Technical Basis Document for Radioactivity Limits in Liquids as a Result of Activation or Contamination
Jefferson Lab
Technical Basis Document for Radioactivity Limits in Liquids as a Result of Activation or Contamination
Jlab Tech Note
JLAB-TN-06-01
Keith Welch, Erik Abkemeier, Bob May
January 20, 2006
Thomas Jefferson National Accelerator Facility
12000 Jefferson Avenue
Newport News, VA 23606
Table of Contents
I.Introduction
1. Scope
2. Background
II.A Review of Regulatory and Jefferson Lab Specific Limits and Guidelines
1. EPA Regulations
2. NRC Regulations
3. DOE Regulations
4. Jefferson Lab Requirements
A. Action Level Development
B. Bases fro Action limits for Liquids
III.Action Levels for Water
A. ENVIRONMENTAL PROTECTION
1. Groundwater Discharge
2. Other Releases to the Surface
3. System Limits and Controls
4. Releases to Sumps
A. Accelerator Ring Sumps
B. End Station Floor Sump
5. Posting
6. Discharge to Sanitary Sewer
B. OCCUPATIONAL EXPOSURE CONTROL
1. Surface Contamination
2. Airborne Radioactivity
IV.Action Levels for Non-Aqueous Liquids and Media
1. Ion-exchange Resins
2. Oils
V.Analytical Requirements
VI.References
VII. Appendices
Appendix A. Summary of Action Levels and Actions
I. Introduction
1. Scope
This document addresses the control of radioactivity in water, water-borne media and other liquidsin order to (a) control dose to exposed workers, (b) prevent the spread of contamination, and (c) minimize the potential for exceeding statutory or permit limits on environmental releases in the event of a spill or leak from an affected system. This document also describes the conditions and allowable methods for release of these liquids from radiological control. Action levels will be established requiring certain controls or mitigating actions, depending on the type and location of the system.
Theseissues have been raised recently due to increased levels of activity being found in a low conductivity cooling water (LCW) system. In response to this discovery, a review of the applicable limits and standards was conducted, and it became apparent that many of the specific conditions related to radioactivity in liquids have not been specifically addressed in Jlab radiological control requirements or procedures. This document attempts to fill some of the gaps we have found with respect to specific controls for activated liquids at the lab. The bulk of the information focuses on LCW systems, but we also address other common or potential situations involving controls on potentially radioactive liquid.
2. Background
Historically, activity levels in LCW systems have been so low that controls for handling and disposition of the water have not been required. The activity concentration in (non-beam dump) LCW has never exceeded the EPA drinking water limit. Detectable levels of some radionuclides have been found, as expected, in filter and resin media used to maintain water purity. This material is either (conservatively) disposed of as Low Level Radioactive Waste (LLRW) or, in the case of resin, released for regeneration if below previously established action limits (These action limits will also be reviewed in this document).
Tritium (H-3) is a primary nuclide of concern, in that it is easily producible in water, has a relatively long half-life of 12.3 years, and has a tendency to disperse rapidly throughout fluids and surfaces. Be-7 is also easily produced in water via spallation of oxygen, but has a relatively short half-life of 53.7 days. Some other nuclides are produced which have longer half-lives than Be-7 (eg. Mn-54, Co-58, Co-60), but their production rates are considerably lower. All these nuclides (except H-3)have been detected in LCW resins, but not in the cooling water itself.
Recently, LCW samples were obtained from components in Hall C that had measurable levels of H-3 and Be-7. These samples were taken during the removal of HKS (E01-011) experimental equipment (magnets in the chicane region of the beamline). (Note:beam loss in this region was unusually high with this experiment, due to an unprecedented beam line configuration involving a “split beam” setup, including steering of the beam downstream of the target. This resulted in considerable beam loss into the downstream magnets and their associated cooling water jackets.) Analysis of the local cooling water samples yielded a tritium concentration of 1.92E-6 uCi/ml and Be-7 activity on the order of 3E-5 uCi/ml. Samples were also taken of the LCW system at the main system headers in both Hall A and Hall C,and in building 92 at the main system ion-exchange sidestream loop. Be-7 was detected at the Hall C header (comparable to the concentration at the magnets). No activity above MDA for any nuclide was detected in the water at building 92 (end station LCW supply system).
