API PUBL 7105-1997 Probabilistic Estimates of Dose and Indoor Radon Concentrations Attributable to Remediated Oilfield Naturally Occuring Radioactive Material (NORM)《对补救措施后的油田 NORM.pdf

1、 STD.API/PETRO PUBL 7105-ENGL 1997 Sls U732290 ObOLd T3B c - =!i!: American Ins titute Petroleum / Probabilistic Estimates of Dose and. Indoor Radon Concentrations Attributableto Remediated Oilfield Naturally. Occurrings Radioactive Material (NORM) I Exploration and Production Department API Publica

2、tion 7105 November, 1997 STD. AP I/Pk TRO PUBL I One of the most significant long.term trends affecting the future vitality of the petroleum industry i5 the publics concerns ahut the environment, health and safety. Recognizing documenting performance; and communicating with the public. I trend, API

3、member companies have developed a positive, forward-lookjng strategy called 1, I. API ENVIRONMENTAL, HEALTH AND SAFETY MISSION AND “he members of the American Petroleum Institute are dedicated to continuous efforts to improve the compatibility of our operations with the environment While economicall

4、y devel- oping energy resources and supplying high quality products and services to.consumers. We recognize our responsibility to work with the public, the.govemment, and others to develop and.to use natural resources in an environmentally sound manner while protecting the health . and safety of our

5、 employees and the public. To meet these responsibiliries, API members pledge tg manage our businesses according to the following principles using sound science ts, prioritize risks and to implement cost-effective management practices: To recognize and to respond.to community concern about our raw m

6、aterials, prod- ucts and operations. : To perate our plants and facilities, and to handle our raw materials and products in a . GUIDING PRINCIPLES , . . manner that protects the environment, and the safety and health of our employees and the public. To make safety, health and environmental consider-

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11、or dispose of siniilar raw materi- als, petroleum products and wastes. i . , STD.API/PETRO PUBL 7L05-ENGL 1977 W 0732290 bL77L b7b D Probabilistic Estimates of Dose and Indoor Radon Concentrations Attributable to Remediated Oilfield Naturally Occurring Radioactive Material (NORM) Exploration and Pro

12、duction Department API PUBLICATION 71 05 PREPARED BY: SENES Consultants Limited, June 1997 for the API NORM Issue Group NOVEMBER 1997 American Petroleum Ins titu t e - STD.API/PETRO PUBL 7105-ENGL 1777 0732290 ObOL2 522 D FOREWORD API publications may be used by anyone desiring to do so. Every effor

13、t has been made by the Institute to assure the accuracy and reliability of the data contained in them; however, the Institute makes no representation, warranty, or guarantee in connection with this publication and hereby expressly disclaims any liability or responsibility for loss or damage resultin

14、g from its use or for the violation of any federal, state, or municipal regulation with which this publication may conflict. Suggested revisions are invited and should be submitted to the director of the Manufactur- ing, Distribution and Marketing Department, American Petroleum Institute, 1220 L Str

15、eet, N.W., Washington, D.C. 20005. Excnriw Summary EXECUTIVESUMMARY The objective of the work described in this report was the preparation of a brief technical doaunent evaluating the concentration limit of 30 pCi/g Ra-226 in pipe scale and sludge left near the surce of remediated oil field sites an

16、d returned to unrestricted public acctss. Radiation swcy protocols used by the oil companies and the variability of radioactivity in the NORM material ensure that only smdi isolated arcas may contain Ra-226 at the concentration limit, while the concentration throughout most of the site is wd below t

17、he limit. Analysis was based on estimates (by modding) of the potential transfer of radioactivity through environmental pathways and of potential exposures to people using the remediated site. The scope of work induded an assessment of potential dose from radioactiviry in pipe sde and sludge to user

18、s of remediated pits, tank battery sites, and land frms. In this assessment, an estimated distribution of radium concentration in NORM materiai, ranging from 30 pCi/g down to natd background lcvcls (based on Octos data 1989), was induded as an integral component of the pathways and exposure models.

