ML20237L256
| ML20237L256 | |
| Person / Time | |
|---|---|
| Issue date: | 08/31/1987 |
| From: | NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | |
| Shared Package | |
| ML20237L233 | List: |
| References | |
| REF-PROJ-M-32 NUDOCS 8709080310 | |
| Download: ML20237L256 (14) | |
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1 SAFETY EVALUATION REPORT ON THE WEST VALLEY DEMONSTRATION PROJECT CEMENT SOLIDIFICATION SYSTEM PROJECT M-32 l
U.S. NUCLEAR REGULATORY COMMISSION OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS
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INTRODUCTION.................................................
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THE CEMENT SOLIDIFICATION SYSTEfi.............................
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2.1 'The: Physical. System....................................
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.2.2 The CSS Process'.........................................
2-2c 2.3 Administrative Controls..................................
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PERFORMANCE EVALUATION.......................................
3-1 3-1 3.1, Norma 1 Operations'.......................................
3.2 Off-Normal and: Accident: Conditions.............'.........
3-1 3-3 REFERENCES........................................................-
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LIST OF. FIGURES' q
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- Figure 2;l ' CSS Ventilation System Schematic.....................
2-4 Figure 2.2 - CSS Process Schematic................................
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INTRODUCTION The U.S. Department of Energy (DOE) is conducting a high-level radioactive waste solidification demonstration program at the Western New York Nuclear Service Center. Part of the demonstration includes the solidification of low level and transuranic wastes and slurries in a cement matrix.
The system used to perform this solidification is called the Cement Solidification System (CSS). The major source of information used in evaluating this system is the DOE report titled " West Valley Demonstration Project Safety j
Analysis Report, Vol. IV, Rev. 1."
This Safety Analysis Report (SAR) describes 1
the structures and equipment that will be used for the process system, the l
process itself, the discharges that will occur during normal operation, and the discharges that could occur during off-normal or accident conditions.
The CSS has been reviewed by the NRC staff with a focus on estimating j
the impacts that facility operation will have on public health and safety.
The results of this NRC review are presented in this Safety Evaluation Report (SER).
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This SER presents a brief overview of the CSS, focusing on its equipment, process, and operating procedures as they relate to public health and safety.
f The SER examines the releases to the environment that are expected during nonnal operations and the releases that could occur during potential accidents.
The off-site dose consequences of these releases are estimated and compared to applicable standards.
i The conclusions of the staff review and evaluation are:
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The anticipated maximum off-site exposure during normal operation, according to the SAR ard the NRC staff's independent calculation, is expected to be negligible (probably less than 1E-8 mrem / year).
j This is much less than any relevant standards, f
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Maximum credible accidents would involve off-site. doses;of.less than 1
25 mrem..
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- The' NRC will. conduct a' preoperational assessment to verify the key design features'of the CSS as described in the SAR, concentrating on features related to.public. health ~and. safety, such as effluent monitors and effluent routes.
., Operational. safety procedures and some aspects of.the operator training program
!will also be' reviewed during the preoperational assessment..
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THE CEMENT SOLIDIFICATION SYSTEM The CSS is located in the 01-14 building southwest of the main process building at the West Valley site. The major CSS operations will include storage and transfer of dry cement, receipt and handling of waste slurries and solutions, nixing of low-level or TRU waste with cement, and handling of empty and cement-waste-filled drums. The largest feed stream to the CSS will be decontaminated Tank 8D-2 supernatant. Smaller feed streams will include sludge washing solu-tions, filter backwash slurries, and decontamination liquids. All liquid waste streams from the CSS will be transfered to the Liquid Waste Treatment System (LWTS). Handling of radioactive materials will be confined to two cells, which are equipped with sumps and maintained at negative pressure relative to sur-rounding areas by the building ventilation system. The ventilation system exhaust will be the only discharge stream for the CSS in nonnal operating conditions. The CSS will have area radiation alarms, process control instru-mentation, and administrative controls designed to prevent releases of radioactive material or detect them should they occur. Due to the nature of the process and the relatively low radioactive inventory the CSS has a low potential for danger to public health and safety.
2.1 The Physical System STRUCTURE The 01-14 building, which contains the CSS, is a 38'x 38'x 60' high facility originally built as the off-gas treatment facility for the West Valley reprocessing plant. The Waste Dispensing Cell, located in the north-east corner of the building, contains vessels which feed the cement mixers and support mixer flushing. The south half of the building houses the cement mixing equipment and filled-drum handling equipment on the first fleor. The second floor of the south half of the building supports the dry cement feeding system while the third and fourth floors support the ventilation system.
