ML20198K212
| ML20198K212 | |
| Person / Time | |
|---|---|
| Issue date: | 01/09/1998 |
| From: | Jim Hickey NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Bell M NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| References | |
| REF-WM-3 NUDOCS 9801140347 | |
| Download: ML20198K212 (5) | |
Text
_ ._. . _ _
- st January 9,1998 MEMORANDUM TO: Michael J. Bell, Acting Chief Performance Assessment and HLW Integration Branch Division of Waste Management, NMSS
- FROM: John W. N. Hickey, Chief [0RIGINAL SIGNED BY:]
Low Level Waste and Decommissioning Projects Branch Division of Waste Management, NMSS !
SUBJECT:
REVIEW OF
SUMMARY
OF THE BASE ASSUMPTIONS IN THE '
PART 61 WASTE CLASSIFICATION SYSTEM Your essistance is requested in reviewing the attached report on, " Summary of the Base A.sumptions in the Low Level Radioactive Waste Classification System - 10 CFR C1.55," and providing me '.ith your comments. The purpose of this summary report is to provide Carl Paperiello with a quick reference that describes the low level waste classification system and its bases. The requested completion date is January 16,19%. If you have any questions, please call the contact below.
Attachments: As stated ;
Contact. Sherry Wu, NMSS/DWM/LLDP (301)415-6619 D IB l'd all w/ att) i a Central Fhu PUBLIC NMSS r/f LLDP r/f RJohnson RNelson LBell DOCUMENT NAME:C:\ OFFICE \WPWIN\WPDOCS\ PROJECTS \ WASTE R1.WPD ,
OFC LLDP- F LLDP ,f LLDN ,
AI NAME SWu M TCJo h JHhy DAT," , 1/8/98 1/h/D8 1/ [/98
~ -'
C = COVER E = COVER & ENCLOSURE N = NO COPY OFFICIAL RECORD COPY h
ACNW: YES _ NO _ Category: Proprietary _ or CF Only _ .g }
IG: YES _ NO _
LSS: YES _ NO _, Delete file after distribution: Yes _ No _ l.
I
. .m O s Illllllll.lll. lit.
me g > ,i WM-3 N PDR h
. _ . .. - _ . . __ _ ~.
- paa "8eoq p t UNITED STATES s" j t
NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. speeHo01
".....'f i
f,, ,
January 9,1998 MEMORANDUM TO: Michael J. Bell, Acting Chief Performance Assessment and HLW Integratica Branch Division of Waste Management, NMSS '
FROM: John W. N. Hickey, Chief ,
Low-LevelWaste and hmmissioning h'/[ 7
\
Projects Branch -
D5 vision of Waste Management, NMSS
SUBJECT:
REVIEW OF
SUMMARY
OF THE E ASE ASSUMPTIONS IN THE PAP.T 61 WASTE CLASSIFICATION SYSTEM Your assistance is requested in reviewing tha attached report on, " Summary of the Base ,
Assumptions in the Low-Level Radioactive Waste Classification System - 10 CFR 61.55," and providing me with your comments. Tne purpose of this summary report is to provide Carl Paperiello with a quick reference that describes the low-level waste classification system and its bases. The requested completion date is January 16,1998. If you have any questions, please call the contact below.
Attachments: As stated
Contact:
Sherry Wu, NMSS/DWM/LLDP (301)415-6619
SUMMARY
OF THE BA3E ASSUMPTIONS IN THE LOW LEVEL RADIOACTIVE WASTE CLASSIFICATION SYSTEM - 10 CFR 61.55 PuroW2 The purpose of the Low Level Radioactive Wasto (LLW) classification system in Par 161 is to provide reasonable assuranco, on a non-site specific basis, that the performance objectives for protection of the off-sito public (661.41), the inadvertent intre. ( 61.42), and site workers
($61.41) will be satisfied.
Mooting the LLW classification scheme is a component of the systematic approach used in Part 61 to moet the performanco objectives. As part of the systematic approach to mooting the performance objectivos LLW classification is supplomonted by site specific analyses (performance assessments) for mooting 61.41, and the inclusion of engineered barriors, active and passivo institutional controls, sito soloction critoria, etc.
