ML19259B580
| ML19259B580 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 04/04/1978 |
| From: | Galligan T BOSTON EDISON CO. |
| To: | Volgenau E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE) |
| Shared Package | |
| ML19259B576 | List: |
| References | |
| NUDOCS 7903060101 | |
| Download: ML19259B580 (14) | |
Text
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DOSTON EDIDON COMPANY ExEcuTivt Orrects 800 DQYLETON S T R E CT DosTcN. MASSACHUSETTS O2199 THOMAS J. GALLIGAN..JR.
ee s s.osert April 4, 1978 Docket No. 50-293 License No. DPR-35 Mr. Ernst Volgenau, Director Of fice of Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington, D.C.
20555
Dear Sir:
This letter is in response to your March 8, 1978 letter, received by us on March 16, 1978, which refers to an incident of exoosure of an individual to a radiation dose of 3.56 rems'at Boston Edison Company's Pilgrim Nuclear Power Station on November 23, 1977.
Appendix A to your March 8, 1978 letter identifies certain activities as apparent items of noncompliance with NRC regulatory requirements.
Our response to the Notice of Violation is submitted as Attachment A to this letter pursuant to the terms of the Notice and Section 2.201 of the NRC's " Rules of Practice", Part 2, Title 10, Code of Federal Regulations.
' As requested in your letter, included in Attachment A are the specific corrective actions either taken or planned for the purpose of preventing future noncompliance.
Appendix B to your March 8, 1978 letter proposed to impose civil penalties in the cumulative amount of Sixteen Thousand Dollars ($16,000) for the apparent items of non-com-pliance identified in Aopendix A.
Our response to the Notice of Proposed Iroosition of Civil Penalties is submitted as Attachment B to this letter oursuant to the terms of the Notice and Section 2.205 of 'the NRC's " Rules of Practice",
Part 2, Title 10, Code of Federal Regulations.
As you will note Boston Edison Company has elected not to contest the proposed civil penalty and thus our check in full payment is enclosed.
2073 134 7903060loi
Mr. Ernst Volgenau April 4,1978 Your March 8,1978 letter also requested additional information concerning the techniques for determining radiation doses received by employees at Pilgrim Nuclear Power Station.
Our response to this request is submitted as Attachment C to this letter.
Appendix C to your March 8, 1978 letter reviews the enforcement history relating to radiation protection at Pilgrim Nuclear Power Station for t'he eighteen month period between May of 1976 and November of 1977.
Although no speci-fic reply was requested to this Appendix, we have, in our.
discussion of corrective actions in Attachment A, mentioned a number of particular improvements which have taken place over the past year and which are planned for the future.
We wish to assure you that the matters identified in your letter have executive attention at the highest levels within Boston Edison Company and management shares your concern that the radiation safety program at Pilgrim Nuclear Power Station be in full compliance with all regulatory requirements so as to fully assure the health and safety of our workers and the public.
We are confident that the actions described in Attachment A to this letter are responsive to the concerns raised in your letter.
We will be pleased to answer any further -questions you may have and to work with you to assure that your concerns are met.
__trul yours
/Ve U
A
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Enclosures:
Attachment A:
Response to Notice of Violation Attachment B:
Response to Notice of Proposed Imposition of Civil Penalties Attachment C:
Response to Question Regarding Radiation Dosimetry Technique BECo Check No. 590290 cc:
Messrs.
M. J. Feldmann J. E. Howard G. C. Andogaini D. G.
Stoodley B. H. Grier, Director Region I Boston Edison Company Reading Room
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ATTACHMENT A Docket No. 50-293 License No. DPR-35 RESPONSE TO NOTICE OF VIOLATION Pursuant to 10 CFR 2.201 Boston Edison Company herewith responds to the Notice of Violation dated Parch 8, 1978, received by Boston Edison Company on March 16, 1978, referencing the inspection conducted by representatives of the Region I (Philadelphia) office on November 28-30, 1977.
In the following paragraphs each identified item of noncompliance will be set forth followed by Boston Edison Company's response there-to.
Steps taken to preclude the recurrence of the identified items and corrective actions planned will be discussed together at the end of this response.
Item I "10 CFR 20.101(a), ' Exposure of individuals to radiation in restricted areas,' limits the whole body dose to an individual in a restricted area to one and one quarter rems per calendar quarter except as provided by 10 CFR 20.101(b).
