ML20214P580
| ML20214P580 | |
| Person / Time | |
|---|---|
| Site: | 05000128 |
| Issue date: | 09/18/1986 |
| From: | Richardson H TEXAS A&M UNIV., COLLEGE STATION, TX |
| To: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE) |
| Shared Package | |
| ML20214P584 | List: |
| References | |
| EA-86-105, NUDOCS 8609230260 | |
| Download: ML20214P580 (8) | |
Text
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TEXAS ENGINEERING EXPERIMENT STATION Office of the Director 18 September 1986 Director Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington, D.C.
20555 Docket No.:
50-128, License No. R-83
Reference:
EA 86-105
Subject:
Licensee Reply to Notice of Violation and Proposed Imposition of Civil Penalty Dated July 22,1986 (NRC Inspection Report No. 50-128/86-01)
Dear Sir:
The following response is submitted by the Texas Engineering Experiment Station (Licensee), a part of the Texas A&M University System, in regard to the notice of violation and proposed imposition of civil penalty issued on July 22, 1986 by the U.S. Nuclear Regulatory Commission, Region IV Office. This reply is submitted l
under oath of affirmation and represents the views and opinions of the adminis-i tration of the Texas Engineering Experiment Station and the management of the Nuclear Science Center Reactor (NSCR). A final report covering the May 1, 1986 Reportable Occurrence was issued to Region IV on May 16, 1986 with additional information provided concerning the self limiting safety features of FLIP TRIGA reactors on June 4, 1986.
Only portions of these documents will be repeated in this reply. These original documents may be referred to for more detailed l
information if needed.
l Stated Violations: Items A, B and C A.
Technical Specification (TS) 3.6.1(a) requires that during reactor operation non-secured experiments shall have a reactivity worth of less than one dollar.
Contrary to the above, on March 10, 1986, and on May 1, 1986, a non-secured experiment (boron rotisserie - experiment 86-123) which had a reactivity worth of approximately $1.08 was removed from reactor core position B-5 while the reactor was operating.
B.
TS 4.6.c requires that the reactivity worth of an experiment be estimated or measured, as appropriate, before operating the reactor with the experiment installed.
8609230260 860918 PDR ADOCK 05000128 G
The Texas A&M University System o Engineering Research Center College Station, Texas 778434577 e (409) 8451321 flg
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'Page"2 Contrary to the above, on March 10, 1986, and again on May 1, 1986, the reactor was operated with an experiment (the boron rotisserie - experiment 86-123) installed without the reactivity being adequately estimated or measured.
o C.
TS 6.6.2 requires that for any reportable occurrence defined in Section 1.2[9] of the TS,-a report shall be made to the NRC Region IV Office by telephone no later than the following working day and shall be followed by a written report that describes the circumstances of the event within la days of its occurrence.
TS Section 1.29 defines a reportable occurrence in paragraph (b) as operation TS and in paragraph (d)g conditions for operation (LCO) established in the in violation of limitin as an unanticipated or uncontrolled change in reactivity greater than one dollar.
Contrary to the above, on March 10, 1986, a reportable violation of TS occurred in that the reactor experienced an unanticipated change in reactivity of $1.08, but a report was not made to NRC Region IV by telephone on the following work day nor was a written report describing the circumstances of the event forwarded within 14 days of its occurrence.
Response to Stated Violations:
Items A and B 1.
The alleged violations A and B are admitted to as stated with no disagree-ment with the findings of the NRC inspection of May 5,1986 following re-porting of the violations by the Licensee on May 1, 1986.
The alleged violations as stated in Item C and the grouping of the events of March 10, 1986 and May 1,1986 as a Severity Level III problem are inappropriate in the opinion of the Licensee. The response to Item C will be addressed later in this report.
2.
The violations listed in Items A and 8 occurred primarily due to incorrect.
Judgement in the handling of the Boron Rotisserie experiment.
In the opinion of the operational staff, the reactivity worth of the experiment was less than one dollar.
This estimate was based on an earlier irradiation of the same sample in another location in the core. However, the worth was in-correctly assumed to be similar for the new core location. There were also associated errors in log entries and use of the experiment authorization form 514.
In both events of March 10, 1986 and May 1, 1986, standard procedures were followed for the removal of samples from the core with the reactor critical.
