ML20151B023
| ML20151B023 | |
| Person / Time | |
|---|---|
| Issue date: | 03/18/1988 |
| From: | Ballard R NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Surmeier J NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| References | |
| REF-WM-82 NUDOCS 8804080016 | |
| Download: ML20151B023 (28) | |
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MAR 181988 CHP/WM-82 MEMO TER MEMORANDUM FOR: John J. Surmeier, Chief Technical Branch Division of Low-level Waste Management and Decomissioning FROM: Ronald L. Ballard, Chief Technical Review Branch Division of High-Level Waste Management
SUBJECT:
Technical Evaluation Report for the Dow Chemical Company Topical Report, DNS-RSS-200-NP The attached document is a Technical Evaluation Report (TER) for the Topical Report (TR) entitled "The Dow Waste Solidification Process for Radioactive Wastes-Generic Waste Fonn Certification Results". The process itself and the associated Process Control Program were approved by the Office of Nuclear Reactor Regulation in 1980.
Laboratory-scale waste forms made from seven generic waste types were found to satisfy most of requirements of 10 CFR Part 61 and the recommendations of the Technical Position on Waste Form. However, full approval cannot be given at this time to the 55-gallon size waste form because further work by Dow is needed on the thermal cycling tests. Also, approval of the filter aid sludge waste type should be withheld pending development of an NRC position on an acceptable degree of surface cracking or other surface deterioration of test specimens. In addition, certain minor editorial changes should be made in the text of the TR. Waste forms larger than 55-gallons cannot be approved for lack of data on correlation of properties with laboratory scale tests.
The original nonproprietary version of the TR was submitted to other Offices and Divisions within the NRC for review and comment. The names of the organizational units used here were those in effect at the time of submittal.
The Division of Fuel Cycle and Material Safety (now the Division of Industrial and Medical Nuclear Safety) concluded that a review by them was not needed inasmuch as neither methods to protect solidification workers nor description of the transport package were covered. The waste forms also could not be considered as special form radioactive material as defined in 10 CFR 71.4 The Safeguards and Materials Programs Branch of the Division of Quality Assurance, Safeguards, and Inspection Programs, IE, had no specific coments.
The Waste Management Branch of the Division of Radiation Programs and Earth l
i Sciences (now the Division of Engineering), RES, had eleven comments. These have been discussed with Dow. The Meteorology and Effluent Treatment Branch of i the Division of Systems Integration, NRR, offered three comnents which have l also been discused with Dow. However, NRR should reexamir,e their pre tious
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CHP/WM-82 MEM0 TER' 2-approval of the Topical Report and Process Control Plan because the concen-trations of PWR and BWR wastes are greater than approved earlier.
The evaluation in the TER represents a logical point for turnover of responsibility for this TR to your Branch. Accordingly, with this memo, we are completing the direct work by our Branch on it, but wi'1 continue to be available on a consulting basis if needed. If you have any questions, please +
call me on x23455, or Chuck Peterson on x20531. l t
Ronald L. Ballard, Chief '
Technical Review Branch Division of HIgh-level Waste Management ;
Enclosure:
As noted i
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CHP/WM-82 MEM0 TER BR 18 28 3-0FFICIAL CONCURRENCE AND DISTRIBUTION RECORD MEMORANDUM FOR: John-J. Surmeier, Chief Technical Branch Division of low-Level Waste Management and Decomissioning FROM: Ronald L. Ballard, Chief
. Technical Review Branch Division of High-Level Waste Management
SUBJECT:
Technical Evaluation Report for the Dow Chemical Company Topical Report, DNS-RSS-200-NP DATE:
MAR 181988 i
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TECHNICAL EVALUATION REPORT FOR WASTE FORMS FR0M THE DOW WASTE SOLIDIFICATION PROCESS.
Introduction Low-level radioactive waste shipped to near-surface disposal facilities must meet the requirements of 10 CFR Part 61 (Ref. 1) which provides in particular that:
- 1. The waste must be classified as per Section 51.55.
- 2. The waste form must meet minimum requirements of Section 61.56(a).
- 3. Stability, where required, must satisfy Section 61.56(b).
Guidance to waste processors for meeting the stability requirements for Class B and Class C wastes is provided by the Technical Position on Waste Form (TPWF)
(Ref. 2). The objectives of the waste fonn and disposal site requirements are:
- 1. Protection of the general population from release of radioactivity
- 2. Protection of individuals during inadvertent intrusion
- 3. Protection of individuals during operation
- 4. Stability of the site after closure.
Waste stabilization may be achieved through solidification systems. Vendors of such systems and services have prepared topical reports to facilitate demonstration of stability. These reports contain test data for specific solidified wastes qualifying these products for near-surface land disposal.
The reports may be referenced by waste generators, processors, and shippers to demonstrate compliance with 10 CFR Part 61 waste form regulations in applying for licenses for their activities.
This Technical Evaluation Report (TER) is a detailed evaluation of the waste form qualification test data provided by the Dow Chemical Company (Dow) in their Topical Report (TR) for their polymer solidification system (Ref. 3).
The evaluation was performed to determine if the products of the system would meet the regulatory requirements of 10 CFR Ptrt 61 and those of the States of South Carolina and Washington.
Description of Topical Report The Dow System is a batch process for converting aqueous low-level radioactive wastes into stable monolithic waste forms suitable for land disposal. The process itself is described in a previous TR (Ref. 4) that was approved by NRR in 1980 (Ref. 5). A Process Control Program (PCP) as described in Section 7.0, Quality Assurance Program (QAP), of this TR was also approved. The System has been in commercial operation for over seven years.
A n, CHP/WM-82 DOW TER WF In the Dow System, a preset quantity of waste is transferred from a metering tank to a carbon steel drum containing a predetermined quantity of binder.
Through mechanical mixing, a stsble water-in-oil emulsion is produced to which catalyst and promoter are added sequentially. After polymerization is complete, the drum is sealed and inspected for radiation level and external contamination. If satisfactory, the drum is set aside for storage pending shipment to a disposal site.
The TR contains descriptions of the process, the process control factors, sample preparation procedures, test nethods, test results and a section on scale-up testing.