Paragraph (b) allows a whole body dose of three rems per calendar quarter pro-vided certain specified conditions are met.
Contrary to this requirement, on November 23, 1977, one individual working in a restricted area received a whole body dose of 3.56 rems during the fourth quarter of 1977, which exceeded the applicable limit of 3 rems."
Response
As was reported in Licensee Event Report 77-039/13C-0, one individual, a contractor repairman, did receive a whole body dose of 3. 56 rems during the fourth quarter of 1977 and thus exceeded the 3 rem limit set forth in 10 CFR 20.101(b).
The reason for this occurrence was the individual's mistaken entry into the wrong room in the course c~ a repair assignment.
The individual and a co-worker were assigned to repair a valve in the Clean Waste Tank Room (general area dose rates of 300 mrem /hr),
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Attachment A Page 2 however they instead entered the nearby Sludge Tank Room */
(general area dose rates of 30 rem /hr).
The reason for this mistaken entry was an apparent miscommunication between the workers, their supervisor and station personnel.
A Radiation Work Permit (RWP) was issued for the mainte-nance work which included a map of the area the men were to enter.
Directions to the Clean Waste Tank Room, a description of the room and the location of the damaged valve were discussed with the individuals prior to commencement of the work assign-ment.
Despite these instructions the two individuals mistakenly entered the Sludge Transfer Pump Room, the door to which is immediately adjacent to the door to the Clean Waste Tank Room, using the key given them for entry into the assigned area and then gained access to the Sludge Tank Room by circumventing a second locked door.
The workers realized their error when the appearance of the room they entered (Sludge Tank Room) did not agree with the description of the Clean Waste Tank Room and they were unable to locate the valve they were to repair.
Upon exiting the room the workers' pocket dosimeters were read by the Health Physics technician and discovered to be off-scale whereupon the workers were instructed to cease working and immediately report to the Health Physics Office.
Item II "10 CFR 19.12, ' Instructions to workers' states, in part,
'All individuals working in or frequenting any portion of a restricted area shall be kept informed of the storage, transfer, or use of radioactive materials or of radiation in such portions of the restricted area; shall be instructed in the health pro-tection problems associated with exposure to such radioactive materials or radiation, in precautions or procedures to minimize exposure.
- / It should be noted that t '.
diagram of the area in which this incident occurred, which is marked as Figure 1 accompanying Inspection Report No. 50-293/77-31, erroneously refers to a
" Sludge Tank Receiver Room" (also referred to in the Inspection Report as " Sludge Receiver Tank Room").
This room is correctly identified on the station's mechanical equipment layout drawings as the Sludge Transfer Pump Room (or the " Clean Up Sludge Transfer Pump Roon").
The Sludge Tank Room (or the " Clean Up Sludge Tank Room") is the adjoining room identified on Figure 1 as containing the Sludge Receiver Tanks.
It should be noted, and emphasized, that the Sludge Transfer Pump Room had general area dose rates of less than 10 rem /hr on November 23, 1977 although the Sludge Tank Room had general area dose rates in excess of 10 rem /hr.
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Attachment A Page.3 Contrary to the above, on November 23, 1977, two contrac-tor employees working on the Rad Waste floor, a restricted area, were not properly instructed to minimize their exposure in that instructions were not sufficient to preclude inadvertent entry into the Sludge Tank Receiver Room which is a high radiation area.
This failure to properly instruct personnel contributed to the overexposure of an individual described in Item I."
Response
This item appears to be based entirely upon the fact that two workers inadvertently entered the wrong room rather than upon any substantive deficiency identified in Boston Edison Company's overall instruction program, or in the instructions given to the two individuals.
It should be noted that:
(1)
Both individuals had completed Boston Edison Company's General Employee Training (GET) course which includes the basic precautions and procedural limits which are applicable to activities conducted in rediation areas.
Also, both workers had previously been employed at Pilgrim Station.
(2)
In accordance with Procedure 6.1-022, a Radiation Work Permit (RWP) was issued for the valve repair job.
Included in the RWP was information such as the radiation dose rates at various locations within the room, the protective clothing and respirator requirements, as well as a survey map of the work area.^/
(3)
In addition, verbal instructions for the specific task were given to the workers only a short distance from the entrance to the Clean Waste Tank Room.
