ML20237C791
| ML20237C791 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 05/31/1987 |
| From: | Henderson T, Williams F YANKEE ATOMIC ELECTRIC CO. |
| To: | |
| Shared Package | |
| ML20237C764 | List: |
| References | |
| NUDOCS 8712220185 | |
| Download: ML20237C791 (9) | |
Text
_
.c SEPARATE ACCOMPANYING
SUMMARY
REPORT OF TYPE B AND C RESULTS SINCE THE TYPE A TEST OF MAY 1984 AND RESULTS OF THE TYPE A TEST PERFORMED MAY 1987 May/ June 1987 YANKEE ATOMIC ELECTRIC COMPANY R0WE MASSACHUSETTS 01367 Prepared by:
[c Engineer Reviewed by:
7d/
m Reactor Engineering Manager Approved by:
77r F A -
Technical Director Approved by:
d//ft (T u4o Plant Superintendent 8712220185 871216 PDR ADOCK 05000029 P
PDR 010/48
During the interval from May 1984 to July 1987, Type B and C testing was performed on an 18 month frequency in accordance with Yankee Nuclear Power Station Technical Specifications. The Type B surveillance of the Containment Personnel Hatch was performed on a 6 month frequency.
Notable events pertaining to Type B and C tests performed during this interval are listed in i
Table 1.
No significant findings arose during the testing of October through j
December of 1985.
One LER was submitted to the NRC due to discovery of an I
excessive leakage rate during the testing conducted in May through July 1987.
I That LER, 87-11, is included in this Summary Report and provides the necessary discussion and analysis of the test results as required by Appendix J Section V.B.3 of 10 CFR 50.
The May 1987 Type A test failed to meet the acceptance criterion prescribed in Appendix J III. A.5(b).
It should be noted that although the resultant 95% upper confidence level leakage rate (after corrections for Type B and C systems isolated durir.g the Type A test) exceeded 0.75 La, it did not exceed La, that I
is, containment integrity was verified.
Selection of all instrumentation used to measure or calculate the containment i
air mass was performed in accordance with the Instrumentation Selection Guide l
formula specified in ANS-N274.
Thet e are two factors which contributed significantly to the final leakage rate value.
These are the Type B and C leakage pathways discussed in the LER referenced above and included in this report. The correction of these sources of leakage was performed prior to the ensuing plant startup.
Figures 1 and 2 represent the weighted-average containment temperature and the calculated air mass during the Type A test, respectively.
Consideration of the time of day and the weather associated with various regions of these graphs and the unique design of the Yankee Rowe containment structure can account for the pronounced deviations observed during the test.
The Yankee Nuclear Power Station containment structure consists of a steel sphere 125 feet in diameter with a minimum thickness of 7/8 inches.
The structure is wholly above ground and otherwise uninsulated.
The containment average temperature as presented in Figure 1 was determined using 20 resistive temperature detectors (RTDs) located in diverse regions throughout containment.
Each of the temperatures indicated by these RTDs was weighted by a factor indicative of the volume fraction of containment represented by that RTD. The resultant sum of the products of the temperatures and the weighting factors was then normalized by the sum of the weighting factors, yielding the temperatures as presented on Figure 1.
The Type A test period was begun at 2115, 5/6/87. The weather at this time and for the previous two days had been overcast and rainy, resulting in relatively uniform outdoor temperatures and, therefore, steady state average containment temperatures as well, independent of diurnal effects.
Over the first ten hours of the test period, an atmospheric high pressure system had moved into the area, resulting in significant clearing of the cloud cover.
Upon sunrise on May 7, this produced localized solar heating of the containment building and introduced diurnal effects for the duration of the test..-
A pumpback verification test was commenced at 0031 on May 8.
Air equivalent to 75% of the allowable leakage was pumped into containment and the test instrumentation measured a value of 68% of this air mass.
This test was performed in order to verify the measurement system's sensitivity and accuracy.