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. VENTILATION SYSTEM The 01-14 buildina has a self-containe'd ventilation system servicing the operating areas, the process cells and rooms, and the vessels..It employs the standard practice of maintaining air flow from areas of lower activity or con-tamination to areas of higher activity or contamination. Figure 2.1. presents the flow patterns and rates for this ventilation. The ventilation system includes two fans rated at 100 percent of system capacity, two sets of two-stage HEPA filters, and an exhaust stack.
SUMP SYSTEM The process cell containing the feed and support vessels contains two sumps, one on each side of a shield wall. The process room where the cement mixing occurs also contains a sump. These sumps have high-level alarms and their contents can be pumped to tank 70-13, an existing underground tank that will become part of the feed tankage system for the LWTS.
2,2 The CSS Process The cement solidification system will receive contaminated low-level and transuranic liquids and slurries, and will mix this material with cement to produce drums of solidified low-level and transuranic waste. The following paragraphs briefly describe the CSS processing steps. A schematic of the major process vessels is presented in Figure 2.2.
Feed for the CSS will be generated by several Fest Valley Demonstration
. Project activities, mainly supernatant treatment. All waste feeds will pass through the Waste Dispensing Vessel, located in the south half of the Waste
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Dispensing Cell. This 1900-liter vessel has spray headers and a conical bottom I
to facilitate thorough cleanout of the tank when necessary. Waste in this l
vessel can be sampled prior to processing, although routine sampling will be limited to the much larger collection tanks upstream from the Waste Dispensing Vessel. The Waste Dispensing Vessel has a diagonally mounted eoitator. A Moyno progressive cavity pump continuously circulates the material in the Waste Dispensing Vessel and also pumps material to the two high-shear mixers. The I
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high-shear mixer is intended to produce a homogeneous mixture of waste, cement, and any additives needed to modify cement setting time. Each mixer produces approximately 8S liters of waste / cement mixture, which is transferred to drums.
After the drums are filled, a lid is placed on each drum, it 1: weighed, the drum is sealed by crimping the lid, a contact dose rate is determined, and axternal contamination levels are checked.
LIQUID EFFLUENTS The liquid effluents from the cement solidification process will be mixer flesh water, water used for the transport of resins and filter slurries from the LWIS to the Waste Dispensing Vessel, cement drum decontamination solutions, l
and spills processed through the CSS Eumps. All of these materials will be i
routed back to the LWTS. The SAR does not provide an estimate of these quantities but une NRC staff estimates the total waste water from all these sources could be as much as 100,000 liters per year or about 10 percent of the CSS feed rate. The staff estimates that this would contain a small fraction of the feed activity, probably less than 0.1 percent.
I INSTRUMENTATION AND CONTROL The SAR provides a general description of process instrumentation and controls for the CSS. The instrumentation most directly important to public health and safety is the monitoring system for gaseous effluents. Levels of alpha-emitting and beta-emitting particulate in the effluent stack will be continuowly monitored and charted in the control room. An alarm will sound if either of these particulate emission rates gets too high. A sample of the gaseous effluent will be continuously drawn through fiber and charcoal l
absorption filters, which will be analyzed weekly for the presence of gamma-f emitting radionuclides. The NRC staff believes that these measures will provide i
edequate assurance that levels of radioactivity in the gaseous effluents from the CSS can be monitored and that excessive radioactivity in the gaseous effluent can be quickly detected and corrected.
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l' Accurate and reliable control of the cement-mixing process itself is l
important in terms of the long-term durability of the cement waste product, a topic not otherwise addre; sed in this SER. Dry cement will be metered into the high-shear mixers from a 0.43m3 hopper. A weight indicator on the hopper is connected to the cement feed mechanism through a micro-processor-based controller, so that the cement feed rate will be continuously adjusted until a predetermined weight of cement has been added to each mixer batch. The waste z
slurry will be metered to the mixers using a constant-volume-displacement pump, so that the flow rate of waste will be accurately krown and controlled. The same pump circulates the waste slurry within the Waste Dispensing Vessel, ensuring that the vessel's contents are thoroughly mixed. An analytical sample of the waste slurry will normally be taken from one of the two large (5,000 gallon and 10,000 gallon) holding tanks directly upstream from the Waste Dispensing Vessel.
It will be possible to take a sample from the Waste Dispensing Vessel itself, although this will not be the normal practice. The waste slurry samples will be analyzed for Cs-137 and fissile isotope concen-trations.
In addition to the feed metering cortrols, the mixers themselves are equipped with load cells to determine when they are full and protect against overfilling. The NRC staff believes that the CSS instrumentation and controls are sufficient to provide for accurate and reliable operation of the cement-mixing system under ordinary operating conditions. The staff has not analyzed the effect of abnormal occurrences on process or product control.
2.3 Administrative Controls i
Administrative controls also play a role in protecting public health and j
safety. The WVDP has administrative controls that implement the requirements l
of 00E Orders. WVNS procedures address the requirements of projects as they move from the design stage through the operational phase. The general WVNS j
policies and procedures were previously reviewed by the NRC staff, who found l
that they provided a satisfactory system for protecting the public health and safety (Reference 1).