19、This fndamental difference in waste characterization sets this assessment apart from d previous work The probabilistic method used br caldating the potential doses and indoor radon concentrations is consistent with the new policy announced by EPAs Science Policy Council in February 1997 which recomm

20、ends application of such methods. Thii assessment focussed on external gamma doses and indoor radon concentrations to which users of remediated oil field sites as housing developments would be potentially exposed. An empirical model using the large data base of measured radon concentrations in homes

21、 across the United States was developed to estimate the annual average radon concentration in homes built on remediated sites. The external gamma radiation model was based on dose calculations and ficcors reponed in NCRP #34 (1987). Both models were assessed using probabilistic methods so that the p

22、redicted distribution of doses incorporated the uncertainty and variability of input parameters. Using the disuibution of Ra-226 concentrations in NORM material predicted by Rogers et al. (1989) and based on Ottos measurements (1989) (except chat all materiai above 30 pCi/g was removed), the increme

23、nta gamma radiation doses to residents of homes built on remediated sites (no cover over the NORM) and total indoor radon concultracions were calculated to be: 32105 - 16Junc 1997 s-1 STD.API/PETRO PUBL 7105-ENGL 1997 0732290 DbD199q 3T5 = Runcdiutd site Pit and Tank Bacrey Landfum Natuml Background

24、* Inmend External Gamma Dase, Indoor Ridon Concrntrahn mredy from Ra-226 only (tomb, pci/L Mcui 95* Pcrccntik Mcui 95“ Percentile 17 70 1.4 4.6 6.9 35 1.4 4 .O 4.2 5.9 1.3 3.9 Cunm? dose for tomi Ra-226 in naturai background. Runcdiurd Site Pit and Tank Bancry Landfarm The dues for natural backgroun

25、d were modeied using a Ra-226 concentration in soil of i. i pCi/g. Mcui 95* Percentile Mcui 95* Pcrntiie 110 160 6.1 21 . 48 100 2.5 8.4 The distributions of predicted indoor radon levels from the distribution of Ra-226 concentrations in remediated pits and land hm appliutions wen almost indistingui

26、shable hm the measured distribution of indoor don lev radon exhalation rate the rate at which radon is mined per unit surface area of soil, pCi m-z s- radon dation rate factor the rate at which radon is emitted per unit surface arca of soil per unit Ra-226 concentration in the soil, pCi m-2 s” per p

27、Ci (Ra-226) g” WL Working Level - 100 pCi/L each of Rn-222 and short-lived progeny down to Po-214 WLM Working Level Month - exposure to 1 WL for 170 hours 32105 - 16 JUC 1997 - V SENES Consultanu Limited STD-APIIPETRO PUBL 7LOS-ENGL 1997 0732290 Ob02001 133 1.0 INTRODUCTION 1.1 BACKGROUND Oil and na

28、tural gas reservoirs typically contain large quantities of saline water which arc produced with the oil and gas. Approximately 92% of produced water is reinjeaed for disposal or enhanced recovery, and the remainder may be disposed on the surface or reused for other purposes such as a source of irrig

29、ation water. Radioactivity concentrations in produd water from most wells (at least 75%) are at natural background levels, but in water from some wells, the radium (Ra-226, Ra-228) concentration can be as high as thousands of picoatria per liter (pCiL) usually amibutable to Iod high concentrations o

30、f radium in the rock formations. Occurruices of elevated levels of naturally occurring radioactive matcrial (NORM), particularly radium, in produced water have ben reported widy around the world. At the surfce, produced water is exposed to changing physicai and chemical environments that ofkn cause

31、the radium, when it is present, to precipitate onto piping and other proacss vessels. Typicaiiy, the radioaaivity is found in pipe de near the wcll head or in sludges separated from the produced water. At intervais, pipe scale and sludge are removed and disposed to maintain process equipment. The pi

32、pe scale and tank bottoms can end up in waste pits, in seepage into soil under tank baneriu. or at land frms. Severai researchers have identified the radioactive species in oil field NORM and have measured their concentrations in pipe scale and sludge. Other charaaeristics have also been measured su

33、ch as radon (Rn-222) emanation haion, radon exhalation rate, leachabiiiry, etc Bascd on these data, aumata of potential radiation doscs to members of the public who may live on or othenvise use remcdiated oil field sites have been made. The results of some of thex assessments indicate that potential

