ML20195G587
| ML20195G587 | |
| Person / Time | |
|---|---|
| Issue date: | 08/26/1988 |
| From: | Surmeier J NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Parry S NRC ADVISORY COMMITTEE ON NUCLEAR WASTE (ACNW) |
| Shared Package | |
| ML20151C617 | List:
|
| References | |
| FOIA-88-470 NUDOCS 8811280171 | |
| Download: ML20195G587 (1) | |
Text
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. ~g UNITED STATES
! e NUCLEAR REGULATORY COMMISSION f
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HEMORANDUM FOR: Sydney J. Parry, Senior Fellow Advisory Comittee on Nuclear Waste FP0M: John J. Surmeier, Chief Technical Branch ,
Division of Low-Level Waste Management and Decomissioning, f0Lys
SUBJECT:
REPORT ON LLW STABILITY Enclosed for the infomation of the Advisory Comittee on Nuclear Waste (ACNW) is a copy of a report developed by the Technical Branch of the Division of Low-Level Waste Management and Decomissioning (LLWM) transmitted totheDirectoroftheOfficeofNuclearMaterialSafetyandSafeguards(hASS)
( on stability of low-level wastes.
John J. Sumeier, Chief ;
Technical Branch Division of Low-Level Waste itanagea nt and Decomissioning, HMSS
Enclosure:
Report on LLW stability i
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REPORT TO THE DIRECTOR OFFICE OF NUCLEAR MATERIAL SAFETY ,
AND SAFEGUARDS REGARDING ,
CURRENT STATUS AND PROPOSED ACTION FOR REGULATION OF LLW STA81LITY
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Prepared by Division of Waste Management r and Decomissioning Staff '
i, June 21, 1988 !
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I CONTENTS CURRENT STATUS AND PROPOSED ACTION FOR REGULATION OF LOW LEVEL WASTE STABILITY P.H1
- 1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
- 2. FART 61 REQUIREMENTS 2.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2.2 Classes of Waste ......................... 1 2.3 Waste From Requirements . . . . . . . . . . . . . . . . . . . . . . 2 2.4 Concepts . ........................... 3
- 3. TECHNICAL POSITIOP.ON WASTE FORM STABIL:TY 3.1 Background ............................ 3 3.2 Test Parameters . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.3 Comments from ACRS and NUMARC . . . . . . . . . . . . . . . . . . . 4 3.4 Star.dard Methods of Test ..................... 7 3.5 Waste Solidification and HIC Preblem Areas ............ 7
- 4. THE TOPICAL REPORT REVIEW PROCESS 4.1 Background ............................ 7 4.2 Development and Evaluation .......,............ 8 4.3 Grandfathering .......................... 9 4.4 NRC Process Control Plans (PCP) Reviews . . . . .......... 9
( 4.5 Current Review Status . . . . . . . . . . . . . . . . . . . . . . . 10
- 5.
SUMMARY
DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . . . 11
- 6. CONCLUSIONS AND RECOMMENDATIONS .................. 12
- 7. REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 APPENDIX - Waste Form Testing Discussion . . . . . . . . ....... Al A1. Intreduction to Waste Form Testing ...... ......... Al A2. Compressiention . . . . . . . . . . . . . . . . . . . . . . . . . . Al A3. Thsrmal Cycling . . . ...................... A5 A4. Irradiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . A7 A5. Biedegradation .......................... A8 A6. Santha Pramer Test ........................ A10 A7. Immersion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A12 A8. Leach Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . A13 A9. References ............................ A17 TABLES A1. Topical Report Review, Status Summary, Solidified Waste Form and High Integrity Containers (HICs) . . . . . . . . . . . . . . . . . . . . A19 A2. Topical Report Review, Status Summary, Waste Solidification System and Process Control Pregram . . . . . . . . . . . . . . . . . . . . A20
( . A3. Solidification Media and High Integrity Containers (HICs) Accepted at A22 Existing Sites . . . . . . . . . . . . . . . . . . . . . . . . . . .
a CURRENTSTATUSANDPROPOSEDACTIONFORREGULATIONOFLOWIEVELVASTE(LLW) 5TABILITl 1 INTRODUCTION Over the past several months, there has been increasing interest in matters deal-ing with waste form stabilit Concern has been expressed by several groups,y and tepical Report reviews.
includin guards (ACRS), which has identifiedRef. (g the l') aAdvisory need to Committee forthe better define Reactor Safe-scientific bases for some Technical Posit!cn (TP) criteria and recommended tests, and the Nuclear Utilities Management and Resources Council (NUMARC), which has com-missioned a study and Report (Ref. 2) on the technical bases for meeting the waste form stability requirements of 10 CFR Part 61. Low-)evel waste generators and vendors of solidification aedia and high integrity containers (NICs) and state regulatory bodies and site operators have.also voiced concern. The everall level of concern has increased because, for some solidification media and HICs, there has been increasing evidence, from test data, from field experience and/or from analytical calculations, that some waste forms and HIC: may not have the long-term stability characteristics required by 10 CFR Part 61, this paper dis-cusses: (a) the evolutien and current status of the regulatory requirements and criteria for low-level waste form stability and topical Report reviews; (b)
( problems encountered in using the current criteria and in following the current regulatory nrecedures; and (c) recommendations on ways to improve the current situation. The purpose of this discussion is to provide office of Nuclear Mat-ertalSafetyandSafeguards(NMSS)seniormanagementwitntheinformationused to decide on a recommended course of action for correcting some perceived deft-ciencies in the way Classes B & C low-level radioactive wastes are regulated.
2 PART 61 REQUIREMENTS ,
2.1 General NRC regulation 10 CFR Part 61 (Ref. 3) establishes, for land disposal of radio-active waste, the procedures, criteria, and terms and conditions upon which the Commission issues licenses for the disposal nf radioactive wastes containing byproduct, source and special nuclear material received from other persons.
2.2 Classes of Waste Section 61.55 of Part 61 establishes three categories or claires of wastes; 11., 1
, Class A. Class B, and Class C, in a g4,nera11y ascending order with regard to degree of hazard (i.e., type and concentration) of radio-nuclides. Class II &
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Class C wastes are required to meet both minisue as well as stability require-4 ments that are set forth in 10 CFR 61.56. Class C saste must also be protected j (at the disposal faciljty) against inadvertent intrusion.
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2.3 Waste Frem Requirements Waste characteristics requirements are established in 10 CFR 61.56. There are two types or categories of requirements: (1) minimum - addressed in Section 41.56(a); (2) stability - addressed in Section 61.56(b). All classes of waste must meet the minimum requirements in 10 CFR 61.56(a). The "minimum" require-ments concern: (a) a prohibition against the use of cardboard fiberboard boxes; (b) treatment, packaging and maximum quantities of liquid wastes; (c) restric-tions concerning disposal of explosive or detonatable wastes * (d) restrictions againstwastescontaining,orcapableofgenerating,quantitlesoftoxicgases, vapors, or fumes; (e) a prohibition against pyrophoric wastes; (f) a limit on a
the maximum pressure and curie centent for packaged gaseous wastes;orand (g)infec-general requirement tious material for to to reduce treatment of hazardous, the maximum biological, the extent practicable pathogenic,l potentia hazard from non-radiologicarpater'.als.
Requirements for stability are provided in 10 CFR 61.56(b). Stability is defined in 10 CFR 61.2 as meaning "structural stability." While the ters, structural stabilit 61.56(b)y, is "stability" that itself not defined anpherestability)
(i.e., structural in Part 61, it is indicated is intended in Section to ensure that the waste does not structurally degrade and affect overall stability of the site through slumping, collapse, or other failure of the disposal unit and thereby lead to water infiltration. Stability is also stated to se a factor in limiting exposure to an inadvertent intruder, since a stable waste form should be recognizable and nondispersible. Therefore, in addition to recognizability and nondispersibility, the Class B & Class C waste forms are supposed to contri-( bute to the ability of the facility to retain overall stability and to thereby resist water infiltration. Resistance of the disposal facility to water infil-tration is thus fundamentally associated with waste form structural stability.
Although not explicitly so stated in Part 61, the concern about water infiltra-tion stems from the fact that migration through groundwater is a potentially maior pathnay for radionuclide release to the offsite environment. The relation-shipofthisconcern,whichisathreadthatrunsthroughPart61,tothetech-nical criteria and recommendations for immersion and leach testing will be addressed further in detail in this paper.
Further discussten of structural stability is provided in 10 CFR 61.56(b)(1),
where it is stated that "a structurally stable waste form will genere.ily maintain its physical dimensions and its fors, under expected disposal condit' ions such
- as weight of overburden and compaction equipment, the presence of naisture and 5 microbial activity, and internal factors such as radiation effects and chemical changes." This section of Part 61 also indicates that structural stability can be provided in any one of three different wayst (1) by the waste fors'itself i (as in an activated metal component); (2) by processing the waste to a stable
- waste form (for example, by mixing and solidifying the waste with a cementitious by placing the waste in a disposal satorial containersuch as Portland or structure that cement); or (3)ility after disposal (such as a HIC). -
provides stab Section 61.56(b) also provides further requirements concerning waste character-istics with reCard to: (a) limitations on the amount of frot standirg or cor-rosive liquid (3.4 by volume of the waste when it is in a di.posal container, or 0.5% by volume of the waste when processed to a stable fors); and (b) void
( spaces within the waste and between the waste and its package that must be reduced to the extent practicable.
2.4 Concepts Thou!hthebasicrequirementsforwasteformstabilityareprovidedinSection 61.5 of Part 61, the discussion of fundamental concepts or rationale is contaired in Section 61.7. In that section is provided a fairly detailed discussion of stability - of the waste as well as of the disposal site. As stated there, "a cornerstone of the system is stability ...so that...[through stability of the waste and site, ... access of water to the waste can be minimized (emphasis added)." In th's way "migration of racio nuclices is minimfred...." Imp 1(cil in these statements is a recognition of the fact that contact of waste with "leaching") of racionuclides frcm the waste water form. can Thus,lead to extraction leaching (i.e.lides from the waste fom is the first step in of radio nuc subsequent migration of the radionuclides from the waste through the groundwater and off of the site. It is clear therefore, that, though leachina is not seri-tienedexplicitlyinPart61,itIsaphenomenonthatisoffundamentalconcern to low-level waste disposal. Hence, it should come at 60 surprist that waste form leach testing is recemmended in the 1933 "Technical Position on Waste Form."
3 TECHNICAL POSITION ON WASTE FORM STABILITY 3.1 Backcreund Though Part 61 provides the basic licensing requirements for low level waste (LLW) Class B & Class C structural stability, the regulation does not indicate in any detail how those requirements should be demonstrated to be net. That
(- type of detailed guidance is instead provided in a "Technical Position on Waste ,
\ Form" (Ref 4), which was issued in May 1983. For solidified waste forms, the tests (see Table 1) essentially involve subjecting the wasta specimens to con-and ;
ditions thermalofcycling.
compression, Most ofirradiation, the tests, biodegradation, which were selected leaching, imersior,Ive for their relat simplicity and reprocucibility, are based on American Seciety for Testing and Materials (ASTM) or American Nuclear Society (ANS) standard methods of test that were originally developed for specific non-radioactive material appli-cations. Though it is not explicitly so stated in the TP, these methods of test are intended to provide confidened, by eeans of exposing test specimens to relatively short term (minutes to weeks) conditions, that low-level radioactive waste forms will have the desired long-term (300 year) structural stibility.
It is important to remember in this regard that there is a majcr difference in time scale between the periods of time allotted for the tests and the period of time of concern for LLV disposal. Therefore, the test ceMitions cannot match, and are not intended to exactly duplicate, the conditions that sight actually exist in the disposal facility at the time of disposal or which might exist at some point in time following placement of the waste in the facility. For
. example, the irradiation test calls fer the specimens to be exposed to a minimum of 10E+8 rads, which is the maximum level of exposure for the waste forms expected af ter (300 years of) disposal; this requires the test specimens to be exposed to a much higher ga na flux than would actually be encountered under real exposure conditions. Thus, in some ways (some of) the TP tests can !
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be considered to be accelerated tests, while in a more fundamental sense they are actually screening tests that are used to weed out material fnrnulations and designs that do not exhibit sufficient assurance of long term stability.