1/ nspection Report No. 50-293/77-31 associated with this I
incident, indicated that failure to inform the workers of other sources of radiation in the vicinity of the Clean Waste Tank Room did not comply with the requirements of 10 CFR 19.12,
" Instruction to Workers".
Boston Edison Company would note that the specific purpose of an RWP is to identify the particular area where work is to be performed, so that specific instructions for that area may be given to the workers.
The cause of this incident was that the workers inadvertently entered an area other than where the work was to be performed.
Should each worker be instructed in avoiding all radiation areas within the plant, including those outside of their assigned work location, it would undoubtedly confuse rather than enlighten workers.
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Attachment A Page 4 These instructions included directions into the Clean Waste Tank Room, a description of the clean waste tanks and the location of the valve.
(4)
Although the workers thereafter entered the wrong room, the instructions given them were neverthe-less sufficient to enable them to re:dize that they were in.the wrong room causing them to promptly exit and thereby limiting the severity of the inci-dent.
Based upon our review of the instructions given the two
. repairmen and the circumstances of how they gained access to the Sludge Tank Room we feel that the intent of 10 CFR 19.12 was met.
Nevertheless, to the extent that there was a mis-communication between the werkers, their supervisor and s ca-tion personnel, as noted in response to Item I, which contri-buted to the occurrence of this incident, corrective actions are included in the discussion at the end of this attachment.
Item III
" Technical Specification 6.11, ' Radiation Protection Pro-gram' states, ' Procedures for personnel radiation protection shall be prepared consistent with the requirements of 10 CFR Part 20 and shall be approved, caintained and adhered to for all operations involving personnel radiation exposure.'
Radiation Protection Procedure 6.1-012,.' Access to High Radiation Areas', requires that areas with radiation levels greater than 1 rem per hour, but less than 10 rems per hour, be locked as required by Technical Specification 6.13, 'High Radiation Areas.'
The procedure also requires that areas with radiation levels greater than 10 rems per hour be locked with an additional padlock.
Contrary to this requirement on November 23, 1977, the Sludge Tank: Receiver Room, an area in which general radiation levels were as much as 15 rems per hour, was not locked with an additional padlock.
The failure to adhere to procedures contributed to the overexposure of an individual described in Item I."
Response
Although literally there was not an additional ' padlock' on the door into the Sludge Tank Room there were in fact two.
separate locks, actuated by two separate keys serving to pre-vent entry into the Sludge Tank Room.
As noted previously the area with a radiation level in excess of 10 rems per hour 2073 139
Attachment A Page 5 was the Sludge Tank Room, not the Sludge Transfer Pump Room, which is erroneously referred to as the Sludge Tank Receiver Room in the Inspection Report and the Notice of Violation.
Although the use of a door lock rather than a padlock may have constituted a technical violation of the procedure, Boston F.dison Company denies that there was a violation of the intent of Radiation Protection Procedure 6.1-012 which was to provide two separate locks requiring two separate keys in order to enter an area with radiation levels in excess of 10 rems per our.
Procedure 6.1-012 controls access to radiation areas by the use of a key system.
The entrance to radiation areas with whole body radiation levels in excess of 1 rem / hour are locked and can be opened with a Radiation ("R") key.
Certain station.
personnel such as Health Physics technicians and maintenance /
m supervisors are issued mas ter "R" keys.
Access to High-High2 radiation areas is controlled by a second lock (Procedure 6.1-012, states an " additional padlock"), which requires a "special" key which is maintained by the Watch Engineer.
The intent of the procedure ic to require two specific keys in order to enter a High-High radiation area.
At the time of the incident on November 23, 1977, two locked doors protected the entrance of the Sludge Tank Room.
The first door (identified as "A"
in Figure 1 to the Inspec-tion Report) into the room (Sludge Transfer Pump Room) just outside ~the Sludge Tank Room required an "R" key to open it while the second door (identified as "C" in Figure 1 to the Inspection Report) into the High-High radiation area of the Sludge Tank Room required the second "special" key.
Thus the intent of the procedure was met, even though the second lock was an integral part of the second door rather than an addi-tional padlock.
The two repairmen had been supplied with an "R" key by the Health Physics technician.