34、 exposures and doscs may be in excess of regulatory criteria or guidelines. Those assessments were made using simpliFmg assumptions which tended to inmase the predicted doses over those which are likely to occur. Other studies indicate very lide probability that exposures will be in excess of regula

35、tory criteria or guidines. This analysis was carried out to more accurately portray the variability in radium concuitnaon in NORM material and to remove some of those overly- conservative assumptions, while remining many conservatisms in the modelling to ensure that predicted doscs and radon concent

36、rations would exacd those which may actually occur. 32105- 16Jun1997 1-1 SENES Consultam Limited STD.API/PETRO PUBL 7105-ENGL 1777 w 0732290 Ob02002 07T The objective of the work described in this report was to prepare a brief technical anaiysis of the radium concentration limit of 30 pCi/g in pipe

37、scaie and sludge left near the surfacc of remediared oil fieid sites and returned to unrestricted public access. Anaiysis of this limit was based on modelling of the potentiai rransfer of radioaaivity through environmental pathways and of potentiai exposures to people using the remediated oil fieid

38、site. Estimated exposures and doses were compared to regulatory limits and guidelines. This document may ais0 seme as the basis br discussion on limits with state regulators, for arunple concerning put N of the ddi recommendations fiom the Conferencc of Radiation Control Program Directors (CRCPD). T

39、he scope of work induded an assessment of potuitiai dose and indoor don concentration from radioactiviry in pipe scale and sludge to users of remediated pits, rank battery sites, and land hms. The assessment considered existing sites and future sites that have been and will be remediated under the c

40、riterion that dl materid containing Ra-226 at conculmtions greater than 30 pCi/g will be disposed by alternate mans. Therefore, potencial dosa fiom NORM containing Ra-22G concentrations in excess of 30 pCiig were beyond the scope of this report. In this assessment, an estimated disuibution of radium

41、 concentration in waste (based on Ottos dan 1989), ranging from 30 pCi/g down to naid background levcis, was induded as an integni component of the pathway, and exposure models. This fundamend difkencc in waste charaaerization sets this assersmenr apm from ail previous work The probabilistic method

42、used br calculating the potential doses and indoor radon concentrations are consistent with the nm policy announced by EPAs Science Policy Council in February 1997 which recommends application of these methods. 1.3 STUDY APPROACH AND CONTENTS OF THIS REPORT To estimate potenuai doses to members of t

43、he public and indoor radon concentrations to which they may be exposed, a three stage approach was used: (1) radioactive source (NORM) chanacriution; (2) screening asscssment of potentiai exposure pathways by deterministic methods to identify those pathways which contribute the largest dose; and, (3

44、) assessment of the major contributing exposure pathways by probabilistic methods to estimate the potentiai dosa and indoor don concentrations, and the variability in these estimates. A computerized literature search was mied out to identifj. infrmation that would be usehl to this study. Copies of p

45、otentidly useful information that were not available at SENES were requested fiom the American Petroleum Institute and its members, or dinaiy horn the authors. The data were 32105 - 16 JUIBC 1997 1-2 SENES Gnsulunu LiMd reviewed and summarized in Chapter 2 and Appendix A of this report. The review f

46、ocussed on the key parameter values such as the distribution of radium concentration in NORM, the radon emanation fraction, and the radon exhalation rate. The potential doses to users of remediared sires as a housing development would exceed potential doses fiom ali other forsecable uses. The larges

47、t contributors to incremental dose to residents who may live on the remediated oil field sites were identified by a screening assessment which included evaluation of the following pathways: external gamma radiation; inhalation of resuspended dust; ingestion of dust and dirt; ingestion of weil water,

48、 consumption of vegetables fiom a baed garden; and consumption of beef, milk, eggs and poultry meat. The pathways and dose dadations are described in Chapter 3 and Appendix C. Throughout this document, dose refers to committed effective dose unless otherwise indicated. External gamma radiation and e

49、xposure to radon progeny (Po-218 to Po-214) were determined to be the largest contributors to potential doses to residents. Exposure models and the best available distributions for parameter values were developed to implicitly include the uncertainty and variability in the input data. Potential doses from external gamma radiation and the estimated total concuitration of radon in indoor air were estimated by probabilistic calculations. Finally, the estimates of mean and extreme (95* percentile) values of dose and radon con