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).2 Test Paaameters The 1983 "Technical Position on Waste Form" address'es the type of short terie testing that should be performed to demonstrate long term (300 year) structural stability as well as the acceptance criteria for the tests. As shown in Table 1, there are eight types of tests or test conditions for solidified waste forms called out in the 1983 TP. Five of the tests are patterned af ter ASTM or AN$
Itandard Hethods of Test. However, the principal aceptance criterion parameter for most of the tests is compressive strength. The compressive strength crite- .
rienandthetestsarerelatedtoPart61throughthestatement(notedabove) in 10 CFR 61.56(b)(1), where it is stater that a structurally stable waste form will generally maintain its physical dimensions and its form under expec-taddisposalconditions,suchasweightofoverburdenandcompactIonequipment, the presence of moisture (a rationale for imersion and leaching tests) and and internal factors microbialactivity(arationaleforbiodegradationtests]Ilitytests)andchemi-such as radiation c*fects (a rttionale for radiation stab ^
cal changes." In the 1983 Technical Position, a cover material density of 120 lbs./cu.ft, is assumed, which yields a pressure of approximately 37.5 psi at a burial depth of 45 feet (the then maximum burial depth at Hanford). Taking into consideration potential additional loads frem trench compaction equipment, waste contents, etc., the compressive strength criterion was set at 50 psi, which was raised to 60 psi when Hanford increased the depth of its trenches to 55 feet.
Thus, the tempressive strength criterion was not established as a result of some titract correlation of an intrinsic material property to long-term str9ctural stability, but was instead intended to acccm.medate the environmental or in situ l loads at the bottom of a disposal trench. For certain types of solidfication
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media, (e.g., Portland cement or vinyl ester styrene), which typically have (in ,
( the unadulterated form) ccepressive strengths on the order of several thcusand psi, a 60 psi compressive strength criterion does not appear to have a strong correlation to long-term structural stability. Additionally, for viscoelastic media such as bitumen, which continues to deform under load measurements of someotherproperty(suchasviscosity),inadditiontoorInplaceof compressive strength, might be needed to demonstrate long term structural stability.
3.3 Co--ents frem aCR$ and NUMARC The NRC staff and contractor laboratory consultants have not been alone in ques-tioning the appropriateness and applicability of the TP tests and criteria.
Critical coments have been received on this matter from other groups such as ACRS and NW. ARC. In a letter dated November 10, 1987, ACRS raised several issues t regarding the relationship between the tests called out in the 1983 TP, and the requirements for waste form stability established in 10 CFR Part 61. The ACR$ '
stated in the letter that there is a need to better define the scientific bases for the tests discussed in the TP (the basis for the leaching test.: was sin out as not having a clear connection to waste form stability or to Part 61)gle .
The ACR$ also had the impression that scee criteria (such as leaching) were intro-duced only "for the convenience of the Agreement States" or the cperators of disposal facilities. As indicated in earlier discussion in this paper, there is a clear asscciation between the fundaments) objective of Part 61 to minimize contact of the waste with water and the need to conduct leaching and (seersion tests. However, the st<.ff has a reed (as stated in a letter dated Janua 1968, frem Victor Stello to Will am Kerr--Ref. 5) that there is in generb a 11,
( need to better define the scientific bases for the waste form TP and to provida 4 I LLW STABILITY RPT l
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Tabbs1 .
Solidified product guidance Tests Methods Criteria
- 1. Compressive Strength A5TM G39 or 01074 60 psi (af
- 2. Radiation Stability (See 1983 TP) 60 psi comp str. '
after 10E+8 rads
- 3. Biodegradation ASTM W1 & G22 No growth (b) & '
comp. str.) 60 psi
- 4. Leachability ANS 16.1 Leach index of 6 ,
- 5. Imersion (See 1983 TP) 60 pst comp str. I
, after 90 days (
- 6. Thermal Cycling ASTM B553 60 pst comp. str. ,
after 30 cycles ,
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- 7. Free liquid ANS 55.1 O.5 percent
- 8. Full-scale Tests (See 1983 TP) Homogeneous & ,
correlates to lab i size test results (a) The 1983 TP calls for a minimum ccepressive strength of 50 psi. This has been raised to 60 psi to accomodate an increased maximum burial depth at .
Hanford of 55 feet (from 45 feet). .
I i (b)The1983TPcallsforamulti-stegprocedureforbiodegradation testing: if observed culture growth rated greater than 1* is observed following '
i a repeated AS?M G21 test, or any growth is observed following a repeated ASTM G22 test, longer term testing (for at least 6 months duration) is called for, I using the "Bartha Pramer Method." From this test, a total weight loss extrapo-i lated for full-size waste forms to 300 years should produce less than a 10 per-
! cent loss of total carbon in the sample. -
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,u a clearer description of the connection hetween the Positions and the NRC regu-lations they are ir. tended to support. .
In a rather large-scale and comprehensive study conducted for NUMARC by the an Envirosphere evaluation wasCompany perforced(aofdivision the technical of EBASCO Services, and rngulatory Inc.)for bases andspec WMG Inc.Ific recomendations for wute form criteria and stability that were provided in a draft Regulatory Guide (Ref. 6). The document that the industry group reviewed was a werking dr'af t of a Regulatory Guide that was in preparation by th9 NRC staff as a toteritiU update of the 1983 TP. In addition to investigating the bares for tu recommendeo criteria in the draft Regulatory Guide, the intent of the NW.A9C study wa: to evaluate the "relevance" of the criteria and to re w mend alternative criteria and test procedures. It should be noted that some of tne criteria icentified in the oraft Regulatory Guide were new or different fres those that are contained in the 1983 TP. For example, the draft Regulatory Guide addressed proposed Itmits on the reductions in compressive strength that should be allowed after exposure to test conditions for bio degradation immersion, etc. Thisa;proachisnotfollowedinthecurrentTP,whereasIngleminimum value of cort.pressive strength'is recommended.
Some of the conclusions and reco m 'dations reached in the NUMARC study (as pro-vided in its Report) include the f6 1 ewing:
- 1. The imersion tests should use one, not two, leachants, and should run for five, not ninety days. -
( 2. The post-feersion ecmpressive strength test parameters should be changed to show (a) for brittle material, no greater than 20% loss of strength (mint-mum strength of 90 psi), and (b) for viscoelastic materials, no greater than 25% loss (minimum strength of 75 psi).
- 3. The radiation stability test should be emitted for certain wasta forms and waste streams.
- 4. The thermal degradation test should be eliminated.
- 5. The biociegradation test should be replaced with an improved test.
It should be realized that one of the primary considerations involved in the NUMARC conclusions and recommendations appears to be cost. Thus, in proposing elimination of certain tests and reductions in scope of others, the costs for NUMARC contributing utilities would be reduced. (This cost reduction would presum bly be indirect becausa the direct costs of qualifying a waste fors'
' - solidification agent or HIC are borne by the vendor.) A secorid factor appears
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to be an initial assumption on the part of the investigators that the tests called out in the 1983 TP are intended to duplicate ar.tual conditions expected i in the fid d. As noted earlier in this discussion, this is not the case. The TP tests are instead intended ' Rely to subbet the waste form and HIC material
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to conditions that would be sufficiently challenging (in terms of physical para-l eeters such as stress or temperature) to provide indictions of th? ability of j
the waste form to withstand semewhat similar (not necessarily identical) condi- '
tions and to remain integral for 300 years.
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LLV $TABILITY RPT 6
. . 1 3.4 Standard Methods of Test ,
I Though the 1983 TP refers to several ASTM or ANS Standard Methods of Test (see Table 1), none of the Ifsted Standards (Refs. 713) other than the ANS 16.1 test for leachability were developed specifically for the testing of lowlevel waste .
4 forms. All the tests other than the leach test are adaptations of industry stan-
, dards that were developed originally for specific nonradio active material appli-J cations. For example, the ASTM B553 thermal cycling test was developed for j metalplated, plastic automobile parts, and the ASTM 01074 compressive strengtn 1 test (which is used for testing viscoelastic materials) was developed for test-ing road bitumens. As a result, various det .is of the test procedures are open to interpretation, as are the results .if the tests. An apperdix to this Report ra provides a discussion of the Six primary tests r [ compressive strangthstability, along biode withtheassociatedacceptancecriteriathatarecalledoutinthe198.YP.
, This discussion includes: (a) the linkage of the tests to Part 61 waste fore stability requirements; (b) the rationale for the acceptance criteria originally I
and currently in place; (c) the strengths and potential weaknesses of each test;
< and (d) some suggestions on ways the tests afght be modified and improved or j replaced.
3.5 Was*.e Solidification and HIC Problem Area's
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There has been considerable research and fied experience obtained with HICs and waste solidification media since the "Techt.ical Position on Waste Fors" was 1/ developed in 1983. As a result of knowlecge gair.sd through topical Report i \ reviews and the results of tests and/or analytical calculations, the following I problem areas havt been identified:
i o Ce ent - Test results (Ref.14) from programs conducted by National Labor-l atories and t*.a cement solidification vendors, coupled with observed
- problems with swelling, disintegration, or incomplete solidification of power plait cement waste forms, have led the MC staff to racemend that l waste % ding be limited to 18 percent by weight until sufficient data are prese4ted to justify higher 1cadings.
o Bituen - There are two primary ty' pes of bitumen that en used to solidify
- low-level radioactive wastr: (1) distilled" and (2) "oxidized." A topical
! Report has been submitted for review on *.sch of these satcrials by separate
! . vendors. To this date the NRC staff has not been presen d with any
- evidencethatthedistIlledbitumencanprovidestabilizedwasteformsthat I seet the 60 pst compressive strength criterion. Therefore in February
! 1988,thetechnicalreviewofthetepicalReportondistilledbitueenwas 1 - discontinued, and the tcpical Report was returned (Ref.15) to the vendor (AssociatedTechnologies,Inc.). The topical Report for the oxidized bitueen has been approved (Ref.16),
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o High Density Polyethylene . Containers (HPDEs) - As a result of an allegation l that HDPE HICs do not have sufficient strength to withstand the stresses
- imposed by the weight of material placed above the HICs in a burial environ-sent, the NRC contracted with Brookhaven National Laboratory (ENL) to i( analyze existing data on creep of polyethylene and to develop a model and*
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criteria that could be used to evaluate the structural stability of the -
HICs. 4NL recom. mended (Ref.17) that the HICs be shown to be able to resist buckling, to not enter tertiary creep, and to not exceed allowable membrane stresses. Preliminary calculations, using the BNL model, indicate that large HOPE HICs may not satisfy the criteria. The HOPE HIC vendors have all been notified (Ref. 18) (along with the Agreement States) and ,
requestedtoshowvia(a) analyses,(b) testing,(c) administrative !
dures, and/or (d) redesign that their HICs can satisfy the criteria.proce-Each of the HCPE HIC vendors has submitted information that is under review by hRC staff and consultants.
4 THE TOPICAL REPORT REVIEW PROCESS ,
4.1 84ckcreund .
As noted earlier, the purpose of the "1983 Technical Position on Yaste Form" is to provide guidance on an acceptable approach for demonstrating compliance with 10 CFR Part 61 requiremants for LLW structural stability, Under current procedures, the NRC provides a "centrd" review of topical Reports on waste form solidification media and HICs. i..J central review is intended to be applicable for all disposal sites. A brief description of the evolution and current status of this review process is provided below.
4.2 Devete:-ent and Evolutten
( The current process for NRC's reviews of topical Reports on w u te form solidiff-cation, HICs &nd cceputer codes for classifying waste originated as a result of
. several actions that occurred primarily during calendar year 1983; (the founda-tien for these actions and agreements, however, was laid in a series of earlier activities that occurred over several years, but which will not be addressed here in the interest of brevity). The 1983 "Technical Position on Waste Fors" was cc pleted in May 1983 and made available to the public in June 1983. The NRC publicized its topical Report review process in September 1983 with a ,
Fe 11 Recister Netice that stated that a limited waiver of fees would be !
gi 6ee for Aaports sucmitted before June 30, 1984.
The venders responded to this by submitting eighteen topical Reports before the expiration of the fee waiver, while seven Reports have been submitted af ter the June 30, 1984 expiration date.
In Nove-ber 1983, NRC's Division of Waste Management (OwN) participates in a .
review of the South Carolina Agreement State Program. South Carolina ($C) had i established acceptance criteria for HICs in 1980 and had issued seve'al Certift-cates of Compliance (Cs of C) to HIC vendors beginning in May 1981 cased on !
those criteria. The OkN's examination of SC's HIC reviews was lished to a determination that the State had used criteria that appeared to be compatible with the staff's "1983 Technical Position on Waste Form." No dete'aination was made of the adequacy of the reviews with respect to whether reasonable assurance had been provided that the HICs would have 300 year structural staoility.