The existence of detectable Be-7 in the system is somewhat surprising, given assumptions about removal efficiency by the ion-exchange system. This indicates that Be-7 may remain suspended in the system longer than previously assumed due to flow/distribution irregularities or chemical form of the beryllium. The presence of detectable H-3 locally at the magnets with no detectable activity elsewhere also supports the idea that the Halls (or other segments of LCW systems) or individual components may act to restrict cooling water flow such that activity may build up locally to levels of concern for contamination control purposes. Only one of the samples taken exceeded the Derived Concentration Guide (DCG) values for drinking water systems in DOE 5400.5. But we regard the implications as potentially significant, particularly in light of long-term 12 GeV operations and the rather conservative permit limits.
II. A Review of Regulatory and Jefferson Lab Specific Limits and Guidelines
1. EPA Regulations
EPA drinking water standards as delineated in 40 CFR 141.66 specify a limit of 20,000 pCi/l(2E-5 uCi/ml) of tritium concentration in drinking water, as well as a combined limit of 4 mrem/year total dose equivalent from all beta-gamma emitting radionuclides (in the absence of any other nuclides, this implies a limit of 40,000 pCi/l or 4E-5 uCi/ml for Be-7).
2. NRC Regulations
NRC regulations (10 CFR 20.1301)establish a primary dose limit of 100 mrem/y to any individual in the public (uranium fuel cycle operations are further restricted by 40 CFR 190 such that there is “reasonable assurance” that no member of the public will receive a total dose of 25 mrem/yr from such operations).
Accordingly, 20.1302 allows release of liquid effluents in concentrations of 1E-3 uCi/ml (1E6 pCi/l)tritium to the boundary of an unrestricted area (values are listed in Appendix B, Table 2 of the rule). This concentration corresponds to a dose of 50 mrem/yr from continuous exposure based on annual oral ingestion for standard reference man. Part 20 allows for possible adjustments to the effluent concentration values based on chemical/physical characteristics of the effluent. Of course, EPA drinking water standards would still apply to a water source to which an effluent stream containing 1E-3 uCi/ml of tritium is directed. Therefore the NRC rule does not imply a dose limit of 50 mrem from drinking water. Effluent concentration values are a starting point containing conservative assumptions, with implicit expectations of dose pathway analyses.
3. DOE Regulations
DOE O 5400.5 Chg.2 of 1/7/93also begins with a primary dose limit of 100 mrem/y to members of the public. The Order uses a similar approach to controlling effluents as 10 CFR 20, listing Derived Concentration Guide (DCG) values which are based on the same dose-to-concentration relationship as Part 20 (and those referenced in EPA standards). For instance, the DCG value for tritium is2E-3 uCi/ml (2E6 pCi/l), which corresponds to a dose of 100 mrem/y under the same exposure conditions as are used in Part 20. Order 5400.5 explicitly states that the DCG values “are not release limits, but rather are screening values for considering BAT (Best Available Technology) for these [liquid] discharges and for making dose estimates.”
Rulemaking for environmental regulation by DOE is contained in 10 CFR 834, which has been stalled in a draft version for many years. Primary dose limits in the draft mirror the 5400.5 limits. Action levels contained in the draft rule would require (except for H-3)best available technology (BAT) treatment of liquid discharges (not sewage) to limit the radioactivity concentration when the average annual concentration in the discharge exceeds the DCG, or could result in a TEDE greater than10 mrem/y to members of the public (and, of course, drinking water supplies must meet EPA requirements). Action levels in both the draft rule and 5400.5 for sanitary sewer release require the use of BAT treatment above five times the DCG.