This key would permit entrance into the Clean Waste Tank Room (through the door identified as "B" in Figure 1 to the Inspection Report) and also the Sludge Transfer Pump Rocm but would not allow access through the.second door into the High-High radiation area of
- /"High-High" radiation areas are those with whole body rzdiation levels in excess of 10 rems /hr.
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Attachment A Page 6 the Sludge Tank Room.
When the repairmen mistook the second door (i.e., to the Sludge Tank Room) for the door into the Clean Waste Tank Room, they attempt 2d to open it utilizing the "R" key.
This attempt was unsuccessful.
It was at this point that the workers circumvented the lock on the second door by reaching around the barrier and thus entered the Sludge Tank Room.
This act was deliberate and not an acciden-tal case of wandering into.an unbarricaded area.
All barriers to High and High-High radiation areas were immediately surveyed and if necessary, modified to prevent such a recorrence.
Full compliance to the procedure includ-ing placement of padlocks where appropriate has been achieved.
Item IV "10 CFR 20.103, ' Exposure of individuals to concentra-tions of radioactive materials in air in restricted areas,'
requires in part that suitable measure.aents of concentrations of radioactive materials in air be used for detecting and evaluating airborne radioactivity in restricted areas.
Tech-nical Spec!fication 6.11, ' Radiation Protection Program, '
requires that radiation protection procedures be prepared consistent with the requirements of 10 CFR Part 20.
Procedure No. 6.1-022 requires that certain radiological surveys be per-formed as a minimum, including the collection and evaluation of r epresentative air samples from work areas and also requires
- h..t survey results be entered on the Radiation Work Permit O JP).
Further, Procedure No. 6.1-020 recuires that continuous par ;iculate and iodinc air samples be taken in occupied areas
-containing smearable contamination greater than 100,000 dpm per 100 cm2, Contrary to the on November 23, 1977, while personnel performed a, above, valve removal operation in the Clean Waste Tank Room (an operation and area having smearable con-2 tamination levels greater than 100,000 dpm per 100 cm ) the required air concentration measurements were not performed prior to or during the work, to detect and evaluate airborne radioactivity."
Response
Boston Edison Company acknowledges that the air concen-tration measurements in the Clean Waste Tank Room were not performed prior to the maintenance that was accomplished on the referenced date.
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Attachment A Page 7 Contributing to this failure were the following circum-stances.
Prior to scheduling the valve repair work, a Health Physics technician was asked to survey the valve in order to determine the contact dose rate.
Subsequent to this survey, it was determined to establish an RWP for the required mainte-rance.
The results of the original survey were utilized in the preparation of the RWP rather than requiring new surveys in an effort to minimize the accumulated exposure of the Health Physics technicians.
The individuals establishing the RWP were aware of the type of work and time (approximately fif teen minutes) necessary to perform this task as well as being know-ledgeabic in the levels of airborne contamination in comparable areas of the plant and apparently failed to perform the required air sample.*/
As noted in the Inspection Report (and required on the RWP) the individuals performing the repair were wearing respiratory protection equipment.
Air samples taken in the room subsequent to the repair indicated activities to be less than values listed in 10 CFR Part 20.
Corrective Actions Boston Edison Company. shares the Commission's concern with the occurrence of this incident.
Over the past year a conscientious effort has been underway to improve the Radiation Protection Program at P'igria Nuclear Power Station.
This effort will, of course, continue in the future.
Major improve-ments that have been made in the Radiation Protection Program during t;.e past year are as follows:
(1)
The Station Chemical Control and Radiation Protection Technicians have been reorganized and now conduct only chemical and radiation protection functions.
Previous to this reorganization they also conducted radwaste operation functions.
(2)
Two Health Physics Engineers were hired prior to July of 1977 to improve the first line supervision
- / he highest air sample ever recorded at the station, T
under more severe conditions than those experienced in the Radwaste area on November 23, 1977, had never exceeded 50 mpe/ hrs and even that level would not present any difficulty for a repair of this short duration utilizing respiratory equipment.
3 ~/ s l44
)(
'I
Attachment A Page 8 of the Radiation Protection Technicians.
One of the engineers has a degree in Radiological Health and approximately 4-1/2 years of Health Physics experience.
The second Health Physics Engineer has 3-1/2 years of College credit plus 3 years of Boiling Water Reactor Health Physics work.
(3)
Three additional Radiation Protection Technicians were hired, each having at least 8 years of Radiation protection experience.