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LLV STABILITY RPT 8
In December 1983, a meeting (Ref.19) was held tre Bethesda to discuss the overall policy for HICs and tcpical Report reviews. .In attendance were repre-sentatives from the States of South Carolina, Nevada and Washington, as well as 4
NRC's Office of State Programs and DM4. At this meeting, the topical Report review process and the roles of the NRC and the States were discussed. It was recognized that the Agreement States have the licensing authority for the dis-posal sites with respect to whether specific HICs or waste forms would be acceptable for disposal at the sites. Eefore this meeting, the State of South Carolina had issued ten Cs of C and had under review two additional requests for approval of HICs. The State of Washington had two requests for approval.
It was at this meeting that an agreement was reached that NRC would provide a "central" review of tcpical Reports that would be applicable for all the disposal sites.
4.3 Grandfatherino 4
A key outcome of the December 1993 meeting in Bethesda concerned "grandfather-i ing." It was decided that South Carolina (Nevada and Washington had not yet
! issued any HIC approvals) would continue to accept the use of HICs that had i alrear1y been issued a C of C.
l For such HICs, revocation of a C of C would take place only if a problem were identified or if new information indicated that the HICs would not meet the ;
acceptance criteria. For new HICs that were described in topical Reports '
submitted to the NRC, the States wculd not issue Cs of C until the review had i
( been ccepleted by the NRC; (it should be noted, however, that periodic temporary approvals or "variances" for limited quantities of certain types of HICs have been granted by the State of Washington). For solidification processes, those processors who submitted information to NRC in topical Reports submitted before June 30, 1984 would still be acceptable under a grancfathering arrangement. A list of H!Cs and solidification media that are currently accepted at Barnwell, Beatty, and Hanford, respectively, can be found in the Appendix.
4.4 NRR Precess Centrol Plans (PCP) Reviewj !
While HMSS has been reviewing HIC designs and waste solidification media i foreulations in accordance with 10 CFR Part 61 requirements for structural stability, the office of Nuclear Reactor Regulation (NRR) has been reviewing '
generic and plant-specific Process Control Plans (PCPs) requirements for i reactors. The NRR reviews are intended to be focussed on the systems. j interactions of the solidification equipment with the plant systems and operation from the standpoint of reactor safety. There has been some question with respect to the scope of the NRR review and its effects relative to the t NMSS review. This is discussed in the following areas.
- 1. While NRR reviews PCPs from the standpoint of systems effects, NMM also reviews PCPs (and "Use Manuals, for HICs), but from the standpoint of ;
assuring that the processes used in preparing the waste forms and HICs will produce stable products, similar in characteristics to those tested !
, in accordance with Part 61 and the 1983 Technical Position. The division g of responsibilities and the distinction between the types of findings t
\ reached by the two Offices has been found to be unclear to individuals LLW STABILITY RPT S
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8 e
i within the Agency as well as to users of the pnducts; e.g., the utilities.
This ste,ms from the fact that a typical "generic PCP addresses, in part, ;
(a) process variances and ranges and (b) product acceptance critaria, i which are addressed, as well in NM55's reviews cf the topical Aeports !
) dealingwithwasteformstabIlit/. ;
i
i before the promulgation of Part 61. NRR has approved PCPs for solid- !
, ification agents that in some cases address waste concentrations that NM55 !
l 1s now finding to be unacceptable with respect to long-term structural l l stability. thus, there is an apparent need to make it clear to the users t j (and NRC staff) that the prior (and future) NRR approvals apply to the !
e system only, not the waste formulation. :
! 3. Reactnr Plant Technical Specifications typically do not include the PCPs.
j Inspectors, therefore, generally have no criterla or procedures to use for
- inspection of the waste solidification processes. From discussions with '
s
! NRR and inspection staff, it appears that nuclear power plant radwaste
) operations receive only a few hours (4 8) inspection each year. !
! 4 Though NRR reviews and approves plant PCPs,'the utility may then implement :
a changes in the PC? and advise NRR, on a semi annual basis, of the changes, i
) NRR then has the option of reviewing the changes. NRR is, however, way
- behind in its review of the PCP changes because of resource limitations. :
- Thus, whether the procedures that were joveloped by the vendor to assure ;
](
j production of a stable waste form are in fact still being followed by a given utility user is a significant ques'.fon. ;
l 5. The generic PCPs tend to be extremely ge w ral in nature leaving consider- ,
l ablelatitudetotheusertomodifytheprocesstospecIficplantconditions.
1 Thus, even if the plant radwaste operators follow the generic PCPs :
- rigorously, there appears to be a fairly high possibility that the waste !
forms may not possess the requisite long term structural stability because !
l the PCP follewed at the plant may not correspond to the process used in I
- qualifying the waste formulation in lat
- ratory tests.
4.5 Current Review Status !
i i In general the qualification of HICs appears to be a somewhat rimpler process i than that for solidification media, in the sense thnt: the HICs are finished l
) products; they are produced (each H!C by a single vendor) under factory quality assuranci procedures; they have material properties that are either well estab-lished or that can be readily reasured; and the properties can be used in - j c Idesign calculations. Prototypes can then be built and tested, and the test l results can be checked ogsinst tue calculations. In contrast, waste solidift- l cation media interact physically and chemically with the materials comprising ,
the waste stream, and the. r,esultant properties of the waste fore are more !
difficult to predict and reproduce on a routine basis.
l Four solidification media topical Reports have been reviewed and approved by !
NMS$ (by the end of May 1988). The staff's evaluation Reports for solidifice- l'
(, tion media topical Reports are carefully written to clearly specify the waste LW STA81LITY RPT 10
! f. ., l 1
strear.s and concentrations and the method of preparation of the waste forms se
- as to ensure that the ensuing waste forms will exhibit characteristics siellar
! to those held by the test specimens used in the qualifying tests, j As of May 1988, a total of 25 topical Reports has been submitted to NRC's 31,ial Safeguards for review.Of these, seven have been approved,
. Nuclear Mater
! three have been with d .*n, two have been returned, and thirteen are still under i review. A summary of u . review status, with a breakdown of the type rf i product covered by each topical Report, is presented in a table in th0 Appendix.
l A similar breakdown is provided for the PCP topical Reports reviewed by NAR.
j l 5 $UMMARY 035CUS$1CN 1
In sumary,10 CFR Part 61 requires long ters (300 year) structural stability.
l Assurance of long-term structural stability is provided for the most part by l conducting short-term tests and meeting acceptance criteria described in a 1 Technical Position issued in May 1983. The tests called out in the 1983 Technical Position are, in most cases based on ASTM or AN5 Standards that were
) createdforspecificnonnuclearapp1Icationsandmaterials. These tests,
, therefore, require some modification for radweste materials, in either the 1 methods for specimen preparation, the procedures used in the test, the inter-1 pretation of the test data, or the acceptance criteria used. The NRC staff, in a draft Regulatory Guide, has preposed some modifications to the 1983 tests and criteria.
( An industry group has critiqued a working draft of the Guide and has recom-sended that certain tests be eliminated or modified, along with the associated acceptance criteria. In addition, the ACR5 has raised several issues in a letter that called for a better definition of the scientific bases for the tests identified in the Technical Position and a clearer description of the connection between the tests and test criteria and the NRC regulations they are l'
- intended to support. The staff has ag*eed with the ACRS that those relation-ships need to be better explained. The discussion in this Report (including, in particular, the Appendix) addresses the relationships in question and may serve as a vehicle for transmitting the requested information to the ACRS.
1 The ecst widely applied test and criterion identified in the Technical Position j is the compressive strength test, which is recommended for virgin (otherwise j untested)materialaswellaswasteformsthathavebeensubjectedtovarious
/ biodegradation, and theraal cycling. The conditions of imeersion, radiation, currer.t compressive strength criter ton is 60 psi (raised from 50 psi in the i 1983 Technical Position). The coepressive strength test and the 60 psi
- criterion address the ability of the waste fore to withstand the loads placed on the waste form at the botten of a disposal trench at the time the waste is covered over. The criterion and the test do not address, except in an indirect way, the ability cf the waste fem to remain integral for 300 years.
None of the Technical Position tests result in measurement of some intrinsic property that can be directly correlated with long ters (300 year) structural stability. The tests are simply indirect, short term indicators of the potential lony ters stability of the waste forms. They are intended to be
- generically applicable, but as evidenced by both field experience as well as
(
I uw sTA8nm RPT 21 1 .
1
O 1
< g a laboratory tests, some waste forms have exhibited unstabli behavior. In k' particular, there have been problems with cement sol.idified wastes (notably head resins and sludge), with low-viscosity bitusinized waste, and with high-density polyethylene HTCs.
There has been a rather complex evolution of the regulatory process for low- l level radioactive waste forms, involving NRR, the Office of State Programs, ths Agreement States, the vendors, and of NM55. Under an agreement reached'in 1983 t with the Agreement States of Nevada, South Carolina, and Washington, the NRC provides centralized review of Topical Reports on waste form solidification media and HICs. Solidification media and HICs accepted by the States before thi'n agreement continue to be accepted. In addition, variances and interia l approvals have been granted to certain HICs and waste forms, while Topical !
I Reports on the HICs and waste foms have been under review by NRC. As of May J 31, 1988 NRC has reviewed and approved three HIC and four waste solidification
) media Topical Reports,
- while three have w..I withdrawn era twe have been j discont' id. !
While NM55 reviews topical Reports for HICs and solidification media under 10 -
! CFR Part 61. NRR reviews related Topical Reports on process contr31 plans.
j There appears to be scee question in regard to.what the responsibilities of each NRC Office are and how the two Offices interface. The PCPs appear to be j written in a relatively broad and general manner. Few are associated with plant l l
Technical Specifications or are subject to audit by reactor irspectors. In
approval. Consequently, there is little assurance that the procedures ;
I( developed by a solidification medium er HIC vendor are, in fact, actually followed by the reactor raemaste system operators. [
L
! 6 CONCLU5!ONS AND PECCW.WENOATICNS 1 !
Based on the considerations addressed in the discussion provideo earlier in !
l, tt.is document, the following conclusions and recomendations are provided:
i
- 1. While the presently used waste fem stability test; and criteria have i served well collectively as a discriminator for "C:oc" versus "poor" waste fem solidification eedia and formulations, none of the tests or criteria l should be considered "perfect." No single test is a direct sensure of a ,
]
i material's preperty that can be correlated in a quantitative way with !
. long ters (300 year) structural stability. Therefore, one alternative ;
j approach would be to conduct a study of the need for more appropriate j i
tests and criteria for LLW form stru:tural stability. The study night !
! take various foms, but one approach is to fem a task force that would 1 - consist of at least one individual from hM55, the Office of Nuclear l Regulatory Research (RES) and one or more National Laboratories. The sission of the task force would be to ascertain the need for more appro- :
i priate criteria and tests (or changes to the existing tests and criteria) !
and to develop specific recommendations in that regard. It is anticipated j
that the task force would require a minimum period of 15 ponths to cor.clude j its work and to develop its recomendations (which would be subject to i peer review). The task force should be provided with technical assistance reseurces to aid in accomplishing its work, if this option is pursued, i
LLW STABILITY RPT 12 i - _ _ _ _ _ .---
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- 2. An alternative to the attempted development of improved criteria and tests is to retain the current test and criteria with minor modifications. This approach could be justified en the grounds that (1) the' current battery of tests are working as a collet.tive group to eliminate the poorer waste forms and (2) the NRC currently has limited resources with which to conduct er support the development of new criteria.
- 3. Until and unless the task force recomendatiens are implennted, the review of waste form soliditication agents and HICA would continue to be carried out using the cxisting criteria called out in the 1983 Technical Position, as modified to reflet.t. more recent informatien on cement cracking and disintegration, high density polyethylene container creep, buckling, and Jtress, and low-viscosity bitumen. The reasons for continuing the reviews are that the current tests and criteria are serving well, as a collective group, to weed out some of the poorer quality waste forms. It ,
is necessary to continue this important work so that potential users ca9 make inforced choices regarding the types of solidification agents or HICs that can be safely used, i i
- 4. If a task force is formed, and if it were to conclude that new or improved i
criteria and tests are needed and that the new tests and criteria can be i readily identified (not necessarily # sequitor), implementation of the !
task 'orce recommendations would be achieved through the development of a I new ',echnical Position (or revision of the existing 1983 TP) that would !
/ specify testing precedures and criteria for demonstration of long tem
\ stability of HICs and waste forms. Following the promulgation of a new or t~
revised TP, systematic review would be conducted of the previously approved !
HICs and waste forms to determine whither additional qualification testing l were needed. In those cases where additional data were required, the '
vendors would be informed and granted a specified period of time in which to develop and sutmit their data for review.
