NG-75-2210, AO 50-261/75-19:on 751208,boron Concentration Found Below Limits in Safety Injection Accumulator B.Cause Not Stated. Accumulator Partially Drained & Refilled from Refueling Water Storage Tank

From kanterella
Jump to navigation Jump to search
AO 50-261/75-19:on 751208,boron Concentration Found Below Limits in Safety Injection Accumulator B.Cause Not Stated. Accumulator Partially Drained & Refilled from Refueling Water Storage Tank
ML20086F510
Person / Time
Site: Robinson Duke Energy icon.png
Issue date: 12/22/1975
From: Utley E
CAROLINA POWER & LIGHT CO.
To: Moseley N
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20086F513 List:
References
AO-50-261-75-19, NG-75-2210, NUDOCS 8401030360
Download: ML20086F510 (4)


Text

. . .. . ~ . . - --.

o~ 9 l

. -pat .

Carolina Power & Light Company Deceraber 22, 1975 File: NG-3513 (R) Serial: NG-75-2210 N I Mr. Norman C. Moseley, Director U. S. Nuclear Regulatory Commission

\p + /co V

Regien II, Suite S18 230 Peachtree Street, N. W.

b /O.S ~D j b i'( _ y

'(

{

-6{

Atlanta, Georgia 30393 g.

'j gQ,V'

Dear Mr. Moseley:

-f s

o.5 g:og , ;', /.

cp u..

H. B. ROBINSON UNIT NO. 2 ' c.5, h

~-

DOCKET 50-261 'T BORON CONCENTRATION BELok LIMITS IN "B" SAFETY INJECTION ACCUMULATOR In accordance with 6.6.2.a of the Technical Specifications for

H. B. Robinson Unit No. 2, the attached Abnormal Occurrence Report is sub-

.i mitted for your information. This report fulfills the requirement for a 4 written report within ten days of an Abnormal Occurrence and is in accor-dance with the format set forth in Regulatory Guideline 1.16, Revision 1.

Yours very truly,

\

j; j/lOkb c(

E. E. Utley l Vice-President Bulk Power Supply CSB:me Attachment cc: Messrs. D. C. Knuth W. G. Mcdonald l

1 B401030360 751222

, PDR ADOCK 05000261 S PDR 14326

3. . r . . s .eo.

. .s , . . . ... m L

O O v

(/

ABNORMAL OCCliRRENCE P2 PORT Robinson Fils No. 2-0-4-a-1

1. Renort No. 50-261/75-19 2a. Renort Date December 11, 1975 .

2b. Occurrence Date December 8, 1975 3 Facility H. B. Robinson Unit No. 2 i Hartsville, South Carolina 29550 4 Identification of Occurrence l Baron Concentration was found to be below limits in "B" Safety Injection Accumulator. This constitutes a violation of Technical Specificetion 3.3.1.1.c which is a limiting condition for operation as defined in Technical Specification 1.8.b. '

5 Conditions Prier to Occurrence The reactor was critical after refueling shutdown with low power physics tests in progress.

6. Descriution of Occurrence At 0155 hours0.00179 days <br />0.0431 hours <br />2.562831e-4 weeks <br />5.89775e-5 months <br />, December 8,1975, "B" Accumulator was sampled and boron concentration found to be 1915 ppm. A Radiation Control and Teat Te hnician notified the control room of the sample. However, the Shif t Foreman was busy in the plant area cnd the message was relayed to the Control Operator via a startup physics test engineer.

The significance of the sample was not recognized by these personnel and no action was taken. The Shift Foreman was not advised regard-ing the information.

At 0600 hours0.00694 days <br />0.167 hours <br />9.920635e-4 weeks <br />2.283e-4 months <br /> a subsequent sample was ana3yzed to be 1917. ppm baron.

The Control Roo= vas called and the Shift Foreman was notified. He then consulted the Operating Supervisor by telephone and' they con-cluded that the Technical Specifications provided an exception.for the boron requirement since the plant was at low power with physics tests in progress. Specifically, paragraph 3.3.1.1 of the Technical Specifications states, "The reactor shall not be made critical except for low temperature physics tests, unless the following-

conditions are met:....". The interpretation was that the phrase-

" low temperature physics test" applied to low fuel temperatures which exist at low pozer physics testing and thus the exception was applicable.

Another-accumulator sample was taken at 0700 hours0.0081 days <br />0.194 hours <br />0.00116 weeks <br />2.6635e-4 months <br /> and found to be 1916 ppm boron concentration. Action was then taken to partially drain and refill "B" accumulator.

p p d d i Draining of "B" accmulator from 70% level and 644 psig to 0%

level (0-100% level span covers only a small portion of total accumulator volume) and 370 psig was completed at 1018 hours0.0118 days <br />0.283 hours <br />0.00168 weeks <br />3.87349e-4 months <br />. It was then refilled from the refueling water storage tank using the safety injecticn punps. The level at 1032 was 72% at 640 psig.

