ML20205J980

Forwards Statistical Info Re Redistribution of Concrete Rubble Stored in fenced-off Area of Parking Lot,Per Request. Net Radiation Level Above Background Below NRC Criterion. Higher Readings Recorded When Ground Dry

ML20205J980
Person / Time
Site:	05000187
Issue date:	02/17/1986
From:	Benveniste J NORTHROP CORP.
To:	Bernard H NRC
References
301-86-JB-22, NUDOCS 8602260726
Download: ML20205J980 (4)

Text

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o- 301-86-JB-22 NORTHROP February 17,1986 Mr. Hal Bernard USNRC 7920 Norfolk Avenue Bethesda, MD 20814 Attention: Mr. Hal Bernard

Subject:

Northrop TRIGA Reactor

Dear Hal:

In response to your request, the concrete rubble, stored in a fenced-off area of a parking lot, was redistributed over a larger area to reduce the average height of the rubble to the 6-12 inch range. The accompanying figure is a plan view of the fenced area in which the shaded section represents the region in which the rubble was distributed and the unshaded section represents bare parking lot surface. The shaded area was marked off in a 3 meter x 3 meter grid and a set of random numbers was generated to select the squares which would be surveyed.

The results of the treatment of the data are shown in Appendix 1. In brief, they show that at 1 meter above the rubble, the mean value of the radiation level is 8.77 .26 pR/hr while the mean value of the background is 8.44 .09 yR/hr.

Thus, the net radiation level above background is 0.33 .27 pR/hr., well below the NRC staff-adopted 5 R/hr criterion.

In Figure 1, the note in the lower left-hand corner refers to the fact that slightly higher readings (e.g.,0.5 R/hr) were recorded when the ground was dry than when it was wet after a light rain. We believe that there are two possible contributors to this observation. One, wet ground is somewhat more dense and, therefore, more absorbing than dry ground, and two, the stability of the detector at these low ranges is not good enough to credit variations of the magnitude obcerved from one day to the next.  ; ,

jh/C

( J.)[enveniste, Chairman

' Corporate Radiation Committec 8602260726 860217 PDR W

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' ABETAT 4. 0 9 STATISTICAL ANALYd.s OP CONCRETE RUdBLE IN PARKING LOT FILE: CONCLOT REV9 0 PAGE 1 I

COMPAND: DESC MISSING VALUE TREATMENT: VARWISE TH~lRE ARE 1 VARIABLES AND 38 CASES IN THE DATA SET 38 CASES (100.0%) ARE VALID STD ERROR COEPP OF VARIABLE MEAN STD.DEV. VARIANCE OF MEAN VARIATION 1 GR 8.77105 0.264991 0.0702205 0.0429873 3.02120 VARIABLE MINIMUM MAXIMUM RANGE TOTAL 1 GR 8.20000 9.30000 1.10000 333.300 VARIABLE MEDIAN MODE SKEWNESS KURTOSIS 1 GR 8.80000 8.80000 -0.274444 2.22932 -

ABSTAT 4.09 STATISTICAL ANALYSIS OF BACKGROUND IN PARKING LOT FILE: BKGDLOT REV# 0 PAGE 4 COMMAND: DESC MISSING VALUE TREATMENT: VARWISE THERE ARE 1 VARIABLES AND 5 CASES IN THE DATA SET 5 CASES (100.0%) ARE VALID STD ERROR COEFF OF VARIABLE MEAN STD.DEV. VARIANCE OF MEAN VARIATION 1 GR 8.44000 0.0894427 0.00800000 0.0400000 1.05975 VARIABLE MINIMUM MAXIMUM RANGE TOTAL 1 GR 8.30000 8.50000 0.200000 42.2000 VARIABLE MEDIAN MODE SKEWNESS KURTOSIS 1 GR 8.50000 8.50000 -0.843750 2.07812 APPCvDtv i

twbThf 4.0) STATIST 1cau 4 ALYb1S OF CUua m.- m.aunn l a 1 Al E 1.<d L U't {

REVt 0 PAGE 7 FILE: CONCLOT COAMAND: HIST MISSING VALUE TREATMENT: VARWISE VARIABLE: 1 GR AT LEAST 8.00000 5 10 15 20 25 30 BUT NOT OVER: FREQ  % +-------+--------+-------+-------+--------+-------+

8.00000 0 00.0 I 8.20000 1 2.6 IXXXX 8.40000 4 10.5 IXXXXXXXXXXXXXXXXXX .

8.60000 8 21.1 IXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 8.80000 9 23.7 IXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 9.00000 10 26.3 IXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 9.20000 5 13.2 IXXXXXXXXXXXXXXXXXXXXXX 9.40000 1 2.6 IXXXX 9.60000 0 00.0 I 9.80000 0 00.0 I 10.0000 0 00.0 I

+_______+________+_______+_______+________+_______+

TOTAL 38 100.0 5 10 15 20 25 30 ABSTAT 4.09 STATISTICAL ANALYSIS OF BACKGROUND IN PARKING LOT FILE: BKGDLOT REV6 0 PAGE 6 COMMAND: HIST MISSING VALUE TREATMENT: VARWISE VARIABLE: 1 GR AT LEAST 8.00000 10 20 30 40 50 60 BUT NOT OVER: FREQ  % +-------+--------+-------+-------+--------+-------+

8.00000 0 00.0 I 8.20000 0 00.0 I 8.40000 2 40.0 IXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 8.60000 3 60.0 IXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 8.80000 0 00.0 I 9.00000 0 00.0 I 9.20000 0 00.0 I

'9.40000 0 00.0 I 9.60000 0 00.0 I 9.80000 0 00.0 I 10.0000 0 00.0 I

+_______+ _______+_______+-______+________+_______+

TOTAL 5 100.0 10 20 30 40 50 60