- 5. The acceptance of new HICs or solidification media that are addressed in j new tcpical Reports 1rior to the review and approval of the Topical Reports should be '~ahibited. Grandfathering of HICs or solidification ,
media already under review should be discontinued within twelve months !
follcwing the issuance of an Inforsation Notice er Generic Letter announcing the end of grandfathering of new topical Reports, t 6 .* NRR should examine the PCPs of the individual power plants to assure that !
the operat. ors are conforming to the generic PCPs approved by NRR and the process details reviewed by NM55. NRR should consider incorporating the P:Ps into the plant Technical Specifications ao that NRC inspectors can ,
have appropriate documentation for their inspections. The PCPs should be l improved so that they will provide better assurance that the waste forms ;
will correspond to approved formulations. Revisions to the generic PCPs l can be accorplished via amendments to the existing PCP Reports, which t would be subject to review and appreval by NRC. NRR should not issue new l guidance on PCPs without kHS$ concurrence and coordination.
- 7. For weste forms or HICs that are not approved because they are not essured
( of 300 year structural stability, it will be necessary to either attempt f
to provide some quantificattore of the effects of prior dispos .1 of those LLW STABILITY RPT 13
o, . .
L
( .
wastes at the existing sites or to provide at least some qualitative l' 3 rationale for why such analyses are not necessary. Any conclusion that unstablewasteshavebeendisposedof(atBarnwell teatty,andHanford)
,w ill require some consteration of potential reedIal action.
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7 REFERENCES . .
- 1. William Kerr, Chairman, Advisery Committee for Reactor Safeguards, Letter to U.S. NRC Chairman, Lando W. Zech, Jr. , November 10, 1987. ,
- 2. W. Chang, L. Skoski R. Eng, and P.T. Tuite, "A Technical Basis for Meeting t.heWasteFormStabIlityRequirementsof10CFR61,"'NuclearManagementand Resources Council, Inc. Report, NUMARC/NESP-002, April 1988.
- 3. U.S. NRC, 10 CFR Part 61 - Licensing Requirements for Land Disposal of Radioactive Waste, Final Rule, 47 FR 57473, December 27, 1982.
- 4. U.S. NRC, "Technical Position on Waste Form," Lev. O May 1983.
- 5. Victor Stello, Jr. (U.S. NRC), Letter to William Kerr (ACRS), January 11, 1988.
- 6. U.S. NRC, Oraf t Regulatory Guide, "Low level Wasta Form Stability," October 1986.
- 7. American Society for Testing and Materials, Ceteressive Strencth of Cylindrical Concrete Seecimens, ASTM C39, Octocer 1984.
- 8. h erican Society for Testing and Materials, Cetoressive Strer.ath of I litumineus Mixtures, ASTM D1074. ASTM 01074, Feoruary 1543.
- 9. herican Society For Testing and Materials, Ce-eressive Preperities or Rictd Cellular Plastics, ASTM 01621, 1979,
- 10. Merican Society for Testing Materials, Defernatten of Plastics under t. cad, ASTM C621, 1976.
- 11. American Society for Testing and Materials, Thermal Cyclina of Elactoplated Ceramics. ASTM 5553, 1979.
- 12. herican Society for Testing and Materials, Determinino Resistance of Synthetic Polymeric Materials to Funct ASTM G21, 1970.
- 13. Marican Society for Testing and Materials, Oeteminine Resistance of Plastics to lacteria, ASTM G22, 1976.
) 14. P.L. Piciulo, J.W. / dams J.H. Clinton, and B. Siskind, "The Effect of Cure Conditionsonthe$'.abilityofCementWasteFormsafter!amersionin l
1 Water," Ilrookhaven National Laboratory Report, WM 31714, August 1987.
! 15. Malcom R. Knapp (U.S. NRC), Letter to J.E. Day (ATI), Docket No. WM 91,
- March 4, 1 m .
t j 16. Michael Tokar (U.S. NRC). Letter to William J. Klein (Wasteches), Docket No. WM 90 January 22, 1988. -
,j 1( 17. J. Pires, "Review of the High Integrity Cask Structural Evaluation Program (HIC 5EP.)," Brookhaven National Laboratory draft Report, April 6,1987.
e e i REFERENCES, Cont.
- 18. Michael-Tokar (U.S. NRC) Letter to John Chando (TFC Nuclear), October
< 15, 1987: (identical letters to W Hittman and Chem Nuclear Systems).
i
- 19. Cardella N. Maupin and Kathleen N. Schneider (U.S. NRC), "Chronology of Topical Reports and High Integrity Containei's Review Process " memoraMus for topical Reports file, February 14, 1984.
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APPENDIX WASTE F0Pf4 TESTING DISCUSSION A1. INTRODUCTION TO WASTE f%M TESTING l
The main body of this Report is intended to provide the basic information ,
needed to develop a strategy for improving NRC's regulation of low-level . i radioactive waste long-term stability and to provide recommendations in that regard. The discussion provided in this Appendix to the Report focuses primarily on the specific test recommendations in the "1983 Technical Position on Waste Form." Items addressed in this discussion include the linkage between the tests and Part 61, rationale for the criterie, strengths and weakncsses of the tests and criteria, and ways that the individual tests and criteria might be improved.
A2. COMPRESSION Linkage between the compressive strength test recommend, lons in the "1983 Technical Position on Waste Form" (Ref. A1) and 10 CFR fart 61 (Ref. A2) requirements for waste form stability is provided by 10 CFR 61.56(b)(1), where
- it is stated that "a structurally st&ble waste form will generally maintain its physical dimensions and its form, under the expected disp"osal conditions such as weicht of-overburden and comoaction equipment.... (emphacis added).
As noted in the oiscussion of "Test Parameters" in the main body of this f
Report, a cover material density of 120 lbs./co.ft. was assumed in the 1983
( Technical Position (TP). This yielded a pressure of aproximately 37.5 psi at 1 burial denn cf 45 feet, whica was the maximum burial depth at the Hanford,
- Washington LLV disposal site at the time the TP ras promulgated. Taking into i consideration the potential additional loads free trench compaction equipment, waste centents, etc., the compressive strength criterion was set at 50 psi.
Thic " s been raised to 60 psi to reflect an increase in burial depth at Hanfore to 55 feet. It is important to realize that it was noted in the 1983
- TP that "many solidification agents will be easily c6pable of meeting the 50 l
psi limit for properly so'idified wastes." For t.iost: cases, therefore, it was i stated in the TP that process control parameters should be d6veloped to achieve the "maximum practical" compressive strengths, not simply ~ the minimum accept-
. able compressive strength. In the case of cement-solidified wastes, this l
provision appc,rs to have been interpreted in an extremely liberal fashion by l some vendors in as much as some of the waste stream formulations for which com-l pressive strength data have been provided by the vendors exhibit compressive strengths on the order of 100 to 200 psi following the immersion, irradiation, thermal cycling, and/or biodegradation tests. For those cases the position held
.by the vendors is that tne waste forms meet the TP coc.pressive strength criterion because the compressive strengths exceeded 60 psi.
As noted in several places in this Report, compressive strength testing is ,
but also for waste fors specimens that designated not only for have been exposed to various test condit virgin material, ions (see Table 1 of the Report). The 1983 TP called for a minimum compressive strength of 50 psi (now 60 psi) after completion of the tests. Hewever, in a working draft nf a Regulatory Guide on
'( "Low Level Waste Fors Stability" (Ref. A3) that was released for informal i \ comment, allowable reductions in strength on the order of 10 to 20 percent
- were considered. If adopted, this would be significant departure from the 1983 I
_ _ _ _ _ _ _ . - _ - _ _ _ _ _ _ . - . _ ~~
~
TP, where allowable redu:tions iis strength are not addressed even in a conceptual way. In commenting ora the draft Regulatory Guide, the Nuclear Utilities liaiiagement and Resources Council (NUMARC) Report (Ref. A4) recom-mends maximum acceptable strength reductions of 20 to 25 percent (depending on the type of test) as well as minimum post-test strengths of 75 to 90 psi (depending on the type of material - bituminous vs. brittle). NUMARC's revised post-test criteria are intended to incorporate a safety factor es well as to address the variabi11ty of test data that is inherent in the test procedures.
Some additional information and coment on compressive testing are provided below.
A2.1 American Society for Testinar and Materials (ASTM) C39: Compressive 5trenctn of Cylincrical Contrete Speci_ mens Scope: This test method (Ref. A5) covers determination of compressive strength of cylindrical concrete specimens such as molded cylinders and drilled cores.
It is intended to be limited to cane;ete having a unit weight in excess of 50 lbs/cu. ft., but it is currently vsed to test LLW specimens comprised of a variety of materials including vir:y1 ester styrene, gypsum, and vinyl toluene (AZTEC) solidified wastes.
Summary of Method: This test method consists of applying a compressive axial load to molceo cylinders or cores, at a rate which is within a prescribed .
range, until failure occurs.
(
, gg_nificanceandUse: Care must be exercised in the interpretation of the significance of compressive strength determinations by this method since strength is not a funda.tental or int.insic property of concrete made from given materials. Values obtained will depend on the size and shape of the specimen, molding, and fabrication batching, mixing proceducts, the methods of sampling,ing and the age, temperature, and moisture conditions dur curing. l Accaratus: Testing Machine According to the Standard, the testing machine must ce cr.pable of providin rate 1 of loading prescribed in the Standard; viz.,
0.05 in./ min. when the mach ne is running idle (for screw-type machines); F 20 to 50 psi /s. The machine is supposed to be power-operated and should apply'the load continuously rather than intermittantly, and without shock.
Specimens: There are several pres;riptions on specimen dimensional variances such as diameters (must not vary more then 2 percent when measured in different -
directions), perpendicularity o'f the ends (must not depart by more than 0.5
. degrees),etc.
Procedure: This section of the Standard addresses moist storage and testing, permissible time for testing specimens of given test (cure) time, how to place the specimen, and rate of loading.
Calculation: The compressive strength of ihe specimen is calculated by dividing the maximum lead carried by the specimen during the test by the average cross-sectional area. If the length to-diameter ratio is less than
( 1.8, the result is adjusted using a correction factor provided in a table.
" *
- O o 0 g A2.2 ASTM 0 1074 - 83: Comoressive Strenath of Bituminous Mixtures, Relationship-to the 1983 TP: The TP says that compressive strength tests should ce perform a in accordance with ASTM D1074 (Ref. A6).. Note: The August 1987 version of the draft Regulatory Guide on "LLW Form Stability" sayr that "For waste foms capable of viscoelastic flow, e.g., bituminous products, stability can be demonstrated by documenting that the site operator has in-plemented an administrative control procedure that ensures sufficient backfill around the waste containers to minimize the voids." In other words, com-pres:;ive strength testing of bitumen would no longer be required. Thus, it would be up to the site operator to ensure structural stability of the -'-
form through proper backfilling around the waste form. However, it > ra that this could be a violation of Part 61, because according to Subsection 61.56(b)(1), "Structural stability can be provided by the waste form itself, processing the waste to a stable form, or placing the vaste in a disposal container or structure that provides stability after disposal." Backfill meets none of those provisions. Staff no longer supports the position that backfill alone will provide structural stability for bituminized wastes.
Scoce: This method is for compacted bituminous mixtures of "the hot-mixed, hot-laid type for use in pavement surfaces anc base courses...."
Sionificance and Use: This test method also describes the methods for molding, curing, and testing of specimens. Note: This test method pemits the use of reheated mixtures, but acknowledges that the resulting compressive strength f
values will be higher than for newly prepared mixtures due to the change in
( binder viccesity. Question: Could the vendors use this to advantage by reheating the waste fem test specimens before testing to jack up the com-pressive strengths?
Aeparatus: The testing machine must have capacity to prnvide a range of accurately controllable rates of vertical defomation. The reason is that the rate of vertical ceformation far the compression test is specified as 0.05 in./ min.-in. of specimen height, and it may be necessary to test specimens ranging from 2 by 2 in, to 8 by 8 in, to maintain the specified minimum ratio l
of specimen diameter to particle size.
i
- Preparation of Test Mixtures: The Standard contains a lengthy section on l procedures for preparing test mixtures. This section would seem to be largely irrelevant for LLW specimens, which, to be representative of the actual waste foms, should presumably have to be prepared using the type of appar'atus used for solidifying LLW.
l l . Test Specimens: The Standard states that generally the test speimens should be cylinders 4.0 in, in diameter and 4.0 in, in height and note . hat the size i of the test specimens has an influence on the results of the compressive strength test. Specimens other than 4x4 in, may be used with the following j provisions:
(a) The height must be equal to the diameter within 2.5%;
(( (b) The diameter must be not less than 4 times the nominal diameter of the largest aggregate particles; LLW STABILITY RPT A-3
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i (c) The diameter must not be less than 2 in.;
(d) The rata'of deformation must be kept constant during the compression test.