Data are presented on the following seven types of wastes, which were tested as non-radioactive solutions or slurries simulatina typical nuclear power plant low-level wastes:
- 2. PWR Concentrates Mainly a boric acid solution
- 3. Ion Exchange Bead Resin Slurry Dowex MR-7 4 Filter Aid Sludge Celite 545
- 5. Powdered Ion Exchange Resin Slurry Epicor cation / anion mixture
- 6. Decontamination Waste Dow NS-1
- 7. Volume Reduced Dry Salts Sodium sulfate + ash fines.
Maximum permissible loadings are shown in Table A later in this TER. Test specimens produced from these materials were used for all qualification tests except the leach tests. For these, Cs-137 and Co-60 tracer solutions were added to the first four of the above materials. For the fifth material, an actual powdered resin filter sludge from an operating nuclear povier plant was used. For decon waste, the proprietary NS-1 formulation was used in a laboratory decontamination of radioactive nuclear power plant pipe sections.
For the seventh waste, non-radioactive lithium was used as a tracer.
Evaluation Procedu_re A non-proprietary version of the TR was received June 29, 1984 and accepted by the NRC for full staff review. The TR and NRC Staff corrents were sent for review and comment tn the States of South Carolina and Washington. These states have regulatory responsibility over the low-level viste disposal sites at Barnwell, SC and Hanford, WA, respectively.
Staff comments (Ref. 6) were returned to Dow on March 5,1985 for information only pending receipt of corrents fron the Agreement States. Both South Carolina and Washington indicated concurrence with NRC comments by Avaust 1985.
The State comments were transmitted to Dow on September 11, 1985. NRC procedures were later revised to permit the NRC approval process to proceed independently of the State reviews,
CHP/WM-82 DOW TER WF On November 6,1985, Dow was also apprised of an NRC concern regarding the fungal tests that arose from work at INEL by EG8G (Ref. 7). Dow responded fonnally to the NRC coments on January 10, 1986, designating these as Amendment 01 (Ref. 8). Included was a response to the NRC concerns regarding the fungal tests. On June 17, 1986, NRC coninents on Amendment 01 were sent to Dow (Ref. 9). Most of these were editorial in nature and were resolved through discussions with Dow. On October 10, 1986, Dow submitted formal responses to four remaining technical questions while continuing to work on agreed upon editorial revisions (Ref. 10). A revision of the TR was released on November 26, 1986 (Ref. 11).
Meanwhile, EGAG had continued their work on the potential for biological attack on vinyl ester styrene resins and released an informal report in March 1987 (Ref. 12). After a review of the available data, Staff recommended performance of certain additional biodegradation tests (Ref. 13) which Dow carried out (Ref. 14). Details are given later in this TER.
Evaluation The information presented in the TR and other Dow documents as noted above provides the basis for the individual evaluations which follow.
- 1. Minimum Requirements of 10 CFR Section 61.56(a)
- a. Section 61.56 (a)(1): Packing i
The waste forms are contained in steel drums or liners and thus satisfy the requirements of this section.
- b. Section 61.56 (a)(2): Liquid waste Water in aqueous wastes is completely incorporated in the solidified waste in normal operations. This satisfies the requirement of no more than 1 percent by volume of free standing liquid. -
- c. Section 61.56 (a)(3): Free liquids .
Water content of the feed is controlled by sampling prior to solid- !
ification of the wastes. Each drum of product is checked visually for free standing liquid. No free standina liquid remains after solidification. The 0AP also pr0vides corrective measures to be used in the event of failure of the batch to solidify.
- d. Section 61.56 (a)(4): Reactivity of the product After solidification, the waste forms produced from materials simulating normal pcwer plant wastes do not contain any substances :
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CHP/kN-82 D0W TER WF capable of explosive decomposition or reactions at normal pressure and tqeratures. Actual wastes with compositions represented by the simulated wastes therefore satisfy the reactivity requirements.
- e. Section 61.56(a)(5): Gas generation The waste forms do not contain or appear to be capable of generating under expected conditions of production, storage, transportation and disposal quantities of toxic gases, vapors or fumes that are harmful to persons handling, transporting, or disposing of the waste form.
Some gas generation is expected through radiolytic decomposition of resins, water, and possibly unreacted feed materials. Concerns include: development of disruptive pressures within the waste forms, overpressurization of the waste form container, and possible release of radioactive or hazardous materials to the environment. These are treated in the followino sections.
(1) Estimates of Volume of Gases Generated Brookhaven (Ref.15) reported that radiolysis of asphalt and cerent by Co-60 to a cumulative dose of 100 Mrd produced about I cm3 (25*C) of gas /q of cement and 0.7 cm8/g of asphalt. The cas evolved was about 67% hydrogen for the cement samples and nearly 100% for the asphalt samples. Log-log plots of cas release vs cumulative exposure were linear for cement to 1 Grd. For asphalt, the plots were linear to 100 Mrd, thereafter showing an accelerating release to 1 Grd.
Linearity means the gas generation is of the form: .
a Q=cD, where Q is the cm3 of gas generated /a of material irradiated D is the accumulated exposure dose in rads and c and a are constants.
Dividing through by D yields: L a
0/D = ca D -1 ,
The quantity 0/0 is related to the G value, which is the total number of gas molecules produced per 100 eV. The value of the constant a appears to be about 1 or less, at least to 100 Mrd. !
However, the decade from 10 to 100 Mrd is only 90 Mrd, whereas that j from 100 to 1000 Mrd is 900 Mrd. Hence, the quantity 0/0 and, correspondingly, the G-values are expected to decrease with
! continuing exposure, althouah the total quantity of aas generated continues to increase.
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CHP/WM-82 DOW TER WF Brookhaven also observed that, for loadings in the rance 0.01 to 100 Ci/ft3 for BWR and PWR wastes, about 50% of the cumulative dose was generated in the first 10 years.
In a later work (Ref. 16), BNL reported that work done at the Georgia Institute of Technology in 1980 appeared to show a threshold dosage of 50-80 Mrd before significant pressurization could be observed for Dow cation and anion resins in sealed capsules. In the BNL work cited above (Ref. 15), gas releases were indicated at the level of 0.001 cm3/9 at 0.1 Mrd. Thus, any threshold effect would be for exposures less than 0.1 Mrd and would therefore be unimportant.
