Document 15x57BZQRZKrjezzyLea8kxko

Reprinted From The Journal of The American Medical Association August 21, 1967, Vol. 201, pp. 577-581 Copyright 1967, by American Medical Association Occupational Acroosteolysis Report of 31 Cases Rex H Wilson, MD, William E. McCormick, MS, Caroll F. Tatum, MD, and John L. Creech, MD In 31 cases of acroosteolysis of the hands of workmen derma. Some have clubbing of the fingers. Only a few associated with vinyl chloride (CH2CHCI) polymerization of the cases have sought medical attention because processes, the osteolysis was specific to the distal pha of symptomatic complaints; the majority have been langes of hands and was frequently associated with Ray found through x-ray examinations of the hands. naud's symptoms. Affected personnel ranged in age from A summary of the physical findings of the ob 26 to 47. The disorder is believed to have resulted from served cases is shown in Table 1, and a detailed de a combination of physical insult, chemical insult, and scription of the two predominantly common symp personal idiosyncrasy. The specific causes are unknown. toms follows; The prevalence was found to be less than 3% among Raynaud's Phenomenon.--This symptom com employees performing similar work. No cases were found plex has occurred in varying degrees, with one or in workmen using or processing the polymer or manu both hands involved. Generally, its effect is observed facturing commercial resins. as marked discomfort on exposure to cold. None of the cases have exhibited vascular changes of the feet. uring mid-1964, several complaints came to our A unilateral sympathectomy performed on one of D attention of soreness and tenderness of the the most seriously affected cases relieved most of fingertips of workmen in a manufacturing plantthe symptoms on that side. The acroosteolysis was polymerizing vinyl chloride (CH2CHC1). Compre not altered by the sympathectomy. hensive examinations of these individuals revealed Roentgenological Changes.--The most unique nothing of significance except a "Raynaud-like phe characteristic of this syndrome is the unusual roent nomenon" of the hands, and in some cases, definite genological findings. These are described as acroos changes of the distal phalanges were apparent on teolysis and are illustrated in Fig 1. It may be present roentgenograms of the hands. Since then we have in all of the fingers and readily observable, or only in observed additional cases of this unusual syndrome. one finger and barely discernible, as illustrated in It is the purpose of this manuscript to summarize Fig 2. X-ray films of the feet, as well as those of the our observations. long bones and of the skull have been made in some of these cases, with no osteolysis found other than Description of Syndrome in the distal phalanges of the hands. To date we have observed 31 cases of hand dis orders among 3,000 personnel involved in vinyl chloride manufacturing and polymerization. All have been men, between the ages of 26 and 47. We have not observed any ethnic or racial tendency for the syndrome. The great majority have been char acterized by two common factors: symptoms likened to those ascribed to Raynaud's phenomenon and acroosteolysis of the distal phalanges. A few have had no symptoms but have the roentgenographic evidence of acroosteolysis. Several of the patients have external skin lesions on the dorsal surfaces of the hands and forearms, with a rope-like appear ance resembling changes sometimes seen in sclero- From the Medical Division, B F. Goodrich Cov Akron, Ohio. Reprint requests to 500 S Main St, Akron, Ohio 44318 (Dr. Wil son). Acroosteolysis is a rare clinical entity, with only 72 cases of the familial type reported up to 1965, ac cording to Cheney in his excellent review.* The diagnosis of acroosteolysis requires expert roent genological technique and knowledge. It has been our observations that early cases of acroosteolysis will be missed by the roentgenologist not familiar with this condition. All of the cases on which we are reporting have been confirmed by at least two ex perienced roentgenologists working independently. We established the following roentgenographic criteria for our diagnoses. These are the result of our having viewed several thousand x-ray films of the hand in our search for the cause of the syn drome. 