The LLW classification system is particularly important to the performance objectivo for providing prctoction to the inadvertent irtruder (Q61.42), by assuring that wastos with highor radionuclide concentrations (l.o., Class B and Class C wasto) are stabilized prior to disposal and therefore more recognizablo to an intrudor, and by assuring that an appropriato, long term intruder barrier is provided for Class C wasto.
The technical basos, scenarios, and assumptions used in developing the concentration ilmits for each wasto class are given in the Draft Environmental Impact Statomont (DEIS, NUREG-0782) and tho Final Environmental Impact Statement (FEIS, NUREG-M45) for 10 CFR Part 61. The scenarios and assumptions important to wasto classification primarily relato to the inadvertent intruder, and are discussed below. The DEIS and FEIS evaluated four hypothetical, regional LLW tronch-type disposal fccilitios.
Inndvertent Intruder The inadvertent intrudora are the persons who might occupy the sito in the future and engage in normal pursuits without knowing that they were recolving radiation exposure. The events c' this pathway are conservatively assumed to occur based upon consideration of typical human activities.
Protection of inadvortent intruders can involve two principal controls: (1) institutional control over the site after operations by the site owner to ensure that no such occupation or improper use of the site occurs; or (2) designating which wasto could present an unacceptable risk "o an intruder, and disposing of this wasto in a manner that provides some form of intruder barrier that is intended to provent contact with the wasto. [Q 61.7(b)(3)}
Pursuant to 661.42, the inadvertent intruder is protected to a level of 5 mSv (500 mrom) after the period of active institutional controls over the LLW disposal site. The institutional control timo framo is nominally 100 years. [961.7(b)(4)}
Intrusion Scenarios Tho scenarios ovaluated in the DEls and FEIS for inadvertent intrusion included: (1) the intruder-discovery scenario, (2) the intrudor-construction scenario, and (3) the intrudor-agriculturo scenario. The events are conservatively assumed to occur based upon consideration of typical human activities. The key radionuclides observed in " typical" LLW, due to their concentration, environmental mobility, and/or hali-life, were identified and analyzed in the DEIS and FEIS and includoo in the Wasto Classification Tables in $61.55.
Attachinent
2 in the discovery scenario, at tne end of a 100-year institutional-control period, the intruder contacts solid remains of the waste, realizes that something is wrong, and ceases intrusion activities, Any LLW which would cause the intruder to exceed 5 mSv (500 mrom)is designated Class C waste. This is the source of the intrudur barrier reouirement for Class C waste. in the DEIS,500 years was the maximum time for allowing credit for an intruder barrior 5 meters thick.
The Class C upper concentration limits in the table in 961.55 were developed under these assumptions.
The intruder-construction scenario involves exposures to workmen involved in constructing a house directly oc the disposal facility, thus contacting and dispersing the disposed wasto.
Exposures can usult from airborne dispersal of a soll/ waste mixture (leading to exposures due to immersion in a contaminated cloud as well as from inhalation) and fom direct gamma radiation.
The intruder aDriculture scenario involves an individual or several individuals living in the house constructed on the disposal facility end consuming food grown in a small on-site garden.
Exposures can result from airborne dispersion of a soil / waste mixture, direct gamma radiation, dnd ingestion of contaminated foodstuffs.
Enaineered Barriers Engineered barrier is a mr'aod by which the hazard to a potentialintruder may be reduced by disposing the waste in a saanner that would make it more difficult for a potential intruder to contact the waste. Entreered barrier could be used to satisfy requirements of Class C waste disposal at sites where conditions prevent deeper disposal.
Engineered barriers are typically used to enhance overall facility performance by limiting the flux of water that comes into contact with the waste and subsequent release of radionuclides from the disposal units. Significant uncertainty exists in predicting the service life (i.e., design) and the long-term degradation rates of the engineered barriers. The draft BTP on Performance Assessmet (1997) recommends that engineered barriers be assumed to be physically degraded after a period of 500 years. Beyond this, they are assumed to function at a degraded level considerably less than their optimum level, but credit for structural stability and chemical buffering may be taken for longer periods of time. The methodology used in the DEIS and FEIS did not take cieait for performance of engineered barriers beyond 500 years.