These results were well within the prescribed acceptance criterion for system l_.
accuracy verification.
The leakage rate attributable to systems leakage has been shown to be acceptably reduced through repair and subsequent Type B and C testing. Modificat'on of the design of the leaking fuel chute pump-back blank flange has been perforned in order to prevent recurrence of such a leakage path.
I L
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TABLE 1 LER TYPE SYSTEM BARRIER DISPOSITION 87-11 B
Fuel Chute Blank Flange Modified flange g
Dewatering design.
Retested satisfactorily.
87-11 C
Service Water TV-408 Cleaned internals Return from Retested Containment satisfactorily. -
l
IRC Fere 386 U 5. NUCLEAR KECULATO2Y Cote 8805 TON 843) ~
APPROVED OMS NO. 3150-0104 UCENSEE EVENT REPORT (LER)
- 4.CILITY NAME (1)
DOCKET NUMBER (2)
PAGE(3i Yankee Nuclear Power Station, Rowe, MA ol5l0tol010l2l9 1 lOFl Ol 3 flTLE 64)
Type B & C Test Combined Leakage Exceeded Technical Specifications EVENT DATE 45)
LER NUMsER (g)
REPORT DATE (7p OTHER F ACILITIES INVOLVED (Si MONTHI QAY YEAR YEAR
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Technical Services Manager 4 1 3 4 2 4 - 5 2 6l1 1 l 1 1 I I I I COMPLETE ONE LINE FOR E ACH COMPONENT F AILORE DESCR15ED IN THl3 REPORT (13)
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A38 TRACT IL/mrt to Hop speces, t e, espreenmewy refteen sma,e spece rypewrerren haest (166 Durinij Containment Type B & C surveillance testing, the combined leakage rate for all penetrations sub.iect to Type D and C testing was found to exceed the Technical Specification 3.6.1.2.b limit of 0.12 wt%/24 hours.
At the time of this discovery on 6/13/87, the plant was in Mode 6 and the total leak rate was O.1552 wt%/24 hours.
The primary contributors to the combined leakage rate were (1) the Containment Service Water return line isolation valve, SW-TV-408, and (2) the Fuel Chute Dewatering System isolation blank flange.
SW-TV-408 was removed and repaired.
The root cause of the valve leakage was attributed to a small groove on the valve disc.
An investigation into the cause for the blank flange leakage determined that the blank flange had been improperly installed due to personnel errors.
Corrective actions have been taken to revise procedures, instruct personnel and modify the blank flange design.
The overall Type B and C leakage rate was reduced to within the allowable Technical Specification limit.
Previous instances have been reported in LERs 84-06 and 84-10.
The health and safety of the public was not affected as a result of this event.
l "Ed
- NFC Form 3dA U S NUCLE AR F E GUL410av COMrM500N LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Aeraovso ovs so 3'60-o504 E EPIRES S'3t t$
P ACILIT Y hvit tu DOCR L I NUMB E R 12)
LER NUMBER (6)
PAGE G
- EAR st t
$ 4 Yankee Nuclear Power Station Rowe, MA o p l 0 l 0 l o l q il 5 f) N qJ1 QO q2 0F Ol3 TEXT W more specs a reqwred, une ad@twnel MC Foren 3t4A's)(17l During surveillance testing in accordance with OP-4702, " Vapor Containment Type B & C Penetration Tests," the combined leakage rate for all penetrations sub.iect to Type D and C testing wan found to exceed the Technical Specification 3.6.1.2.b limit.
At the time of this discovery on 6/13/07, the plant was in Mode 6 (refueling) and the total leak rate was 0.1552 wt%/24 hours.
The Technical Specification limit is 0.12 wt%/24 hours.
The primary contributors to the combined leakage rate were (1) the Containment Service Water return line isolation valve, SW-TV-408, and (2) the Fuel Chute Dewatering Systen isolation blank flange.
Previouc instances of exceeding Tech. Spec.