(2) Estimates of Potential Overpressures Using a reference level of I cm3/g, a 55-gallon waste form might generate about 200 L of gas, assuming the maximum exposure of 100 Mrd. If half of this was generated in 10 years, and the drums ,
were filled to 90% with solidified waste, the pressure in the void space could increase by a factor of 5. On the other hand, an average diffusion / leakage rate of about 1.2 cm3/h would be sufficient to avert a pressure buildup within the drums.
In Ref. 15, BNL also reported that Dow waste forms exposed for 70 days to ambient air at 72*F and 57% relative humidity lost 18, 28, and 42% of their weight for water / binder volume ratios of 1.0,1.5, ,
and 2.0, respectively. Also, the curves showino weight loss had not leveled out at 70 days. The material lost was presumed to be water.
Dow notes in the latest version of the TR (Ref. 11) that in the proprietary version (Ref 4) heating PWR waste forms at 1000*F for 56 minutes resulted in a loss of 31 weight %, but no radioactive Cs-137 or Co-60 losses were detected.
Thus, there is evidence that any gas aenerated within the waste forms can readily migrate cut of the waste forms without taking radionuclides like Cs-137 or Co-60 with it. With respect to overpressurization of the drum or liner, after burial this is not a concern because no credit for contairment is being taken for the container. In the event of extended storage of drums and liners above grade for up to five years, significant overpressure of the containers is not expected since the amount of cas generated is sufficiently small. However, it is expected that stored wastes will be inspected periodically for evidence of overpressure and corrective action taken if needed.
These considerations indicate there is no problem with radiolytic gas generation for the Ocw waste forms, provided the loading is l
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CHP/WM-82 D0W TER WF limited, as recommended in the Technical Position on Waste Form (Ref. 2), to 10 Ci/ft3 and the waste classification is Class C or less.
- f. Section 61.56 (a)(6): Pyrophoricity The waste forms do not contain materials which are pyrophoric as defined in 10 CFR Section 61.2.
- g. Section 61.56(a)(7): Gaseous wastes This provision is not applicable to the Dow waste form.
- h. Section 61.56(a)(8): Hazardous wastes Under the Resource Conservation and Recovery Act (RCPA), the U.S.
Environmental Protection Agency (EPA), (Ref. 17), has jurisdiction over the manecement of solid hazardous wastes with the exception of source, byproduct, and special nuclear material, which are regulated by the NRC under the Atcaic Energy Act (AEA). Low-level radioactive wastes (LLW) contain source, byproduct, or special nuclear materials, but they may also contain chemical constituents which are hazardous under EPA regulations promulgated under Subtitle C of RCRA. Such wastes are commonly referred to as Mixed low-level Radioactive and Hazardous Waste (Mixed Waste).
Applicable NRC regulations control the byproduct, source, and special nuclear material components of the Mixed LLW (10 CFR Parts 30, 40, 61, and 70); EPA regulations control the hazardous component of the Mixed LLW (40 CFR Parts 260-266, 268 and 270). Thus, all of the individual constituents of Mixed LLW are subject to either NRC or EPA regulations. However, when the components are combined to become Mixed LLW, neither agency has exclusive jurisdiction under current Federal law. This has resulted in dual regulation of Mixed LLW where NRC regulates the radioactive component and EPA regulates the hazardous component of the same waste.
Under Section 10 CFR 61.56(a)(8) waste containino hazardous, biological, pathogenic, or infecticus material must be treated to reduce to the maximum extent practicable the potential hazard from the non-radiological materials. The waste forms consisting of the Dow solidification agents plus the waste stream materials listed in Table B of this TER do not contain biological, pathogenic or infectious material, and thus satisfy these requirements of 10 CFR Part 61.
4" d, CHP/WM-82 DOW TER WF It should be noted, however, that the NRC review of the Dow TR did not address any applicable EPA requirements relating to hazardous solid waste for which the vendor or waste cenerator using the Dow Process may be legally responsible under RCRA. The available evidence indicates that small amounts of unreacted materials may be present in the Dow waste forms that may be able to migrate out of the waste forms. This becomes a question of whether mixed wastes are involved, a question that should be referred to the Environmental Protection Agency, which has ,iurisdiction in this matter.
- 2. Stability Requirements of 10 CFR Section 61.56(b)
- a. Section 61.56(b)(1): Structural stability ,
The waste form must exhibit structural stability under expected disposal conditions. Structural stability means that the waste form must generally maintain its physical dimensions and its form.
Expected disposal conditions include the weight of overburden and compaction equipment, the presence of moisture and microbial activity, and internal factors such as radiation effects and chemical changes. The Dow products will be contained in steel drums but no credit will be taken for the containers. Specific evaluations are presented below under Recorrnended Tests of the TPWF.
- b. Section 61.56(b)(2): Free liquids Water content of the feed wastes is controlled before solidification and all residual water is found to be completely incorporated or encapsulated by the process. The requirement that free liquids be no more than 0.5 volume percent of the waste is satisfied. No free liquids were observed in the qualification testino,
- c. Section 61.56(b)(3): Void spaces Drums containing the waste forms will be filled to about 90% of capacity while the waste form is still fluid. After thorough mixing, solidification is then initiated. Void spaces within the waste and between the waste and the container are, therefore, reduced to the extent practicable. The solidification reactions are familiar polymerization reactions and do not involve formation of gaseous byproducts which might create gas-filled voids within the solidified j waste form.
- 3. Recommended Tests in the TPWF Laboratory scale test specimens were ganerally 4.75 cm diameter x 7.3 cm l
long cylinders prepared by transferring waste mix from one-gallon l
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CHP/WM-82 DOW TER WF
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containers into plastic molds. For the leach tests, the specimens were generally 1.2 cm diameter x 5.0 cm long. In the case of decon waste and ash waste, the specimens were 4.8 cm x 7.3 cm; for the powdered sludge waste, they were 6.0 cm by 6.0 cm.
Volume ratios of simulated waste to binder were 1.5/1.0 for all wastes except powdered ion exchange sludge and volume reduced dry salt and ash, for which the ratios were 2.0/1.0.
For leach tests, loading of radioactive tracers was generally about 8 uCi/g for each isotope. The loading in the head resin was about 15 uCi/g.
- a. Initial Compressive strength The compression test used was ASTM C 39 as recomended in the TPWF.
Specimens tested were aged for 70 to 120 days so that they could also serve as controls for the imersion tests.