These procedures require a reduction in power from 1 MW prior to removal of the sample. Also, the removal of samples from the core at power is a routine operation. The removal of the sample on March 10 resulted in a 3 second period scram. However, this was not a clear indication that the worth of the sample was greater than $1 since sample worths significantly less than
$1 will result in a 3 second period scram.
While the judgement used to k
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arrive at that conclusion was at fault, it was based on prior experience with the sample and on the interpretation of the 3 second scram.
It should also be noted that the 3_second period scram circuit is not required by Technical Specifications for the NSCR.
C n.
3.
The corrective steps taken to avoid further violations were as follows:
a.
Immediate special training was provided all operations personnel on procedures for experiment handling, technical specification require-ments for experiments, reactor theory regarding reactivity of experi-ments and methods of reactivity measurements and estimations.
Written examinations were' administered after the additional training and a passing score of 80 was required.
Class lectures were completed by May 9, 1986 and examinations administered on May 16, 1986. All operators successfully completed the training program.
1
'b.
Operational restrictions were implemented immediately and procedure changes agreed to as follows:
(1) As per a request of the USNRC Region IV, experiments having a reactivity worth greater than $.30 will not be removed from the reactor while the reactor is critical.
'j (2)
The reactor power will be reduced to 600 kW or less for the removal at power of experiments having a reactivity worth of $.30 or less.
(3)
During continued reactor operations the reactivity worth will be verified for experiments removed at power and documented in the Reactor Operations Log.
(4) NSC Form 514 (Experiment Authorization) will include experiment reactivity measured values or estimates at both cold critical and at power.
(5) NSC Form 539 Section V, will have signature blocks to authorize startup following a scram as approved by the SR0 on duty or Management approval in the event the scram resulted in a Reportable Occurrence.
4 4.
Additional steps planned to prevent further violations are as follows:
a.
The NSCR operator training program which is already an extensive and detailed program will be expanded with more emphasis placed on attention to detail in the handling of experiments and properly analyzing their effects on reactor operations.
j 5.
Compliance was achieved immediately regarding operation of the NSCR following l-the event of May 1, 1986. Full compliance was achieved regarding training within a two week period and authorized deviations in operating procedures
Page.4 o
which were implemented immediately were reviewed and approved in their final form by the Reactor Safety Board on July 31, 1986.
Response to Stated Violation:
Item C The incident of March 10, 1986 was not reported because at the time it was not correctly recognized as a reportable event. 'It is only following the findings of May 1 that the violation of March 10 was properly identified. Thus, there is no basis to conclude that the violation was deliberately or purposely not reported.
Concerning Item C and the aggregate grouping of the events of March 10, 1986 and May 1,1986 to establish a Severity Level I!I and subsequent proposed civil penalty, the Licensee is in disagreement and respectfully requests a re-evaluation and reconsideration of the stated severity of these events and the subsequent justification for consideration of civil penalty. A request for remission of the proposed civil penalty has been forwarded by separate letter to the Director, Office of Inspection and Enforcement.
Proposed Considerations and Credits i\\
Concerning the event of May 1, credit should be given for the operators' awareness of the characteristics of TRIGA reactors. They anticipated a sample worth larger than what is normally handled and subsequently reduced reactor power to approximately 50% of maximum.
In most cases, samples are removed after a reduction to 70% of maximum power.
In the routine operation of a system that is capable of producing peak powers of approximately 1200 megawatts and reactor period values of milliseconds t'or large reactivity iasertions, the licensed operators are cognizant that large worth samples can be safely handled with no impact to the system.
The self limiting safety features of TRIGA reactors and the consequences of' operator error during operation of this fuel type must be given full credit in the evaluations.
Self limiting safety features of pulsed FLIP TRIGA fuels indicate that a 3 fold error in assumeo reactivity worth in handling the Boron Rotisserie experiment would have had no significant effect, Additional l studies were made by the Nuclear Science Center staff to establish the self limiting safety value of the reactivity insertion necessary to produce a maximum core temperature equal to the fuel temperature safety limit.