At 1040 hours0.012 days <br />0.289 hours <br />0.00172 weeks <br />3.9572e-4 months <br /> "B" accumulator was sampled and found to have a boron concentration of 1991 ppm. The accumulator was then declared operable at 1055 hours0.0122 days <br />0.293 hours <br />0.00174 weeks <br />4.014275e-4 months <br />. The plant was maintained at low power levels for physics testing during these evolutions based on the previously stated Technical Specification interpretation.

7. Desicnaticn of Annarent Ceuse of Occurrence The Safety Injection Accumulators are required to be sampled once a month with a maximum of 45 days between samples. The last previous sample vas obtained November 1, 1975, and found to be 2383 ppm boron.

This concentration was used for heatup and initial criticality fellowing the November refueling outage. At some' time between November 1,1975 and December 8,1975, during the refueling outage, apparently enough dilution occurred to reduce the concentration below limits. An exhaustive investigation was conducted, but, due to variable plant conditions prevailing during the outage, lack of sample data for the period in question, and numerous tests conducted during the outage it vac not possible to ascertain the exact time and source of apparent dilution. This points out a need for baron analyses following outsges to assure that the accumulator cencentra-tions are adequately defined. The dilution was apparently caused by come outage activity. Regardless of the cause, if an analysis is conducted prior to heatup the problem can be identified and corrected in a timely manner. No further investigation is planned to establish the exact cause nor is it felt auch investigation would be conclusive.

The cause of the delay in proper notifier. tion of the concentration and the realization of the analysis significance is of concern. Upon receiving notification from the laboratory, Control Operators checked their accumulator levels and pressures. However, due to their activity and the fact that the Shift Foreman was out of the Control Room at the time, they failed to notify him concerning the concentration until the second sample was analyzed. This'was an oversight on their part.

Once the Shift Foreman became aware of the problem he acted appropriately in contacting the Operating Supervisor. The decision that the problem did not constitute an abnormal occurrence was then made in good faith.

A follow-up session of the Plant Nuclear Safety Ccmmittee resulted in an indecisive discussion as to reportability of tnis incident and whether a violation had actually occurred. Close scrutiqr of the Technical Specifications revealed that the low temperature referred to regarding physics testing var defined as low reactor coolant 1

L

T o o

_3_

temperature. Therefore the conclusion that lcw power and low temperature physics testing were the same did not appear valid.

The applicability of Technical Specification sections was then questioned. There are sections governing hot shutdown, criticality, and power operation (greater than 2% of rated power) but none that specifically address low power physics testing below 2%

power. This further confused the interpretation and no headway was made in reaching a PNSC consensus. Therefore, with the committee still in cession Mr. Marvin Sincule of the NRC was called at 1455 hourc and requested to resolve the situation with a ruling. He returned the call at 1530 hours0.0177 days <br />0.425 hours <br />0.00253 weeks <br />5.82165e-4 months <br /> with the decision that a violation had occurred and should be reported as such.

8. Analysic of Occurrence There cere no personnel injuries, nor was there a release cf radio-active materials involved in this occurrence.

Initial criticality, after the 37 day refueling outage, was achieved at 1053 hours0.0122 days <br />0.293 hours <br />0.00174 weeks <br />4.006665e-4 months <br /> December 7, 1975, and a trip occurred at 1059 hours0.0123 days <br />0.294 hours <br />0.00175 weeks <br />4.029495e-4 months <br />.

The reactor was brought back critical at 1618 hours0.0187 days <br />0.449 hours <br />0.00268 weeks <br />6.15649e-4 months <br /> for initiation of low power physics test. At the time "B" accumulator boron concentration var determined to be out of limits the reactor had been critical, at essentially hot zero power, for nine hours and 42 minutes. No significant decay heat was produced; therefore, an emergency cooldown from this condition would be essentially the same as from hot shutdown.

9. Corrective Action The accumulator was partially drained and refilled from the refueling water storage tank. Boron concentration was then determined to be 1991 ppm. This completed immediate action.

To rectify the communication problem and failure to premptly recognize that a potential safety hazard existed, Operations have been instructed to notify the Shift Foreman immediately of any condition of this significance.

To assure that accumulator concentrations are positively identified following cold plant conditions which might affect their contents,

, a change has been incorporated into GP-1A checklist (Overall Plant j Operating Procedure) to require sampling and logging of accumulator boron concentration prior to heatup. This action should prevent l reoccurrence of the specific concentration violation.

i 10. Failure Data l There is nc previous failure data regarding boron concentration j specification violations concerning accumulators.

l .

-_ -