The 1983 TPWF recommends that as a minimun the compressive strength be 50 psi. This has been increased to 60 psi to t.ccomodate an increase in burial depth at Panford from 45 to 55 feet. In all cases, the compressive strength of the laboratcry specimens ranged from 1724 psi to over 7500 psi. Variability in triplicate measurements of compressive strengths was within 4% of the r'ean. The data not only satisfies the current 60 psi minimum but also satisfies the recommendation that the waste form exhibit more than the minimum '
acceptable compressive strength of 60 psi.
- b. Radiation resistance BWR, PWR, bead resin, and filter sludge waste forms were irradiated by a Cs-137 source while those based on powdered ion exchange resin, decon solution, and dry salt / ash were irradiated by a Co-60 source.
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The data for compressive strength after irradiation to 100 Mrd for all waste types tested fall in the range 1980 psi to over 7500 psi.
Variability was less than 3% when reported. The specimens were exposed to 100 Mrd cumulative dosage from a Co-60 gama source as recommended in the TPWF. It appears gama irradiation increased mean compressive strengths by factors ranging from 1.0 to 2.0 for some wastes, whereas for bead resins, the mean compressive strength was decreased by factor of 1.0 to 2.0. The compressive strength criterion of 60 psi is nevertheless satisfied.
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3 CHP/WM-82 00W TER WF Dow also prescnted data showing the effect of irradiation beyond 100 Mrd. Compressive strengths actually increased with irradiation up to 100 Mrd for all except decon waste, for which there was a 5%
decrease to 3668 psi. Beyond 100 Mrd, strengths tended to decrease somewhat for the BWR and PWR wastes. For the waste forms tested, i the data indicate there is stability to radiation exposure well in I excess of the 60 psi recomended to perhaps 1000 Mrd, i 1
- c. Biodegradability The TPWF recommendation states that after exposure to bacteria and fungi in accordance with ASTM G 22 and G 21, respectively, there i should be no visible growth on the cultures and the specimens should retain compressive strengths greater than 50 (now 60) psi.
The data presented in the TR indicate that no growth of bacteria was found on any of the test specimens. The corpressive strength after exposure to bacterial attack was in range 1932 psi to over 7500 psi.
Variability was not reported but the results are stated to represent triplicate determinations.
Similar results were obtained for fungal attack, with one exception:
filter sludge. Compressive strenaths following fungal exposure were in the range 1782 psi to over 7500 psi, again representing triplicate determinations.
In work done at the Brookhaven National Laboratory (Ref. 18) and at EG&G (Ref. 1?), possible evidence of biological growth on Dow waste forms was N ported. After careful review of the available data, NRC Staff concluded that there was no evidence of bacterial growth on Dow waste forms, but that the data for fungal growth were not conclusive.
Usino procedures recommended by the NRC (Ref. 13), Dow performed additional testing (Ref. 14). The results support the conclusion i
that no fungal growth was obtained on the waste forms, and that the l waste forms after testing did meet the 60 psi compressive strength l criterion. However, the results confirmed the EG&G conclusions that l unpolyncrized organic feed materials did support fungal crowth.
Since the residual amount of unpolymerized material is expected to be a small fraction (i.e., less than 0.5%) of the total fed, Staff concludes that even if some crowth does occur it will not degrade the structural stability of the waste foms. This is supported by the additional Dow data.
The recomendations of the TPWF on biodegradability are therefore satisfied.
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- d. Leachability Index The TPWF recomendation is that Leach Indices (LIs) obtained as per 3 ANS 16.1 (Ref.19) should be greater than 6 and the leach testing should include 90-day results.
Data are presented in the TR for tests with deionized water and synthesized sea water using two radioactive tracers: cesium-137 and cobalt-60. Loadings used may be illustrated by tnose for BWR and PWR simulated concentrates. Based on 8 uCi/g concentrate, the loadings in the test specimens may be estimated as 4.8 uCi/cm3 of specimen. For comparison, the maximum loading recommended in the '
TPWF (Ref. 2) is 10 Ci/ft3, which is equivalent to 353 uCi/cm3, or 74 times that used in the Dow test specimens.
All samples satisfied the TPWF recommendation. All leach indices exceeded 8.1, with most indices being above 10.0.
In response to the NRC observation that the Dow leach data generally did not cover much beyond about 28 days of leaching, Dow offered 90-day data Tor BWR concentrate, PWR concentrate, and filter aid sludge using Cs-137 and Co-60 tracers and demineralized water.
These data show (1) acceptable Leach Indices, (2) continuing trend toward lower leach rates with time, and (3) no significant difference in Leach Indices from the 28-day data.
In theory, the LIs are based on fractional releases and are supposed to be independent of the actual loading. Staff notes that loadings in commercial practice could be 74 times as great as those actually tested. Staff, however, concludes that the leachability recomen-dations are technically satisfied.
l e. Immersion Resistance i Test specimens of the solidified waste forms should retain compressive strengths of at least 60 psi following imersion for 90 days in water. Specimens from leach testing may be used. The ,
data presented include results from immersion in water, although Dow
- did not state whether the water was demineralized or sea water. The
! results showed compressive strengths af ter inrrnersion to be in the range 1900 to over 7500 psi, with variabilities of 3% of the mean '
- at most. The recommendations in the TPWF are, therefore, satisfied. !
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- f. Thermal Cycling Resistance Solidified waste forms should retain minimum compressive strengths greater than 60 psi after 30 thermal cycles between 60 C and -40*C as per ASTM B 553. The data show compressive strengths after thermal cycling to be in the range 1720 to over 7500 psi, with variabilities of 3% for all except the decon waste. For this waste, the variability increased to 20% after themal cycling. The actual mean compressive strength in this case was 3989 psi, far in excess of the 60 psi recomended.
All solidified waste forms with one exception maintained their appearance and physical integrity after the 30 thermal cycles. The solidified filter aid sludge developed some vertical cracks after 8 to 10 thermal cycles. Nevertheless, physical integrity was retained inasmuch as the compressive strength after 30 cycles was 2000 psi.
However, tne Dow test procedure included a deviation from the i expected procedure in that the waste forms were not removed from the plastic molds in which they were prepared. This raised the possibility that the specimens were never exposed to the desired test conditions, which in turn required answering several questions.