Type B and C acceptance criteria have been reported in LERs 84-06 and 04-10.
Corrective action was taken to reduce the excessive Icakage to within acceptable limits.
SW-TV-400 was removed and disassembled.
The oot cause of the excessive valve leakage has been attributed to a small groove on the valve disc.
The disc was machined and the valve reassembled and retested.
The Type B retest indicated an acceptable improvement in the valve leakage from 0.0419 to O.0210 wt%/24 hours.
The addition of a new containment isolation valve downstream or in place of TV-408 will be evaluated as an acidi t ional corrective action measure.
An investigation into the cause for the blank flange leakage determined that the blank flange had been improperly installed.
The investigation revealed the double resilient seals used to for m the sealing boundary had not been installed.
As subsequently tested with no resilient seals in place, the system yielded a leak rate of 0.048 wt%/24 hours.
A follow-up test performed with resilient seals l
installed produced zero leakage.
The conduct of this follow-up test
{
constituted a verification of the validity of the flange design.
A l
further investigation into this incident determined that:
- A generic installation procedure had been used providing the minimum requirements for routine piping replacement.
No specific details were provided for resilient seal installation, nor were they issued for the installation.
- The installed flange had been previously Type D tested per procedure and passed with zero leakage.
This surveillance test was used to determine both containment integrity and proper flange installation during the cycle XVIII refueling outage.
However, the test connection opening on the blank flange was apparently sealed off metal-to-metal contact between the blank flange and the machined slip-on pipe flange, giving the same result as would be expected if the resilient seals were installed and the space between the resi1ient seals was being measured.
A Type "B"
test was conducted after the 1907 Type "A"
test with the resilient seals removed to detaa ns t r a t e this and resulted in zero leakage. hMC F ORY 366a (9 834
l u s NucLLan atoutatoav commiss.ow l
mac.e.6 assa Aaraov eo oue no siso-oio.
LICENSEE EVENT REPORT (LER) TEXT CONTINUATION E x>iMts pt3t r85 PAGE(31 DOCK 4T NUbiRLH L2i LE R NUMB ( A los Fe,CSliv NAME H3
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W:n:
na Yankee Nuclear Power Station o l5 l0 l 0 l 0 j Oj 2l 9 8l 7 Ol 1l 1 Ol 0 Oj 3 OF O l3
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(W More spec 0 N NQuered, gost EQQattornal NRC fortre 366A 's) U1)
Rowe, MA The root cause of the blank flange leakage has been attributed to personnel errors and the failure to properly convey design features relative to the installation to maintenance personnel performing the installation.
To prevent recurrence, the following corrective g
actions have been taken:
cognizant engineers and maintenance supervisors have been 1.
Plant instructed to ensure that installation personnel are informed of the intent of design features.
-:g 2.
Assignments of maintenance personnel shall consider the capabilities of individuals to assure that qualified personnel perform work.
3.
Specific installation procedures shall be provided for all design 1
changes.
I 4.
Adequate supervision shall be provided for installation work.
5.
No modifications to design changes shall be made without independent engineering review.
(".
Modifications and repairs on safety related equipment shall be performed by or checked independently by a supervisor or senior l
6.
employee with sufficient experience and training at Yankee in that type of work.
7.
The fuel chute water return line blank flange shall be provided with a full gasket and testing performed by internal pressurization of the line.
B.
Other double resilient seal flanges shall be modified to assure that testing will detect the absence of the resilient seals.
The reduction in leakage rates associated with the repair of SW-TV-408 and the blank flange has reduced the overall Type B and C leakage rate to within the allowable Technical Specification limit.
Notwithstanding, the maximum Type B and C leakage rate indicated above was within the Technical Specification for containment integrity (0.2 that site boundary doses would be within w t*/. / 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />), which ensures 10 CFR 100 limits.
It is, therefore, concluded that the health and safety of the public was not affected as a result of this event.
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