Molding and Curina of Test Specimens: There is a large section in the Standard on molcing and curing of test specimens. This section would seem to be soot for LLW test specimens for reasons di: cussed above. -
Procedure: The Standard specifies a test temperature of 77 F, which is to be attained by storing the specimens in an air bath maintained at the test temperature for not less than 4 h. Specimens 4 in, high are supposed to be tested at a rate of 0.2 in./ min. One bitumen solidification vendor has been conducting compressive, strength testing at 60 F because the type of bitumen used in his process has such low strength it has difficulty meeting the 60 psi criterion.
Calculation of Strenoth: The compressive strength is determined by dividing the maximum vertical load obtained during deformation by the orioinal cross-sectional area. An average of a minimum of 3 specimens should be used as the Reported compressive strength value.
Precision: The single-operator standard deviation of a single test result (a single test result is defined as the average of a minimum of 3 sepiirate com-
- pressive strengths) has been found to be 21 psi.
Remarks: isrookhaven National Laboratory (BNL) (in NUREG/CR 3829) (Ref. A7) ,
points out a number of problems with this test, among them the fact that the compressive strength of. bituminous materials decreases with decreasing rate of deformation, and this test was developed for road bed bitvrren, which is sub-jected to very short-term load conditions, compared to a LLW form.
t The TP does not specify E procedure for calculating a compressive strength in those casas where ASTM 010N (Ref. A6) fails to show a mximum in the stress-4 strain curve. In such casos, it has been suggested that the strass to provide a given strain should be determined, but at what percent--5%,10%, more?
Generally, the higher the strain value allowed, the higher the Reported :
strength value will be. Currently, the value of stress at a strain of 10% is t used, but the basis for this is not well-documented (though one possibility (Ref. A8) is that it originated with, or was derived from, ASTM 01621, (Ref.
A9) for testing of rigid cellular plastics). In ASTM 01621, it is recommended that the strength be determined from the stress at the yield point or at a strain of 10% in the absence of a yield point. It has been customary for LLW bitumen vendors to determine the stress / strength value from the intercept on the stress / strain curve obtained by taking a vertical line from a 10% offset on
- the strain (i.e., "X") axis. This procedure is not the same as that used in metallurgical stress / strain testing, where an offset yield strength is obtained by taking a line parallel to the straight line portion of the stress / strain curve. A vendor of low-strength bitumen has petitioned the NRC i to consider revising the method of strength calculation to allow use cf the
- , parallel offset method; this would result in a significant increase in the ,
( values of strength reported.
l l
- * . . . l The August 1987 version of the draft Regulatory Guide on "Waste Form Stability" recommends that if the compressive strength (rather,than a leach index of 6) is used to determine stability after the other TP tests such as immersion, then
. ASTM 01074 should be used and thst the compressive strength should not have decreased by more than 10 to 20%, depending on the type of test (e.g. , immer-sion, radiation, thermal cycling), from the pretest value. The recent NUMARC study, titled, "A Technical Basis fer Meeting the Waste Form Stability Require-meats of 10 CFR 61," recommends a 25% allowable decrease. The reason for this is the 'nigh variability (see remarks on test procesion) in test results.
1 For viscoelastic materials such as bitumen, the fundamental question remains:
should some other mechanical / physical property, other than compressive strength, be used as an acceptance criterion and measure of long-term stabilty?
One other property that has been suggested could be used for tnis purpose is viscosity. Another property that has been considered is creep, which, as indicated in an early working draft of the Regulatory Guide on "Waste Form Stability," was to be determined using a creep test such as a modified ASTM 0621 (Ref. A10). Using that test, stability was to be demonstrated by showing thet the creep of the bituminized waste form would be less than 10 percent extrapolated over 300 years. However, as noted in the NUMARC Report (Ref. A4),
the 0621 test was in the process of being remov'ed from the ASTM listing of procedures "...because the test procedure and testing equipment prescribed in the procedure are antiquated." Also pointed out in the NUMARC study was the fact that to pass the test for a test specimen one-half inch high (as ,
recommended in the 5tandard), the total deformation after 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> must be t less than, or equal to, approximately 20 microns. Furthermore, assuming ten
( data points are required to extrapolate the total deformation to 300 years, the measured deformation at each time interval has to be much less than 20 microns.
NUMARC points out, and the staff agrees, that there are serious questions on the feasibility of preparing the specimen surface with such precision for a visceelastic material such as bitumen. Additional approaches to testing bitumen are provided in a BHL Report (Ref. A7).
A3 THERFAL CYCLING .
l Linkage between the thermal cycling test reccmmendations in the 1983 TP is not as direct as it is with some of the other tests such as compression, irrad-I iation, biodegradation, etc. The reason for this it that thermal effects are I
not called out specifically in 10 CFR 61.56(b)(1), as they are for the other factors. Section 61.56(b)(1) does, however, address "internal factors," and temperature, and temper.ture effects, are unquestionably internal factors, just as irradiattun or chemical changes (which are specifically mentioned in Part
- 61) are. Some facts concerning the thermal cycling test called for in the 1983 l
l TP are as follows:
' A3.1 ASTM B553 - 79: Thermal Cyrlina of Electroplated Plastics ,
Scope: This tcst method (Ref. All) covers the thermal cycling procedure and apparatus used to test electroplated plastics for evaluation of serviceability.
Apparatus: 'The apparatus should consist of a circulatina air heating chamber
( sufficiently powered, insulated, and controlled to closely maintain the preset.
temperatu*e. The controller and recorder used for chamber control and records LLW STABILITY RPT A-5 .
. should be accurate to plus or-minus one degree C. All points within the working area of the test chamber should remain withih plus-or-minus 3 degrees C. The air circulation should be controlled to permit a consistent rate of '
heating or cooling of the parts under test.
Procedure: The parts may be introduced into the chamber unmounted, or mounted in a manner rimulating assembly, if so desired. Each thermal cycle should begin by either placing the samples in a room-temperature chamber and heating .
. the chamber up to the high limit or by placing the samples directly into a chamber at the high limit.
The 1983 Technical Position specifically states that the test procedure should follow the following paragraphs from the Standard: .
5.4.1. Expose the parts for I h at the high limit.
5.4.2. Allow the parts to return to 20 C and maintain at this temperature for 1 h. This may be accomplished by removing the parts from the chamber. Some types of apparatus are so constructed that the parts need not be removed during this step.
5.4.3. Expose the part for 1 h at the icw limit temperature.
~
5.4.4. Repeat 5.4.2. This constitutes one full thermal cycle.
The Standard continues with Paragraph 5.4.5 (which is not specified by the 1983 TP), which requires that the parts be inspected for coating defects produced by
( the thermal cycling. There is no analogous call for inspection for defects by the 1983 TP. The TP only cites the compression test and states that the specimen size should be consistent with that required for the compression test.
Remarks: The 1983 TP calls for a series of 30 thermal cycles to be carried out in accordance with Section 5.4.1 through 5.4.4 of ASTM B55?. Neither the TP or
' the len All the Standard, however, the Standard says is that the specify"parts" gth should of be time for "expostd" a forcceplete 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> at cycle.
the high limit and the low limit. The "parts" or specimens do not have to be thermocoupled. Thus, thermal equilibrium in the speciment is r.ot a require-ment, except perhaps at the 20 C temperature (Section L 4.2) where the Standard says that this temperature should be maintained for 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />. Inasmuch as this Standard was written for elretroplated parts, not for solidfied multiphase media, the Standard, as currently written, may not be fully appropriate for LLW forms.
Grounds given NUMARC in the NUMARC hasReport commented are that: unfavorably (on the thermal stability test.1) there is "..
the test procedures, or the tests specified....." and (2) the ASTM B553 (Ref.
All) procedure is not applicable to thermal testing of waste forms. Therefore, NUMARC recoseends that the, test be eliminated.
The staff does not at this time concur with the NUMARC study with regard to the recommendation to eliminate the thermal cycling tests. The reason for this is f that the test has served the staff well in distinguishing between "strong"(and
- l \ "weak" solidified waste forms. The thermal cycling test impoJes a stress due i
to differential thermal expansion) between the different phases and LLW STABILITY RPT A-6 l
t
( By cycling between the maximum and microconstituents in the waste form.
minimum temperatures called for in the test, cracks.that may have been initiated in the test specimen will propagate and eventually measureably weaken the form. Though the specific maximum and minimum temperatures attained during the tests may not actually be attained during disposal (or transport).of the waste forms, that point is not particulary relevant in that, as discussed in the body of this Report, the tests are not intendd i.o duplicate actual field conditions. The test conditions are intended to provide, on a short-ters and the thermal cycling basis, indications of (relative) long term stability,imens to a short-ters test does this well by subjecting the waste form spec thermal stress that challenges the structural capability of the specimen.
That is not to say that the test should not be modified. As noted, this test not low-level waste foms, and the was developed for metal-coated plastics testprocedureguidancecouldbeapprecIablyimprovedbybetterspecifying J
whether the specimens should be testec. bare or in containers and whether Moreover, thermocouples should be used to measure the specimen temperature.
the surface and bulk condition of the test specimens with respect to the
! observed cracks or other These defects changesshould be considered in test procedure for inclusion and acceptance in the criteria acceptance criteria.
would be of a relatively minor nature, however, and could be implemented with minimal effort.
A4 IRRADIATION Linkage between the irrradiation test rocce endations in the "1983 Technical
( Position on Waste Form" and 10 CFR part 61 recNirements for waste form stability is provided through 10 CFR 61.56(b)(1), where it is stated that "...
i .
a structurally stable waste form will ginerally maintain its physical dimen-siens and form, under the expected dispcsal conditions...and internal factors I
The 1983 TP states that the such as radiation effects...." (emphasis added).
~
specimens for each prcp3see waste stream formulation should remain stable i
after being exposed in a radiatisn field equivalent to the maximum The TPlevel thenof goes exposure expected from the proposed astes to be solidified.on to should be exposed to a minimum of 10E+8 rads in a gama irradiator or equiv-alent. Though the TP also states that testing should be performed at thei expectedmaximumaccumulateddose}onstabilitytestingis,infact, terminated to exceed 10E+8 rads, most radiatThere is no recommended Standard Method of Test at the 10E+8stability.
irradiation rad level. The acceptance criterion applied to the radiation stability testing is a compressive strength value of 60 psi, which, as stated
. in the 1983 TP, 16 to be determined in accordance with ASTM C39 (Pef. A5) (
l brittle materials) or ASTM 01074 (Ref. A6) (for viscot a: tic With bitumen) on irradiation test specimens after the irradiation exposure.
materials su regard to viscoelastic waste forms, the 1986 draft of the waste form Regulatory Guide (Ref. A3) allows the use of either a leach test or compressive strength test, after irradiation.
- If a ecmpressive strength test were to be used, the draft Regulatory Guide specified that ASTM 01074 should be used and that the compressive. strength should not decrease by more than 10 p"ercent from the un-L irradiated compressive strength. An earlier draft of the *
( Stability" Regulatory Guide recomended use of the modified ASTM 0621 creep test (Ref. A10) with an acceptance criterion of less than 10 percent cree extrapolated over 300 years.
i the creep test recommendation has been abandoned. For reasons to be addreised later in this Report, the recomendation allowing stither leach testing or .
compressive testing of viscoelastic materials is also not presently and W sed by the NRC staff.
The basis for the 10E+8 rad minimum irradiation exposure test recommendation is that 10E+8 rads are approximately equivalent to the dose that would be acquired by a waste form over a 300 year period, if the waste form were loaded to a Cesiums-137 or Strontium-90 concentration of 10 Ci/cu.ft. This is the reco= ended (Ref. A12) maximum activity level for nrganic resins based on evidence that while a measurable amount of damage to the resin will occur at 10E+8 rads, the amount of damage will have negligible effect on power plant or disposal site safety. The observed 'iegradation included acid femation, It is decreased ion retention capability, and hydrogen generation (Ref. A13).
noted in the NUMARC Report that the 10E+8 rad recommended ifmit (which is not a requirement) is not . linked to the Part 61 classification limits for Class A, 8, or C wastes. As an example, for Class C Cesium-137 waste loaded to the Class C concentration limit,10E+8 rads are achieved in about 20 years.
However, for the ove--whelming majority of waste forms, the 10E+8 accumulated radiation exposure value is conservative (Ref. A14).
In the NUMARC study, it is concluded that irradiation testing to 100 megarads is reasonable for waste forms that contain organic ion exchange media, but that exposure to this dose doe.s not have an adverse effect on other wastes or on polymer stabilized waste forms of any kind. ..Therefore, NUMARC recommended that such types of waste forms be spacifically excluded from further testing.