(1) ASTM Test Temperatures Consultation with previous and current Chairmen of the ASTP Subcommittee responsible for ASTM B 553 confirmed that the intent of the test was to have the test specimens reach the stated test temperatures. The test was originally developed for automobile parts made of metals electroplated onto a plastic substrate. The object of the test was to detemine whether under thermal cycling conditions over a range of 100*C the bond between metal and substrate would hold. What is involved is the differential expansion and contraction of the two materials.
Staff concludes that a similar objective is appropriate for solidified low-level waste forms. For these the requirement of also l including 0*C in the terperature range used means that if any water ;
is present the waste foms will be subjected to volumetric stresses from the phase change for water.
(2) Actual Test Temperatures The next question was what were the actual temperature changes experienced by the Dow waste foms. Two rethods were available.
g, . . - i.,i CHP/WM-82 D0W TER WF In one, used by BNL (Ref. 20), thermocouples were embedded in i
selected waste forms. BNL concluded that one hour, for bare waste forms, was insufficient for reaching either terperature extreme.
This result needs interpretation because the bare waste forms were actually sealed in metal containers. While metal is a good heat conductor, the air film coefficient of heat transfer was probably lower than for specimens not in cans.
The other resorted to calculation of the temperatures based on theoretical models of heat transfer. Dow used a finite element approach with which Staff concurs. However, their results also show that in one hour the temperatures reached on heating or cooling from 20'C are only 37*C and -6 C respectively. Thus, the waste forms have been subjected to possibly only 43% of the stresses due to thermal expansion that were intended in addition to those due to volumetric changes resulting from freezing of droplets of water in the wastes.
It is also possible to show by other calculations that the required 60 C can be reached by bare waste forms of the size used by ,
Dow in about 15 minutes, assuming there was no thermal resistance due to the air film. By approximate calculations, including the air film resistance increased the heating time so that in the same 15 minute :
period the specimen was heated to only 35'C. Thus, the air film is a ,
significant resistance to heat transfer. With specimens in i polyethylene molds, the heating time will be even greater.
(3) Convection Coefficient An important question in this calculation is the appropriate value for the surface convection coefficient of heat transfer in the test chambers, i.e., was there forced or free convection?. Acain checking with ASTM, the chambers are intended to have air circulation, but only to avoid dead spots. Hence, it may be more appropriate to use a coefficient for free convection. The value used by Dow was stated as 2.0 Btu /hr-ft *F in one document but with the terperature in 'C in anotl:er. The former i? at the upper end cf the range for free convection but may also be used for the case of minimum forced convection. It is thus possible that the heat transfer is actually less than that indicated by calculation. However, other calculations by Dow indicate small sensitivity to the coefficient h.
For heating, with h based on 'C, the average temperature for h = 2 in the waste form in one hour is 30.4*C, whereas for h = 1 it is 25.6'C.
4 "' b CHP/WM-82 DOW TER WF (4) Additional Resistances to Heat Transfer Differential expansion between specimen and mold may have created an additional air gap between waste form and mold that was not accounted for in the Dow calculations.
(5) Thermal Conductivity Values While the thermal conductivity value used for polyethylene was correctly read from the source quoted (Ref. 21), the same source showed that the the k value for polystyrene was an order of magnitude lower than that used by Dow in their calculations (Ref.10,15).
Thus, the polyethylene does serve as an insulator and there is also significant resistance to heat conduction within the waste form.
Staff concludes that the TPWF recomendation is not fully satisfied.
Even though many of the compressive strengths found after thermal cycling are substantially above the minimum of 60 psi, the test ,
specimens were not exposed to the recomended range of temperatures. Since the Dow calculations confirm this, and since there is no way of predicting what the effect of exposing the test specimens to the full range of temperatures recomended would be, the thermal cycling tests should be repeated with bare waste forms.
- g. Free liquid Liquid wastes are completely solidified in normal operation and thus I satisfy the requirement of no more than 0.5% by volume of free standing liquid. No free liquids were cbserved in the qualification testing.
- h. Full-scale results The TPWF recomends that test data frem sections or cores of the full-scale products be correlated with test data from laboratory 1' scale specimens. Correlation here means that results obtained for samples cut from full-scale specimens are comparable to results from i laboratory samples. Tho qualification test data reported in the Dow
. TR cover only laboratory scale specimens and a few data on cored samples as discussed below. While Dow reports that it has used the 4
process with 50, 85, 170, and 195 ft3 liners in comercial practice, this means only that the process is operable for these larger sizes.
q "' .}
CHP/WM-87 00W TER WF The original TR (Ref. 3) did not provide sufficient detail as to the mixing procedures. In a later comunication, Dow provided information to help answer the questions about adequacy of mixing (Ref.8). Dow based its rationale on adequacy of mixing on (1) mixing time and (2) drop size. For reasons discussed in Appendix A to this TER, the rationale is considered inadequate.
Large scale (55-gallons and 50 ft3) waste forms prepared at Dow for all seven generic simulated waster were nbserved to be hard monoliths with no free liquid. The surfaces appeared to be homoceneous.
Although the TR states that most of these specimens were sectioned, no data are given on qualification testing for stability.
Correlation tests were, however, performed on core samples taken from a 50 ft3 waste form prepared from non-radioactive ion exchange bead resin. The compressive strength of samples aged in air for 90 days was 5848 psi and 4128 psi for those imersed in water for the i same time. Correlation was demonstrated to the extent that the compressive strength values are well above the 60 psi minimum. '
While these data satisfy the recomendations of the TPWF, data for !
other wastes are not available.
Core samples were also taken from 55-gallon drum specimens of BWR concentrate, PWR concentrate, and ion exchange bead resin that had been solidified in April 1982. Six samples 1.75 in diameter x 3.5 in high were obtained. Three were compression tested imediately while the other three were imersed in water for 260 days and then compressicn tested.
All results were in the range 1560 to 4388 psi. Variability, l however, was as high as 33%. Also, all values were substantially lower after irnersion. This is in contrast to the behavior af laboratory samples, for which the strengths after imersion were ,
actually higher.
These results support the conclusion that some of the large scale waste forms have compressive strengths and imersion resistances comparable so laboratory scale specimens. Howaver, they do not permit extension of this conclusion to the other untested larger waste forrs. The testing specified in the TPWF is intended to qualify prototypes. Once this is done, then hundreds perhaps thousands of solidified waste forms may be made on the comercial scale. It is clearly important to have full data for the prototypes.
