a total accumulated dose of 10 Rads.
If it is proposed to design the high integrity container to greater accumulated doses, testing should be performed to confirm the adequacy of the proposed materials.
Test specimens should be prepared using the proposed fabrication techniques.
Polyneric high integrity container designs should also consider the effects of ultra-violet radiation.
Testing should be perfonted on prooosed materials to show that no significant changes in material design properties occur following expected ultra-violet radiation exposure, h.
The high integrity container design should consider the biodegradation properties of the proposed materials and any biodegradation of wastes and disposal media.
Biodegradation testing should be perfonned on proposed container materials in accordance with ASTM G21 and ASTM G22.
No indication of cultura growth should be visible.
The extraction procedure described in Section C2(d) of this technical position may be perfonned where indications of visible culture growth can be attributable to contamination, additives, or biodegrariable
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components on the specimen surface that do not affec' the overall integrity of the substrate.
It is also acraptable to determine biodegradation rates using the Bathta pramer Method described in Section C2 (d).
The rate of biodegradation should produce less than a 10 percent loss of the total carbon in the container material after 300 years. Test specimens should be prepared using the proposed material fabrication techniques.
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The high integrity container shculd be capable of meeting the requirements for a Type A package as specified in 49 CFR 173.398(b). The free drop test may be performed in accordance with 10 CFR 71, Appendix A, Section 6.
j.
The high integrity container and the associated lifting devices should be designed to withstand the forces applied during lifting operations. As a minimum the container should be designed to withstand a 3g vertical lifting load.
k.
The high integrity container should be designed to avoid the collection or retention of water on its top surfaces in order to minimize accumulation of trench liquids which could result in corrosive or degrading chemical effects.
1.
High integrity container closures should be designed to provide a positive seal for the design lifetime of the container. The closure should also be designed to allow inspections of the contents to be conducted without damacing the integrity of the container.
Passive vent designs may be utilized if needed to relieve internal pressura.
Passive vent systems should be designed to minimize the entry of moisture and the passage of waste materials from the container, Prototype testing should be perfonned on high integrity m.
container designs to demonstrate the container's ability to l
withstand the proposed' conditions of waste oreparation, handling, transportation and disoosal.
High integrity containers should be fabricated, tested, n.
inspected, prepared for use, filled, stored, handled, transported and disposed of in accordance with a. quality assurance program.
The quality assurance program should also address how wastes which are detrimental to high integrity container materials will be precluded from being placed into the container.
Special emphasis should be placed on fabrication process control for those high integrity contciners which utilize fabrication techniques such as polymer molding processes.
5.
Filter Cartridge Wastes
t 11 For Class B and C wastes in the form of filter cartridges, the waste generator should demonstrate that the selected approach for prov! ding stability will meet the requirements in 10 CFR Part 61.
Encapsulation of the filter cartridge in a solidification binder or the use of 4 high integrity container are acceptable options for providing stability. When high integrity containers are used, waste generators should demonstrate that protective Deans are provided to pre:lude container danage during packaging handling and transportation.
D.
Implementation This technical position reflects the current NRC staff position on acceptable means for meeting the 10 CFR Part 61 waste stability requirements.
Therefore, except in those cases in which the waste generator proposes an acceptable alternativo method for complying with the stability requirements of 10 CFR Part 61, the guidance described herein will be used in the evaluation of the acceptability of waste forms for disposal at near-surface disposal facilities.
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References.
1.
NUREG-0800 Standard Review Plan 2-.
ANS 55.1, "American National Standard for Solid Radioactive Waste Processing System for Light Water Cooled Reactor Plants," American Nuclear Society,1979 3.
ASTM C39, "Compressive Strength of Cylindrical Concrete Specimens,"
American Society for Testing and Materials,1979 l
4.
ASTM 01074, "Compression Strength of Bituminous Mixtures," American Society for Testing and Materials,1980 5.
ASTM G21. "Determining Resistance of Synthetic Polymeric Materials to Fungi," American Society for Testing and Materials, 1970 6.
ASTM G22 "Determining Resistance of Plastics to Bacteria," American Society for Testing and Haterials,1976 7.
R. Bartha, D. Pramer, "Features of a Flask and Method for Measuring the Persistance and Biological Effects of Pesticides in Soils,"
Soil Science 100 (1), pp-68-70, 1965 8.
ANS 16.1, "Measurement of the Leachability of Solidified Low-Level Radioactive Wastes," Arr.arican Nuclear Society Draf t Standard, April 1981 9.
ASTM B553, "Thennal Cycling of Electroplated Plastics," American Society for Testing and Materials,1979 i
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