4. Jefferson Lab Requirements
No specific water concentration limits exist in the Jefferson Lab EH&S RadCon Supplement. The Jlab Work-Smart Standards (WSS) contain references to our primary permits under the Virginia Pollutant Discharge Elimination System(VPDES) and the Hampton Roads Sanitation District (HRSD). No other radiological effluent discharge references are contained in the WSS (the DOE standards are referenced, but not with respect to liquid effluents). VPDES permit #VA0089320addresses groundwater quality, both in-situ (well monitoring) and related to discharges of groundwater to the surface (end station dewatering).
The de-facto limit for the surface discharges is the EPA drinking water standard (at the point of dewatering sump discharge). Other discharges to surface waters are technically not addressed by this permit. Monitoring for permit compliance is conducted at the dewatering sump. However, additional monitoring of the surface discharge channels is conducted, and any degradation of this effluent at any location would be cause for concern and action. HRSD permit #0117 addresses discharges to the sanitary sewer. The primary limit is 5 Ci of H-3 and 1 Ci of all other gamma emitting nuclides. In addition, a monthly averageH-3 concentration limit of 0.1 uCi/ml applies to these discharges, not to exceed 10 mCi/day.
A. Action Level Development
Given the impact of a non-compliance event involving exceedance of a permit limit, it is reasonable and prudent to establish internal action limits for controlling liquids contained in cooling systems or other potentially activated/contaminated liquid-handling systems.
In 1997, JLab established action levels for aqueous demineralizer resins of one tenth of the concentration in 10 CFR 20 Appendix B, Table 2, Column 2, in order to allow release of resin bottles for reprocessing. Below this limit, the resin is to be considered non-radioactive. However, no specific guidance was developed for the designation or control of resin media which exceeds the release limit. The limit is applicable to resin only. Internal procedures establish action levels for sewer disposal of End Station Floor Drain sump water and for addressing contamination in soil. The RCG has alsomade some progress on developing a method for analyzing potentially activated/contaminated lubricating oils to support establishment of release criteria for oils.
B. Bases for Action Limits forLiquids
Controls on liquids and liquid systems are based on a number of factors such as; the location of the system, the type of liquid, statutory limits on environmental release, contamination of surfaces and materials and the potential for dosefrom introducing the material into a given environment. Action limits are associated as closely as possible with existing permits where applicable. Wherever feasible, the DOE 5400.5 DCGs are used (with basic dose pathway evaluations) to derive action limits for liquids not addressed by a permit. The action limits contain considerable conservatism, such that we believe it is reasonable to consider liquids that fall below the activity action limits as non-radioactive (where the limit is used to determine the need for radiological control). In some cases, materials above the action level may also be released from radiological control, where analysis shows potential exposures to be below regulatory concern and the Radcon Manager approves such release.
III. Action Levels for Water
A. ENVIRONMENTAL PROTECTION
This section deals primarily with limits and controls targeted at preventing environmental impacts or doses to the public.
1. Groundwater Discharge
The VPDES permit limits radioactivity concentration in groundwater discharged to the surface to the EPA drinking water standard. Quarterly grab samples are taken for permit compliance purposes. Radcon tracks the activity of the dewatering sump discharge on an ongoing basis.
Action LevelAn action level consistent with the limit for C-ring wells (<MDA, where MDA is specified as 1000 pCi/l for H-3) will be applied to this continuing monitoring.
The permit specifies MDA values for four nuclides and gross beta. Adopting these values for action levels with regard to the dewatering sump is analogous to their use in the C-ring monitoring well system as a means to ensure that no degradation of offsite surface waters occurs.
Action TriggeredShould the action level be exceeded, immediate corrective action is warranted, and would include:
(1) an investigation into the possible sources of the radioactivity, and
(2)follow-up sampling of the sump at increased frequency; and potentially:
(3) curtailment of accelerator operations,
(4) discussions with the Virginia Department of Environmental Quality regarding temporary variance to the permit limits, or
(5) diversion of the discharge flow to sanitary sewer (which would require consultation with HRSD).