(4)
A formal Radiation Protection Technician qualifi-cation program has been implemented and 11 of the 13 Station Chemical Control and Radiation Protec-tion Technicians have now completed the qualifica-tion program.
(5)
A ene month training course for 7 of the Station Chemical Control and Radiation Protection Techni-cians was conducted during April of 1977.
This improved the working knowledge of the technicians in the area of Radiation Protection.
(6)
The position of Senior Health Physics Engineer has been established at the station to supervise the Radiation Protection program.
This position has not been filled to date because of the lack of an acceptable candidate.
(7)
Additional portable radiation detection equipment has been purchased to raise the inventory of equipment to more acceptable levels and replace older equipment with more efficient equipment.
(8)
Station operating procedures relative to the Radiation Protection program have been completely rewritten, reorganized and implemented.
An ongoing policy of continual upgrade of all Volume 6 procedures will continue as the Radiation Protection program is upgraded and new equipment purchased.
(9)
New laboratory instruments for the Radiation Pro-tection program have been purchased to improve the detection of radioactive mat erial and to evaluate personnel internal exposure more effectively by utilizing an onsite whole body counter.
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Attachment A Page 9 (10)
A Respiratory Protection program has been imple-mented which meets with new regulatory require-ments of 10 CFR 20.103.
(11)
The Radiation Protection program records system has been improved by hiring two records clerks to maintain the records.
Procedures have also been established in Volume 6 ot' the station operating procedures to define the control and handling of the records.
(12)
A Corporate Radiation Protection staff has been hired consisting of one Senior Radiation Protection Engineer and one Radiation Engineer.
Their function has been to assist the station Radiation Protection staff in implementing the improvements in the Radiation Protection program at' the station.
In response to the particular items identified in the Notice of Violation Boston Edison Company has taken, or proposes to take the following actions:
(1)
In order to prevent the recurrence of exposure incidents and to improve the control of workers in all radiation areas, Boston Edison has initiated a complete and thorough review of all areas requir-ing barricades.
The necessity for barricades, the quality of existing barricades and the locking mechanisms on barricades will be investigated in detail.
This action is deemed responsivc to Items 1 and 3 in the Notice of Violation.
The estimated completion date is April 15, 1978.
(2)
In order to prevent.the recurrence of exposure incidents and improve the control of workers in high radiation areas several integrating digital readout dosimeters with audio signals have been ordered.
Upon delivery an evaluation program will be conducted by station personnel to deter-mine the desirability of utilizing these instru-ments as a standard procedure when entering high radiation areas.
This action is deemed responsive to Items 1 and 2 in the Notice of Violation.
The estimated delivery date of these instruments is May 31, 1978.
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Attachment A Page 10 (3)
Permanent signs of significant size and distin-guishing color will be installed at the entrance to High and High-High radiation areas.
In forma tion contained on these signs will specify the major components contained within the enclosed area.
In addition, barrier postings will be standardized in a new sign design that will contain four packets.
The packets will contain a recent survey map, the protective clothing required for the area, the specific room postings and the general entry Radiation Work Permit.
This action is deemed responsive to Items 1, 2, 3 and 4 in the Notice of Violation.
These signs are presently on order with an estimated installation date of Fby 15, 1978.
(4)
All survey maps will be reviewed to be certain they indicate all gates and major components with-in the various working areas.
This action is deemed responsive to Items 1 and 2 in the Notice of Violation.
The estimated completion date is M'y 15, 1978.
a (5)
All Station Chemical Control and Radiation Protec-tion Technicians will be scheduled for training sessions to better familiarize themselves with the location of various major components and equipment throughout the station.
The eight-hour documented training session is designed to achieve a more complete working understanding of station layout among all the technicians.
This action is deemed responsive to Items 1 and 2 in the Notice of Violation.
The training is estimated to be com-pleted by April 30, 1978.
(6)
In order to improve communications between the Health Physics staff and workers, Procedure 6.1-022 has been revised to require the Health Physics technician issuing the RWP to conduct a briefing for all workers utilizing the RWP.
The briefing will encompass a description of the survey conditions and will be documented by sign-offs from both the technician and the worker.
This action is deemed responsive to Items 1 and 2 in the Notice of Violations.
This action has been completed.
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Attachment A Page 11 (7)
In order to assure that all required surveys are accomplished the RUP index sheet has been revised so that it contains check-off blocks for all requested surveys.