1. General: Roentgenographically, acroosteolysis, as found in workers who are exposed to vinyl BFG04176 20606001 578 ACROOSTEOLYSIS--WILSON ET AL chloride and polyvinyl chloride manufacturing processes, is somewhat different from that found in familial osteoporosis with acroosteolysis and in fa milial osteosclerosis with acroosteolysis. In osteopo rosis with acroosteolysis there may be compression fractures in the spine, and basilar impression of the skull, along with destruction of the midpha langes. None of these findings have been seen in these workers. The changes in the distal phalanges are similar in both conditions. Osteosclerosis acroosteolysis observed by Andren et al2 (University Hospital, Malmo, Sweden) in twins showed diffuse sclerosis, with cortical thick ening of the shafts of the long bones and clubbing of the metaphyseal ends. The phalanges of the hands and metacarpals were foreshortened, and the distal phalanges showed acroosteolytic changes. The feet showed the same changes, except that the distal phalanges were not fragmented. There has been no evident destruction in the mid or proximal phalanges of the thumbs or fingers of these individuals and no evidence of a lytic, destruc tive lesion in the feet. We have not observed any loss of calcium salt in the bones of the wrist and remaining bones of the hand and phalanges in any of these individuals, and there has been no evident sclerosis of the wrist and hand bones. 2. Mild stage: The earliest change found in acroosteolysis in these workers has been a loss of the cortex of one or more of the tufts of the distal pha langes, with no destruction of the tuft or shaft of the distal phalanx. The next more advanced stage may be a small, half-moon cut in the cortex of the tuft of one or more Table 1.--Summary of Symptoms and Findings Symptoms Acroosteolysis without Raynaud's symptoms, one hand Acroosteolysis without Raynaud's symptoms, both hands Acroosteolysis with Raynaud's symptoms, one hand Acroosteolysis with Raynaud's symptoms, both hands No. of Cases 4 5 5 17 Total 31 Clubbing of fingers Skin nodules 8 8 2. Mild stage of acroosteolysis with half-moon de fect of distal phalanx of mid finger. 1. Acroosteolysis with involvement of distal phalanges of all fingers. 20606002 BFG04177 ACROOSTEOLYSIS--WILSON ET AL 579 distal phalanges, or a so-called slice effect along one or more of the tufts. Figure 2 illustrates the small, half-moon cut in the cortex of the distal phalanx of -^the mid-finger. 3. Advanced stage: A more severe lytic destruc tion may be a complete loss of the tuft and a por tion of the shaft of one or more distal phalanges as illustrated in Fig 1 in which the tuft of the distal phalanx of the right thumb and the tuft of the distal phalanx of the left fifth finger are completely absent. Additionally, there may be in the same hand a portion of the distal rim of the tuft remaining, with loss of the proximal portion of the tuft and a portion of the shaft of the phalanx, which can also be identified in the remaining phalanges in Fig 1. This loss may be of a transverse nature through the shaft and the tuft, or of an oblique type loss of bone structure. 4. Healing stage: In this phase, there is often definite fragmentation of the remaining tuft and of the filled-in area where the previous destruction was noted through the shaft of the distal phalanx. This may go on to a complete bony union or remain as a fibrous union with fragmentation. In Fig 3 and 4, x-ray films of the same individual well demon strate this. This employee had almost complete reunion of the multiple fragments when first seen in November 1965 and again in November 1966 (Fig 3). In the latter, the completely healed shafts and tufts of the distal phalanges are indicated by no residual fragmentation with fibrous union. There is a definite shortening of the shaft and a widening of 3. Above, Acroosteolysis with marked fragmentation of distal phalanges in November 1965. Below, Same individu al in November 1966. 20606003 JAMA, Aug 21, 1967 Vol 201, No 8 BFG04178 580 ACROOSTEOLYSIS--WILSON ET AL the shaft and tuft, both in the transverse and the anteroposterior diameter. This is most likely due to a combination of constant pressure, and by the nor mal tension of the soft tissues, particularly the ten dons to the distal phalanges. Occupational Aspects of Syndrome Based upon our observations of these 31 cases, it appears as if this syndrome may be of occupational origin and is somehow related to the process of vi nyl chloride polymerization. Its specific cause if not presently known. We are performing extensive re search in an effort to find the cause. Two other pa pers referring to the condition have appeared in the literature. The publication by Suciu et al3 contains no specific information, and merely alludes to some hand problem. That of Cordier et al4 presents case histories with symptoms similar to many of the cases we describe. This syndrome differs from idiopathic and familial acroosteolysis in that only the hands are involved. Vinyl Chloride Polymerization Process Polyvinyl chloride is a widely used synthetic resin. It has been manufactured commercially for more than 30 years and is used in upholstery fabric, floor and wall tile, wire insulation, phonograph records, and many other commonly used commodities. For many of these uses, the resin (CH2CHC1)X is mixed with other materials to achieve the desired physical characteristics. The hand syndrome occurs apparent ly only in those people exposed to vinyl chloride or to other chemicals used in the manufacturing process of the resin itself or both. In addition to our exami Table 2.