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l CHP/WM-82 DOW TER WF 4
Staff concludes that demonstration of correlation of full-scale results with laboratory-scale results is incomplete. While there is reasonable assurance that 55-gallon drum size waste forms will have adequate homogeneity based on the results of the compression i
strength tests, the homogeneity of larger waste forms needs to be demonstrated as discussed in Appendix A.
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CHP/WM-82 DOW TER WF Waste Content of the Dow Product
- 1. General One of the objectives of the waste fonn tests is to provide a basis for identifying the maximum permissible loading (MPL) for each type of waste.
This is the loading at which the waste form retains at least a 60 psi compressive strength after exposure to the recommended test conditions.
The determination of this maximum, however, must take into account not only the loading at failure but the overall variability of the process.
"Failure" here means the test conditions have caused the compressive strength to fall below 60 psi, or that the waste forms show evidence of unacceptable degradation. "Overall variability" relates to the likelihood that the actual waste loading in the products will be sufficiently below the maximuin permissible loading as to allow for variations due to such contributors as instruments, valves, pumps, degree of mixing, deviations from calibrations and feed source and corposition.
- 2. Process limits The acceptance letter for the process TR (Ref. 5) stipulated that:
"The process control is based on tests oorformed with the following simulated waste formulations:
(1) BWR evaporator bottoms with a pH of 8-11 and 7-12% of solids (2) PWR evaporator bottoms with a pH of 2.5-6.8 and 7-12%
solids (3) lon exchange resins, 90/10 by volume % resin / water (4)Filteraidandslurrier,90/10byvolume% resin / vater (5) Decontamination solutions with a pH of 3-5 and 9-10 with j 6-40% solids."
The solids concentrations in (1) and (?) are substantially lower than those of the correspondino waste forms. The process TR should therefore be amended and resubmitted to the Office of Nuclear Reactor Regulation (NRR) for their review.
- 3. Maximum Pernissible loadings Table A sumari:es the MPLs that appear ,iustifiable based on the submitted data. Maximum permissible waste loadings allow for a 10 percent variability in process conditions. However, actual operations are
- a. "' . , ,
CHP/WM-82 DOW TER WF approved based on exceeding the values listed in Table A only on an infrequent basis. Actual process controls must be observed to ensure that t- maximum permissible loadings are achieved on this basis giving conside-ration to normal process variability and variability in waste stream composition.
Certain reservations must be noted. In the case of ioni exchange bead resin slurry, the resin was equilibrated with tap water, not with nuclear power plant waste streams. Ion loading was therefore low as well as not representative of spent power plant resin.
- The ash in the volume reduced d.y salt + ash waste was an incinerator ash :
supplied by Aerojet Energy Conversion Company. It was not identified :
further. Dow has commented on a previous experience with another !
incinerator ash supplied by Pacific Northwest Laboratories, stating that f tne solidified product did not meet Dow quality standards. This appears to be another way of saying that the product failed to solidify. Dow explained this result with the observation that the ash had a reactivity i similar to activated charcoal (although how this was determined was not ;
stated) and appebred to contain relatively high amounts of copper and iron.
The above information has these implications:
- a. Dow must characterize the chemical nature of the ash they used i in the qualification tests so that users of the process car-know what kind of ash can be satisfactorily solidified.
- b. Dow statements to the effect that their process is an
, encapsulation process in which the binder does not react chemically with the wastes should be at least qualified if not actually deleted: e.g., Ref. 11, p 17, last sentence.
- c. Users raust be made aware that relatively small amounts of particular materials such as copper and iron could interfere with satisfactory operation of the process. This must be made clear in the revised proprietary and non-proprietary versions of the TR, and in the Process Control Plan (PCP), and in any sales literature used by Dow. Upper limits 9n the amount of
! copper and iron should be specified in the PCP.
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o CHP/WM-82 DOW TER WF Table A Maximum Pemissible loadings in Dow Process Waste Foms Pemissible Volumetric Waste Type Loadings Simulated Principal Components Waste / Binder Waste, Vol.%
BWR Concentrate '22.1 wt% Sodium sulfate 1.5/1.0 60.0 25.5 wt% Total solids PWR Concentrate 9.0 wt% Boric acid 1.65/1.0 62.3 1.5 wt% Sodium borate 12 wt% Total solids a
IE Bead Pesin Slurry 7.2 wt% Dowex MR-7 2.0/1.0 66.7 Filter Aid Sludge 30.0 wt% Celite 545 1.5/1.0 60.0 Powdered IE Resin Slurry 15.0 wt% Each of Epicor 1.5/1.0 60.0 anion and cation resins Decontamination Waste Dow fomulation, NS-1 1.5/1.0 60.0 (Contains chelating agents)
Volume Reduced b
Dry Salts Sodium sulfate + 5% Ash 2.0/1.0 66.7
[Equilibratedwithtapwater Incinerator ash supplied by aerojet Energy Conversion Company
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.CHP/WM-82 DOW TER WF Regulatory Position The Dow Topical Report, amended as of November 26, 1986, together with the D0W responses to NRC comments and questions are acceptable as reference documents for licensing the waste form produced by the Dow Process, subject to certain limitations and further actions by Dow:
Limitations
- 1. Maximum waste loadings should be those in Table A, subject to a maximum process variability of 10%.
- 2. The waste forms produced are limited to those made from the reactants specifically identified in the TR as those used to prepare the test specimens on which the data were obtained.
- 3. The maximum total radionuclide loading in the waste forms shall be such that the cumulative dosage to the waste form shall not exceed 100 Mrd.
- 4. The waste forms shall be prepared in containers not larger than SS-gallons. Full-scale waste forms (larger than 55-gallons) cannot be approved at this time because correlation testing is incomplete.
- 5. Since the lab scale specimens of solidified filter aid sludge showed surface cracking, the Dow process should not be approved for this waste type until the NRC determines what degree of such cracking or other surface deterioration is acceptable. The effect of such deterioration on leachability and immersion resistance should be considered in making this determination.
l Subject to the above limitations, and after completing the further actions nnted below, the Dow waste forms should be capable of meeting the
! stability requirements of 10 CFR Part 61 when produced using the process l control program described in the Topical Report (Ref. 4).
Further Actions l For laboratory scale specimens:
- 1. Dow should submit a modified test procedure for the thermal cycling test for approval by the NRC. This procedure should include provisions for ensuring that the specified test temperatures are reached within the waste forms. This may mean leaving the specimens at the test chamber temperatures for longer than one hour before removing them to ambient temperature.