These studies showed that a value of $3.00 reactivity insertion would produce limitingttemperatures for the incident of March 10, 1986 and a much greater reactivity insertion would be required when applied to the incident of May 1, 1986. Also, the reactivity worth of a boron sample having a geometry such that it completely filled the B-5 core notch was calculated using Exterminator-2 reactor code and found to have a worth of $2.98. The removal at low power of a sample of this worth (3 times the worth of the Boron Rotisserie) wou?d be required to produce peak core temperatures approaching the safety limit for FLIP fuel (ll50'C).
These results are presented in Appendix A to this report.
.~ P age. 5.
Summary Statement In conclusion, we do not concur with the stated violation of Item C.
Failure to report the incident was by no means intentional, as implied in Item C of the Notice of Violation, and is contradictory to our history of reporting even very minor incidents to the USNRC.
The Licensee is also concerned that the events are not being evaluated from a perspective relevant to the type of reactor involved and conclusions of severity of the incidents are-being drawn within the context of other reactor systems.
We disagree with the subsequent grouping of the March 10 and May-1 events to obtain an aggregate of violations for designation as a Severity Level III.
In our judgement these events should be categorized as Severity Level V if properly considered as separate events and no greater than Severity _ Level IV when considered in aggregate since, as defined by 10CFR2, Appendix C, Supplement I - Severity Categories, these events had no potential for injury to the reactor or to personnel.
Respectfully submitted M
Dr. H. H. Richardson, Director Texas Engineering Experiment Station Sworn to before me the undersigned authority this M day of MbdIh>
1986.
/
Y un l$, lWh Notarf pepublic.
(
(Date)
Brazos County, Texas \\
cc:
R. D. Martin, USNRC, Region IV C. Erdman, Associate Dean, College of Engineering 3.
L. Peddicord, Head, Department of Nuclear Engineering F. Jennings, Chairman, Reactor Safety Board D. Feltz, Director, Nuclear Science Center
APPENDIX A Results of NSC Staff Studies To further understand the possible threats posed to the NSC reactor by incidents such as occurred on 1 May 1986, the NSC staff undertook a series of investigations involving computer'modeling codes of the NSCR. The codes used were the EXTERMINATOR-2 diffusion code used for reactor physics modeling, and a code written for a U.S. Air' Force contract which models the core kinetics during a reactor pulse.
EXTERMINATOR-II Results The neutron diffusion code EXTERMINATOR-2, which is used for all core modeling at the NSC, was run in order to estimate the maximum possible worth of a sample located in the B-5 experiment notch. For this run, the complete three inch square area of the notch was modeled as containing natural elemental boron.
It is felt that this would be a limiting case for the type experiments that could conceivably be placed in tF' position. The computer code was then run to produce estimates of the core effective multiplication constant (keff) and the neutron flux in _the core with the experimental notch filled with boron. The reactivity worth of the boron filled notch was then calculated as the difference in the k of the core with boron and that of the original core with the eff experimental notch filled with water. The EXTERMINATOR-2 run with the boron filled notch produced a k of 1.04027 compared to a k
=1.06243 for the water eff eff filled notch. Thus a reactivity worth _of $2.98 was obtained for the B-5 experimental notch filled with natural boron as follows:
p = (k
-keffo)/keffo
= -$2.98 eff
a In addition, the thermal neutron flux in the experimental notch changed from 18 8
2 1.5 x 10 n/cm.s in the water notch to 4.5 x 10 n/cm.s in the boron filled notch.
This calculation was carried out without allowances for fuel burnup, xenon poisoning, etc.
Pulse Modeling The computer program used in the study of the reactor peak power and temperature versus pulse reactivity insertion was developed at Texas A&M University. The code is based on a reactor point kinetics model utilizing six delayed groups. The program calculates the power, energy and time of pulse in the NSCR performing calculations over small variable time steps using empirical transient rod worth data. A linear feedback coefficient and heat capacity data from GA Technology were used to calculate the peak temperature and resultant feedback reactivity in each time step.
The results of this study indicate that a pulse reactivity insertion of approximately-$3.00 would be required to produce a maximum core temperature of-1150'C-which corresponds to the fuel safety limit.
The code.used for these studies was not written expressely for the cases studied.
However, benchmarking versus normal pulsing was performed with the code and the results were in agreement with the experimentally derived results.
In addition,.the program has been tested and verified by the U.S. Air Force Weapons Laboratory.
A graphic representation of the findings of the pulse calculations performed with this code is provided (see attached graph). General agreement with actual pulsing data can be seen in this graph also.
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