( NUMARC also reco= ended that safety factors of 1.5 and 1.25 be applied to the allowable minimura compressive strengths for brittle and viscoelastic materials, respectively, and that a decrease of 25 percent in compvsive strength be 111 owed for vis;oelastic materials.
At this juncture, the staff tends to agree with NUMARC's observation regarding radiation effects, or non-effects, on waste forms that do not contain ion exchange media, to the extent that this appears to be true for cement-solidified wastes and vinyl ester styrene. It does not necessarily apply to bituminous wastes, which have been shown to undergo swelling upon irradiation (Ref. A7).
This behavior of asphalts is believed to be due to internal pressurization and formation of gas bubbles caused by radiolytic gas generation, and appears to be a function of the rate of flux and type of bitumen and waste (Ref. A13). Gas generation in bitumen is a complex process, which at this point is not well understood. Because of the swelling effects, and because of the inherently low strength of bitumen at elevated temperatures (the iri sdiation causes tempera-ture increases in the bitumen test specimens), the bf tuminized waste form speci-
. mens are wrapped in tape during the irradiation in an attempt Duetotoretain their the complexity shape so that they can subsequently be compression-tested.
of the phenemena in bituminized low-level waste, the NRC staff does not have any recomendations at this time regarding ways that the irradiation test might t,a improved for such waste forms.
This is an area that requires further study, i
A5 8100EGRADATION l
Linkage betw e n the biodegradation test recommendations in the 1983 Technical
( Position and 10 CFR Par *. 61 requirements for wsste form stability is provided LLW STABILITY RPT A-8
- v. ~ .
i through 10 CFR 61.56(b)(1), where it is stated that "... a structurally stable waste form will generally maintain its physical dimensions and its form, under the expected. exposure conditions such as... microbial activity...." Biodegrada-tion testing is one of the more complex areas (with regard to the test pro-cedure) addressed in the 1983 Technical Position. The TP states that specimens for each proposed waste stream formulation should be tested for resistance to biodegradation in accordance with t,oth ASTM G21 (Ref. A15) (for resistance to fungi) and ASTM G22 (Ref. A16) (for resistance to bacteria) and that "no in-dication of culture growth should be visible." Is is further stated that speci-mens should be suitable for compression testing in accordance with ASTM C39 or ASTM 01074 and that following the biodegradation testing, specimens should have compressive strengths greater than 50 (now 60) psi.
For polymeric or bitumen waste forms, the TP provides some additional guidance.
In the expectation that, while some visible culture growth would be encountered for such waste forms (due to contamination, additives, or bio-degradable com-ponents on the surface of the specimens), such culture growth might not relate to overall substate integrity, the TP allows for some additional testing to be performed. In that regard, the TP discusses a procedure for re-doing the tests and provides additional acceptance e.riteria with respect to acceptable levels of culture growth ("level 1" for the repeated AS1H G21 test and no observed growth" for the repeated ASTM G22 test, along with a compressive strength greater than 50 psi).
If growth is still observed after the extraction procedure, the TP recommend:
longer term testing of at least six menths duration. A test called the Bartha-Pramer test (Ref. A17) is listed as acceptable for such testing. The accep-( tance criterien listed in the TP for the Bartha-Pramer method involves a determination of the loss in weight of the specimens and extrapolation cf the loss of weignt over a 300 year period to shew that there would be less than a 10 percent loss of total carbon in the waste form.
Some additional information and comment on biodegradation t6 sting are provided below.
AS.1 ASTM G21: Determinine Resistance of Synthetic Polymeric Materials to Funal S. cope: This Standard Practice (Ref. A15) is intended to be used to determine the ef fects of fungi on the procertiesj synthetic polymeric materials in the form of solded and fabricated articles, tubes, rods, sheets, etc. (emphasis added). The Standard states that changes in properties, (e.g., mechanical and physical properties), may be determined by applicable ASTM methods.
Sicnificance and Usa: Although not explicitly stated in the Standard, the fact that the empnasts in the text is on the ef fects of the test on the electrical and optical properties of plastics indicates that the Standard was primarily developed for plastic electrical cceponents. The Standard states that the resin portion of these material is usually fungus-resistant in that it does not serve as a carbon source for the growth of fungi and that it is generally other components, such as plasticizers, cellulosics, lubricants, stabilizers, and -
colorants, that are responsible for fungus attack.
i
( .
}
l
- l Apparatus: The discussion of apparatus in the Standard focuses on glassware I
and incuoation equipment. . l Reacents and Materials: The Standard addresses purity of reagents and water in some detail. Also, ince the procedure involves handling and working with fungi, it is recommended in the Standard that personnel trained in microbiology perform the portion of the procedure involving handling of organisms and inoculated specimens.
Test Specimens: The Standard indicates that the simplest specimen may be a 2 by 2-in. piece of the material to be tested. This is consistent with the Technical Position recommendation that the specimens should be suitable for compression testing in accordance with ASTM C39 or ASTM D1074. For visual evaluations, the Standard states that three specimens should be inoculated.
Procedure: The proc suitaole sterile dis,edure essentially hes, inoculating consists the surf ace ofof theplacing the specimens specimens with a in composite spore suspension, incubating for a minimum period of 21 days, and observing for visible effects. Visible effects, in the form of observed growth on the specimens, is judged on a scale of 0 to 4, where 0 is no growth and 4 is "heavy" growth (60 to 100% coverage).
A5.2 ASTM G22: Determining Resistance of Plastics to Bacteria Sceee: ThisStandardPractice(Ref.A16)wasdevelopedfordete$1ningthe effect of bacteria on the properties of plastics in the form of molded and It cover two procedures, A and B,
( fabricated articles, tubes, sheets, etc.
where B provides more extensive contact between the test bacteria and the specimens than does A. Consistent with ASTM G21, the Standard indicates that changes in properties may be determined by applicable ASTM methods.
Summary of Practice: The procedure described in the Standard consists of: (1) selection of suitable specimens; (2) inoculation of the specimens; (3) exposure of the specimens under conditions favorable to growth; (4) examination and rating for visual growth; and (5) removal, sterilization, and evaluation of
- specimens.
Sicnificance: Analogous to ASTM G21, the Standard states that the resin i portion of plastic materials is usually resittant to bacteria, in that it does I not serve as a carbon source for the growth of bacteria and that it is generally other components that are responsible for bacterial attack.
Apparatus: As in ASTM G21, the discussion of apparatus focuses on glassware .
anc incuoation equipment.
Reacents and Materials: The discussion of reagents and materials is similar to A5Th G21.
Test Specimens: The test specimen discussion is similar to that provided in A5TM G21. -
Procedure: There is considerable discussion of Procedure A and Procedure B in
( Ine 5tsndard. The 1983 Technical Position dcas not indicate which is l preferred.
l 1
LW STABILITY RPT A-10 1
~
. A6 BARTHA-PRAMER TEST .- 1 I
As noted in a BNL Report (Ref. A18) on biodegradation testing of low level waste streamr, the ASTM G21 and ASTM G22 tests "... are sufficient for distinguishing between materials that are susceptible to biode gradation and those that are net," but they""...Ascannot be used to quantify the rate of acknowledged by BNL in another Report (Ref.
biodegradation of a specimen.
A7), the G21 and G22 tests are primarily screening tests. It has been suggested (Raf. A19) that more realistic estimates of the nature and extent of microbial attack on materials can be provided by an environmental simulation test. The so-called Bartha-Pramer (Ref. A17) method is one such test. In this test, samples are placed in soil in a flask with a side-arm containing a potassium hydroxide (KOH) solution. The KOH solution absorbs carbon dioxide given off as a result of microbial respiration. Monitoring the carbon dioxide
- production with time thus provides a means of estimating the rate of biodegradation. A lengthy and comprehensive discussion and evaluation of the ,
Bartha-Pramer method, including its limitations and applicability to low-level radioactive waste stream . testing, are provided in Reference A7. Further discussion of the reasonableness of the criteria and test methods is provided in Reference A18. In view of the extensive treatment provided in the BHL Reports, only some particularly pertinent conclusions and recommendations are addressed in the following discussion.
Remarks: The NUMARC Report (Ref. A4) contains a recommendation that biode-gracation testing should be eliminated for cement, gypsum and polymer types of stabilization media and that more research should be perfomed on bitumen i for representative power plant waste stream compositions to determine their
( susceptibility to microbial growth. It is further recommended by NUMARC that a more realistic test procedure for biodegradation be identified and aCopted "...
at a later date." NUMARC concludes also that the G21 and G22 tests "... were not designed to evaluate the effects of strength of microbial growth on the structural strength of a material."
The basis for NUMARC's statement that "... applying the G21 and G22 tests to determine waste fcrm stability is unnecessary" appears to rest on a reported conversation with the Chairman of the ASTM Section Committee responsible for the G21 and G22 procedures. According to the NUMARC Report (p.4 55), he indicated that "... no micro-organism will grow in the presence of low-level gamma radiation fields (above background)...." This is a rather curious statement in view of the times required for self-sterilization of low-level waste packages. It can be shown from BNL work (Ref. A20) that it would take i only 1-2 years to acquire sufficient cumulative dose (approximately 10E+6 rads) to be lethal to microbes (assuming a waste form that is loaded to a Cesium-137 concentration of 10 Cf/cu.ft., which is the maximum recomended concentration for bead resin). However, that does not take into consideration the fact that the dose rate declines with time or that the radionuclide concentrations in
- .6ual waste forms will vary. Thus, at a point in time some years after disposal, and after the waste forms have been subjected to other long-term environmental effects, the dose rate could decline to a value such that bio-logical attack could be initiated.
With regard to the effects of the biodegradation test conditions on waste form specimens, NUMARC cites data that are purported to show that the test pro-I
( cedures "... have no effect on cement stabilized samples." NUMARC's data base, I
~
however, evidently did not include some proprietary data submitted by the cement media vendors in support of their topical reports. In one case involving cement-solidified bead resin, the post-biodegradation test com-pressive strength decreased approximately 85 percent from the pre-test value.
Changes of this magnitude cannot automatically be attributed solely to statistical variation in the ASTM C39 test procedur(, though NUMARC attempts to make such attributions in its Report. It seems rea1onable to conclude that, while cement as a medium would not support biological growth (since it is not itself a source of carbon), that is not to say that the waste material incorporated in a cement-solidified was A form would not support growth that could have an indirect effect on the mecnanical properties and stability of the waste form. Hence, the staff is not at this time ready to endorse the idea of deleting biodegradation testing for cement-solidified waste forms.
HUMARC's contention th x tne 321 and G22 tests were not designed to evaluate the effects of microbial grmth on the structural strength of a material is ,
also curious in view of thi Sact that, as noted in earlier discussion, the Standards specifically note tiat changes in properties, including mechanical ;
properties, may be determined by applicable ASTM methods. Whether it is always necessary to determine the compressive strength of a specimen after a G21 or G22 test is questicsable, howevar. The 1983 TP indicates that a compression tests should be p , formed aft 9r the G21 and G22 test, but if the tests do not result in growth, it is extrndy unlikely that there would be any observable effect on strength of the specia ns. Moreover, specimens suitable for bio-degradation testing are not necessarily of the size and shape most appropriate for compression testing. Therefore, it is the opinion of the staff that the procedures used in biedegradation testing and the type of acceptance criteria
( ,
that should'be used for the biodegradation tests are subjects worthy of further study. Several suggestions and comments on this matter are provided in the BNL Reports (Refs. M and A18) on biodegradation testing.
A7 IMMERSION Linkage between the immersion test recomendations in the 1983 "Technical Position on Waste Form Stability" (Ref. A1) and 10 CFR Part 61 (Ref. A2)
- requirements for waste form stability is provided by 10 CFR 61.56(b)(1), where it is stated that "... a structurally stable waste form will generally retain
- its physical dimensions and its form, under the expected disposal conditions such as the presence of moisture...." (emphasis added). There is no Standard Metnod of Test for imersion testing, but as indicated in the 1983 Technical Position, the imersion testing may be performed in conjunction with the leach testing. Inasmuch as both the leach testing, which is to be performed in ncordance with the procedure in ANS 16.1 (Ref. A21), and the imersion testing are recomenced to be performed for a minimum period of 90 days, there is an incentive to do the immersion and leach testing as one operation. The 1983 TP called for a minimum compressive strength value of 50 (now 60) psi, as deter-mined using ASTM C39 or ASTM D1074, af ter comp"letion of the imersion tests.