Engineered barriors can, therefore, be used as an intruder barrier (e.g., vaults) and to assist in overall site stability and infiltration management for the first 500 years after disposal.
Waste Classes Table 1 (long-lived nuclides) and Table 2 (short lived nuclides - less than 30-year half-life) of s61.55 provide the concentration limits for the nuclides that the DEIS or Fels identified as important to meeting the LLW intruder or off site (public) pathway performance objectives. All nuclides important to waste classification, as well as 1 129, C-14, H 3, and Tc-99; are required to be reported and recorded using the LLW disposal manifesting system. ,
Class A, B, and C waste are required to muet the minimum waste form characteristic requirements (e.g., minimum free !! quids content) of 961.56(a); Class B and C waste (and Class A waste that is to be co-disposed of with Class B or C waste) are required to meet the waste stability provision of 661.56(b).
.. -- = - .
,.3 c.-
=3= ,
Class A waste is LLW for which after the 100-year institutional control period, an intruder would ;
not receive more than a 500-mrem whole body exposure. The great majority, by volume, of LLW disposed of is Class A.
Class B waste is LLW for which after a period of 100 years, an intruder would receive more than a 500-mrem whole body exposure. To address this, an additional requirement is specified in 661.7, that the Class B waste be stabilized for at least 300 years. The stability requirement in Par 161 permits the assumption by the DEls and FEIS that the waste will be recognizable and the intrusion will be halted. Stability can be provided by the waste form itself (e.g., solidified waste or large metal activated cor sponents), by a high integrity container, or by the disposal site itself (e.g., vault disposal). In practice, the great majority of LLW is stabi aed by placement in high-integrity containers or concrete overpacked polyethylene liners.
Class C waste would cause an intruder to receive more than a 500 mrem whole body exposure after 100 years, even if the LLW is recognized and the intrusion stopped. Therefore, in addition to stabilization as discussed above for Class B waste, an additional barrier to intrusion is required by $61.7(b)(5) for Class C waste. This waste is disposed of at a greater depth (the top of the waste is a minimum of 5 meters below the top surface of the cover) than Class A or B so that subsequent surface activities by an intruder will not disturb the waste. Whers site conditions ;
prevent deeper disposal, intruder barriers such as concrete covers may be used. Stability for Class B and C waste also provides a measure of protection for off site releases via the groundwater, erosion, or gaseous pathways by assuring that nuclide releases will be gradual (by diffusion / dissolution) in time. Examples of Class C waste include activated metal components (due to Ni 63 or Nb 94 content), and primary dewatered resins.
Greater than Class C (GTCC) LLW is v!aste which may never de able tc satisfy the inadvertent intrusion performance objective in 661.42. Therefore, GTCC waste is generally not acceptable for near surface disposal (661.55(a)(2)(iv)). Examples melude reactor intemals (core baffle) sections, sealed sources, and high transuranic content wastes.
10 CFR 61.55(a)(8) does permit that the concentration of a radionuclide may be averaged over the volume (or weight) of the LLW. Guidance acceptable for these practices is the subject of the Branch Technical Position (BTP) on Concentration Averaging and Encapsulation (1995).
Relevant NRC Guidance on LLW Classification
- 1. Draft Environmental Impact Statement on to CFR Part 61 (DEIS, NUREG-0782), Sept 1981.
2.- Final EnvironmentaHmpact Statement on 10 CFR Part 61 (FEIS, NUREG-0945), Nov 1982.
- 3. Branch Technical Position on Waste Classification, May 1983.
- 4. Branch Technical Position on Concentration Averaging and Encapsulation, Jan 1995.
- 5. Branch Technical Position on Waste Form, Msy 1983.
- 6. Branch Technical Position on Waste Form, Rev 1,1991.
- 7. Branch Technical Position on a Performance Assessment Methodology for Low-Level Radioactive Waste Disposal Facilities, (Draft NUREG-1573), April 1997.
- - _