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4 CHP/WM-82 00W TER WF
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- 2. After receiving NRC approval for the test procedure, Dow should repeat the thermal cycling test for all of the waste types unless an acceptable rationale can be offered for selecting a lesser number of types.
- 3. Dow should provide the NRC with information on the composition of the incinerator ash used and on the incinerator equipment used to produce the ash.
- 4. Make editorial changes as noted in Appendix B of this TER. :
i For waste forms larger than 55-gallons:
L
- 1. Show the adequacy of mixing in scale-up by compressive strength data for cored samples from at least six representative locations in the solidified waste forms (top, middle and bottom '
along the drum axis and one cylindrical element).
4
- 2. Demonstrate correlation of characteristics of lab-scale and r full-scale waste forms for at least the waste considered to offer the most difficulty in meeting the stability requirements.
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i CHP/WM-82 DOW TER WF !
APPENDIX A (
Evaluation of the Degree of Mixing in the Dow Solidification Process Qualification tests are based on laboratory scale' specimens. As recomended in the TPWF, the vendor should demonstrate by data on specimens from the full ;
scale waste foms that structural stability comparable to that for the '
laboratory specimens is obtained in the full scale waste forms. An important aspect of this demonstration, particularly in the absence of such data, is an analysis of the degree of mixing at the two scales to support the conclusion ,
that adequate mixing is provided at the full scale. ;
t The original TR'(Ref. 3) did not provide sufficient detail as to the mixing :
In a later comunication, Dow provided information to help answer
< procedures.
the questions about adequacy of mixing (Ref. 8). Dow based its rationale on !
adequacyofmixingon(1)mixingtimeand(2)dropsize. The rationale is considered inadequate.
(1)MixingTime Dow asserts that the mixing time (required) is generally five times the i circulation time. It is possible to derive such a factor from Figure 3.3 in Nagata (Ref. 22), but it would appear to apply to baffled tanks and for turbulent flow. For unbaffled tanks, the factor might be as high as 15.
Dow should provide a basis for their assertion, preferably supported by ,
experimental observations for particular systems. Also, the circulation time is not an unambiguous indicator of degree of mixing because it does ,
not indicate how much shear is being developed in the liquids being mixed. ;
i Further, in calculating the circulating time for the full scale system, t i what Dow has calculated is merely the time for one turnover of the tank i contents, not the mixing time required, j (2) Drop Size 1 o 1 Dow references a text on mixing by Nagata (Ref. 22) to show that the drops i in the 55-gallon container would be 1.6 times as large as those in the ['
1-quart laboratory test jar. Also, the average drop sizes would be 7 microns and 11.2 microns, respectively. ;
, Since these sizes seemed unreasonably small, the calculations were checked 1 and the results suggest a graph in Nagata has been incorrectly read. The j
- corrected drop size for the 55-gallon tank appears to be 103 microns. <
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CHP/WM-82 DOW TER WF 4
There is probably considerable latitude in the permissible range of drop
, sizes. It is more important to show a uniform distribution of drops j within the solidified matrix than to show the waste has been dispersed to a particular drop size. Dow should also discuss dispersal of solids, since the previous discussion relates only to liquid-liquid dispersions.
(3) Scale-up Parameters 4
Nagata in Oldshue does (Ref. not23say)much
. Table A-1about scale-up, compares butparameters relevant a fuller treatment for is given laboratory and full-scale mixing based on Dow information. Mixing theory i shows that it is impossible to hold every parameter constant in scale-up.
The vendor should decide which ones are important for his process.
Examination of the values in Table A-1 shows that tip speed was held about constant, which resulted in an increase in the Reynolds Number for the full-scale case. Thus the shear forces were decreased relative to the
- inertia forces. The Froude Number was decreased, meaning that gravity 1 forces were increased relative to inertia forces. Hence, there would be a greater tendency for settling out of suspended material. Power input per unit volume of mix was 60% of that in the laboratory scale mixing, while circulating rate was about a third.
! Overall, these data suggest that mixing was better in the laboratory scale than on the full-scale. However, the mixing on the lab scale may have been better than required. Dow needs to show either what is the minimum degree of mixing required on the laboratory scale i or that the mixing actually obtained on the large scale (greater than 55-gallon drum size) waste forms is adequate. This means showing that the properties of the full-scale waste forms (larger than 55-gallons) are reasonably uniform over the waste form volume and that the wastes are
- reasonably uniformly distributed within that volume.
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CHP/WM-82 DOW TER WF Table A-1 Comparison of Mixing Parameters for Dow Waste Forms Parameter Test Jar 55-Gal. Drum D, in. 2 15 N, rpm 2300 400 rps 38.33 6.67 M, gal. 50 ft3 0.00529 6.68 V: ft/s 20.07 26.18 Fr: NrD 244.9 55.6 Re: NDr 1.065 10.42 Q: NDS 0.1775 13.02 P/M 1367 133 Q/M 33.50 1.95 Nomenclature D Impeller diameter N Impeller rotationai speed M Volume of mix V Impeller tip speea Fr Froude Nurrber Pe Reynolds Number Q Volumetric pumping or circulating rate P Power Number Note: The expressions listed in the table opposite Fr. Re, and Q are the variable portions of the indicated Numbers.
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APPENDIX B l r
Editorial Changes Required for the Dow Topical Report '
dated November 26, 1986
- 1. p 5: Describe how the mixing is done in the case of large liners.
- 2. p 31: Dow concludes that BNL data support the Dow claim that use of a V/S [
ratio of 0.5 instead of 20 had no effect on the LIs. "
Comment: The graphs are difficult to read but they appear to show that the amount leached at 40 days, for example, is three to four times that obtained by Dow. The net effect, however, is to subtract ;
0.5 to 0.6 units from the LIs. ;
Action: Insert the word "significant" before the word "effect" in the next to the last sentence on pg 31. .-
Since there are backup data from BNL, the deviations in experimental technique from ANSI 16.1 are acceptable. However, Staff emphasizes this is not a general conclusion applicable to every waste ty)e and i every solidification medium. In addition to the above, for t1e i sizes of waste forms used by Dow, as much as 20% of the leachate may [
remain as a film on the waste form and carried over to the next leaching interval when the leachant is changed.