It should be noted that MDA for H-3 analysis at Jlab is routinely about a factor of two better (lower) than the permit-required MDA. Any detectable activity in a location for which MDA is the action level will trigger action, including anomalous sample results that indicate activity but do not meet the statistical requirements for MDA.
2. Other Releases to the Surface
Although the VPDES permit does not specifically address surface discharges other than from groundwater, it is reasonable to follow a similar approach for all surface water regardless of the source. That approach is applied as follows.
Discharge Limit Primary onsite limit for all surface discharges: Under normal conditions of operation, no liquids with activity greater than the EPA drinking water standard* shall be intentionally discharged to the surface without the express written permission of the Radcon Manager.
Action Level For the system of surface water discharge (stormwater) channels around the site, an action level equal to the C-ring wells (<MDA) will be used.
Action TriggeredShould this action level be exceeded at the site surface water outflow points (location of routine sampling), immediate remedial action is warranted, and would include:
(1) investigation to determine the source of the activity,
(2) follow-up sampling in additional water channels leading to points of site outflow, and if necessary
(3) isolation of the sluice gates at the site outflow.
3. System Limits and Controls
Controls on activity levels in various liquid systems will be implemented to minimize the potential for environmentally significant discharge events. The threat to surface water quality exists mainly from two broad categories of discharge: (1) discrete spills of small quantities of significantly contaminated water, and (2) large volume or long term leaks or spills from mildly or minimally radioactive systems. Large releases of highly radioactive water (i.e. 10 times the drinking water limit) directly to the environment are not considered credible events due to enhanced integrity and containment design employed in the affected systems.
It is unlikely that small spills of water (even if highly contaminated) could present a condition that would jeopardize the quality of the surface water leaving the site. High activity water (or other liquids) will be primarily controlled based on limiting conditions such as potential surface contamination or uptake by workers. However, controls on handling such water must also ensure that environmental hazards are minimized. The specific criteria for establishing these controls are described elsewhere in this document.
*Reference to the EPA drinking water limit refers to the stated limit of 2E4 pCi/l for tritium, and the implied concentration limit (based on dose) of four percent of the DCG for other single nuclides. For mixtures, the sum of the fractions of the concentration of each nuclide to four percent of its DCG must be less than 1.
The most likely scenariofor environmental releases is the loss of water from a large volume system such as a low conductivity cooling water (LCW) system. Action levels addressing this condition will be conservatively applied to all systems or storage tanks meeting the following criteria:
-System or storage tankcapacity greater than 100 gallons, and;
-System piping or tanks located outside, or in buildings which, in the event of a system rupture, have no features designed to contain a spill (eg. cofferdams)
Action LevelAn action limit equivalent to the EPA drinking water standard is applied to these cases, such that any such system or storage tank exceeding the limit is scheduled for remediation at the earliest possible time. Normally, this would be in conjunction with scheduled accelerator maintenance periods.
Action Triggered
(a) Remediation for an LCW system will entail purging the system (to sanitary sewer) and refilling with clean water (this process requires about three days).
(b) Portable or fixed storage tanks exceeding the action limit will be moved, drained or equipped with secondary containment provisions if the concentration can not reasonably be reduced.
Maintaining these systems to levels below the drinking water limit minimizes the probability of causing detectable radioactivity in surface water, even in the case of a complete loss of the system contents due to a catastrophic rupture. A hypothetical example is given below.
If we assume the loss of the entire contents of a typical LCW system onto the surface, the spill volume is assumed to be 5000 gallons (personal communication w/Bill Rust of Facilities Management). If the H-3 concentration in the water was at 20,000 pCi/l, the total activity would be:
(2E4 pCi/l)(3.785 l/gal)(5000 gal) = 3.8E8 pCi (380 uCi) in 1.9E4 liters.
We estimate that the site has approximately 3 linear kilometersof surface drainage channels. For this estimate, a channel is assumed to have a semi-circular cross section with a radius of about 180 cm. The storm channels typically contain a volume of standing water which varies with weather conditions. We will assume a baseline condition where the ditches contain 20 cm of water. The initial volume of water in the surface channel is: