IV. STACK SAMPLING - plutonium-238 Particle emissions

V. NON-POINT SOURCE MONITORING EVALUATION

VII. Issues Peripheral to the Scope of the Audit

APPENDIX A: IEER'S MEMOS AS REPRINTED IN THE ITAT'S FINAL REPORT

In relation to the first of these substantive technical deficiencies, IEER has also concluded that the ITAT should have found LANL to be in substantive breach of its compliance obligations under the Subpart H and related requirements under the Clean Air Act. As a result IEER finds that the main findings of the ITAT that LANL is in compliance with Subpart H and that the compliance program of LANL has no substantive technical deficiencies to be in error.

IEER's conclusions regarding the substantive breach of Subpart H are based on the monitoring of the audit, which included review of the data, review of the regulations, and review of the specific examples of a lack of quality assurance in user supplied data that came up in the course of the audit. As regards these examples, IEER detailed them to the ITAT in the course of its monitoring. (The IEER memoranda, as reprinted in the ITAT Final Report, are appended to this report.) In these memoranda, IEER also specifically recommended to the ITAT that it investigate the issue of quality assurance in regard to user supplied data in more detail with specific reference to compliance.

In reviewing the ITAT's findings and analysis as well as the conduct of the audit itself, IEER has concluded that the ITAT's failure to find a substantive technical deficiency in this area arose partly from a near-exclusive focus of the ITAT's audit on the work of the MAQ, rather than on the performance of LANL as a whole, in complying with Subpart H. The problem in this case does not lie in the work of the MAQ, but in the failure of LANL as a whole to require users to adopt a quality assurance program to ensure the integrity of the data supplied to MAQ. In effect, the ITAT Final Report implicitly deals with the compliance issue as if it is MAQ rather than LANL that must be in compliance. This implicit narrowing of the focus is incorrect, since Subpart H does not apply to MAQ but to LANL as a whole. IEER therefore finds that the ITAT's third audit was not as complete as it should have been, even given the limitations of the resources available for the audit.

We found that the ITAT's evaluation of the 1989 EPA Guidance Document cited in Appendix D of 40 CFR 61 was inadequate. Further, the ITAT Final Report did not present a careful evaluation of:

• the lack of adequate technical expertise in the MAQ for assessing the accuracy and quality of the data supplied by the facilities;
• the implications for quality assurance of the exemption that the EPA granted to the DOE from periodic confirmatory measurements of emissions from minor sources.

The ITAT did not evaluate at all the internal DOE quality assurance (QA) requirements that contractors are obliged to follow to protect health and the environment. Further, despite the prominence of quality assurance issues during the third audit, and despite the fact that they were part of the original lawsuit filed by CCNS, the ITAT did not interview any LANL quality assurance personnel outside the MAQ, past or present, during the third audit.

In view of these omissions, IEER finds that the ITAT third audit was not thorough, even within the limitations of the resources available to it.

Finally, in view of our conclusion of LANL's substantive breach in compliance with Subpart H, as well as the other substantive technical deficiencies itemized above and discussed in more detail below, IEER has concluded that that ITAT should have called for a fourth audit in order to ensure that LANL comes into full compliance. The Consent Decree requires the auditor to make a judgment about whether a fourth audit is needed based on whether there are substantive deficiencies in the program. Since IEER finds that the audit was in error in not finding such deficiencies (because the audit was neither complete nor thorough), we find that the ITAT also erred in terminating the audit process at the third audit.

II. Quality of Usage Survey Data Used in Emission Estimates

Usage data are part of an estimation process that serves as a substitute for periodic confirmatory measurements of unmonitored sources, which measurements are required under 40 CFR 61 Subpart H. IEER has reviewed Subpart H as well as related regulations and guidance from the EPA regarding quality assurance (QA) as it applies to usage data. We have also reviewed the June 1996 Federal Facilities Compliance Agreement (FFCA) between DOE and the Environmental Protection Agency (EPA) in this regard.

The issue of quality assurance in regard to compliance has a long history at LANL. CCNS raised it in the lawsuit it filed against DOE that resulted in the Consent Decree. Years before that, in early 1992, the Tiger Team report raised QA issues in regard to LANL's air quality compliance. In 1991, the DOE scientist responsible for evaluating LANL's clean air program, Frank L. Sprague, noted in regard to dose estimation that "the model and its output is valid; it is the input data that is questionable." (DOE Albuquerque Operations Office, August 7, 1991.)

Appendix D of 40 CFR 61 has implicit QA requirements for user supplied data. While Appendix D of 40 CFR 61 does not itself make explicit reference to quality of data, it does refer to an EPA guidance document for compliance as it applies to NRC-regulated and other non-DOE facilities and suggests that the procedures in it be used (reference 1 in Appendix D). ^c This EPA document contains the following statements regarding data that are to be used in calculations:

Further, the fact that the FFCA has exempted LANL from the requirement under Subpart H that it make periodic confirmatory measurements of unmonitored sources itself places a requirement upon LANL to ensure that the quality of the input data into the process of estimation of doses is equivalent to that which would have been obtained by those periodic confirmatory measurements. Without the assurance of input data quality, the FFCA exemption is itself invalid, since it then comes into conflict with the requirement of periodic confirmatory measurements.

Finally, since the FFCA has expired and the federal government has not replaced this with another agreement, LANL would appear to be employing usage data in place of periodic confirmatory measurements without any explicit legal basis. The ITAT should have investigated this issue because it was raised during the course of the audit; it did not do so.

In sum, the ITAT seems to have evaluated the compliance of the MAQ, rather than LANL. Its failure to audit the relevant parts of LANL contributed to its erroneous conclusion that LANL was in compliance. IEER has concluded that the ITAT should have found LANL in substantive breach of its Subpart H compliance obligations in regard to dose estimation for unmonitored sources.

Section 4 of DOE Order 414.1A sets forth the specifics of DOE QA program requirements. Among other things, it requires the development of procedures to "detect and prevent quality problems." (Italics added). The LANL program for estimation of radionuclide usage, and hence of doses based on this data, completely fails the test of prevention of quality problems, since there is neither a QA program nor any institutionalized check on the quality of data supplied by the facilities themselves. The MAQ has a procedure for checking some of the data, and has corrected mistakes in this way. But the quality of most of the usage data from sources deemed to have very low emissions (Tier IV sources^g Specifically, he raised some questions as to whether and when the ITAT had consulted LANL personnel outside MAQ regarding QA procedures and requirements. We also interviewed a former lab employee, Mr. William J. Parras, at the suggestion of Mr. Mechels. Mr. Mechels was also the one who pointed us to the general laboratory QA requirements. Mr. Mechels was an interested member of the public who had raised similar questions during a public meeting at the first or second audit. Yet the ITAT neither followed up with him nor reviewed the DOE QA program requirements, of which he has considerable knowledge, particularly as they concern LANL.

Besides the problem of quality of data that is routinely maintained and reported by the facilities to MAQ, the lack of an independent QA program that is thoroughly implemented for all data also raises the possibility of cover-ups of embarrassing incidents. This possibility is raised by the charges that Bill Parras made when IEER interviewed him:

Further, the issue of QA and lab whistleblowers was raised in a vigorous way by CCNS during the very first audit. But apart from one interview with one whistleblower, Joe Gutierrez, during the first audit, the ITAT did not systematically follow up this issue. The ITAT did not conduct interviews with whistleblowers during the third audit even when very specific issues regarding QA came up during that time.

The allegations made by Mr. Parras are not part of IEER's findings. But they have raised our level of concern regarding the integrity of environmental, health and safety data at LANL. If the allegations made by Mr. Parras are verified, and if the problems have not been systematically corrected, the problem of non-compliance may be even more complex and broad than indicated here. However, an investigation of these problems is beyond the scope of IEER's monitoring work. We find that it was the responsibility of the ITAT to investigate them, but it did not.

IEER finds that LANL has not met the minimal conditions for assuring the integrity of the usage data that would make the process of dose estimation allowed by the FFCA for minor point sources equivalent to the process mandated by Subpart H of making periodic confirmatory measurements. LANL is in violation of requirements for quality assurance that are clearly implicit in Subpart H, in Appendix D and in the EPA guidance document to which it refers, as well as to internal DOE QA requirements. The ITAT should therefore have found that LANL is in substantive breach of its compliance obligations in this regard. The ITAT should also have recommended that the EPA revoke the substitute procedure and require periodic confirmatory measurements for all unmonitored sources. We believe that LANL has not earned the prerogative of using a less onerous substitute process because it has failed to institute a process of quality assurance for user data and because facility personnel have refused to participate in setting up a LANL-wide database that might have addressed this problem. Finally, the FFCA has lapsed. This re-enforces the primacy of periodic confirmatory measurements for sources that are not continuously monitored. The ITAT should have recommended the institution of periodic confirmatory measurements as the main basis for compliance assessments for these sources.

III. Evaluation of TA-54 Waste Characterization Dose Calculations

IEER finds that the ITAT's approach to the issue of monitoring emissions from TA-54 mobile waste characterization efforts is not adequate. The dose calculated by LANL from this potential source is a mere 20% smaller than the dose that would require monitoring. The ITAT recommends "additional demonstration to show that the calculation done to determine monitoring requirements for the proposed TA-54 operations is valid so that it can be more thoroughly defended. Ideally, the operations would be monitored for a period of one year or more, during which the highest-wattage drums could be processed, to clearly demonstrate low emissions." (p. 37)

Given the uncertainties in the assumptions, (e.g., the source term is likely to be non-uniform over the year because re-suspended material is associated with high-wind speed situations), IEER finds the ITAT's recommendation to be insufficient. IEER's conclusion is that the ITAT should have judged the LANL plan to be substantively deficient and recommended that the proposed TA-54 operations be continuously monitored. Doses above the monitoring limit may otherwise go unmonitored.

IV. Stack Sampling - Plutonium-238 Particle Emissions

IEER expressed a concern in the second and third audits that releases of large particles of Pu-238, which has a high specific activity, could be a source of confusion that could affect response to increased emissions from a LANL facility. The ITAT's response to our concerns did not address the central issue that IEER raised. The ITAT Final Report simply evaded the issues raised by its own calculations in the draft report, giving rise to the problems with the calculations cited in the IEER comments. It remains true that at the reported level of estimated doses from CMR Stack 28 and 10 micron AMAD particles (the example originally used by the ITAT), the procedure used by LANL would not be sufficient to detect the level of doses being estimated. For an estimated dose of 1.1 x 10^-3 mrem due to Pu-238, a small fraction of one particle would be collected on the air monitoring filters cumulatively over the entire year, if the particle size were 10 microns. Only about 0.07 particle would be collected annually on the half-filters that are being analyzed. (In practice, this means it would take about 14 identical systems for 1 particle of 10 microns to be collected cumulatively on the half-filters of all of them put together over one year.) Hence, the sampling rate of 2 cubic feet per minute, while adequate for doses of 1 millirem or more, fails to provide meaningful results at doses of less than ~10^-2 mrem (less than one particle per year on an annual collection of half-filters), assuming a particle size of 10 microns. System performance at a dose of 10^-2 mrem from a single radionuclide is important from a compliance point of view. 40 CFR 61.93 (b)(4)(i) requires measurement of all radionuclides that contribute 10 percent of the dose for any release point, and monitoring of all release points that produce a 0.1 mrem dose or larger. It should be noted that the system acceptability improves as the particle size decreases, since the number of particles for a given dose increases rapidly as particle size decreases. However, the system remains marginal even for a particle size of 5 microns. Assuming 2,800 picocuries per 10 micron particle, for a dose of 1.1 x 10^-3 mrem, the number of particles collected in the air sample would be 4 orders of magnitude less, that is, about 0.14 particles per year. Therefore the measurements are in fact likely to be erratic and inaccurate (still using the above assumptions). The sampling rate of 2 ft³ per min is not adequate to measure the level of releases corresponding to a 1 x 10^-3 mrem per year dose from Pu-238 to with in an order of magnitude of accuracy under the stated assumptions for large particles. The issue is not the number of particles for a 10 mrem dose, but the number of particles for the level of emissions and doses that are claimed to be measured and estimated accurately. At the level reported by LANL, emissions estimates for Pu-238 are likely not accurate for large particles even if the whole filter were being analyzed, let alone just half the filter. The system is of dubious value even for 5 micron particles.

It may be, as the ITAT has concluded that emission of particles of this size is unlikely. However, it also remains true that at the reported level of emissions, the LANL system would not be able to detect the emission of these particles. If only the second factor were to be considered, LANL would be violation of the requirements of Subpart H. But given that the exhaust air has HEPA filters, we have not found that LANL is in violation of the monitoring requirements in this area. Still, we have concluded that the ITAT should have found this as a substantive technical deficiency. Moreover, we are dismayed that the minimal action that could be taken to improve the accuracy of the reported dose estimate - the analysis of both halves of the filter - was not recommended by the ITAT as a routine requirement for those areas where Pu-238 emissions are possible.

V. Non-Point Source Monitoring Evaluation

The ITAT's review of the issue of measuring of plutonium-238 particles in the AIRNET system is not in conformity with prevailing U.S. regulations. So far as we can determine, the ITAT has used the lowest dose conversion factor from ICRP 72 in making these dose calculations (though that is not explicitly stated in the ITAT Final Report). The prevailing EPA regulations do not use ICRP 72 but use EPA Regulatory Guide 11. Further, the ITAT has not explored the statistical aspects of the situation fully in regard to potential doses to the public from Pu-238 particles. Further the ITAT scenario does not correspond to the single-particle-over-two weeks scenario that we had asked it to explore. We present the details of our calculations and reasoning below.

In the MAQ-AIRNET system, the largest allowable Minimum Detectable Limit (MDL) for any radionuclide is set to be equivalent to a dose of 0.1 mrem/year. A pure Pu-238 oxide particle with 1 �m aerodynamic diameter (AMAD) has an activity of 2.8 pCi; a particle with 3.4 �m AMAD has an activity of about 100 pCi. With this information we can assess the dose that would arise if there were just one particle deposited on the filter every two weeks.ⁱ We present our calculations here because our analysis shows that the ITAT appears to have misinterpreted the nature of the problem and hence arrived at an incorrect conclusion.

The scenario we postulate, which we asked the ITAT to review, is that of a single particle deposited in one two-week period on the filter of an AIRNET station. A single pure Pu-238 particle of 1 �m AMAD, if breathed in by someone, would produce a dose of 1.1 mrem.^j If the particle were 3.4 �m AMAD, the dose would be 39 mrem. Using the same assumptions as the ITAT for breathing rate, the AIRNET station draws in air at about seven times the breathing rate of an adult. In such a situation, there is a 13 percent probability that a person would breathe in at least a particle in the two-week period. Another way of looking at this situation is that if five people were to breathe in the ambient air being sampled, there would be a 50 percent probability (approximately) that at least one of them would breathe in at least one particle in the two-week period.^k

Yet another way to view this situation is that the expected value of dose over a two-week period would be about 0.155 mrem. Further, it would take only a handful of people exposed to ambient air such that there is one particle of plutonium-238 deposited on the filter in two weeks for at least one of them to get a dose of at least 1.1 millirem in the case of a 1 �m AMAD particle and 39 millirem in the case of a 3.4 �m particle with 50 percent probability. The former is greatly in excess of the 0.1 mrem dose corresponding to the target MDL; the latter is greatly in excess of the Subpart H legal limit. In case several people are exposed, the target MDL may be exceeded even if the postulated event occurred only in one two-week period in several years, with the frequency (or rarity) depending on the particle size distribution and the size of the exposed population. The ITAT did not provide any analysis regarding the issue of multiple people being exposed to the ambient air sampled by the AIRNET station during the two-week period postulated in the scenario.

IEER disagrees with the ITAT statement that "[t]he IEER concern about a single particle of 238Pu being missed and resulting in a significant dose seems to be unfounded" (p. 57). The ITAT has failed to properly consider the various statistical aspects of the situation and also used the smallest number for dose conversion factor from ICRP 72. While the assumption of insoluble plutonium is reasonable for plutonium oxide, the ITAT should have used the dose conversion factor from the prevailing EPA regulations to which LANL must conform. Had it done that it would have found that the target MDL would not be met in the postulated scenario, contrary to its finding. Finally, the ITAT did not consider the situation when multiple people might be exposed to the polluted air. We therefore find that the ITAT conclusion that IEER's concerns are unfounded is in error. We reiterate that the current LANL practice of analyzing only half of the filter paper by alpha spectrometry increases the likelihood of a significant dose being undetected if the particle were to remain on the half-filter composite that is not subjected to alpha spectroscopy, especially in the case of small particles.^l The ITAT should revise its dismissal of our concerns and issue a recommendation that both halves of the filter be analyzed.

The problem constitutes a substantive technical deficiency of the AIRNET system and the ITAT should revise its Final Report and identify it as such. The assertion that the postulated situation is unlikely to arise does not resolve the issue. The estimated doses are high enough, especially if more than one person is exposed to the air, that a quantitative probabilistic analysis of the problem, including an analysis of the possible Pu-238 particle size distribution is needed. Such an analysis, including particle size distribution analysis, is necessary if LANL's claim of an MDL corresponding to an annual average dose of 0.1 mrem is to be scientifically credible. The ITAT should have recommended that it be done.

The ITAT has recommended that LANL "reevaluate the sampler siting with respect to the North Mesa residences and the MDA-U diffuse source...." (p. 62) However, the ITAT did not cite the problem of the lack of such an evaluation or the failure to install an AIRNET station corresponding to a "TA-21 East" source, which in the absence of such an evaluation should be a substantive technical deficiency. The procedure that was adopted by LANL for sampler siting north of the Laboratory was based on an annual average source term from a diffuse source whereas it is clearly established that a diffuse sources of resuspended material has a markedly different time-release function. The LANL procedure does not account for that fact and hence is a substantive technical deficiency. The ITAT should have cited it as such. IEER also has concluded that until such a time as it can be definitively shown that such a station is not needed, that the ITAT should have recommended that additional AIRNET station be installed at the eastern edge of North Mesa residences at this time.

VI. Complex Terrain Modeling Comparisons

The ITAT provided additional calculations comparing complex terrain model with the model used by LANL (EPA-approved CAP-88) and concludes that the latter one would still provide a conservative estimate of dispersion at relevant distances. This, however, is only correct if the assumption of continuous releases is valid. Thus, the assumption that CAP-88 provides a conservative estimate of dispersion under all the circumstances relevant to dose estimation at LANL is not correct. Considerable further investigation, using specific source characteristics, both for point and diffuse sources, is needed to arrive at a definitive conclusion.

The calculations presented by the ITAT are based on annual average c /Q values. LANL is not required by Subpart H to use this assumption; for the LANSCE facility, doses are calculated based on monthly averages. Many stationary sources and all diffuse sources are highly non-uniform. Particle releases from stationary sources often occur over short periods of time. Emissions from diffuse sources due to resuspension are associated with high-wind speed situations (see IEER memo of September 16, 2002). It is possible that the c /Q values of such releases are significantly larger than the annual average one and that resulting doses are larger than if the same release is assumed to be equally distributed over the year. The comparison of annual average c /Q values does not address this concern.

The ITAT Final Report shows that the doses based on an assumption of short-term releases could be far higher than annual average doses. The fact that in the example chosen the dose is still far below the regulatory maximum is not relevant to the choice of the model. Until a complete and definitive comparison of the complex terrain model under the prevailing conditions of episodic releases can be done for the entire LANL site to sufficient degree of accuracy to show that the CAP-88 approach is uniformly conservative, the use of CAP-88 will continue to be a substantive technical deficiency and should be regarded as such. The IEER commends the ITAT for having carried out the sample calculations using CALPUFF and for responding in detail to IEER's comments. However, the facts remain that LANL is located on complex terrain and has episodic emissions and there is still no demonstrated conservative procedure for modeling the site's emissions even though the ITAT has declared an end to the required audit process. The ITAT's ending of the audit process at the third audit was therefore inappropriate.

VII. Issues Peripheral to the Scope of the Audit

During this audit, IEER again raised concerns (Final Report, Appendix B) about the quality of the Neighborhood Environmental Watch Network (NEWNET) data and the usefulness of the NEWNET web site. The ITAT recommends that LANL continue to take steps to ensure the quality of web-posted data, resolve any apparent calibration problems, and investigate the most appropriate method for developing a representative characterization of background. IEER agrees with this recommendation. IEER further stresses that the presentation of the data on the NEWNET web site should contain a description of the limits of the system detailing under which conditions the system is able to monitor routine or accidental emissions from the LANL site and which are not detectable by the NEWNET system. The NEWNET web site should also contain continuously updated reports on the steps taken to improve the quality assurance and quality control (QA/QC).

The ITAT has not addressed the issue of uncertainties in CAP-88 dose calculations although it had been raised during this and past audits. We still consider this issue peripheral to the scope of the audit because estimates of uncertainty are not required by the regulation. The calculations made by LANL using CAP-88 do not include estimates of uncertainty because the EPA has not deemed it necessary; however, in theory, the model does appear to compensate for not explicitly addressing uncertainty by producing results that are biased high in those cases where the assumption of continuous releases is valid. However, as discussed above, this is not true in all cases.

VIII. ITAT Model for Future Stakeholder Involvement

IEER has provided its comments on the stakeholder involvement to the ITAT in reviewing the draft report. The current context is not suitable for a voluntary compliance model recommended by the ITAT, though there might be a time in the future when it might be more appropriate.

A part of the reason for our conclusion is the fact that throughout the audit process, up to and including the third audit, LANL and DOE have never acknowledged that they were in violation of Subpart H, despite the finding of non-compliance by the audit tem and the concurrence in that finding by the IEER monitors of the audit. Further, the failure of the third audit to cite the substantive technical deficiencies in the program as well as the lack of thoroughness and completeness of the third audit, which was conducted under the Consent Decree, lead IEER to the conclusion that the basis for a truly independent voluntary compliance program does not now exist. IEER will therefore not go beyond what it has already stated in public as part of the comments on the draft third audit report at this time regarding the process. These comments were published by the ITAT. IEER may make further comments on a proposed process if a fourth audit is conducted under the Consent Decree, depending on the outcome of that process.

Endnotes ^{a b} Carl E. Edlund, Director, Mulitmedia Planning and Permitting Division, U.S. EPA, Region 6. Letter to David Gurule, Area Manager, Los Alamos Area Office, U.S. DOE, December 17, 1999. Frank Marcinowski, Director of the Radiation Protection Division of the EPA Office of Radiation and Indoor Air confirmed on 17 December 2002 that there is no new agreement with the federal government that has replaced the lapsed FFCA. Personal telephone communications with Arjun Makhijani, 17 December 2002.