! 3. p 41: Dow states that their process involves a physical encapsulation and thus produces a fairly uniform leach rate for all radioactive ,
species. l
! Comment: which -
is a factor ThedatashowtheLIscoverarangefrom8.1to17.3(pg36) of about one trillion. Dow has correctly stated !
that the LIs are logarithmic and that a difference of one unit means
! a factor of 10. Thus, the LIs are certainly not "fairly uniform".
' As to the possibility of concluding that only a physical
! encapsulation is present, this might be true in the case of j materials like sodium sulfate or boric acid, but there are other i
factors such as the mobility of the ions that would affect the LIs. r l The fact that the L!s for bead resin were 16 to 17 whereas for BWR
- and PWR concentrates the LIs were 10 to 12 suggests that a stronger t bond between radionuclide and resin exists. On the other hand, l powdered resin LIs were 12 to 13.
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CHP/WM-82 00W TER WF Dow also states on pg 67 that (certain) materials have been known to affect the free radical cure mechanism.
Action: Delete all statements about the process involving a physical encapsulation unless some other evidence is available to support them.
- 4. p 41: Dow states the waste forms were irrrersed in 250 ml of water for 90 days.
Action: State whether the water was seawater or demineralized water, i
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CHP/WM-82 DOW TER WF i
References .
- 1. Code of Federal Regulations, Titie 10, Part 61. Licensing Requirements for Land Disposal of Padidctin Waste. Nuclear Regulatory Commission, i Washington, DC. January 1,1985. !
- 2. Technical Position on kaste Form. Rev. O. Low-Level Waste Licensing Branch, Division of Waste Managament, Nuclear Regulatory Comission, Washington, DC. May 1963.
- 3. Topical Report: The Dow Waste Solidificatico Process for Low-level Radioactive Wastes-Geieric Waste Fort Certification Results. DNS-RSS-200. :
The Dow Chen, cal (empany, Midland- MJ. June 1984. , !
- 4. Topical Report: Ther hw Tystem for Solidification of Lw-Level Radioactive MastC Trom N9r,leir Power Plants. DNS-RSS-b01-P-A. The Dow <
Chemical Company, MidlanJ, MI. June 1980. l
- 5. Miller,3J.R. Letter tb J.B. Owen, The Dow Chemicel Company, Midland, MI.
Review and freeptanu, of Topical Report DNS-RSS-001P. June 19, 1980.
- 6. -Paterson, C.H. (lttertoH.E. Tilter,TheDowChmicalCompany, ;
Midland, Mi. . A1.tadsi;t (: Specific NRC Coments on the Dow Topical i Peport, f( rch 5,198!. t 9
- 7. Petersoa, C.H- Lstter to H." Filten The Dow Chemical Company, Midland, l MI. Transmitscoisiesof'J.G&d,FmpressReportsonEPICOR-IIResin/ Liner Investigatior: Nov ember 6, 1985. ;
- 8. Filter. H.E. Le,er to CM. Mtersan. Retponses to Attachment 1, L Specific NRC Corrents on the Der Topicrl R; port. DNS-kSS-200-NP, ;
Amendment 01. The Dow Chemical Com,ntry, Midlanti, MI. January 10, 1986. l
- 9. Petersen, C.H. Letter to T.R. Boyce. The Dow Chemical Company, ;
Midland, MI. Comments on Anendmei.c 01. June 17, 1986. ,
i 10. Boyce, T.D. Letter to C.H. Peterson. Formal rssponsas to four NRC comments. The Dow Chemical Cdgany, Midlend, Mt., October 10, 1986.
l ,
- 11. Boyce, T.D. Letter to C.H. Peterson. T;ansmits latest revision of the ;
Dow Topical Report as in Pefererce 3. The Dow Chemical Company, .
l Midland, MI. November 26, 1986 !
i 12. Rogers, R.D. and J.W. McConnell, Jr. Biodegr Jattor, iesting ef TM-2 ,
EPICOR-II Waste Forms. W -Thl-7583. EG&E Idaho, .'ne . . Ilaho r311s, ID.
March 1987. l I
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CHP/WM-82 DOW TER WF
- 13. Peterson, C.H. Letter to G. Klecka, The Dow Chemical Company, Mid-land, MI. Biological Stability of Waste Forms from the Dow Low-Level Waste Solidification Process. July 10, 1987. -
14 Davis, J.W. and H.E. Filter. Microbial Susceptibility and Compressive Strength Testing of Vinyl Ester Styrene Binder. ES-DR-0131-7891-1. The Dow Chemical Company, Midland, MI. November 17, 1987,
- 15. Colombo, P. and R.M. Neilson, Jr. Properties of Radioactive Wastes and Waste Containers. First Topical Report. NUREG/CR-0619. Brookhaven National Laboratory, Upton, NY. August 1979.
- 16. Swyler, K. , R.E. Barlette, and R.E. Davis. Review of Recent Studies of the Radiation Induced Behavior of Ion Exchange Media. Informal Report BNL-NUREG-28682. Brookhaven National Laboratory, Upton, NY. Novem-ber 1980.
D. Code of Federal Regulations, Title 40, Part 261. Identification and Listir.g of Hazardous Waste. Environmental Protection Agency, Washington, DC. July 1, 1983
- 18. Piciulo, P.C., C.E. Shea, and R.E. Barletta. Biodegradation Testing of Solidified Low-Level Waste Streams. NUREG/CR-4200. Brookhaven National Laboratory, Upton, NY. May 1985.
- 19. Measurement of the Leachability of Solidified Low-Level Radioactive Wastes. ANS-16.1-1986. The American Nuclear Society, La Grange Park, IL.
April 1986.
- 20. Piciulo P.C. and S.F. Chan. Thermal Stability Testing of Low-Level Waste Forms. NUREG/CR-4201. Brookhaven National Laboratory, Upton, NY.
May 1985.
- 21. Perry, R.H. and C.H. Chilton. Chemical Engineers' Handbook, 5th edition.
McGraw-Hill Book Company New Yort, NY. 1973.
- 22. Nagata, S. Mixing: Principles and Applicati:ns. Halsted Press.
l John Wiley & Sons, Inc., New York, NY. 197E.
l' 23 ,, O',dshue, J.Y. Fluid Mixing Technology. McGraw-Hill Publications l Company, New York, NY. 1983.
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