In a working draft of the' Regulatory Guide on Low Level Waste Form Stability" (Ref. A3), allowable reductions in strength of 20 percent were proposed, along
- with a recomendation that a technical rationale justifying the decrease in
- strength (and/or observed surface degradation) be provided by the applicant.
I I
A-12 E
. . a In an opinion expressed in the NUMARC Report (Ref. A4), "... the immersion test is by for the most severe of all tests...." Whether' that statement is in facy, accurate is perhaps debatable, but it is undeniably true that the immersion test has seived well in identifying potential problems with certain waste formulations. The NUMARC Report refers to a 1978 study that resulted in catastropnic failure of bituminized sodium sulfate waste specimens. Since that early L4L work (Ref. A22), bituminized waste formulations have been success-fully immersion-tested. However, in a more recent BNL study (Ref. A23) on stabilized cement and gypsum waste forms, problems were observed, in the form of a typical cement strength behavior with tine (along with cracking and spalling) and softening of gypsum-solidified waste forms. A brief summary of this more recent BNL work is provided in Reference A24.
The recent BNL work indicated that waste loading, i.e., concentration of waste material incorporated in the waste form, is a very important parameter affecting vaste form stability. As noted in the NUMARC Report, vendors try to maximize the wasi.e leading for their solidification medium to :.ake it econos-ically attractive in comparison to competitors' systems. The immersion test (and related leaching test) has proved to be an extremely useful indicator of potential problems with excessive loading, as indicated not unly by the BHL work, but also by vender generated data. Hence, the staff agrees with the conclusion reached by NUMARC that "... the immersion test is important for determining the compatibility of the stabilizing medium to certain specific waste streams, and for determining the maximum permissible waste loading fer a stabilization medium."
/ The staff also agrees with NUPARC's conclusion that the acceptance criteria
\ should be reassessed (for reasons that h.ve been addressed at length earlier in this Report). However, some of the specific recommendations provided by NUMARC in this regard appear to be unreasonable. For example, HUMARC recom-or a minimum post-mends that either compression a maximum strength test compressive loss of less than of 90 psi 20 (uppercent, from 6 Tpsi to account for variability in the procedure) be permitted. If such an approach were followed, it would allow a reduction in compressive strength of 90% or more to occur (from 5000 psi to 100 psi, for instance), while still categorizing the result r as an indication of "structural stability." In the opinion of the NRC staff, decreases in strength of such magnitude could not occur u.nless there were concomitant major changes in the structure of the waste form. Therefore, by definition, the waste form would have demonstrated instability that would
- r. ender it unacceptable. ,
A8 LEACH TESTING Resistance to leaching is not specifically mentioned in 10 CFR Part 61, nor is i radionuclide containment called out as a specific requirement for low-level waste packages. This is in contrast to the 300 to 1000 year "substantially complete containment" requirement for high level waste packages in NRC's regulation for geologic disposal of high level waste, 10 CFR Part 60 (Ref.
A25). As a result, this has' led some (Ref. A26) to question the rationale far i leach testing of solidified Classes B & C low-level waste forms. Though the -
relationship between the 1983 Technical Position recommendations for leach k
testing and the requirements of Part 61 may not be as obvious as is the
( - situation fer high-level waste containment, the discussion below is intended to provide some. clarification of this relationship.
As discussed in the main body of this Report (see "Concepts"), minimization of l the contact of waste by water is fundamental concern) of Part 61.
a fundamental As stated concern in 10 CFR(is, 61.7,in fact,
"... Tcornerstone 4
of the system is stability ...so that .. access of water to the waste can be minimized (emphasis added). Mi ration of racionuclides is thus minimized..." In addition, in Section 1.51 it is stated that" (a) covers must :
be designed to minimize to the extent practicable water infiltration, to direct !
percolating or surface water away from the disposed waste, and to resist degradation by surface geologic processes and biotic activity, (b) surface features must direct surface water drainage away from disposal units ...., and (c) the disposal site must be designed to minimize to the extent practicable the contact of water with waste during storage, the contact of standing water ,
with waste during di'sposal, and the contact of percolating or standing water with waste after disposal."
What is the underlying reason for this preoccupation concerning the potential contact of waste by water? Though not stated specifically anywhere in the regulation, it is clear that these statements are in recognition of the fact that contact of waste with water is the first step in a potentially major pathway for radionucifde release and migration off-site. Thus, leaching, or
- extraction, of radionuclides through contact of waste with water is the first step in subsequent migration of the radionuclides from the waste through the groundwater and off of the site. Therefore, though leaching is not mentioned
( explicitly in Part 61, it is a phenomenon that is of funcamental interest in low-level waste disposal. The relationship of leach testing, as called for in the the 1983 Technical Position, to Part 61, is thus rather straight-forward, when viewed in this context. Some further discussion of the details of the 4
leaching tests, analyses of the results, and ways the tests might be improved is provided below.
1 A8.1 ANSI /ANS 16.1: Heastrement of the t.eachability of Solidified low-1.evel i Radioactive wastes by a short-Term Test Procedure
! Scope: This standard (Ref. A21) provides a uniform procedure to measure and 1 incex the release of radionuclides from waste forms as a result of leaching in
( domineralized water for three months.
Sumary of Method: The ANS/ ANSI 16.1 leach test is a modification of an "!AEA
- i .leacn test" proposed by Hespe (Ref. A27). In the ANS/ ANSI 16.1 test, a test
' specimen is completely immersed in a measured volume of deionized water lea-chant, which is changed on a prescribed schedule. Upon removal, the leachant is analyzed for the radionuclides (or elements) of interest. The data obtained by the procedure are expressed as a material parameter of the leachability of .
l each leached species. This parameter is called the "Leachability Index" (L),
which is the arithmetic mean of the L values obtained for each leaching interval (where the L value is the logarithm of the inverse of the effective diffusivity). ,
k Specimens: Specimens are supposed to have a well-defined shape, mass, an
! volume. Cylinders are preferred.
l
1 _
Procedure: The Standard goes into considerable detail regarding procedures for rinsing and suspending specimens and removing leachate. Basically, the lea-chate is sampled, and the leachate is completely repl ".ef after cumulative leech times of 2,7, and 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> from the initiation -
Etest. Subsequent leachate sampling and leachate replacements are sat hour intervals for the next four days. Three additional leach interw 4, 28, and 43 days each extend the entire test to 90 days. t l
Remarks: As specified in the 1983 Technical Position, the leachib(11ty index, l as calculated in accordance with ANS/ ANSI 16.1, should be greater than 6. The i 1983 Technical Position alsu indicates that other leachants in addition to domineralized water should be used in the testing. The preferred leachant is listed as synthesized sea water. The draft Regulatory Guide (Ref. A3) also stated that certain radioactive tracers should be used (preferrably cobalt, cesium, and strontium) for proposed nuclear power station waste streams. As in early (circa 1982) versions of the draft ANS 16.1 Standard, the draft Regu-latory Guide addressed certain "discard criteria," which are not contained in the current (1986) version of che Standard.
In the NUMARC Report (Ref. A4), the leachability test and its basis are examined in considerable detail. NUMARC concludes that the ANS/ ANSI 16.1 procedure is "... a reasonable indicator of waste form leachability," although a 5-day test is preferred over the 90-day test and sea water is a preferred leachant over dominera11 red water. NUMARC contends that its study confims the assumptions and supporting theory, as well as the intended application of the Standard. NWARC also indicates that an applicable technical basis to support
( the acceptance criterion of a leachability index of greater than 6 could not be founo, but concludes that the criterion is reasonabie, based on, in part, "... ,
the demonstrated ability of the criterion to eliminate poor waste forms."
The NRC staff agrees with some of the observations made by NUMARC, in '
particular with respect to the need to clarify whether confidence ranges and correlation coefficients should be Reported, whether 1 or 2 leachants should be ;
used, whether the dicard criteria should be implemented, etc. These are matters that can and should be addressed as part of any continuing study on waste form testing and criteria. As to the recomendation that 5 day leach testing is sufficient, or whether 90-day tests should be performed, the staff currently believes that the 90 day tests should be retained (at least for the !
i present). NW. ARC's contention that 5-day tests are all that is needed apr ears to be founded on the belief that any changes in leach mechanism would be detected early and that changes during the latter stages of the test geners :1y have little, if any, impact on the test results. As indicated in Appendix E of the Standard however several researchers have observed that some low-level waste foms fespecia1}y wastes incorporated in cement or asahalt) can undergo a dramatic increase in leachability after a few weeks or sentis. Therefore, if 4
term stability, it the is the staff s curent opinion that the period of test shou continue to be 90 leaching' test is to be retained as an indicator of longld days.
Basic uestions remain: what does leach testing (as apart from immersion testin ) have to do with long term stability, and what is tha significance of '
or rat onale for the "leach index greater than 6" acceptance criterion? A
( major part of the answer to these questions is provided in a Dames and Moore Report (Ref. A28) that deals with a sensitivity analysis of the effects of 1.LW STA81LITY RPT A-15 .
1" _ _ _ . _ , - - _ _
l varying (a) waste stream leaching characteristics, (b) alternative disposal site environmental characteristics, (c) alternative disposal site design characteristics, and (d) operating practices on resulting potential human . l exposures dus to groundwater migration. The results of the analysis indicated I that reducing the leaching potential of the waste streams suitable for i solidification reduces the calculated exposures due to groundwater migration. l However, the relationship between the leaching potential of these solidified i waste streams and the calculated exposures, appeared to be approximately asyeptotic rather than linear. Thus, as the leaching potential of the waste streams was reduced, a point was rapidly reached in which further reductions in j the leaching potential had little effect on the calculated impacts. The authors concluded that there appeared to be "... no need to establish an extremely rigorous leach criteria (sic) on waste streams suitable for solidifi-cation to assure safe disposal of low-level waste. A leach criteria (sic) which can be met by existing state-of-the-art solidification products.... would appear to be acceptabl.e provided that the product is structurally stable (emphasis added); such a criteria woulo really only neeo to exclude extremely poor quality solidification binders from use. Experimental evidence has indicated that binders exhibiting poor structural stability have also tended to exhibit poor leaching performance."
The results of the Dames and Moore study and the conclusions quoted above thus formed the basis for the leachin PositiononWasteFormStablity.grecommendationsinthe"1983 Technical A leach index of "greater than 6" was selected as the acceptance criterion because it was believed to be readily achievable by solidification agents such as cement, bitumen, vinyt aster styrene and synthetic polymers, even though leach indexes of such magnitude are I considered to be roughly equivalent to "free ions in water." Thus, based on
\ the results of the Dames and Moore study (and the input assumptions used in the study) the leach index value has no critical relationship to 10 CFR Part 61, and the ability of the disposal facility to meet the part 61 off-site dose cri eria. However, the greater than 6 leach index acceptance criterion, whild readily achievable by "good" (i.e., "structurally stable") solidification agents, is high enough to have eliminated media such as urea formaldehyde and some gypsum-solidified waste streams. Therefore, the staff believes that the current leach index acceptance criterion has served reasonably well to separate poor solidification agents from acceptable ones.
The fundamental relationship between leach resistance and structural stability is still rather poorly defined, however. At best, it appears that resistance to leaching of Cesium-137, Strontium-85, or Cobalt-60 has only an indirect correlation to long term structural stability in the sense that waste forms that have very low leach indexes may have large open porosity or fairly soluble matrix phases that would eventually lead to breakdown of the waste forms if contacted by sufficient quantities of water. Therefore, in the opinion of staff, it may be possible to improve the leach test by modifying it to include the measurement of leach indexes for the solidification agent materials as well as, or even instead of, the radionuclides currently measured. Such an approach would provide more direct indication of the relative stability of the ,
solidification medium than does the current method. It might, however, be more difficult to perform such tests since it would probably require more chemical analyses, and it would be even more difficult to develop an acceptance f criterion that would be generically applicable. This is another area that would benefit from further study.
j \
LW STABILITY RPT A 16
A9 REFERENCES ;
( A1. U.S. NRC, "Technical Position on Waste Fors," Rev. 0, May 1983. ,
A2. U.S. NRC 10 CFR Part 61 "Licensing Requirements for Land Disposal of .
Radioactive Waste," Final Rule, 47 FR 57473, December 27, 1982. ,
1 A3. U.S. NRC, Draf t Regulatory Guide, "Low-Level Waste Form Stability," October 1986.
and P. T. Tutte, "A Technical Basis for A4.W. Chang,L.Skoski,R.EngIlityRequirementsof10CFR61,"Nuclear Meeting the Wasta Form Stab Management and Resources Council Inc. Report, NUMARC/NESP-002, April 1988.