^c U.S. Environmental Protection Agency, Office of Radiation and Indoor Air. "A Guide for Determining Compliance with the Clean Air Act Standards for Radionuclide Emissions from NRC-Licensed and Non-DOE Federal Facilities," EPA 520/1-89-002, Washington, D.C., January 1989, p.4-3.

^d Ibid., italics added.

^e U.S. Department of Energy Order 414.1A, Subject Quality Assurance, Approved 9-19-99, Review date 9-29-01.

^f Tier IV are "[a]ny source that does NOT have the potential to contribute greater than 0.001 mrem/yr to any member of the public according to the last usage survey." Los Alamos National Laboratory, Environment, Safety, and Health Division, Quality Assurance Project Plan for the Rad-NESHAP Compliance Project, ESH-17-RN, R2, 10-9-2001. p. 20.

^g IEER interview with Chris Mechels, October 23, 2002.

^h Interview with William J. Parras, October 25, 2002.

ⁱ The ITAT analyzed a case of one particle deposited every week, which would double the estimated doses to people given here since it doubles the concentration of plutonium-238 in the ambient air. The ITAT used a Class S particle assumption. This may be appropriate for plutonium oxide but not for all possible forms of plutonium that might be emitted at LANL. The ITAT obtained a weekly dose of 0.0234 millirem using dose conversion factor. Class F and Class M dose conversion factors would have yielded considerably higher doses -- 0.16 and 0.067 mrem respectively. While Class F and perhaps Class M are not appropriate for plutonium oxide, they are appropriate for other forms of plutonium. We have used conservative dose conversion factors for dose estimation since our choice of plutonium oxide for the calculations is a convenience rather than a technical judgment. The ITAT has published the radioactivity estimates for plutonium oxide particles, and so we used this chemical form as an example in order to have as close a correspondence in parameter choice to the ITAT for the purposes of comparison. Higher dose conversion factors cannot be excluded without more consideration of the matter than the ITAT gave it. Pure Pu particles may also have higher or lower densities than the case of Pu oxide particles considered here.

^j We have used a dose conversion factor of 1.06*10^-4 Sv/Bq for Class W material from Federal Guidance Report No.11, (United States. Environmental Protection Agency, Office of Radiation Programs. Limiting Values of Radionuclide Intake And Air Concentration and Dose Conversion Factors For Inhalation, Submersion, and Ingestion. EPA-520/1-88-020, Washington, DC, September 1988), which is the prevailing regulatory document. A somewhat lower dose is obtained if one assumes a Class Y particle, but the overall conclusions remain the same, since the ratio of dose conversion factors of Class Y to Class W in the EPA Reg. Guide 11, cited above, is about 0.735. The expected value of dose in this case is 0.11 mrem, which is still above the limit corresponding to the target MDL.

^k We use a Poisson probability distribution, and assume that one Pu-238 particle in oxide form is taken in, on average, in two weeks by an AIRNET station. This yields a mean waiting time for a person to breathe in a single particle, � = (air intake rate of the AIRNET station)/(air intake rate of a person) = 163/23, which is about 7 periods of time (of two weeks each). The probability that a person exposed to this air would breathe in at least one particle in a two-week period is given by the cumulative probability, P = 1^-e(-1/�) = 0.13, or 13 percent. For an exposed population of N people, the probability that at least one person breathes in at least one particle in the two-week period is given by P = 1 ^{- e}(-N/�). For � = 7 and P = 0.5, N works out to 4.9, which is rounded up to 5 people.

^l The problem is especially relevant for small particles because LANL does a gross alpha scan on the whole filter as a preliminary screening technique that would be more likely to pick up larger particles.

Appendix A: Selected IEER Memos As Reprinted in the ITAT's Final Report

[not available online]

Appendix B: Other Documents

[not available online]