--Age Distribution of Cases Acroosteolysis Without Age Group Raynaud's Symptoms 20-29 1 30-39 4 40-49 4 Acroosteolysis With Raynaud's Symptoms 4 12 6 nations of 3,000 personnel performing vinyl chloride manufacturing and polymerization, we have exam ined more than 1,000 individuals who handle the finished resin or who process it into plastic prod- ducts. No cases of acroosteolysis have been found in these 1,000 persons. Basically, the manufacture of polyvinyl chloride consists of polymerizing vinyl chloride. The reac tion is accomplished in closed containers (polymerizers) with suitable catalysts and emulsifiers. Copolymers, formed by combining vinyl chloride with other monomers, create variations of the homopolymer. These are commercially produced. Following polymerization, the resin is washed, dried, and sold as a finely divided white powder. The polymerization operations are carried out in closed processes and provide little opportunity for employee exposure. Following the completion of the polymerization reaction, periodic cleaning of the walls and agitator of the polymerizer is necessary. The frequency of this cleaning and its method varies with the type of material used in these vessels and with different manufacturers. The most common practice has been to accomplish the cleaning man ually by using hand scraping techniques, with work ers spending several hours each day on this job assignment. Personnel performing this job are com monly referred to as "polycleaners." 20606004 BFG04179 JAMA, Aug 21, 1967 Vol 201, No 8 ACROOSTEOLYSIS--WILSON ET AL 581 Epidemiology We have attempted to study the relationship of job history to the occurrence of the disease. Twen ty-seven of our 31 cases have either been on the "polycleaner" job assignment at the time the syn drome appeared or have had that assignment at some time in the past. This job assignment is the only one showing any positive correlation with the occurrence of the syndrome. Attack Rate.--The syndrome has a low attack rate. Our experience indicates it occurs only in less than 3% of all production employees who at one time have had polycleaning experience. Age Distribution.--The youngest of our cases is 26 years old, and the oldest is 47, with the majority falling in the 30 to 39 age group. The complete dis tribution is shown in Table 2. The appearance of the syndrome among younger employees may be influenced by the fact that the polycleaning job is one of the initial job assign ments into which employees in such plants are hired. Incubation Period.--If this syndrome is related to occupational factors, as we believe, then the time of exposure to these factors should be significant. We have investigated the time spent on polyclean ing and, although accurate job-time assignment in formation is difficult to develop, it appears as if none of these cases has had less than 12 months poly cleaning experience. Comment To our knowledge, this is a unique and, with the exception of references 3 and 4, previously unre ported disorder. The specific cause is presently unknown, although it appears to be related to the manufacture of vinyl chloride and polyvinyl chlo ride. Not only are the x-ray findings of themselves unique, but when accompanied by the symptoms of Raynaud's phenomenon, the syndrome becomes ex tremely specific. As far as we are aware, this has not been an observed response to any toxicant in any of the animal species. We have attempted to arrive at an explanation of its cause, as well as the physio logical mechanism whereby the extreme specificity for the distal phalanges of the hands occurs, but have been unsuccessful. We believe the condition is the result of three factors, all of which must be present for occurrence: (1) a chemical insult, (2) a physical insult, and (3) a personal idiosyncrasy. The chemical insult could occur from one or more of the monomers, catalysts, and intermediate reaction products existing in polymerizers. A low degree of exposure to these could occur from contact with the solid, slightly moist, residue in the polymerizer or to small quantities of vapor, absorbed either percutaneously or by inhalation. Research studies are in progress in an attempt to verify the chemical in sult factor theory. The physical insult is present in all "polyclean- ers" to some degree through the prolonged hand scraping operations as well as the occasional use of hammers to remove the residues. In support of the physical insult factor, we have quite recently ob served the effects of a finger injury to an existing case of this syndrome. Figure 4 (left) shows an x-ray film of the left hand of the first of these cases of acroosteolysis (accompanied by Raynaud's symp toms and skin nodules on the dorsal surfaces of the hands). The bone damage is quite limited. Figure 4 (right) shows the same hand with the roentgeno gram taken