ML20206G355
| ML20206G355 | |
| Person / Time | |
|---|---|
| Site: | 07000824 |
| Issue date: | 06/30/1986 |
| From: | BABCOCK & WILCOX CO. |
| To: | |
| Shared Package | |
| ML20206G351 | List: |
| References | |
| RDD:87:8665-19:, RDD:87:8665-19:2, NUDOCS 8606250193 | |
| Download: ML20206G355 (11) | |
Text
SUPPLEMENT NO. 1 TO LICENSE TERMINATION SURVEY REPORT FOR THE CX-10 CRITICAL EXPERIMENT FACILITY AT LYNCHBURG RESEARCH CENTER LYNCHBURG, VIRGINIA REPORT NUMBER:
RDD:87:8665-19:2 JUNE 1986 BABCOCK & WILCOX LYNCHBURG RESEARCH CENTER LYNCHBURG, VIRGINIA r606250193 860603 pR C
ADOCK 07000824 PDR
SUPPLEMENT NO. 1 TO LICENSE TERMINATION SURVEY REPORT FOR THE CX-10 CRITICAL EXPERIMENT FACILITY TABLE OF CONTENTS SECTION PAGE
1.0 INTRODUCTION
1-1 2.0 DISCUSSION 2-1
3.0 CONCLUSION
S 3 -1
4.0 REFERENCES
4-1 LIST OF TABLES TABLE PAGE 2-1 Summary of Final Gamma Survey Results 2-3 LIST OF FIGURES 2-1 External Gamma Survey Plat 2-4 2-2 Regional Summaries of External Gamma Surveys 2-5 2-3 RSS-111 Gamma Survey Results-North Region 2-6 I
SUPPLEMENT NO. 1 TO LICENSE TERMINATION SURVEY REPORT FOR THE CX-10 CRITICAL EXPERIMENT FACILITY
1.0 INTRODUCTION
Reference (1) summarized the licensed survey report in support of a license request to terminate the CX-10 license and release the facility for unrestricted use.
The report concluded that all NRC criteria for release of a facility from licensed control had been met or surpassed.
One of the release criteria was that no residual radiation field more than 5 4R/hr. above natural background remain from CX-10 licensed activities.
However, because of instrument variability and enhanced outdoor background levels, it was determined that the gamma survey data, as it was presented in Reference (1), could be misinterpreted to conclude that the above criterion had not been met.
It was therefore determined that additional discussion of the outdoor grounds surveys was needed to clarify this point.
This supplement provides that additional discussion.
1-1
SUPPLEMENT NO. 1 TO LICELJE TERMINATION SURVEY REPORT FOR THE CX-10 CRITICAL EXPERIMENT FACILITY 2.0 DISCUSSION The location of outdoor grounds surveys are shown in Figure 2-1.
Gamma survey results, including those of the outdoor grounds, are summarized in Table 2-1.
This survey plat and table of results were presented and discussed in Section 5.0 of Reference 1.
As discussed in paragraph 5-2 of Reference 1, the background radiation level for indoor areas was conservatively set 0 9.6 nR/hr, based on readings in the Bay 2 basement labyrinth.
As shown in Table 2.1, none of the RSS-lli readings, indoors or outdoors, were more than 5 nR/hr above this level except in the outdoor-grounds surveys.
Additional discussion and interpretation of the outdoor-grounds readings are therefore presented in the following paragraphs.
In considering the outdoor-grounds gamma surveys, two points need to be made.
First, only the RSS-111 data should be considered when evaluating radiation readings relative to the 5 nR/hr criterion.
The PRM-7 readings should be considered for information only.
This is because the PRM-7 uses a NaI scintillator and therefore does not provide a true dose equivalent response.
It will accurately read dose equivalence (Rem) only in a 600-700 hev gamma field; it will over-respond to lower energy gammas and underrespond to higher energy gammas.
The RSS-lli, on the other hand, provides true dose equivalence over the energy range of interest because it uses an ion chamber as sensor.
Second, the 9.6 uR/hr background level established for the interior of Building A/CX-10 is not valid for outdoor areas because of " shy-shine" from highly radioactive waste stored in LRC's Building J Annex.
The hypothesis that the high outdoor radiation levels are attributable to the Building J Annex shine is supported by at least three facts:
(1)
The ratio of the PRM-7 to RSS-lli readings is significantly higher outdoors than indoors.
This indicates that a low energy gamma component is present outdoors that is not present indoors.
This is consistent with significantly scattered /
attenuated gamma radiation.
If the increased readings were due to, say, uncollided Cs-137 and/or co-60 gammas, this ratio would have remained constant or dropped.
(2)
A gradual and steady rise can be seen in radiation levels as one moves closer to Building J, which is about 800 ft. north of the retention tank.
The continuity of this gradual change was broken only by readings taken right next to outdoor walls, where shadow shielding and wall scattering affects the readings.
The total north-south gradient across the outdoor survey area shown in Figure 2-1 2-1
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SUPPLEMENT NO. 1 TO LICENSE TERMINATION SURVEY REPORT
{
FOR THE CX-10 CRITICAL EXPERIMENT FACILITY l
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j is 4-6 nR/hr.
This point is illustrated in Figure j
2-2, which presents region-wise arJunaries of the RSS-lli outdoor-grounds surveys.
