ML17305B595
| ML17305B595 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 05/30/1991 |
| From: | Tenbrook W, Yuhas G NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | |
| Shared Package | |
| ML17305B596 | List: |
| References | |
| 50-528-91-20, 50-529-91-20, 50-530-91-20, NUDOCS 9106180030 | |
| Download: ML17305B595 (10) | |
See also: IR 05000528/1991020
Text
U. S.
NUCLEAR REGULATORY COMMISSION
REGION V
Report Nos. 50-528/91-20,
50-529/91-20,
50-530/91-20
Iicensee:
Arizona Public Service
Company
P. 0. Box 52034
Phoenix, Arizona
85072-2034
Facility Name:
Palo Verde Nuclear Generating Station Units 1,
2 and
3
Inspection at:
Walnut Creek,
California'nspection
Conducted:
May 20-29,
1991
Inspected
by: /~~
~<~@.
r
r 2
W. K. TenBrook, Radiation Specialist
g-so- V~
Date Signed
Approved by:
Q, P
G.
Reactor
~Summa
as,
C ief
adiological Protection Branch
5'o
I
ate'gne
Areas Ins ected:
Inspection of outstanding
items, including licensee
event
reports
an
inspection followup items.
Inspection procedures
90712
and
92701 were used.
Results:
The licensee's
radiostrontium procedure
did not appear
capable of
consistently measuring radiostrontium in reactor coolant within the
NRC and
vendor laboratory acceptance
criteria (Section 3).
9106180030
910530
ADClCN 05000528
Q
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l
DETAILS
1.
Persons
Contacted
Iicensee
L. Johnson,
Chemistry Manager, Unit Two
J. Santi,
Chemical Engineer,
Chemistry Technical Services
J. Scott, Site General
Manager,
Chemistry
De artment of Ener
D. Percival, Senior Scientist
2.
In-Office Review of Iicensee
Event
Re orts
(LER) (90712)
0'ER
50-528/91-05-LO
(Closed):
This report concerned
a spurious
"A"
train containment purge
>so ation actuation signal followed by
cascading trips of "A" and "B" control room essential filtration
actuation signals.
All systems
performed
as designed.
The root cause
of the safety system actuation
was stated to be
a failure of the
Geiger-Muller tube associated
with RU-37, "A" power access
purge area
radiation monitor.
The licensee
replaced
the detector
tube
and
successfully tested the system.
The licensee's
corrective actions
were
properly directed to prevent recurrence.
Followu
(92701)
en Items 50-528/90-56-01
50-529/90-56-01
50-530/90-56-02
(
en):
hese
items concerned
ana yses
o
a reactor
coo ant
samp
e
or
confirmatory measurement
of Sr-89,
Sr-90 and tritium by each Unit.
The
coolant sample
was split between
each Unit and the
NRC.
The r'esults
were compared using the
NRC verification test criteria.
The results of
the intercomparison
are presented
below.
Iab
II
NRC
Licensee
NRC
Random
Ratio:
Agreement
Result
Result
Uncertainty Licensee/NRC
Range
Analyte
(uCi/ml) (uCi/ml) (uCi/ml)
Unit 1
6.70E<<01
6.74E-01
1.00E-03
0.99
0.85-1.18
Sr-89
1.77E-04 9.90E-05 4.00E-06
1.79
0.75-1.33
Unit 2
6.10E-01
6.74E-01
1.00E-03
0.91
0.85-1.18
Sr-89
1.31E-04 9.90E-05 4,00E-06
1.32
0.75-1.33
Unit 3
5.86E-01
6.74E-01
1.00E-03
0.87
0.85-1.18
Sr-89
1.41E-04 9.90E-05 4.00E-06
,1.42
0.75"1.33
The uncertainty of the
NRC strontium-90 measurement
was too great to
allow a meaningful intercomparison,
and was not included.
The tritium
measurements
agreed well.
However, Unit One and Three measurements
of
il
strontium-89 did not agree.