With the submittal of specific information or the CSS, the NRC staff reviewed those CSS administrative controls that provide for public health ard
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safety. These specific administrative procedures are identified in Chapters 10 l
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L and 11 of the CSS SAR. Chapter 10 addresses preoperational test procedures, training programs, normal operating procedures, and emergency procedures.
Chapter 11 presents the operational s6fety requirements which place limits on CSS operation.
i The preoperational tests are intended to test the functioning of the various components. The information in the SAR indicates that the alarm and control systems will be checked out in the preoperational tests.
Performing these checks will provide greater assurance of the ability of the system to protect public health and safety.
The discussion of the training program in the SAR identifies the topics that will be covered in operator training.
It addressed formal classroom training, on-the-job training, and testing. The training program described in the SAR appears to be satisfactory in general terms. The NRC staff will l
review aspects of the training program that affect public health and safety, such as emergency response and ventilation system maintenance, during the preoperational assessment.
WVNS Operational Safety Requirements (OSR's) are presented in Chapter 11 of the CSS SAR for ventilation system blower and HEDA filtration system opera-bility, feed stream composition, and emergency power availability. The ventilation OSR specifies that the primary and backup blowers must both be available at the start of a campaign and that the operability of the cackup blower be checked every two weeks. The filtration OSR specifies the minimum number of filters required, pressure differential instrumentation and stack monitor availability, and maximum filter operating pressure differential. The feed stream OSR specifies maximum cesiun-137 and fissile material content for each batch. The emergency power OSR specifies diesel power backup for the ventilation system, battery backup power for the stack monitors and the filter system relays and instrumentation, and adequate power for building lighting and temporary operation of the high shear mixers. NRC staff has reviewed these requirements and concluded that they are adequate for protection of the public health and safety.
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PERFORMANCE EVALUATION The NRC staff has reviewed the CSS and made independent assessments of the potential scenarios for the release of material to the environment.
For those situations where releases were judged to be credible, independent I
estimates were made of release quantities, and off-site dose estimates were
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prepared. This inapter of the Safety Evaluation Report presents the results of this independent evaluation. The releases that could result from normal operation are presented in Section 3.1, and 'he releases which could occur under accident conditions are presented in Section 3.2.
3.1 Nonnal Operations For normal operations, the only effluents from the CSS will be those from the 01-14 building ventilation system. The amount of material released will be related to the material being processed through the facility. The NRC aralysis assumed that all of the concentrated, decontaminated supernatant was processed through the CSS in the course of one year. Assuming a decontamination factor of 1,000 in the supernatant treatment system ion exchange columns, the decon-taminated supernatant will contain about 25,000 Ci of radioactivity, mostly Cs-137, Sr-90, and Pu-241. The quantity that will be released into the gaseous effluent can be estimated by considering the fraction of the decontaminated supernatant that can be expected to evaporate from the process vessels into the vessel off-gas system (about IE-3), the radionuclides partition coefficients associated with the evaporation process (about IE-4), and the double-HEPA fi',ter penetration factor (about SE-6). These factors combine for an overall decon-tamination factor of SE-13, so the radioactivity released through gaseous effluents in the course of solidifying the decontaminated supernatant will be ebout 1.25E-8 Ci. Using dose conversion factors previously estimated for elevated atmospheric releases at the West Valley site (Reference 1), the dose at the site boundary would be less than IE-8 mrem / year, far below any relevant standards.
3.2 Off Normal and Accident Conditions The SAR recognizes that off-normal or accident conditions could develop and could result in release rates or quantities which are greater than those associated with normal operation. The CSS containt low-level and transuranic 3-1
wastes in limited quantities with low energy content. Flammable substances such'as gas or oil, which could provide. energy for dispersing radioactive materials, are nnt used in the CSS. Criticality incidents are inpossible due to the small quantities of material in the feed stream, the nature of the process, and implementation of operational safety requirements limiting feed concentrations of fissile material. The impact of spills on the public is considered negligible due to the presence of sumps and means for transfer of spilled material to storage tanks.
The principal accidents of concern were determined to be a HEPA filter fire or and undetected loss of HEPA filter. The HEPA filter fire was the most severe and, for very pessimistic assumptions (i.e., twelve filters loaded with 0.075 Ci of Cs-137 each plus a proportionate quantity of other radionuclides, with half of the loading released during the fire), the maximum off-site dose from a two-hour fire was 25 mrem. The principal isotopes for this dose were
-Sr-90 and Pu-238.
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REFERENCES l
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U.S. Nuclear Regulatory Connission, " Safety Evaluation Related To The i
West Valley Demonstration Project - Principal Design Criteria And l
Management Organization," April 1987.
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