(To minimize the j
impact of shadow shielding and wall scattering on these sumaries, readings taken right next to i
outside walls, i.e.,
less than 1 foot from wall surface, have not been included.)
j (3)
No licensed activities were performed under the i
reactor licenses that could plausibly account for the uniformly higher outdoor readings.
Although the highest outdoor readings occur in the same region (i.e., North) in which the radioactive i
liquid waste holding tank (RLWHT) and soil i
excavations are located, the data indicate that this is a strictly fortuitous circumstance.
This is evidenced by the observation that the RSS-lli readings taken in the drain trenches, above the excavation near the RLWHT, and above the RLWHT are e
j indistinguishable from readings taken over i
undisturbed ground at nearby locations.
- Here, j
" nearby" means close enough that the gradient i
caused by the Building J shine would not cause the I
readings to be different, but far enough that the i
)
out-of-ditch reading would not be significantly influenced by contamination in the ditch or RLWHT.
This can be seen by inspection of Figure 2-3, which provides a detailed map of the RSS-lll survey i
results in the north region.
Quantitatively, the average of all RSS-lli readings in the north i
region, excluding those: (1) in the excavations; l
(2) above the retention tanks or (3) within 5 feet i
of the excavation edges, is 14.7 4R/hr These 54 readings range from 12.2 to 16.5 4R/hr.
The 25 readings directly above the RLWHT and in the excavations average 14.7 4R/hr, and range from 13.0 to 15.9 4 R/hr.
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SUPPLEMENT NO.1 TO LICENSE TERMINATI0M SURVEY REPORT FOR THE CX-10 CRITICAL EXPERIMENT FACILITY I
TABLE 2-1
~
SUMMARY
OF FINAL GAMMA SURVEY RESULTS Location Instrument Readings
- Number
<----PRM-7--->
<---RSS-111--->
of Grids AVE MAX AVE MAX (pR/hr)
Bay 1 3.9 4.5 5.7 6.6 108 Sub-assembly 1 5.3 6.0 7.4 8.3 100 Counting Room 5.5 6.0 7.7 8.1 45 Old H.P. Office 8.4
.10.5 10.2 12.1 39 Penthouse 4.5 5.5 7.0 8.1 166 Offices 9.7 10.0 10.5 13.3 62 Drainlines 5.1 7.0 14 I
outside (Roof, Walls & Yard)
I17.8 26.0 10.4 14.5 419 Storage Building 11.0 11.0 10.3 11.4 35 i
i Average 10.9 8.9
)
Maximum 26.0 14.5 Total k
988 i
\\
~ --
- PRM-7 does not measure true dose equivalence over all energy ranges.
These data are provided for information only.
S 2-3
SOUTH SIDE F-m - - o---o- - o A s
I E-IDE
- B 1
2 3
4 5
6 7
8 9
10 11 STORAGE
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SHED
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TAf K 10 1
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BUILDING c,d,
DOA Figure 2-1 External Gamma 12
- \\d 2-4 Survey.
13
S OUTH REGION ( 51 Readings )
AVE.: 10.1 RANGE: 8.4 to 12.2 WEST REGION EAST (110 Readings)
REGION #1 AVE: 11.1 (32 Readings)
N GE: 7.8 to M AVE: 13.3 RANGE: 12.2 to 14.S E AST REGION #2 (26 Readings)
AVE: 14.0 RANGE: 13.I to 14.8 F
I AVE: 14.7 NORTH REGION W GE: 12.2 to 16.5 (104 Readings )
JoL TAP K Figure 2-2. Regional Summaries of External Gamma Surveys
.,oS (All readings in gR/hr)
(
2-5
(
Figure 2-3.
RSS-Ill Gamma Survey Results - North Region
( all readings in pR/hr )
./
ss BUILDING A
e 13.2 13.5 14.2 12.2 13.8 e
o e
eo l3 2
,I 3. 4,14.6 (4.0{ e12.8 e15 2 e15 0 el5.6 q p O
14.0 14.0 0 14.0 14.2 34.0
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g 15 METERS 2-6
SUPPLEMENT NO. 1 TO LICENSE TERMINATION SURVEY REPORT FOR THE CX-10 CRITICAL EXPERIMENT FACILITY
3.0 CONCLUSION
S From the data presented and discussed in Section 2.0, the following conclusions were drawn:
1)
Only the RSS-111 readings should be used when evaluating the gamma radiation surveys relative to the 5 nR/hr above background release criterion.
2)
The 9.6 nR/hr background level established for the indoor areas of Building A/CX-10 is not valid for outdoor areas.
3)
The higher radiation levels outside Building A/CX-10 (compared to readings inside Building A/CX-10) can be attributed to radiation originating from the highly radioactive waste stored in the Building J Annex.
This enhanced background caused a radiation field gradient across the outdoor Building A areas that prevents establishment of a single (enhanced) background radiation level suitable for all these areas.
4)
No radiation levels more than 5 nR/hr above background and owing to residual activation /
contamination from activities under the CX-10 license remain in or around Building A.
1 3-1 I
SUPPLEMENT NO. 1 TO LICENSE TERMINATION SURVEY REPORT FOR THE CX-10 CRITICAL EXPERIMENT FACILITY
4.0 REFERENCES
1.
" License Termination Survey Report for the CX-10 Critical Experiment Facility,"
RDD:87:8665-19:1, Babcock & Wilcox Co., June, 1986.
1 4-1 c.
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