The licensee's
measurements
were grouped
within approximately 16/ of their mean,
suggesting
a bias between the
NRC and licensee results.
The licensee's
execution of procedure
74CH-9XC30, Revision 2, "Rapid
Radiostrontium Analysis."
The inspector discussed
the results with the
Radiological
and Environmental Sciences
Laboratory
(RESL), which had
performed the
NRC analysis.
The RESL strontium analysis
employed
a
'two-step" separation
process
which first precipitated strontium for an
initial measurement
of total Sr-89
and Sr-90,
and later precipitated
yttrium for determination of Sr-90 from Y-90 ingrowth.
The Sr-90
result
was then subtracted
from the total radiostrontium to determine
Sr-89.
The licensee
procedure
employed
a single separation of strontium
followed by an initial count'f total Sr-89
and Sr-90,
and
a subsequent
count of total Sr-89, Sr-90
and Y-90 ingrowth.
The activity of Sr-89
and Sr-90 was then inferred from the two beta
measurements
using
simultaneous
equations.
The inspector noted. that the total uncertainties
of the techniques
used
by the licensee
and RESL had been reviewed in the literature
(Bowman,
et. al., Health Ph sics,
V. 31, pp 495-500).
The licensee's
technique
had
a hig
eve
of uncertainty except where Sr-89 activity was
one to
five times that of Sr-90, while the
RESL technique
had well-controlled
uncertainty across all concentrations
of radiostrontium.
The split sample in question
had
a Sr-89/90 ratio of approximately
60.
Although the licensee's
Sr-89 measurement
would be expected
to have
a
relatively low uncertainty,
the Sr-90 uncertainty could approach
100'j.
Examination of the licensee's
Sr-90 results
revealed
the Unit's Sr-90
analyses
ranged from +63'j to -45/ of their mean,
supporting the
literature.
The licensee's
radiostrontium analyses
were evaluated in inspection
reports 50-528/87-24
and 50-528/89-17.
In these
cases,
the inspector
observed inconsistencies
in licensee
strontium analyses
of NRC and
vendor blind samples.
Although the licensee
had refined their
laboratory technique to attempt to address
these prior disagreements,
the licensee's
procedure
did not appear
capable of consistently
measuring radiostrontium in reactor coolant within the
NRC and vendor
laboratory acceptance
criteria.
This matter will be reviewed during a
subsequent
inspection.
en Item 50-528
529
530/91-20-01
(0 en):
During the inspection
perio
, t e inspector
carne
o
ateria
Nonconformance
Report,
No.
91-Sg-9010,
concerning potential inoperability of channel
2 of RU-142,
RU-144 and RU-146 due to background
shine under post-accident
conditions.
The licensee
was evaluating their preliminary
calculations.
This matter will be reviewed during a subsequent
inspection.
Exit Meeting
The inspector discussed
the results of the measurement
comparison with
licensee
management
on May 29,
1991.
The licensee
acknowledged
the
differences
between the RESL and licensee
radiostrontium analyses
and
stated
they were investigating potential chemical interferences
that
could affect their method.
The licensee
was also examining the Unit
Three data for a possible reporting error.
i
0
Enclosure
Criteria for Acce tin
the Licensee's
Measurements
Resolution
Ratio
<4
4
"
7
8
-
15
16
-
50
51
200
200
No comparison
0.5
"
2.0
0.6
"
1.66
0.75 -
1.33
0.80 -
1.25
0.85 -
1.18
Com arison
1:
Divide each
NRC result by its associated
uncertainty to obtain the
resolution..
(Note:
For purposes
of this procedure,
the uncertainty is
defined
as the relative standard deviation,
one sigma, of the
NRC result
as calculated
from counting statistics.)
2.
Divide each licensee result by the corresponding
NRC result to obtain
the ratio (licensee
result/NRC).
3.
The licensee's
measurement
is in agreement if the value of the ratio
falls within the limits shown in the preceding table for'the
corresponding
resolution.
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