four months after a crushing injury to the mid finger, with lysis having resulted to the tuft of the distal phalanx. We believe this activity was stimulated by the trauma. Personal idiosyncrasy appears to be an important factor because of the low incidence of occurrence of the disorder. This is especially significant because, although all polycleaners are subjected to essential ly similar chemical and physical insults, the inci dence of this syndrome is very low, and the explana tion for this can only be made on tbe basis of person al idiosyncrasy. We suspect pertinent factors here are related to the individual's vascular system, the nerves controlling the blood supply to the fingers, and to the specific type of collagen in the individ ual's hands. We are in the process of investigating these factors. We have observed no serious disability in any of these cases. A few have been partially disabled be cause of hand soreness, to tbe extent that some restriction in manual activity was necessary. Im provement in the symptoms, as well as in the roent genological findings, has occurred in many cases without adequate explanation. We wish to emphasize that no cases have been found, after extensive search, in individuals either working with the finished polyvinyl chloride or its copolymers, or in processing the polymer into plastic products. In these processes, more exposure to the polymer occurs than does in the manufacturing of the polymers themselves. We presently believe that personnel assigned to polycleaning should be evaluated, prior to assign ment, for any evidence of collagen disease, oste olysis of the hands, or abnormal response of the hands to cold insult. Any evidence of the existence of any of these factors should contraindicate the as signment of an individual to "polycleaning," and thus remove, or at least minimize, tbe personal idio syncrasy factor. References 1. Cheney, W.D.: Acro-oeteolysis, Amer J Roentgen 94:595-617 (July) 1965. 2. Andren, L., et al: Osteopetrosis Acrooeteolytica: Syndrome of Osteopetrosis, Acroosteolysis and Open Sutures of Skull, Acta Chir Scand 124:496-507 (Dec) 1962. 3. Suciu, I.; Drejman, I.; and Valaskai, M.: Contributii Studiul Imolnavirilor Produse de Clorura de Vinil, Med Intern 15:967978 (Aug) 1963. 4. Cordier, J.M., et al: Acroosteolyse et Lesides Cutanees Associees Chez Deux Ouvriers, Affectes au Nettoyage D'Autoclaves, Cah Med Travail 4: (Jan) 1966. JAMA, Aug 21, 1967 Vol 201, No 8 20606005 BFG04180 To: P. H. Lawrence cc: P. I. Whitmire R. S. Reynolds R. N". Rylands R. W. McKay C. L. Woods S. B. Farbstein C. B. Cooper J. P. Piers A. R. Webber W. D. Robb L. H. Crunkleton S. 8. Michels T. R. Linak J. A. Klupar A. R. Berens B.F.GOODRICH CHBQCAL COMPANY DEVELOPMENT CENTER O.F.Beckmeyer W. F. Bixby J. L. Nelson G. D. Schaaf R.D.Scott - A.Vittone, Jr. H. L. Wuerth L. A. Bennett S. M. Davis A. M. Fairlie P. J. Horvath R. M. Kreager E. G. Schvaegerle R. J. Wolf Technical Council -ate: From: $JU> / ?, 7c-z tenLcr H. H. Marty HHK-30-67 I//.7 Status of PVC TaskForce Activities In our Task Force meetings, we have reported what activities are going on in various parts of the company. The following is an up-to-aow report for the benefit of the Plant Managers and Technical Managers on studies we have been keeping an eye on. 1. Conversion Control This is the most Important single objective the Task Force has. No final decision has been reached as to the beat method to use. a) Louisville is still operating a single poly on the hydrofull method. Their results are still encouraging. The conversion of twelve polys to hydrofull operation is continuing. b) Long Beach is waiting for delivery of a temperature integrator system so they can fully evaluate a AT approach. Initial results looked premising. c) Long Btasfe has dome further work on evaluating a system of early vinyl chloride removal. A prassura drop occurs In direct relation to the amoamt at vinyl chloride removed. For example, when 9000 lbs. at K1 are ehargsd^lOOO lbs. of VC1 are removed toward the end of the polymerisation, a pressure drop will occur at about 70H coaverslam. Sw effort now is cm trying to determine the effect of rate of VC1 removal, how predictable the method Is, how consistent the results are and the effect upon properties. A production dried pl* is to be sent to AIHC for sssmlnstion of stability and other properties. A control will also be sent. Henry was prepared to look at this method uaii two ; polys for polymerisation and two U300-gallon poly* f( Increased production tabled their study. 