A5. American Society for Testing and Materials Compressive Strenoth of I Cylindrical concrete Specimens, ASTM C39, Octoser 1984.
A6. American Society for Testing and Materials, Compressive Strenoth of Bituminous Mixtures ASTM 01074, ASTM 01074, Fearuary 1983.
A7. B.S. Bowerman, et al., "An Evaluation of the Stability Tests Recommended in the Branch Technical Position on Waste Forms and container Materials,"
Brookhaven National Laboratory Report, NUREG/CR-3289 (BNL-NUREG-51784),
March 1985.
. A8. R.E. Davis and E.P. Gause, "Development of Low-Level iaste Form Criteria Testing of Low Level Vaste forms," Brookhaven National Laboratory Report,
( ,
NUREG/CR-2813 (BNL-NUREG-51556), November.1983.
! A9. American Society for Testing and Materials, Compressive Procerties or Riaid Cellular Plastics, ASTM D1621, 1979.
l A10. . American Society for Testing and Materials, Oeformation of Plastics under Load, ASTM 0621, 1976. -
All. American Society for Testing and Materials, Thernd L'yclina of Electroplated Ceramics, ASTM B553, 1979. ,
A12. 0.R. MacKenzie, M. Lin, and R.E. Barletta, "Permissible Radionuclide
. Leading for Organic Ion Exchange Resins from Nuclear Power Plants,"
Brookhaven National Laboratory draft Report, BNL-NUREG-30668, January 1982.
.! A13. K.J. $wyler, C.J. Dodge, and R. Dayal, "Irradiation Effects on the Storage and Disposal of Radwaste Containing Organic Ion-Exchange Media,"
Brookhaven National Laboratory Report, NUREG/CR 3383 (BNL-NUREG 51691), '
October 1983. ,
i A14. .T.J. Johnson, Persoral Communication, April 26, 1988.
A15.
Materials, ;D Americ'anSocietyforTestinystoFunai,ASTMG21,1970.and Synthetic Polymeric Materia ,
I 1
,um.,--.. - . - , _-_.m_--~-~_ .- -. .. -.__._,_
I ~.
1 I
-A9 REFERENCES, Cont.
A16. American Society for Testin and Materials, 0'eterminino Resistance of Plasttes to Bacteria, ASTM 22, 1976.
A17. R. Bartha and 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.
A18. P.L. Piciulo, C.E. Shea, and R.E. Barletta, "Biodegradation Testing of Solidified low-Level Waste Streams," Brookhaven National Laboratory Report, NUREG/CR-4200 (BNL-NUREG-51868), May 1985. i A19. P. A. Gilbert and C. M. Lee, "Biedegradation Tests: Use and Value," in Biotransformation and Fate of Chemicals in the Aquatic Environment, Eds.
et al. American Society for Microbiology, Washington, DC A. W. pp.
(1980) Maki, 3 N, A20. C. R. Kempf, B. Siskind, R. E. Barletta, and D. R. Dougherty. "Character-ization of Radioactive Waste Packages of the Minnesota Mining and t Manufacturing Coapany," NUREG/CR-3844, July 1988.
A21. American Nuclear Society, Measurement of the Leachability of Solidified low-level Radioactive Wastes by a Snort-Term Test Proceoure, ANS 16.1, 1986. ,
A22. Brookhaven National Laboratory, Properties of Radioactive Wastes and
( Waste Containeas, Broekhaven Naticnal Laboratory Progress Report No. 7, May 1978.
A23. P. L. Piciulo, J. W. Adams, J. H. Clinton, and B. Siskind, "The Effect of Cure Conditions on the Stability of Cement Waste Forms af ter Immersior.
in Water," Brookhaven National Laboratory Report, W-31714, August 1987.
A24. Thomas L. Jungling, Keith K. McDaniel, LeRoy S. Person, and Hichael Tokar, "Status of NRC's Waste Form Regulatory Guide," presented at the Ninth Annual 00E Low-Level Radioactive Waste Management Conference, Denver, CO, August 27, 1987.
A25. US NRC,10 CFR Part 60, "Disposal of High Level Radioactive Wastes in Geologic Repositories."
A26. William Kerr, Letter to NRC Chairman, Lando W. Zech, Jr. , November 10,
. 1988.
A27. E.D. Hespe, "Leach Testing of Immobilized Radioactive Waste Solids, A Proposal for a Standard Method," International Atomic Energy Agency, Atomic Eneray Review, (9) (1), 195 207 (1971).
A '.3. O. I. 0ztunali, C. J. Pitt, and J. P. Furfaro, "Influence of Leach Rate and Other Parameters on Groundwater Migration " Dames and Moore Report, -
NUREG/CR-3130, February 1983. ,
- i
~
Table Al -
. Topical Report Review Status Summary Solidified Waste Form and High Integrity Containers (HICs)
Hay 30, 1988 Vender Docket No. Type Dispo:itten Waste Chem W-90 Solidification (bitumen) Approved.
General Electric W-88 Solidification (polymer) Approved.
U.S. Gypsum W-51 Solidification (gypsum) Approved *.
Chichibu W-81 HIC (poly impreg/ concrete) Approved.
Nuclear Packaging W-45 HIC (ferralium/FL-50) Approved.
Nuclear Packaging W-85 Approved.
DOW W-82 HIC (ferralium/fanily)
Solidification (polymer ) Approved **.
ATI W-91 Solidification (bitumen) Discontinued.
VIKEN W-13 Solidification / oil (coment) Discontinued.
Nuclear Packaging W-71 Solid /Encap (coment/ gypsum) Withdrave..
LN Technologies W-57 HIC (polyethylene) Withdrawn.
( Chem-Nuclear W-47 HIC (fiberglass / poly) Withdrawn.
Chem-Nuclear W-19 Solidification (cement) Under review.
Chem-Nuclear TBD Solidification (eement/26) Under review.
U4 Technologies W-20 Sc11dification(cement) Under review.
Hittran W-46 Solidification (cement) Under review.
Stock W-92 Solidification (cement) Under review.
Hittman W-79 Solidification (cement) Under review.
Chem-Nuclear W-18 HIC (polyethylene) . Under review.
Hittman WH-80 HIC (polyethylene) Under review.
TFC W-76 HIC (polyethylene) Under review.
Nuclear Packaging W-83 HIC (316-stainless) Under review.
LN Technologies W-93 HIC (fiberglass / poly) Under review.
Bondico W-94 HIC (fiberglass / poly) Under review.
Babcock & Wilcox TBD HIC (coated carbon steel) Under review.
i
- Approved for single wast's stream for one year.
- Approved pending satisfactory completion of thermal cycling tests. ,
k -
- A19 -
I e
9 n
e .
Table A2
. Topical Report Review Status 5ummary for .
Waste Solidification System And Process Control Program by Plant Systems Branch 0ffice of Nuclear Reactor Regu1 Mion Vendor Report No. Type Disposition Areojet AECC-1 Fluid Bed Dryer Approved Hittman HH-R1109 Cement Approved Werr.er&pfleiderer WpC-VRS-1 Bitumen /.pproved Polymer Approved
( DCW DNS-RSS-001 Atcor ATC-132 Cement Approved i
Newport llews RWR-1 Fluidized Bed Approved Calcinaticn Chem-Fuclear 4313-01354 Cement Approved JGC JGC-TR-001 Bitumen Approved i
Aerojet AECC-2 Fluidized Bed Approved l Calcination derojet AECC-4 Incineration Approved l ATI ATI-VR-001 Bitumen Approved NUS PS-53-0378 Cement Approved Chen-Nuclear CNSI-0W 11118 Dewatering Appreved l Atcor ATC 8019-1 Coment Approved
- A20 -
i l
l.
Table A2 (Continued)
Vendor ,
Report No. Type Disposition Nuclear Packaging TP-02 Dewatering Approved .
GE NEDE-30878 Azteck Approved Kock KPS-1 Incineration Approved Aerojet AECC-3 Fluidized 8ed Appe,<ed Calcination UNC UNC-5-8000 Cement Approved Bartlett BN-1 Cement Approved Westinghouse / STD-R-05-011 Dewatering Approved Hittma, Stock SRS-003 Dewatering Approved Chem Nuclear R05-25506-1 Dewatering Urder Review
( Duratek 0-EVR/HED-1 Dewatering Under Review Nuclear Packaging TP-03 011/ Cement Under Review Nuclear Packaging TP-04 Cement / portable Under Review Nuclear Packaging TP-06 Encapsulation / Under fieview Cement Nuclear Packaging TP-01 Cement Withdrawn Nuclear Packaging TP-05 Cement Withdrawn
. Stock SRS-001 Cement Withdrawn e
. u.t .
Table A3 Certificates of Comp 11anc's State of South Carolina 4/27/88 HIC Certificates of Como'11ance issued to issued what: Issued when:
Adwin Equipment Company 55 gallon HIC 5/29/84 Chem-Nuclear HOPE HICs (x 14) 5/28/81 Chem-Nuclear .
FRP HIC 2/23/82 Chem-Nuclear . Overpack HICs (x3) 4/8/83 Philadelphia Electric Comp. PECO-HIC-1 0/28/81 Hittman Radiok-55 HIC 6/17/82 Hittman Radiok-100 HIC 6/17/82 Hittman Radiok-200 HIC 5/5/33 Hittman Radlok-500 HIC 9/31/65 LH Technologies Barrier-55 HIC 9/1/33 TFC NUHIC-120 HIC 31/1/83 KPAC HDPE 142 HIC 8/20/84 NUPAC FL-50 HIC 9/26/83 Chichibu Concrete HICs (x2) 8/12/'36 HOPI HIC 10/10/83
( ,
Vermont Yankee Aer?oved Stabilization Media
- Vinyl Est'er Styrene Cement Bitumen
- Processes shall meet and have been evaluated in accordance with the NRC "Technical Position on Waste Form" or other evaluation criteria specif-
,1ca11y approved by the NRC, Cther solidification media shall be accept-able for which a topical Report has been prepared and received approval from the NRC and State. .
9 9
9 g
- A22 -
O
'2
- t Table A3 (Continued) ,
Certificates of Compliance
- a. >
State of Washington 4/27/88 HIC Certificates Of Compliance issued to: Issued what: Issued when:
Chichibu Concrete HICs (x2) 9/29/86 NUPAC FL-50 HIC 4/4/86 US Ecology NUPAC 505 HIC 3/23/84 Approved Stabilization Media
- f Aztech (General Electric)
Bitumen (oxidized ATI and Waste Chem)
Chem-Nuclear Cement Dow Media (Vinyl Ester Styrene)
Envirostone (U.S. Gypsum Censnt)
Westinghouse Hittman Cement ,
( LN Technologies Cement Stock Equipent Cement ,
\
l 4
t h
80n1 those stabilization media which have been evaluated or are in the process of b ing evaluated and are used with the stability guidance requirements of the NRC "Technical Position on Waste Form" or are specifically approved by the Depart-ment are considered acceptable stabilization media. Other stabilization media and
- processes may be approved which have been reviewed and approved by the NRC and/or the Department as meeting waste form str.bility criteria. . -
. ( .
-n3- i i
4
'..i_ . - . _ , . , - , - , - - _ _ - , - - . . . _ . . - , . - , . , . _ _ _ _ - _ _ _ , , , . . - - _ _ _ - _ _ . _ . _ - . . - _ , . _ _ - _ _ , _ _ , _ , , . - . . - ,
![' he, NUCLEAR REGULATORY COMMISSION UNITED STATES
,{.g ,</
., ACVISORY COMMITTEE ON NUCLEAR WASTE W ASHINoToN, D.C. 20066 o o ...
. September 1,1988 .
l MEMORANDUM FOR: ACNW Members
. (.
FROM: 5. J. 5. Parry, ACNW Senior Staff Engineer . )q,jz 4.q
SUBJECT:
REPORT TO NMSS DIRECTOR ON LLW STABILITY John Suimeier of NMSS has provided the attached resort in preparation for +he presentation by Dr. Tokar on September 13th. The >asic recomendations focus '
on the creation of a "task force" to ascertain the need for more appropriate LLW for:n criteria and tests. The question of the dual licensing procedure ;
used by NRR and NMSS is addressed. A definitive position on the suitability of cement-based LLW is not reached. Nor does the staff consider exposure risk to the public or tha site operators as a determinant.
On January 28, 1988, I sub.nitted a survey reprt on LLW solidification
( processes and HICs. Subsequently, April 16, 1988, draft recomendations were provided. A copy of those recomendations is provided for reference. l 1
l Attachments:
As stated l cc: M.' Carter D. Orth i
. P. Shewmon i R. Fraley i M. Libarkin R. Savio R. Major i S. Merrill I .
I( !
1
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