This index sheet is reviewed prior to the issuance of the RUP.
In addition, a survey documentation sheet has now been implemented
~
which includes the surveys requested of the techni-cian, by the Health Physics Engineer.
Additional information concerning the area in which the survey was conducted wi'11 also be included on the doc'umen-tation sheet.
These improvements which have already been implemented will help to prevent recurrence of the failure to perform the air sample as cited in Item 4 in the Notice of Violation.
We believe that the foregoing actions are responsive to the Commission's request for Boston Edison Company's plans for control of activities in high radiation areas and improved communi-cation among individuals working in those areas.
We are confi-dent that these actions demonstrate Boston Edison Company's con-
~
tinuing commitment to radiation safety for its workers and the public.
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ATTACHMENT B Docket No.
50-293 License No.'DPR-35 RESPONSE TO NOTICE OF. PROPOSED IMPOSITION OF CIVIL PENALTIES Pursuant to 10 CFR 2.205, Boston Edison Company herewith remits the sum of $16,000 in full payment of the Notice of Proposed Imposition of Civil Penalties dated March 8,1978, received by Boston Edison Company on March 16, 1978.
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O
ATTACHMENT C Docket No. 50-293 License No. DPR-35 RESPONSE TO QUESTION REGARDING RADIATION DOSIMETRY TECHNIQUE The March 8, 1978 letter of Mr. Ernst Volgenau requested additional information con ~cerning the techniques for deter-mining radiation doses received by employees at Pilgrim I.
The letter referred specifically to the determination of dose of an individual who was reported to have received 2.91 rems.
Inspection Report No. 50-293/77-31 mailed to Boston Edison Company with a letter dated March 14, 1978 presents the TLD results for this individual (Repairman A) as follows:
Card Type Chip 1 Chip 2 Repairmat A G-7 3.156 rem 2.910 rem NG-67 3.181 rem 3.029 rem As noted by the inspector the procedure applicable to the-vendor-supplied TLD system in use at Pilgrim I provides that the whole body dose to be assigned to an individual is taken from the value exhibited by Card G-7, Chip 2.
The more techni-cal basis as to why Card G-7, Chip 2 is used to determine the reported whole body exposure from penetrating radiation follows.
The equipment used to make dosimetry measurements was manufactured by the Harshaw Chemical Company.
The dosimetry device utilized was a standard Harshaw badge consisting of four lithium fluoride (LiF) chips.
Two types of chips, having different sensitivities to neutron radiation, are used.
The badge contains two holders, G-7 and NG-67, each of which has two LiF chips.
One chip,2 identified as G-7, Chip 1, is situated behind a 7 mg/cm filter and is used only to furnish data for determining exposure to the skin of the whole body.
A second chin identified as G-7, Chip 2, is situated between two 222 mg/cmI filters and is used to determine the whole bodyexposurefrompenetratingradiagion.
The two NG-67 Chips are each situated behind a 476 mg/cm filter and are used to detect neutron radiation.
20/5 148 b
a Attachment C Page 2 10 CFR 20.401(a) requires that individual personnel exposure records be maintained on an NRC Form 5 or the equivalent.
The directions for completing an !!RC Form 5 require that exposure to skin of the whole body be reported as the amount of radiation measured af ter being filtered by a 7.mg/cm2 or less filter.
The only LiF chip that will pro-vide this data from the standard Harshaw badge is G-7, Chip 1.
Exposure to whole body penetrating exposure is to be reported as that which is measured af ter being filtered by a 300 mg/cm2 or less filter.
The LiF chip that will provide this data from the Harshaw badge is G-7, Chip 2.
The two NG-67 Chips may be used to make estimates of the whole body penetrating radiation, if neutron radiation is not present.
They are not used for determining compliance with 10 CFR 20.101(a) and (b) for two reasons.
First, the quantity of filtration in holder NG-67 exceeds the guidelines described on NRC Form 5.
Second, only one side of the chips in h~lder NG 17, the front side, is protected by a filter.
o Thus body scattered radiation is not eliminated by a backside filter, as is the case with G-7, Chip 2.
We trust that this explanation adequately sets forth the technical basis for concluding that the whole body radiation dose received by the second individual was 2.910 rems as deter-mined in accordance with all regulatory requirements.
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