20607001 2. Alr-Fr** Pearl Charges In May, Henry completed a series of runs comparing air free and nerval level air at hydrofull and normal charge sizes. The resin was 102EF F-5. Although it may require an effort to set up an experimental series (especially one statistically designed) and to complete the plant work, it takes far longer to get the resin tested and an evaluation made. The major result obtained in the plant work was the observation that the hydrofull charges required two hours less to run to the desired porosity level than non-hydrofull charges. This was true for both the air-free and normal level air charges. Otherwise no process diff erence vaa noted. The testing work is incomplete as of this date. a) Bo difference in fisheyes was found using the Filmco test. John Whitney's lab tried several different extrusion conditions. But no significant change was detected. b) The TOPS #37 evaluation by Warren Reed failed to show a difference between the materials tested. This test is used to evaluate heat stability characteristics of resin. c) The Henry lab testing program is nearing colletion. d) The testing backlog was high for the Instron rheometer. Then it "broke down" for a time. To try to get an answer as soon as possible, we asked that only four samples be run. These included our two hydrofull lot samples, (sir free end normal air level) and two which might have been the two extremes in the TOPS #37 test. Both of these were non-hydrofull chargee; one was normal air level end the other was air-free. Bo difference was noted in the stability results in the fear simples using the CVHB test. Boldrlck used a 6fa6l recipe in evaluating the resin. It was _ that light stgmtr differences, colored compound would show up color unfortunately the lead stabilizer or (S-27) acted as an Indicator for the BPA shortstop. As a result, the teat lots were pink and dark. Bow a darker caspound will be used where the BPA-basic lead reaction will not be so obvious. f) At the time of writing, we are not clear if Jack Quint, ALDC, will axtruda wire to aee If this will pick up differences. 20607002 BFG04182 3. Productivity of Hydrofull Approach vs. Long Beach Method For several Booths a study of the productivity of the hydrofull process and of the so-called Long Beach method has inched along. When first initiated at the end of March, the t'-j methods were of the same productivity. The basis for hydrofull production was 3300-gallon polys using IPP catalyst. The Long Beach basis was 2550 gallon polys using lauroyl peroxide catalyst and top recovery of VC1. Now the Long Beach productivity is based upon IPP catalyst. This condi tion finds Long Beach productivity being better than the Henry hydrofull productivity. The report comparing the two routes is scheduled for issuance at the end of September. h. Air-Free Paste The oxygen analyzer was checked out. At present a wiring change in the instrument prevents ose of the high range of our dual range capability. He can cover multiple ranges with the range cards we have now. These cards are 0-10/0-10,OCX) ppm Og; 0-10/0-100 ppm Og; 0-100/0-1,000 jqa Og. So we can go from 0-10 up to 10,000 ppm Og. He can use the instrument for batch or continuous measurement. With the instrument so close to being used as a monitor, the air-free paste study was not started. It is now being started. The studies cover five variables - bead peaking, temperature, catalyst (IFF) level, cocygen scavenger (sodium hydrosulfite) end oxygen level. The Otmart gauge is being used in this study. 5- Heat Transfer Measurements o experiments hacvw been run on Poly 113 since June. In the first two series, large errors wars found between heat input and output. The errors were of 200 to 25C$ magnitude. Since the flow meter for the water was believed to be the eanse of error, it was decided to reactivate the orifice in tbe recirculation Una as a check on the magnetic now meter. This is now dons. Vs also J&an to calibrate the two resistance bulbs, used to measure T I toe Jmofcat (T out-T In), for accuracy the diffmKlA Mmd toe bulb readings is not corr tlan .6 Catalysts a) Louisville looked at Lucidol IPP. On pearl they asm no difference in reaction rate, the product propertiea were within specification and tha catalyst was aaslar to handle. 20607003 L On the latter point, the IPP is supplied in a disposable plastic tray. The catalyst can be popped out frost free, ready to nix with the hexane. Five paste charges were made. The reaction rate might have been slightly slower (0.1 hour) but this could be due to a difference in catalyst concentration. b) Henry worked with Lupersol 225 (di-sec lentyl peroxy dicarbonate). Lupersol 2?5 is easier to handle (liquid) and has better solubility in hexane. This catalyst was charged in 102EP F-5 and 103EP F-72. No difference in reactivity or action was found when making either resin. Samples of each test resin and of IPP control resins were sent to ALDC for evaluation. c) Niagara Falls tested Lupersol 11 (t-butyl peroxy pivilate) and Alperox C (lauroyl peroxide). There is no recoemendation to use Alperox C in 202 manufacture - the eoet runs higher, the reaction is slower. Lupersol 11 - started reaction quickly, produced even polymerization, died at end of polymerisation, the reectioo time vae longer then for csparylyl. The resin (202) wee in spec. d) Long Beach is taking a while to get over on IPP. An E.A. ves written to Install the catalyst injection system. The Ipp/hexene solution will be added thru the seel addition line. 7. Shortstops Research recoamended thiocarbanilide (TCA) as a shortstop for VC1 polymerization. An Initial teat series was caepleted an 102EP F-5 resin. 1100-gallon polys were used with the hydrofull technique. A charge in one hydrofull poly wee shortstopped with TCA end one in the second poly wee shortstopped with the regular amount of BPA. The TCA addition was made at three levels. First am amount equivalent to the molar concentra tion of ratal jef originally charged, then at one-half the catalyst weight charged and third at uue fouith. eg the catalystweight charged. The heat stability af the products shortstopped with TCA was equivalent to that of BPA shertetompd resin, ttis wee found on the Be-Cd-Zn test. TCA was a more affsetiwe dartitop then BBA but, in the tests run, it did not stop the poiiaMiimttem ceepletely. The series will be repeated. Injection water will be kept on during a six hour holding period for both HA and TCA shortstopped charges. The water addition rate will serve as a good Indication of how effective the shortstop is. Haggles will be taken at ehertstop and 6 hours after shortatopping. BFG04184 20607004 At Research, e aixed BPA-TCA shortstop produced a product stability equivalent to that of either shortstop when used individually. A single Geon 124 charge (15 gallon size) was made and 0 .01 parts of sodi-ua borohydride was added. There was no substantial shortstopping effect, as such. However, there was an improvement in product heat stability that vas greater than for BPA. Thin is worth following further. Concentration must be reduced or the effect must be outstanding to balance the cost of the material. 8. lynatrol Viscometer A box was constructed to house the Dynatrol probe inside Poly 112. For a tlae, leaks shorted the instruments. This was corrected. After a couple charges, the probe was damaged during cleaning, A new probe has arrived. It is to be installed again. He are trying to neasure the vlscoelty profile of a pearl polymerisation. The lynatrol has given an indication of this profile. But to date we don't know how reproducible the instrument is and how'much individual charges vary. Care is required in handling the vlscoaity proble. Today I doubt that it will be used for more than experimental studies - though they ere an isq>ortant aspect of thia work. 9. Blowdown Tank vs. Bo Blowdown Tank Study An analysis of costs and process advantages of a plant with blordovn tanks and of ooe with no blowdown tanks has been completed. The advantsges of the Long Beach design were reviewed at Henry with 0. 0. Schaaf and H. V. Long taking part. The preliminary costa were examined by Long Beach and Henry people. A report is ready to be issued now. For a 60 Million pounds/year plant, a no blowdown tank plant costs $130,000 less then a blowdown tank plant. More storage space for slurry, recovery^ and carry over wee provided. One point to vetch isi that provisions are/'V node to provide far a bydrofull system if we employ' this routes f\ \ V 10. Asltetioa Kmdlee Various egltsdleo equations are being put into a computer program for the Cleveland ncmqwitsi The plan is to write the progrmi(s) so they can be available vie teletype terminals. In this way man in the plants can use the system. Design and process charges will be more easily acccnqplished in the future. Long Beach examined the effect of slower speed agitation upon resin quality. This was done in trying to solve e particle slse problem for Anaconda. The 20607005 speeds studied were 60, 75, and 95 rpm. The 60 rpm speed gave buckshot particle else. The 70 rpm level produced 26 on a 60 mesh screen though the flow tine vas fast. The 95 rpn material had a very small amount of both coarse particles and fines and its flow time was better than normal production. 11. Math Model of the Pearl Polymerization Process The development of a nath model is being approached from two angles. A. T. Schoolsy and P. Y. Adams of the Research Center went through an analysis of the data available, the necessary efforts to write a model and the expected outcaae. Due to the complexity of the model, about two man years would be needed to rough out a nodal and two more man years for checking it out and polishing it. Dr. S. 1. Chang is attesting to construct a modal. Be has given the problem considerable thought over the last year. On September 20 he is to present his method of developing a modal and the reasoning involved in his approach. 12. Clean Poly Studies The data from 110 - 15 gallon Oeon TOO charges are being statistically examined. About ooe-thlrd of the time the poly was as clean after a charge as it was initially. This study is expected to shad a light on what causes the reactor wall to becane dirty or to remain clean. H. H. Marty cl